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and we have a really special talk for

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you tonight somebody who just popped up

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on my email saying oh I'd love to give a

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our website for more information if you

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go to your favorite browser and putting

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public talks Republican couple public

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lecture series you can't say speech you

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could say Space Telescope probably - all

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this with the list of the upcoming

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lectures the watch live online you can

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watch the past lectures all the way back

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to 2005 so that's 12 years of and you

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can also sign up for our email that one

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one or two emails a month is too much

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you can also unsubscribe - or if you are

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fashioned just make sure you get added

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to the list if you have comments or

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questions I'm sending to public STS yeah

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that edu it'll come into my mailbox and

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we'll make sure you get your question

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answered okay let's see social media

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Facebook Twitter YouTube Instagram

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there's a lot of those if you would like

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to follow Space Telescope we are

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available social media

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I myself have Twitter but I'm as I say

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every month I'm only so often on there

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lots of other things to do and I do

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sometimes a blog on Hubble site if you

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want to follow me unfortunately the

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weather is not permitting tonight -

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those of you who brought the umbrellas

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in no definitely not pretty and

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unfortunately the observatory is not

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permitting the observatory is closed for

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repairs until further notice they had

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some problems with their dome and they

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emailed me today that they don't know

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when they'll be able to reopen

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so you

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go to md dot space grant org you will

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find this webpage over here on the right

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and the observatory status will not say

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check back on Friday it will say that

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check back next month or in a few weeks

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and will be able to tell you when the

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repairs will be done ok

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so unfortunately for the next couple of

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months possibly we will not have the

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Maryland space grant observatory ok all

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right now our news from the universe for

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November 2017 the first story tonight a

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wrinkle in space-time as you know I like

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to make small puns here this is of

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course is playing off Madeleine L'Engle

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famous story a wrinkle in time and what

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I'm talking about of course is the LIGO

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project the laser interferometer

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gravitational-wave Observatory which I

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told you about early last year has these

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two detectors one in Hanford Washington

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one in Livingston Louisiana and you can

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see they are these big long arrays that

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they send laser beams down each one of

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them and they the Blazer beans bounce

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off a mirror and come back and they

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measure the distance very very very

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accurately so that when the distances

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change they could tell by an incredibly

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small amount and they did measure an

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incredibly small amount of change and

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see what was observation done I can't

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remember the exact date of this

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observation but this was the detection

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of a black hole black hole merger that

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was about 1.3 billion light years away

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the first detection of gravitational

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waves and it was seen here is the data

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versus the predicted for langston and

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same for Hanford in fact it was detected

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in both of them and with the proper time

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delay for the light them to travel

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between them first detection of

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gravitational waves and on October 3rd

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of this year it was awarded the 2017

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Nobel Prize in Physics to these three

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gentlemen of the LIGO Virgo

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collaboration for the decisive

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contributions to the LIGO detector and

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the observational gravitational waves

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now we all sort of knew this was going

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to come because I could detect

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gravitational waves for the very first

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time

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yeah that's worthy of a Nobel Prize I

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personally did not expect it to come so

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quickly all right but you know since the

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discovery of those first black hole

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mergers they've discovered three or four

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more black hole black hole mergers so

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they're getting more observations but

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last summer on August 17th they also saw

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a neutron star neutron star merger okay

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so black holes are even alright so

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neutron it's a star can end up in

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several different ways okay a medium

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mass star low mass star ends up is

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what's called a white dwarf and that's

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about the the the density of the the

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atop the at the atom okay and it's

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supported by electron degeneracy

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pressure yada yada yada but it's about

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the density of an atom about the size of

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Earth okay all right and then there is a

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if you are more massive you can collapse

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down to what we call a neutron star

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which is about the density of an atomic

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nucleus okay and that's about the mass

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of the Sun compacted to about ten

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kilometers across or about the size of

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the Baltimore Beltway okay so take all

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the Sun could pass to the Baltimore

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Beltway size a ten kilometer cross and

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that's you get a neutron star a black

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hole goes even further than that is even

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more massive even even higher density

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okay so these neutron stars when they

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collide they're incredibly dense when

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they merge together they will also

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produce gravitational waves but not

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really as strong as a black hole black

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hole but this neutron star collision was

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only 130 million light years away which

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I know sounds pretty far but compared to

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the 1.3 billion light-years away that

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black hole black hole merger was is

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actually only 10% of that distance so

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they're able to see this neutron star

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neutron star collision with LIGO and

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Virgo

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is the European version of Lego however

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what made it even more exciting is it

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also was observed in optical light using

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both the LIGO detectors here in the US

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and the Virgo detector in Italy they

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were able to relatively relatively

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accurately determine where it was on the

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sky and astronomers were able to search

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for that point on the sky and found that

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there was an excess of radiation coming

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from this dot within the galaxy NGC 4990

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3 so they actually are able to do

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follow-up observations and neutron star

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neutron star collisions will have a lot

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of material around them and it will

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generate a lot of optical light okay so

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this is Hubble's observation from August

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22nd through August 28th over six days

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watching did you try and start a neutron

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star clip the light from that collision

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fade away all right and it's not just

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that it was seen by Hubble

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matter-of-fact Hubble was not the first

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one to see it it was actually first seen

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by family in gamma rays so it was seen

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in gravitational ways by LIGO and Virgo

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it was seen in gamma rays by Fermi

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integral and Swift it was seen in x-rays

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by Chandra it was seen in visible light

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by Hubble it was seen in infrared light

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by spitzer and it was seen by visible

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and infrared light by things like

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pan-starrs and other ground-based

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observatories so this is when

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astronomers can really get to work when

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it can really characterize the event

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when we see it in this many different

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wavelengths we see what's happening at

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lots of different energies and we can

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understand the event a lot more the

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black hole black hole merger that was

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that you know that won the Nobel Prize

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there were no follow-up studies we

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didn't see it in any other wavelengths

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this neutron star neutron star merger we

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were able to see in other wavelengths

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were able to get different

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characteristics of it and we're able to

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understand the processes that are going

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on and the basic result so far has been

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that hey it sort of fits what we think

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happens which is actually kind of crazy

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ideas you know and we say all right well

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this is our predictions we usually

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expect to be surprised oh nature be

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slightly differently than we predicted

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most of the predictions seem to be

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working out pretty well for this

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although there was one thing in terms of

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seeing it in ultraviolet that they

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didn't expect and the fact that it was a

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relatively faint gamma ray okay it's a

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short duration but it's a faint

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gamma-ray burst

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okay the short duration bursts for

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something so close it actually have been

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larger and they're not quite sure why

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but these are all the questions that

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come up when you have this many

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different ways of looking at it and are

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able to study it in so many ways so this

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not only have we moved into

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gravitational wave astrophysics but

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we've got follow-ups to be able to

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correlate it which makes it so much more

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valuable our second story tonight on the

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trail of asteroids now Hubble had this

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amazing project called the frontier

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fields okay and the frontier fields

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looked at six really massive clusters to

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look for gravitational lensing so this

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is the mass of galaxy cluster Abell 370

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and all these streaky things in here are

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gravitationally lens arcs okay and we've

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talked about that a lot and at the same

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time while they were doing the well

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they're looking at the galaxy cluster

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they also looked at what they called

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parallel fields so one detector of

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Hubble was looking at the cluster

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another detector was looking at the

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parallel field and then actually they

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rotated and then that one detector

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looked the parallel field and the other

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detector look at the cluster okay and

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they spent about a hundred hours of

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observation time on each of these

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clusters well these are the cleaned-up

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images that you see okay and of course

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the real observations have lots of you

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know cosmic rays and other things that

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happen you know detector artifacts that

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have to be cleaned up but there's also

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another thing that they had to clean up

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out of this these images that is

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illustrated by this movie so as this

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movie plays you'll start to see these

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little streak

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here and there numbered one through

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seven because these are seven unique

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asteroids that passed through the field

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over the hundred hours that Hubble was

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observing now Hubble doesn't observe it

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continuously it does a bit of

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observation and then it'll go off and do

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something else and I'll come back to the

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field and do some more observation etc

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which is why number seven here you can

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see is split into four separate little

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loops alright and why are they streaks

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and curved loops

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well Hubble and Earth are moving

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relative to the asteroid while we're

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taking observations so the asteroid

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actually ends up streaking and the

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parallax motion produces that little

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curve on there alright so for a Bell 370

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and it's parallel field here are the

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cleaned-up images and there are the

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images with the asteroid streaks now

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you'll notice we use the movie on the

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parallel field simply because there are

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ready these streaks in the in the

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gravitational lens those are actually

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galaxies that are beyond the

276
00:12:19,840 --> 00:12:17,000
gravitational lens but if I blink back

277
00:12:23,050 --> 00:12:19,850
and forth you can see the asteroids and

278
00:12:25,270 --> 00:12:23,060
where they appear in the field and this

279
00:12:28,510 --> 00:12:25,280
is kind of cool because what you've got

280
00:12:31,000 --> 00:12:28,520
here in one image is you've got some

281
00:12:32,620 --> 00:12:31,010
things within the solar system as well

282
00:12:35,980 --> 00:12:32,630
as you've got things that are billions

283
00:12:37,450 --> 00:12:35,990
of light-years away and it reinforces

284
00:12:39,280 --> 00:12:37,460
one of the things that we have to deal

285
00:12:41,560 --> 00:12:39,290
with an astronomy when you look out into

286
00:12:43,270 --> 00:12:41,570
the universe it's the sum of everything

287
00:12:46,090 --> 00:12:43,280
that you're looking through the solar

288
00:12:47,740 --> 00:12:46,100
system to the galaxies to the distant

289
00:12:49,540 --> 00:12:47,750
galaxies all the way to the edge of the

290
00:12:52,660 --> 00:12:49,550
universe that when you take an image

291
00:12:54,550 --> 00:12:52,670
you're combining all of that into one of

292
00:12:56,650 --> 00:12:54,560
those and here you can see some of the

293
00:12:58,690 --> 00:12:56,660
nearest things and some of the father's

294
00:13:00,540 --> 00:12:58,700
things in the universe all combined

295
00:13:04,090 --> 00:13:00,550
together that's kind of cool

296
00:13:06,970 --> 00:13:04,100
all right so now we'll go to our

297
00:13:10,600 --> 00:13:06,980
featured speaker and our featured

298
00:13:12,940 --> 00:13:10,610
speaker tonight let's see if her laptop

299
00:13:17,440 --> 00:13:12,950
takes over yes it does

300
00:13:19,650 --> 00:13:17,450
his doctor Elizabeth Tasker and she is

301
00:13:22,110 --> 00:13:19,660
from the originally from the UK

302
00:13:24,720 --> 00:13:22,120
she did her undergraduate work at Durham

303
00:13:27,900 --> 00:13:24,730
University and then did her graduate

304
00:13:29,520 --> 00:13:27,910
work at University of Oxford then she

305
00:13:31,620 --> 00:13:29,530
came across to the United States and

306
00:13:35,420 --> 00:13:31,630
Canada and did some post doctoral work

307
00:13:38,130 --> 00:13:35,430
here before going even further from home

308
00:13:42,060 --> 00:13:38,140
where she is an associate professor at

309
00:13:44,310 --> 00:13:42,070
the Japan aerospace exploration agency

310
00:13:46,110 --> 00:13:44,320
and I love JAXA because that's a great

311
00:13:48,470 --> 00:13:46,120
acronym to say it's almost it's it's

312
00:13:51,180 --> 00:13:48,480
like NASA but it has sort of an

313
00:13:53,910 --> 00:13:51,190
intriguing sound Jack's I just you know

314
00:13:58,500 --> 00:13:53,920
sounds as good as NASA in terms of a

315
00:14:01,410 --> 00:13:58,510
Space Agency she does her research work

316
00:14:04,350 --> 00:14:01,420
on the formation of stars and planets by

317
00:14:07,380 --> 00:14:04,360
doing computer simulations and today is

318
00:14:09,360 --> 00:14:07,390
a very special day for her because she

319
00:14:11,520 --> 00:14:09,370
has a book that is being published today

320
00:14:13,500 --> 00:14:11,530
and I'm sure she'll mention that in her

321
00:14:21,050 --> 00:14:13,510
talk ladies and gentlemen dr. Elizabeth

322
00:14:30,930 --> 00:14:23,070
well thank you very much

323
00:14:33,060 --> 00:14:30,940
is this something good okay so today I'm

324
00:14:36,090 --> 00:14:33,070
going to be talking about planets

325
00:14:38,250 --> 00:14:36,100
especially those beyond our solar system

326
00:14:41,670 --> 00:14:38,260
but I'm going to start with what I hope

327
00:14:42,930 --> 00:14:41,680
is a vaguely familiar image in a minute

328
00:14:46,050 --> 00:14:42,940
so I'll be starting with what I hope is

329
00:14:48,300 --> 00:14:46,060
a vaguely familiar image there we go so

330
00:14:50,730 --> 00:14:48,310
I hope these guys look somewhat familiar

331
00:14:54,329 --> 00:14:50,740
to everyone and I say this is a Sun and

332
00:14:57,630 --> 00:14:54,339
then just past the Sun we have our four

333
00:15:00,870 --> 00:14:57,640
smallest planets Mercury Venus Earth and

334
00:15:03,630 --> 00:15:00,880
Mars and just past Mars we have this

335
00:15:06,570 --> 00:15:03,640
band of rubble rubble rocky leftovers

336
00:15:09,210 --> 00:15:06,580
from the planet formation process that

337
00:15:12,420 --> 00:15:09,220
we call the asteroid belts which also

338
00:15:14,850 --> 00:15:12,430
contains the dwarf planet Ceres and then

339
00:15:17,640 --> 00:15:14,860
beyond the asteroid belt we have the

340
00:15:21,180 --> 00:15:17,650
giants Jupiter Saturn Uranus and Neptune

341
00:15:23,640 --> 00:15:21,190
and then we have this another pile of

342
00:15:26,280 --> 00:15:23,650
rocky leftovers from planet formation

343
00:15:28,140 --> 00:15:26,290
which is the Kuiper belts and of course

344
00:15:30,240 --> 00:15:28,150
it's most famous member is the dwarf

345
00:15:35,520 --> 00:15:30,250
planet Pluto that we never really talk

346
00:15:41,100 --> 00:15:35,530
about that anymore and you are here all

347
00:15:43,020 --> 00:15:41,110
right so if you were to base all our

348
00:15:46,110 --> 00:15:43,030
understanding of planet formation on our

349
00:15:48,900 --> 00:15:46,120
solar system we would note that you have

350
00:15:51,060 --> 00:15:48,910
two types of planets you have rocky

351
00:15:54,230 --> 00:15:51,070
planets so these guys Mercury through to

352
00:15:57,540 --> 00:15:54,240
Mars and here you have a solid surface

353
00:16:00,329 --> 00:15:57,550
with a relatively thin atmosphere and

354
00:16:03,360 --> 00:16:00,339
then beyond the asteroid belt you have

355
00:16:05,610 --> 00:16:03,370
gas giant planets where most of their

356
00:16:09,449 --> 00:16:05,620
volume is taken up with their atmosphere

357
00:16:13,170 --> 00:16:09,459
around a much smaller dense central core

358
00:16:16,199 --> 00:16:13,180
and this colossal atmosphere results in

359
00:16:19,170 --> 00:16:16,209
absolutely crushing pressures near their

360
00:16:21,300 --> 00:16:19,180
core so much so than in fact our

361
00:16:23,640 --> 00:16:21,310
hydrogen on Jupiter by the time you

362
00:16:26,190 --> 00:16:23,650
approach Jupiter's core it becomes so

363
00:16:29,449 --> 00:16:26,200
dense that it starts behaving as this

364
00:16:33,519 --> 00:16:29,459
kind of metallic compound

365
00:16:36,489 --> 00:16:33,529
so until 1990s these were all the plan

366
00:16:38,350 --> 00:16:36,499
we knew and we didn't think that our

367
00:16:41,019 --> 00:16:38,360
solar system was the only one out there

368
00:16:43,600 --> 00:16:41,029
but we haven't actually seen any others

369
00:16:49,780 --> 00:16:43,610
so nothing was definite but then

370
00:16:51,850 --> 00:16:49,790
everything changed so our Sun is one of

371
00:16:54,249 --> 00:16:51,860
about a hundred billion stars in the

372
00:16:57,249 --> 00:16:54,259
Milky Way galaxy and when we talk about

373
00:17:01,509 --> 00:16:57,259
extrasolar planets we mean extra as in

374
00:17:04,059 --> 00:17:01,519
outside and a solar as in of the Sun so

375
00:17:06,579 --> 00:17:04,069
an extrasolar planet or exoplanets

376
00:17:10,270 --> 00:17:06,589
is any planet that is not in our solar

377
00:17:13,720 --> 00:17:10,280
system and the story of extrasolar

378
00:17:20,059 --> 00:17:13,730
planets begins in 1990 when the Arecibo

379
00:17:44,700 --> 00:17:37,160
[Music]

380
00:17:51,970 --> 00:17:49,690
structural cracks so around the same

381
00:17:54,100 --> 00:17:51,980
time a similar radio telescope in Green

382
00:17:55,900 --> 00:17:54,110
Bank in the u.s. also has structural

383
00:17:58,390 --> 00:17:55,910
cracks which were ignored and the whole

384
00:17:59,860 --> 00:17:58,400
thing collapsed so in a fit of panic a

385
00:18:01,800 --> 00:17:59,870
receiver was like okay we've got the

386
00:18:05,290 --> 00:18:01,810
message we're gonna fix this

387
00:18:08,260 --> 00:18:05,300
but during repairs the telescope was not

388
00:18:11,320 --> 00:18:08,270
taken completely offline but it couldn't

389
00:18:13,120 --> 00:18:11,330
be moved so typically during a night to

390
00:18:16,360 --> 00:18:13,130
the telescope will move very slightly

391
00:18:18,250 --> 00:18:16,370
across the sky as it tracks objects but

392
00:18:20,350 --> 00:18:18,260
during these repairs nothing could be

393
00:18:23,620 --> 00:18:20,360
done it had to be absolutely stationary

394
00:18:26,650 --> 00:18:23,630
and this made it unfit for almost all

395
00:18:28,600 --> 00:18:26,660
projects however at the time was a

396
00:18:32,410 --> 00:18:28,610
postdoctoral researcher called Alex bull

397
00:18:34,990 --> 00:18:32,420
Shen and he asked to use a telescope for

398
00:18:37,090 --> 00:18:35,000
a month-long survey because this survey

399
00:18:40,000 --> 00:18:37,100
could be done while the telescope wasn't

400
00:18:42,400 --> 00:18:40,010
moving and normally such a proposal

401
00:18:42,970 --> 00:18:42,410
would never have gone through because he

402
00:18:45,100 --> 00:18:42,980
required

403
00:18:47,020 --> 00:18:45,110
half the telescope's time and this was

404
00:18:49,710 --> 00:18:47,030
the biggest telescope in the world for

405
00:18:52,090 --> 00:18:49,720
radio so people would be like you know

406
00:18:54,040 --> 00:18:52,100
but as it happened no one else could

407
00:18:57,700 --> 00:18:54,050
really use it he was based the telescope

408
00:19:00,750 --> 00:18:57,710
and they said fine and what Alex wanted

409
00:19:03,220 --> 00:19:00,760
to find were dead stars called pulsars

410
00:19:06,580 --> 00:19:03,230
so actually we've just had a very nice

411
00:19:09,220 --> 00:19:06,590
summary of these because a pulsar is

412
00:19:11,070 --> 00:19:09,230
what forms when a star that is much

413
00:19:13,840 --> 00:19:11,080
larger than our Sun more than 8 times

414
00:19:17,380 --> 00:19:13,850
eventually reaches the end of its life

415
00:19:19,720 --> 00:19:17,390
and it runs out of fuel to burn and when

416
00:19:22,660 --> 00:19:19,730
that happens the star dies in a

417
00:19:25,420 --> 00:19:22,670
supernova explosion and the bit that's

418
00:19:28,540 --> 00:19:25,430
left behind collapses to incredible

419
00:19:31,240 --> 00:19:28,550
densities so dense that its atoms

420
00:19:33,220 --> 00:19:31,250
actually starts to disintegrate and the

421
00:19:37,780 --> 00:19:33,230
protons and the electrons inside the

422
00:19:40,600 --> 00:19:37,790
atoms and so we therefore call these

423
00:19:41,920 --> 00:19:40,610
neutron stars which is exactly the same

424
00:19:45,580 --> 00:19:41,930
source of the gravitational waves

425
00:19:47,950 --> 00:19:45,590
mentioned earlier however as yeah and as

426
00:19:49,930 --> 00:19:47,960
mentioned these are tiny so only

427
00:19:53,440 --> 00:19:49,940
city-sized or indeed the

428
00:19:55,900 --> 00:19:53,450
the Baltimore Belt and yet they weigh

429
00:19:58,120 --> 00:19:55,910
between 1.4 and twice this master's son

430
00:19:59,980 --> 00:19:58,130
so they're incredibly dense objects and

431
00:20:03,160 --> 00:19:59,990
as they collapse their magnetic field

432
00:20:06,700 --> 00:20:03,170
also strengthens a lot and this magnetic

433
00:20:08,920 --> 00:20:06,710
field causes any remaining charges left

434
00:20:13,860 --> 00:20:08,930
on the neutron star to be ripped off and

435
00:20:18,160 --> 00:20:13,870
fired into the cosmos as powerful Jets

436
00:20:22,510 --> 00:20:18,170
now if these Jets happen to swing by the

437
00:20:26,020 --> 00:20:22,520
earth as the star rotates then we see a

438
00:20:29,950 --> 00:20:26,030
periodic light pulse and therefore we

439
00:20:33,700 --> 00:20:29,960
call these April's are now the accuracy

440
00:20:35,350 --> 00:20:33,710
for these pulses is incredibly high it's

441
00:20:37,240 --> 00:20:35,360
so high that when they were first

442
00:20:39,810 --> 00:20:37,250
discovered they were thought that they

443
00:20:42,250 --> 00:20:39,820
might even be extraterrestrial sources

444
00:20:43,900 --> 00:20:42,260
but in fact when more sources were

445
00:20:45,790 --> 00:20:43,910
discovered across the sky it was

446
00:20:48,700 --> 00:20:45,800
realized that actually a natural process

447
00:20:51,070 --> 00:20:48,710
must be causing these but their accuracy

448
00:20:56,200 --> 00:20:51,080
is such that it rivals that of atomic

449
00:21:00,280 --> 00:20:56,210
clocks except for this one pulsar that

450
00:21:04,000 --> 00:21:00,290
Alex Vause Shem saw so this pulsar was

451
00:21:07,300 --> 00:21:04,010
called PSR b12 57 plus 12 that very

452
00:21:10,390 --> 00:21:07,310
catchy name and for this particular

453
00:21:12,430 --> 00:21:10,400
pulsar so PSR is pulsating source of

454
00:21:14,670 --> 00:21:12,440
radio and then that's completely our

455
00:21:17,410 --> 00:21:14,680
memorable letters and numbers is the

456
00:21:20,110 --> 00:21:17,420
position in the sky but for this

457
00:21:23,830 --> 00:21:20,120
particular pulsar the time between the

458
00:21:26,080 --> 00:21:23,840
flashes changed very slightly and it was

459
00:21:28,990 --> 00:21:26,090
ultimately concluded that this was due

460
00:21:32,230 --> 00:21:29,000
to two planets orbiting the Pulsar and

461
00:21:34,840 --> 00:21:32,240
as the planets orbited the Pulsar the

462
00:21:37,420 --> 00:21:34,850
Pulsar wobbled very slightly due to the

463
00:21:39,850 --> 00:21:37,430
planet's gravity and as it wobbled his

464
00:21:42,610 --> 00:21:39,860
distance from the earth was changing a

465
00:21:44,290 --> 00:21:42,620
tiny amount and this was causing the

466
00:21:45,820 --> 00:21:44,300
flashes to have to travel slightly

467
00:21:48,310 --> 00:21:45,830
further and slightly less far and

468
00:21:53,350 --> 00:21:48,320
therefore their timing started to become

469
00:21:55,390 --> 00:21:53,360
off so the discovery was two planets

470
00:21:59,860 --> 00:21:55,400
which were again very imaginative named

471
00:22:01,430 --> 00:21:59,870
PSR b12 57 plus 12 B and C and they were

472
00:22:04,039 --> 00:22:01,440
roughly four

473
00:22:06,409 --> 00:22:04,049
times the mass of the earth and their

474
00:22:10,249 --> 00:22:06,419
years they're all bits around the Pulsar

475
00:22:13,009 --> 00:22:10,259
were 65 and 98 days so for comparison

476
00:22:15,830 --> 00:22:13,019
but Korea our innermost planet has an

477
00:22:17,749 --> 00:22:15,840
orbit of 88 days so if these two were

478
00:22:20,869 --> 00:22:17,759
around our own Sun they were sick either

479
00:22:23,149 --> 00:22:20,879
side of mercury and they are a rather

480
00:22:25,759 --> 00:22:23,159
staggering two thousand light years away

481
00:22:28,879 --> 00:22:25,769
which tells you exactly how sensitive

482
00:22:31,610 --> 00:22:28,889
this technique was now these were the

483
00:22:34,580 --> 00:22:31,620
first planets ever to be found outside

484
00:22:36,379 --> 00:22:34,590
our solar system and the discovery was a

485
00:22:38,600 --> 00:22:36,389
pretty enough published in the

486
00:22:42,919 --> 00:22:38,610
international journal Nature on the 9th

487
00:22:45,649 --> 00:22:42,929
of January in 1992 however he actually

488
00:22:48,350 --> 00:22:45,659
was linked earlier than that by the

489
00:22:51,669 --> 00:22:48,360
British British broadsheet newspaper the

490
00:22:54,980 --> 00:22:51,679
independence on the 29th of October 1991

491
00:22:58,039 --> 00:22:54,990
with the headline radio astronomer finds

492
00:22:59,269 --> 00:22:58,049
two planets in distant space now Alex

493
00:23:01,820 --> 00:22:59,279
Borstein was approached by the

494
00:23:03,710 --> 00:23:01,830
independent and asked by for a quote and

495
00:23:05,539 --> 00:23:03,720
this must have been fairly nerve-racking

496
00:23:07,129 --> 00:23:05,549
because obviously he wanted this

497
00:23:12,139 --> 00:23:07,139
discovery to be published in a journal

498
00:23:14,539 --> 00:23:12,149
such as nature but if news gets out

499
00:23:15,950 --> 00:23:14,549
early sometimes nature might be like

500
00:23:18,499 --> 00:23:15,960
well it's no longer news so we don't

501
00:23:20,659 --> 00:23:18,509
want it so as a result there's a very

502
00:23:22,789 --> 00:23:20,669
guarded comment by Alex Vause shown here

503
00:23:24,110 --> 00:23:22,799
saying professor volscian was not

504
00:23:26,149 --> 00:23:24,120
prepared to talk about his research

505
00:23:27,919 --> 00:23:26,159
because he feared it might prejudice the

506
00:23:32,269 --> 00:23:27,929
chances of being published in a

507
00:23:34,759 --> 00:23:32,279
scientific journal however despite this

508
00:23:37,730 --> 00:23:34,769
even after the nature publication there

509
00:23:39,019 --> 00:23:37,740
was very little public notice which when

510
00:23:41,149 --> 00:23:39,029
you think of the fuss that new

511
00:23:43,100 --> 00:23:41,159
discoveries have nowadays where you have

512
00:23:46,009 --> 00:23:43,110
multiple reports against the whole world

513
00:23:48,529 --> 00:23:46,019
media is very surprising that the first

514
00:23:50,840 --> 00:23:48,539
planets we ever found no one really

515
00:23:52,759 --> 00:23:50,850
talked about indeed at the time when my

516
00:23:54,259 --> 00:23:52,769
parents were taking the independent and

517
00:23:55,850 --> 00:23:54,269
this newspaper must have sat on our

518
00:23:59,690 --> 00:23:55,860
kitchen table and I don't remember it at

519
00:24:02,330 --> 00:23:59,700
all so what was the problem was it that

520
00:24:05,180 --> 00:24:02,340
just pulsar planets were just a bit too

521
00:24:07,070 --> 00:24:05,190
weird I mean you know pulsars dead stars

522
00:24:09,129 --> 00:24:07,080
can't really relate to those hopefully

523
00:24:11,389 --> 00:24:09,139
never will be able to relate to those

524
00:24:14,460 --> 00:24:11,399
maybe people just didn't really feel a

525
00:24:17,140 --> 00:24:14,470
connection connection

526
00:24:20,970 --> 00:24:17,150
so as a result these are sort of

527
00:24:23,350 --> 00:24:20,980
overlooked but pulsar timings

528
00:24:27,070 --> 00:24:23,360
unsurprisingly it can only be used to

529
00:24:29,350 --> 00:24:27,080
find planets around pulsars so what

530
00:24:32,200 --> 00:24:29,360
about finding planets around regular

531
00:24:34,690 --> 00:24:32,210
stars so we found the Pulsar planets

532
00:24:37,690 --> 00:24:34,700
because there is this slight change in

533
00:24:39,430 --> 00:24:37,700
the timing of the Pulsar flash due to

534
00:24:42,490 --> 00:24:39,440
this wobble in the Stars position

535
00:24:44,920 --> 00:24:42,500
because of the planets orbit so could we

536
00:24:47,470 --> 00:24:44,930
do this with normal star light as well

537
00:24:48,520 --> 00:24:47,480
and obviously the answer is yes or I

538
00:24:52,930 --> 00:24:48,530
would not have taken us in this

539
00:24:54,700 --> 00:24:52,940
direction so when you have a more

540
00:24:57,130 --> 00:24:54,710
regular star you have a system like this

541
00:24:59,470 --> 00:24:57,140
so here are we on the earth there's our

542
00:25:01,300 --> 00:24:59,480
star here and here is our planet and due

543
00:25:04,420 --> 00:25:01,310
to the planets orbit the star is going

544
00:25:07,000 --> 00:25:04,430
to make a small wobble now as the star

545
00:25:08,470 --> 00:25:07,010
moves away from the earth its light

546
00:25:11,200 --> 00:25:08,480
that's reaching us is going to get

547
00:25:14,110 --> 00:25:11,210
stretched out and this is going to cause

548
00:25:15,820 --> 00:25:14,120
it to become redder now as it swings

549
00:25:17,950 --> 00:25:15,830
around the other side of it's wobbling

550
00:25:20,260 --> 00:25:17,960
position the light waves are going to

551
00:25:22,660 --> 00:25:20,270
become compressed as the star starts

552
00:25:23,500 --> 00:25:22,670
approaching the earth and when they get

553
00:25:26,830 --> 00:25:23,510
compressed

554
00:25:29,230 --> 00:25:26,840
they liked gets bluer so what you see is

555
00:25:32,170 --> 00:25:29,240
this tiny shift from red to blue to red

556
00:25:34,780 --> 00:25:32,180
to blue as the star wobbles due to its

557
00:25:37,210 --> 00:25:34,790
orbit from the planet and we call this

558
00:25:40,140 --> 00:25:37,220
the radial velocity technique or

559
00:25:44,830 --> 00:25:40,150
sometimes a Doppler wobble technique

560
00:25:47,020 --> 00:25:44,840
however this is not a big shift the tiny

561
00:25:48,450 --> 00:25:47,030
tiny shift in light and it's incredibly

562
00:25:53,530 --> 00:25:48,460
hard to measure

563
00:25:56,410 --> 00:25:53,540
however in 1988 a new technique was

564
00:25:58,180 --> 00:25:56,420
established so in this technique you

565
00:26:00,400 --> 00:25:58,190
have your star emitting lights and

566
00:26:02,620 --> 00:26:00,410
you've got your telescope and in front

567
00:26:06,520 --> 00:26:02,630
of the telescope we're going to put a

568
00:26:08,500 --> 00:26:06,530
jar of gas and the point is here that

569
00:26:10,300 --> 00:26:08,510
here is your star and it's light is

570
00:26:14,590 --> 00:26:10,310
going to be slowly shifting from red to

571
00:26:16,930 --> 00:26:14,600
blue tiny tiny tiny shift but our jar of

572
00:26:18,970 --> 00:26:16,940
gas is also going to be a missing light

573
00:26:20,920 --> 00:26:18,980
that is not shifting because it's

574
00:26:23,650 --> 00:26:20,930
completely stationary in front of our

575
00:26:26,140 --> 00:26:23,660
telescope so what it is is it's a bit

576
00:26:27,970 --> 00:26:26,150
like slamming down a ruler and because

577
00:26:30,250 --> 00:26:27,980
you have a stationary point

578
00:26:32,470 --> 00:26:30,260
with which to compare that starlight it

579
00:26:35,980 --> 00:26:32,480
becomes much easier to measure tiny

580
00:26:37,990 --> 00:26:35,990
shifts so this allowed us to have much

581
00:26:42,370 --> 00:26:38,000
higher accuracy when trying to measure

582
00:26:45,880 --> 00:26:42,380
this radial velocity change and using

583
00:26:48,990 --> 00:26:45,890
this technique as early as 1988 a wobble

584
00:26:54,640 --> 00:26:49,000
was seen around a star called gammas Fe

585
00:26:55,830 --> 00:26:54,650
could this be from an exoplanet so there

586
00:26:58,930 --> 00:26:55,840
were some problems

587
00:27:01,630 --> 00:26:58,940
gammas Fe is part of a binary star

588
00:27:05,110 --> 00:27:01,640
system meaning it has a companion star

589
00:27:07,270 --> 00:27:05,120
and the two stars orbit one another so

590
00:27:09,460 --> 00:27:07,280
this was the first question mark would

591
00:27:12,430 --> 00:27:09,470
we even expect planets around a binary

592
00:27:13,690 --> 00:27:12,440
system if you had a sister star would

593
00:27:18,310 --> 00:27:13,700
that disrupt the planet formation

594
00:27:21,070 --> 00:27:18,320
process secondly the star that was

595
00:27:23,470 --> 00:27:21,080
wobbling was thought to be a giant star

596
00:27:26,380 --> 00:27:23,480
now this is the phase that stars reach

597
00:27:28,150 --> 00:27:26,390
near the end of their life and as they

598
00:27:31,180 --> 00:27:28,160
approach the end of their life they get

599
00:27:33,520 --> 00:27:31,190
quite crotchety so what you find is the

600
00:27:36,520 --> 00:27:33,530
outer layers of the star start to have a

601
00:27:39,039 --> 00:27:36,530
lot of vibrations and pulsations that

602
00:27:43,240 --> 00:27:39,049
look just like a small bubble from a

603
00:27:45,880 --> 00:27:43,250
planet so the astronomers were a bit

604
00:27:48,460 --> 00:27:45,890
suspicious and in the end they concluded

605
00:27:50,560 --> 00:27:48,470
oh it's a giant star it's a binary we

606
00:27:52,570 --> 00:27:50,570
don't really expect to see a planet here

607
00:27:55,240 --> 00:27:52,580
there are lots of other reasons for this

608
00:27:57,400 --> 00:27:55,250
possible wobble now we see a wobble but

609
00:27:59,620 --> 00:27:57,410
it's not a planet and when they

610
00:28:02,440 --> 00:27:59,630
announced that they missed discovering

611
00:28:04,780 --> 00:28:02,450
the first exoplanets because this wobble

612
00:28:06,850 --> 00:28:04,790
was due to a planet but its discovery

613
00:28:09,270 --> 00:28:06,860
was not finally announced I think until

614
00:28:12,850 --> 00:28:09,280
2013

615
00:28:15,730 --> 00:28:12,860
so the first discovery that actually

616
00:28:19,240 --> 00:28:15,740
everyone remembers is a planet called a

617
00:28:21,730 --> 00:28:19,250
51 pegasi B that was found in 1995 with

618
00:28:24,850 --> 00:28:21,740
this same radial velocity technique with

619
00:28:26,650 --> 00:28:24,860
a light shifting from red to blue and it

620
00:28:29,590 --> 00:28:26,660
was the first planet that was found

621
00:28:31,930 --> 00:28:29,600
around a star like our Sun rather than a

622
00:28:35,799 --> 00:28:31,940
giant star or a long-dead star like a

623
00:28:38,200 --> 00:28:35,809
pulsar and it opened the floodgates to

624
00:28:40,620 --> 00:28:38,210
finding thousands more because it proved

625
00:28:43,500 --> 00:28:40,630
this radial velocity wobble

626
00:28:45,660 --> 00:28:43,510
was detectable we could see it and from

627
00:28:46,730 --> 00:28:45,670
there we started discovering planets in

628
00:28:50,490 --> 00:28:46,740
droves

629
00:28:55,920 --> 00:28:50,500
however this planet was also rather

630
00:28:58,440 --> 00:28:55,930
strange so back to our own solar system

631
00:29:00,840 --> 00:28:58,450
and one thing that we note is there are

632
00:29:03,750 --> 00:29:00,850
giant planets these huge gaseous ones

633
00:29:06,270 --> 00:29:03,760
sit a long way from the Sun we have the

634
00:29:09,810 --> 00:29:06,280
rocky ones close and we have the gaseous

635
00:29:13,080 --> 00:29:09,820
ones further away but this planet 51

636
00:29:16,890 --> 00:29:13,090
Pegasus B was a gas giant on the orbit

637
00:29:21,210 --> 00:29:16,900
of just four days so if remember mercury

638
00:29:25,230 --> 00:29:21,220
is 88 days that puts 51 Pegasus B really

639
00:29:28,230 --> 00:29:25,240
really close to its star so how do you

640
00:29:30,150 --> 00:29:28,240
form a planet there well let's just take

641
00:29:34,050 --> 00:29:30,160
a step back and ask why this is at all

642
00:29:36,930 --> 00:29:34,060
surprising so young stars are surrounded

643
00:29:39,750 --> 00:29:36,940
by disks of gas and dust known as

644
00:29:42,210 --> 00:29:39,760
protoplanetary discs now this image here

645
00:29:46,460 --> 00:29:42,220
is an artist's impression however this

646
00:29:48,690 --> 00:29:46,470
one is not this is a genuine image of a

647
00:29:54,210 --> 00:29:48,700
protoplanetary disc around a young star

648
00:29:56,430 --> 00:29:54,220
taken with Alma and in this disk of dust

649
00:29:59,970 --> 00:29:56,440
and gas dust starts off at micrometer

650
00:30:02,580 --> 00:29:59,980
sizes and it starts to collide and slick

651
00:30:05,940 --> 00:30:02,590
so we go from a chromatid to millimeter

652
00:30:07,290 --> 00:30:05,950
to centimeter up to meet her sizes and

653
00:30:10,320 --> 00:30:07,300
now we're starting to look a bit like

654
00:30:13,170 --> 00:30:10,330
the asteroids and eventually gravity

655
00:30:16,290 --> 00:30:13,180
finally gets seriously interested and it

656
00:30:18,570 --> 00:30:16,300
squishes our newly formed planet into a

657
00:30:21,270 --> 00:30:18,580
ball and we start to say yes okay I

658
00:30:24,240 --> 00:30:21,280
notice that's a planet now there is one

659
00:30:28,110 --> 00:30:24,250
subtlety to this process I'm sure will

660
00:30:31,860 --> 00:30:28,120
astound everyone if you are forming near

661
00:30:33,450 --> 00:30:31,870
the new star you're hot on the other

662
00:30:37,560 --> 00:30:33,460
hand if you're forming a long way away

663
00:30:40,290 --> 00:30:37,570
you're cold and this has one important

664
00:30:42,990 --> 00:30:40,300
effect there comes a point as you step

665
00:30:45,660 --> 00:30:43,000
away from the star that ice starts to

666
00:30:48,240 --> 00:30:45,670
form and we call this point the ice line

667
00:30:50,340 --> 00:30:48,250
the snow line or the frost line if you

668
00:30:53,220 --> 00:30:50,350
are inside the ice line and closer to

669
00:30:54,330 --> 00:30:53,230
the star water is a vapor on the other

670
00:30:58,169 --> 00:30:54,340
hand if you are the others

671
00:31:00,750 --> 00:30:58,179
side of it then it is a solid and that

672
00:31:03,269 --> 00:31:00,760
means you get a huge boost in

673
00:31:05,669 --> 00:31:03,279
planet-forming material the other side

674
00:31:07,470 --> 00:31:05,679
of the ice line because here you've got

675
00:31:09,600 --> 00:31:07,480
your silicates like what the earth is

676
00:31:11,909 --> 00:31:09,610
mainly formed off but out here you've

677
00:31:14,820 --> 00:31:11,919
got the silicates but also a huge a

678
00:31:16,560 --> 00:31:14,830
number of ices so you get a big step in

679
00:31:20,970 --> 00:31:16,570
density it's like being given a whole

680
00:31:23,310 --> 00:31:20,980
new letter set so as a result we expect

681
00:31:25,649 --> 00:31:23,320
small planets to form here where we have

682
00:31:27,960 --> 00:31:25,659
less building material and giant planets

683
00:31:30,510 --> 00:31:27,970
to form here where we have a lot more

684
00:31:32,610 --> 00:31:30,520
and this should be the same around every

685
00:31:34,409 --> 00:31:32,620
star because the only assumption I put

686
00:31:36,120 --> 00:31:34,419
in here is then you're hot if you're

687
00:31:40,590 --> 00:31:36,130
close to the star which you think would

688
00:31:42,810 --> 00:31:40,600
be universally true so how do we get a

689
00:31:45,029 --> 00:31:42,820
planet here there should be barely any

690
00:31:47,070 --> 00:31:45,039
building material there and yet 51

691
00:31:51,450 --> 00:31:47,080
pegasi B was roughly the same size as

692
00:31:54,120 --> 00:31:51,460
Jupiter so this is what we think happens

693
00:31:55,740 --> 00:31:54,130
as the planet grows it eventually

694
00:31:57,810 --> 00:31:55,750
reaches the size of Mars

695
00:32:01,049 --> 00:31:57,820
now Mars is not a big planet it is

696
00:32:03,029 --> 00:32:01,059
roughly a tenth of the mass of Earth but

697
00:32:05,220 --> 00:32:03,039
however at that point the planets

698
00:32:07,740 --> 00:32:05,230
gravity gets strong enough that it

699
00:32:09,930 --> 00:32:07,750
starts to pull on the surrounding gas

700
00:32:13,320 --> 00:32:09,940
and dust that still circle the young

701
00:32:16,230 --> 00:32:13,330
star and this gas and dust pulls back

702
00:32:19,590 --> 00:32:16,240
and the result is like being on a

703
00:32:21,090 --> 00:32:19,600
running track so here you are and you're

704
00:32:24,529 --> 00:32:21,100
going to be running this circular race

705
00:32:27,899 --> 00:32:24,539
with two buddies a buddy and a detective

706
00:32:30,419 --> 00:32:27,909
and a little later on oh no I'm sorry

707
00:32:31,980 --> 00:32:30,429
yes there's been a terrible addition

708
00:32:35,310 --> 00:32:31,990
where for some reason you've been tied

709
00:32:37,889 --> 00:32:35,320
to your friends with a piece of loop but

710
00:32:39,930 --> 00:32:37,899
a little later on war here now your

711
00:32:41,340 --> 00:32:39,940
bunny friend was on the inside running

712
00:32:43,440 --> 00:32:41,350
track and as I'm sure everyone remembers

713
00:32:46,139 --> 00:32:43,450
from school PE lessons that gives you a

714
00:32:47,909 --> 00:32:46,149
very unfair advantage so they're on a

715
00:32:50,399 --> 00:32:47,919
much shorter running track and he's

716
00:32:52,260 --> 00:32:50,409
pulled ahead of you on the other hand

717
00:32:54,570 --> 00:32:52,270
your detective friend or was on the

718
00:32:56,820 --> 00:32:54,580
outside running track and had further to

719
00:32:59,130 --> 00:32:56,830
go and therefore she is a little bit

720
00:33:01,200 --> 00:32:59,140
further behind but you're still tied

721
00:33:03,419 --> 00:33:01,210
together with this rope so you start to

722
00:33:05,190 --> 00:33:03,429
feel a force with the bunny pulling you

723
00:33:07,830 --> 00:33:05,200
forward and a detective pulling you back

724
00:33:10,320 --> 00:33:07,840
and the same thing happened

725
00:33:12,840 --> 00:33:10,330
due to gravity with our new planet in

726
00:33:15,299 --> 00:33:12,850
our disk where the gas closer to the

727
00:33:16,860 --> 00:33:15,309
star is pulling ahead and dragging on

728
00:33:19,529 --> 00:33:16,870
that planet to move it forward

729
00:33:21,630 --> 00:33:19,539
whereas the gas further out is pulling

730
00:33:25,890 --> 00:33:21,640
back and trying to slow that planet down

731
00:33:29,039 --> 00:33:25,900
and as a result you end up in this tug

732
00:33:33,750 --> 00:33:29,049
of war and the net result is usually

733
00:33:36,870 --> 00:33:33,760
that the planet feels a push inwards so

734
00:33:39,570 --> 00:33:36,880
what this means is oh yes and we call

735
00:33:42,210 --> 00:33:39,580
this migration so what this means is

736
00:33:43,889 --> 00:33:42,220
your planet can start far out it can

737
00:33:46,110 --> 00:33:43,899
form where there's lots of ice there's

738
00:33:49,289 --> 00:33:46,120
lots of building material and it can get

739
00:33:52,680 --> 00:33:49,299
big and jupiter-sized but it can then

740
00:33:54,990 --> 00:33:52,690
migrated inwards due to this pull from

741
00:33:57,779 --> 00:33:55,000
the gas disc and when the gas disc is

742
00:34:00,720 --> 00:33:57,789
finally evaporated by the star you end

743
00:34:03,810 --> 00:34:00,730
up with a large planet close to the star

744
00:34:07,560 --> 00:34:03,820
and we call these hot Jupiters because

745
00:34:11,220 --> 00:34:07,570
they're Jupiter size and hot so this

746
00:34:13,109 --> 00:34:11,230
explained 51 Pegasus B but what about

747
00:34:16,800 --> 00:34:13,119
the Pulsar planets what could explain

748
00:34:19,020 --> 00:34:16,810
them and were they even surprising well

749
00:34:21,419 --> 00:34:19,030
the problem with pulsar planets is as

750
00:34:25,409 --> 00:34:21,429
they briefly mentioned pulsars a start

751
00:34:27,899 --> 00:34:25,419
with an explosion a supernova so when

752
00:34:30,810 --> 00:34:27,909
they explode if they still have planets

753
00:34:34,139 --> 00:34:30,820
orbiting them too awful things can

754
00:34:37,020 --> 00:34:34,149
happen to those planets the first is one

755
00:34:39,329 --> 00:34:37,030
could be vaporized the second is the

756
00:34:42,270 --> 00:34:39,339
shockwave from that explosion can kick

757
00:34:44,609 --> 00:34:42,280
the planet out of the solar system so

758
00:34:47,040 --> 00:34:44,619
generally speaking we do not expect

759
00:34:50,430 --> 00:34:47,050
these planets to be able to survive this

760
00:34:52,680 --> 00:34:50,440
supernova explosion so how on earth do

761
00:34:56,700 --> 00:34:52,690
you end up with a pulsar orbited by

762
00:34:59,220 --> 00:34:56,710
planets well evidence to what might have

763
00:35:01,589 --> 00:34:59,230
happened was discovered in 2012 when a

764
00:35:05,579 --> 00:35:01,599
tiny star was found that seemed to be

765
00:35:08,849 --> 00:35:05,589
flashing red and then blue and it turned

766
00:35:10,829 --> 00:35:08,859
out to be orbiting a pulsar every and 93

767
00:35:13,480 --> 00:35:10,839
minutes which is actually the average

768
00:35:16,510 --> 00:35:13,490
commute time in the UK

769
00:35:19,000 --> 00:35:16,520
but as this planet orbited the Pulsar

770
00:35:22,420 --> 00:35:19,010
you actually started to see different

771
00:35:24,550 --> 00:35:22,430
sides of it so if the Pulsar is here and

772
00:35:26,800 --> 00:35:24,560
you are the earth first of all you're

773
00:35:29,140 --> 00:35:26,810
seeing the front side and the front side

774
00:35:32,740 --> 00:35:29,150
was being hit by the pulsars Jets and

775
00:35:35,470 --> 00:35:32,750
becoming very hot however as the star

776
00:35:39,070 --> 00:35:35,480
orbited you started to see the backside

777
00:35:41,200 --> 00:35:39,080
and this was much colder so what you

778
00:35:42,880 --> 00:35:41,210
were seeing was intermittently the hot

779
00:35:45,070 --> 00:35:42,890
side of the star then the cold side

780
00:35:49,359 --> 00:35:45,080
seeing this flash from red to blue and

781
00:35:51,370 --> 00:35:49,369
back again but because the Pulsar was

782
00:35:54,520 --> 00:35:51,380
being hit but purrs the star was being

783
00:35:58,210 --> 00:35:54,530
hit by the pulsars Jets the Pulsar was

784
00:36:00,880 --> 00:35:58,220
blowtorching it to pieces so you have a

785
00:36:02,890 --> 00:36:00,890
system a little bit like this one where

786
00:36:06,040 --> 00:36:02,900
the pulsars Jets were ripping over the

787
00:36:08,710 --> 00:36:06,050
star and shredding it and as the star

788
00:36:11,800 --> 00:36:08,720
ripped as a pulsar ripped this other

789
00:36:15,520 --> 00:36:11,810
star to pieces and disc formed from it's

790
00:36:17,140 --> 00:36:15,530
ruined body and in this disk planets

791
00:36:19,960 --> 00:36:17,150
could start to form again

792
00:36:22,570 --> 00:36:19,970
so pulsar planets have rather a morbid

793
00:36:25,359 --> 00:36:22,580
origin they require another star to be

794
00:36:32,650 --> 00:36:25,369
shredded to pieces and is broken body to

795
00:36:35,640 --> 00:36:32,660
form the birth ground of new planets so

796
00:36:39,250 --> 00:36:35,650
these first finds were strange worlds

797
00:36:40,870 --> 00:36:39,260
but later we found many planets that

798
00:36:44,349 --> 00:36:40,880
were much closer in size to the earth

799
00:36:46,270 --> 00:36:44,359
orbiting around normal stars around now

800
00:36:48,960 --> 00:36:46,280
we have found I think about three and a

801
00:36:51,700 --> 00:36:48,970
half thousand planets beyond our Sun and

802
00:36:53,859 --> 00:36:51,710
roughly a third of those have a radius

803
00:36:56,830 --> 00:36:53,869
that is less than twice of that of the

804
00:37:03,780 --> 00:36:56,840
earth so this brings us to the obvious

805
00:37:06,550 --> 00:37:03,790
question can we find earth 2.0 well

806
00:37:08,440 --> 00:37:06,560
let's look what we know with an example

807
00:37:11,349 --> 00:37:08,450
that hit the news at the beginning of

808
00:37:12,849 --> 00:37:11,359
this year and the telescope that made

809
00:37:14,890 --> 00:37:12,859
this news with a telescope called

810
00:37:17,650 --> 00:37:14,900
transiting planets and planetesimals a

811
00:37:20,680 --> 00:37:17,660
small telescope and it's a 60 centimeter

812
00:37:23,440 --> 00:37:20,690
telescope in Chile and if you take these

813
00:37:26,710 --> 00:37:23,450
letters very slightly randomly you can

814
00:37:28,480 --> 00:37:26,720
spell trust which I

815
00:37:30,550 --> 00:37:28,490
sure entirely ko is deadly because it's

816
00:37:34,599 --> 00:37:30,560
a Belgium telescope also happens to be

817
00:37:37,180 --> 00:37:34,609
the name of a Belgian beer but in

818
00:37:38,010 --> 00:37:37,190
February Trappist made an incredible

819
00:37:42,250 --> 00:37:38,020
discovery

820
00:37:44,440 --> 00:37:42,260
it found a star orbited by seven planets

821
00:37:46,810 --> 00:37:44,450
now as a telescope that made the

822
00:37:49,420 --> 00:37:46,820
discovery the star was named Trappist

823
00:37:54,849 --> 00:37:49,430
one and the planets became Trappist one

824
00:37:58,960 --> 00:37:54,859
b c d e f g and h so was this a solar

825
00:38:00,060 --> 00:37:58,970
system like our own well the press got

826
00:38:02,950 --> 00:38:00,070
pretty excited

827
00:38:05,290 --> 00:38:02,960
we had headlines like NASA's discovery

828
00:38:07,660 --> 00:38:05,300
of a solar system with seven earth-like

829
00:38:10,599 --> 00:38:07,670
planets will change how we hunt for

830
00:38:13,000 --> 00:38:10,609
alien life we had four new scientist

831
00:38:13,900 --> 00:38:13,010
exoplanet discoveries seven earth-sized

832
00:38:16,930 --> 00:38:13,910
exoplanet s--

833
00:38:19,240 --> 00:38:16,940
may have water or from the guardian

834
00:38:22,410 --> 00:38:19,250
exoplanet discovery seven earth sized

835
00:38:24,730 --> 00:38:22,420
planets found orbiting a nearby star

836
00:38:26,140 --> 00:38:24,740
clearly if you just read the press

837
00:38:30,609 --> 00:38:26,150
headlines you would think we'd found

838
00:38:32,770 --> 00:38:30,619
this clearly seven earth septuplets all

839
00:38:37,900 --> 00:38:32,780
identical probably already have

840
00:38:42,339 --> 00:38:37,910
Starbucks on them but what do we really

841
00:38:43,960 --> 00:38:42,349
know about them well these planets were

842
00:38:46,240 --> 00:38:43,970
discovered not with the radial velocity

843
00:38:49,540 --> 00:38:46,250
technique but with the transit technique

844
00:38:52,329 --> 00:38:49,550
and this is when the planets moves in

845
00:38:54,820 --> 00:38:52,339
front of the Stars surface and causes a

846
00:38:56,740 --> 00:38:54,830
tiny dip in the Starlight and it's how

847
00:38:59,770 --> 00:38:56,750
the Kepler space telescope finds its

848
00:39:03,220 --> 00:38:59,780
planets so in the case of the Trappist

849
00:39:07,030 --> 00:39:03,230
seven we see seven periodic dips as the

850
00:39:10,060 --> 00:39:07,040
planets passed by the star surface now

851
00:39:12,220 --> 00:39:10,070
transits usually give what they do they

852
00:39:14,380 --> 00:39:12,230
give you the planet radius the physical

853
00:39:16,320 --> 00:39:14,390
size of the planet so the bigger the

854
00:39:19,270 --> 00:39:16,330
planet the more light it blocks out and

855
00:39:21,820 --> 00:39:19,280
you can pick this up with the transit it

856
00:39:26,890 --> 00:39:21,830
doesn't normally tell you the planet

857
00:39:30,579 --> 00:39:26,900
mass normally but the Trappist planets

858
00:39:33,849 --> 00:39:30,589
were slightly different so Trappist one

859
00:39:37,000 --> 00:39:33,859
has many planets it has seven and as

860
00:39:40,600 --> 00:39:37,010
they orbit the star the planets pull on

861
00:39:43,150 --> 00:39:40,610
one another and as a result this slope

862
00:39:44,740 --> 00:39:43,160
change the time for each orbit so this

863
00:39:46,750 --> 00:39:44,750
is like if you're running around you're

864
00:39:48,850 --> 00:39:46,760
circular running track again but this

865
00:39:52,420 --> 00:39:48,860
time you've taken your dog along for the

866
00:39:54,850 --> 00:39:52,430
run and your dog is not always terribly

867
00:39:57,070 --> 00:39:54,860
cooperative sometimes your dog is

868
00:39:59,470 --> 00:39:57,080
pulling you forward and that means you

869
00:40:01,720 --> 00:39:59,480
make your lap time slightly quicker but

870
00:40:04,210 --> 00:40:01,730
sometimes your dog just wants to sniff

871
00:40:06,280 --> 00:40:04,220
stuff and it's pulling you back and so

872
00:40:09,970 --> 00:40:06,290
your lap time becomes slightly slower

873
00:40:10,540 --> 00:40:09,980
and these changes in lap time can be

874
00:40:12,310 --> 00:40:10,550
measured

875
00:40:15,580 --> 00:40:12,320
due to the planets pulling on each other

876
00:40:21,310 --> 00:40:15,590
and we call this transit timing

877
00:40:26,940 --> 00:40:21,320
variations or TT V so I have a movie

878
00:41:37,300 --> 00:40:38,140
[Music]

879
00:41:39,310 --> 00:41:37,310
and now what we see is a so the great

880
00:41:44,380 --> 00:41:39,320
bernard is going to have a ward effect

881
00:41:46,900 --> 00:41:44,390
on your lap time so ttv actually gives

882
00:41:49,840 --> 00:41:46,910
the mass of the planet in addition to

883
00:41:52,720 --> 00:41:49,850
the planet's physical size so what did

884
00:41:54,790 --> 00:41:52,730
we see with these seven worlds well

885
00:41:56,980 --> 00:41:54,800
let's look at radius as a function of

886
00:41:58,810 --> 00:41:56,990
Earth mass and we see we have three

887
00:42:02,710 --> 00:41:58,820
planets with almost exactly the same

888
00:42:05,110 --> 00:42:02,720
size as Earth and three planets with a

889
00:42:07,600 --> 00:42:05,120
slightly smaller size on earth and one

890
00:42:10,480 --> 00:42:07,610
slightly larger and if we look at the

891
00:42:13,780 --> 00:42:10,490
masses we have anything between 40 and

892
00:42:18,520 --> 00:42:13,790
140 times the matter percentage of the

893
00:42:21,300 --> 00:42:18,530
mass of the earth so we have roughly we

894
00:42:26,640 --> 00:42:21,310
have seven roughly earth sized planets

895
00:42:32,020 --> 00:42:26,650
so here is the question does earth size

896
00:42:35,800 --> 00:42:32,030
mean earth-like well what else do we

897
00:42:38,290 --> 00:42:35,810
know about this system now on earth a

898
00:42:42,070 --> 00:42:38,300
year so our lap around the Sun takes

899
00:42:46,600 --> 00:42:42,080
approximately 365 days if you were on

900
00:42:50,260 --> 00:42:46,610
Mars it would take 687 days if you're on

901
00:42:55,090 --> 00:42:50,270
Venus will be 225 and Mercury would be

902
00:42:56,980 --> 00:42:55,100
88 the Trappist planets the one furthest

903
00:43:02,010 --> 00:42:56,990
from the star that's going to take the

904
00:43:06,640 --> 00:43:02,020
longest orbital time will take 20 days

905
00:43:10,930 --> 00:43:06,650
twelve days nine days six days for 2.4

906
00:43:13,240 --> 00:43:10,940
and 1.5 days to make that orbit so if

907
00:43:16,620 --> 00:43:13,250
these were around our Sun all of these

908
00:43:19,900 --> 00:43:16,630
planets would sit inside Mercury's orbit

909
00:43:22,510 --> 00:43:19,910
so does this mean that the Trappist one

910
00:43:25,350 --> 00:43:22,520
worlds are in fact larva worlds with

911
00:43:28,890 --> 00:43:25,360
melted crusts of magma

912
00:43:31,829 --> 00:43:28,900
well something fortunately saves us

913
00:43:34,799 --> 00:43:31,839
and that is the Trappist one is very dim

914
00:43:36,420 --> 00:43:34,809
if we were to compare the size of the

915
00:43:39,779 --> 00:43:36,430
Sun with a basketball

916
00:43:43,109 --> 00:43:39,789
then Trappist one only has the size of a

917
00:43:46,019 --> 00:43:43,119
golf ball and it has only a thousands of

918
00:43:48,450 --> 00:43:46,029
the sun's brightness so that means you

919
00:43:51,180 --> 00:43:48,460
can afford it to be a lot closer but not

920
00:43:53,819 --> 00:43:51,190
that much hotter so if we compare

921
00:43:55,920 --> 00:43:53,829
instead the amount of radiation the

922
00:43:58,470 --> 00:43:55,930
planets receive then the amount of

923
00:44:01,950 --> 00:43:58,480
radiation that we get from the Sun over

924
00:44:04,200 --> 00:44:01,960
Venus Earth and Mercury is approximately

925
00:44:08,880 --> 00:44:04,210
equal to the amount of radiation

926
00:44:12,150 --> 00:44:08,890
received by planet C D E and F so very

927
00:44:15,420 --> 00:44:12,160
similar radiation for these planets so

928
00:44:17,970 --> 00:44:15,430
what about water well when we talk about

929
00:44:19,920 --> 00:44:17,980
water especially with exoplanets we

930
00:44:23,670 --> 00:44:19,930
typically talk about something called

931
00:44:25,829 --> 00:44:23,680
the habitable zone and this is the

932
00:44:29,039 --> 00:44:25,839
location where an earth-like planet

933
00:44:31,049 --> 00:44:29,049
could have water on its surface so you

934
00:44:33,870 --> 00:44:31,059
can imagine taking the earth and giving

935
00:44:36,210 --> 00:44:33,880
it a push towards the Sun and at the

936
00:44:38,640 --> 00:44:36,220
point where our water and our oceans

937
00:44:40,579 --> 00:44:38,650
become steam and evaporates that is the

938
00:44:42,779 --> 00:44:40,589
inner edge of the habitable zone

939
00:44:44,910 --> 00:44:42,789
conversely if we took the earth and

940
00:44:47,759 --> 00:44:44,920
pushed it outwards then there comes a

941
00:44:50,569 --> 00:44:47,769
point where the oceans freeze and that

942
00:44:53,309 --> 00:44:50,579
is our outer edge of our habitable zone

943
00:44:55,799 --> 00:44:53,319
so if we look at the planets around

944
00:45:00,960 --> 00:44:55,809
Trappist one the same habitable zone

945
00:45:03,569 --> 00:45:00,970
exists here over planets EF and G so

946
00:45:07,380 --> 00:45:03,579
does that mean we have three planets

947
00:45:09,479 --> 00:45:07,390
with water well not so fast

948
00:45:12,989 --> 00:45:09,489
we have to look at the small print of

949
00:45:16,499 --> 00:45:12,999
this habitable zone contract the

950
00:45:18,150 --> 00:45:16,509
habitable zone is defined as follows the

951
00:45:21,749 --> 00:45:18,160
habitable zone is where an earth-like

952
00:45:25,009 --> 00:45:21,759
planet can maintain liquid water on its

953
00:45:28,620 --> 00:45:25,019
surface and a small print here is

954
00:45:31,890 --> 00:45:28,630
earth-like so if you have a planet that

955
00:45:34,049 --> 00:45:31,900
is not an exact Earth clone it heavy has

956
00:45:36,450 --> 00:45:34,059
a larger mass a smaller mass a different

957
00:45:38,309 --> 00:45:36,460
atmosphere different rock type there is

958
00:45:40,650 --> 00:45:38,319
no guarantee at all

959
00:45:42,690 --> 00:45:40,660
that it will have water inside the

960
00:45:45,090 --> 00:45:42,700
habitable zone in

961
00:45:47,370 --> 00:45:45,100
of the exoplanets we've discovered we

962
00:45:49,950 --> 00:45:47,380
found roughly five times as many gas

963
00:45:52,470 --> 00:45:49,960
giants like Jupiter inside the habitable

964
00:45:55,770 --> 00:45:52,480
zone as we have planets that may have a

965
00:45:58,830 --> 00:45:55,780
rocky surface so then the question

966
00:46:02,340 --> 00:45:58,840
becomes these three planets there earth

967
00:46:04,440 --> 00:46:02,350
sized but are they earth-like earth-like

968
00:46:06,560 --> 00:46:04,450
enough for the habitable zone to be

969
00:46:09,630 --> 00:46:06,570
meaningful

970
00:46:11,490 --> 00:46:09,640
so with exoplanets we typically know two

971
00:46:13,560 --> 00:46:11,500
things and this doesn't just apply to

972
00:46:16,860 --> 00:46:13,570
the Trappist one it applies to all

973
00:46:19,200 --> 00:46:16,870
exoplanet discoveries we typically know

974
00:46:20,880 --> 00:46:19,210
either the planet radius if it's found

975
00:46:23,370 --> 00:46:20,890
through the transit technique looking at

976
00:46:25,740 --> 00:46:23,380
that light dip all we know the planet

977
00:46:28,290 --> 00:46:25,750
minimum mass if it's found from that red

978
00:46:30,630 --> 00:46:28,300
and blue Doppler wobble and occasionally

979
00:46:32,160 --> 00:46:30,640
like the Trappist system we know both so

980
00:46:36,090 --> 00:46:32,170
we know something about the planets

981
00:46:38,940 --> 00:46:36,100
physical extent we also know how much

982
00:46:41,190 --> 00:46:38,950
radiation it receives from the star now

983
00:46:43,620 --> 00:46:41,200
the small print here is this is not the

984
00:46:45,390 --> 00:46:43,630
same as surface temperature and the

985
00:46:49,140 --> 00:46:45,400
warning to that is in our own solar

986
00:46:51,570 --> 00:46:49,150
system so Venus receives roughly twice

987
00:46:54,090 --> 00:46:51,580
the amount of radiation that the earth

988
00:46:56,130 --> 00:46:54,100
does and if you were therefore to make a

989
00:47:00,860 --> 00:46:56,140
guess as a surface temperature of Venus

990
00:47:04,470 --> 00:47:00,870
you would guess 27 30 Celsius which is

991
00:47:05,610 --> 00:47:04,480
19 Fahrenheit maybe anyway it seems very

992
00:47:09,300 --> 00:47:05,620
pleasant we should go there for a beach

993
00:47:11,310 --> 00:47:09,310
holiday but in fact that is not true of

994
00:47:14,160 --> 00:47:11,320
the surface of Venus the surface of

995
00:47:15,120 --> 00:47:14,170
Venus is at 460 Celsius it doesn't even

996
00:47:16,680 --> 00:47:15,130
really matter whether it is in

997
00:47:20,010 --> 00:47:16,690
Fahrenheit it's just ridiculously hot

998
00:47:23,160 --> 00:47:20,020
and the longest a spacecraft has ever

999
00:47:26,100 --> 00:47:23,170
survived on the Venetian surface is less

1000
00:47:29,070 --> 00:47:26,110
than two hours and the difference is

1001
00:47:31,590 --> 00:47:29,080
Venus's huge atmosphere which we cannot

1002
00:47:34,650 --> 00:47:31,600
tell currently at a distance when we

1003
00:47:36,900 --> 00:47:34,660
look at exoplanets so we don't know

1004
00:47:41,370 --> 00:47:36,910
anything about the surface conditions of

1005
00:47:43,710 --> 00:47:41,380
these new worlds we found and what do we

1006
00:47:46,710 --> 00:47:43,720
need to know to say yes this is

1007
00:47:48,900 --> 00:47:46,720
earth-like well most certainly size is

1008
00:47:51,600 --> 00:47:48,910
important if you have a planet that's

1009
00:47:53,010 --> 00:47:51,610
Jupiter sized we can be pretty sure that

1010
00:47:56,020 --> 00:47:53,020
it's not going to have a solid surface

1011
00:47:58,090 --> 00:47:56,030
it's not going to be earth-like so you

1012
00:48:01,210 --> 00:47:58,100
definitely need to be in the ballpark of

1013
00:48:03,460 --> 00:48:01,220
the Earth's radius and mass but our

1014
00:48:05,590 --> 00:48:03,470
planet also has a protective magnetic

1015
00:48:08,020 --> 00:48:05,600
fields and this protects us from the

1016
00:48:10,720 --> 00:48:08,030
flares from the Sun that would strip our

1017
00:48:12,400 --> 00:48:10,730
atmosphere instead charged particles for

1018
00:48:14,320 --> 00:48:12,410
the Sun get caught safely in our

1019
00:48:15,670 --> 00:48:14,330
magnetic field and come down as the

1020
00:48:17,830 --> 00:48:15,680
northern and southern lights at our

1021
00:48:19,990 --> 00:48:17,840
poles occasionally we might have some

1022
00:48:22,000 --> 00:48:20,000
damage to our GPS systems but the

1023
00:48:26,350 --> 00:48:22,010
surface of our planet is mercifully not

1024
00:48:28,030 --> 00:48:26,360
sterilized volcanoes so you might think

1025
00:48:30,280 --> 00:48:28,040
a planet with no volcanoes sounds like a

1026
00:48:31,780 --> 00:48:30,290
rather good idea but it turns out

1027
00:48:34,330 --> 00:48:31,790
they're rather important for our

1028
00:48:36,130 --> 00:48:34,340
atmosphere during the early Earth we

1029
00:48:37,630 --> 00:48:36,140
needed volcanoes in order to get the

1030
00:48:40,180 --> 00:48:37,640
atmosphere that ultimately developed

1031
00:48:42,100 --> 00:48:40,190
life and indeed now it's one of the ways

1032
00:48:45,630 --> 00:48:42,110
that greenhouse gases are controlled

1033
00:48:48,340 --> 00:48:45,640
over geological timescales rock-type

1034
00:48:50,920 --> 00:48:48,350
again is how we control our greenhouse

1035
00:48:53,260 --> 00:48:50,930
gases over geological timescales and how

1036
00:48:55,740 --> 00:48:53,270
our planets manage to maintain very good

1037
00:48:59,200 --> 00:48:55,750
conditions for forming life for so long

1038
00:49:01,540 --> 00:48:59,210
the presence of water just because you

1039
00:49:04,780 --> 00:49:01,550
can support water there's no guarantee

1040
00:49:06,850 --> 00:49:04,790
you have water to support so as I

1041
00:49:09,130 --> 00:49:06,860
mentioned the earth formed inside the

1042
00:49:11,950 --> 00:49:09,140
ice line this may have meant it was

1043
00:49:13,900 --> 00:49:11,960
actually formed as a dry planet and as

1044
00:49:16,810 --> 00:49:13,910
how water could well have been delivered

1045
00:49:18,490 --> 00:49:16,820
later on by icy meteorites scattered

1046
00:49:20,860 --> 00:49:18,500
inwards by the giant planets like

1047
00:49:23,110 --> 00:49:20,870
Jupiter and Saturn so if you have a

1048
00:49:25,930 --> 00:49:23,120
different planetary system without those

1049
00:49:27,790 --> 00:49:25,940
big beefy planets outside you do you get

1050
00:49:31,570 --> 00:49:27,800
a scattering of icy meteorites to

1051
00:49:34,060 --> 00:49:31,580
deliver water we're not sure and plate

1052
00:49:37,300 --> 00:49:34,070
tectonics our crust our surface is

1053
00:49:39,160 --> 00:49:37,310
divided up into chunks and these chunks

1054
00:49:42,940 --> 00:49:39,170
allow our planet cool which helps

1055
00:49:45,850 --> 00:49:42,950
generate our magnetic fields and when we

1056
00:49:47,740 --> 00:49:45,860
observe a planet around another star we

1057
00:49:49,840 --> 00:49:47,750
only know about the first two we don't

1058
00:49:52,810 --> 00:49:49,850
know about any of these other effects at

1059
00:49:55,720 --> 00:49:52,820
the moment so it takes a lot to be like

1060
00:50:00,430 --> 00:49:55,730
Earth and we don't know very much about

1061
00:50:03,550 --> 00:50:00,440
any of these exoplanets however in the

1062
00:50:06,670 --> 00:50:03,560
case of Trappist one unusually we do

1063
00:50:09,550 --> 00:50:06,680
know one other thing the planet orbits

1064
00:50:12,640 --> 00:50:09,560
of Trappist warned are in resonance

1065
00:50:14,680 --> 00:50:12,650
and that means that if you look at the

1066
00:50:18,070 --> 00:50:14,690
time for each planet to orbit the star

1067
00:50:20,470 --> 00:50:18,080
you see something rather interesting in

1068
00:50:23,200 --> 00:50:20,480
the time it takes for planet B to orbit

1069
00:50:27,820 --> 00:50:23,210
the star 24 times it takes planet

1070
00:50:30,550 --> 00:50:27,830
planets see orbits 15 times 15 not 15

1071
00:50:32,680 --> 00:50:30,560
point 5 not fifteen point three not

1072
00:50:35,380 --> 00:50:32,690
fifteen point one two seven eight three

1073
00:50:38,920 --> 00:50:35,390
it's an exact integer or very close to

1074
00:50:41,830 --> 00:50:38,930
it and the pattern continues 24 15 nine

1075
00:50:44,230 --> 00:50:41,840
six four three two one very close to

1076
00:50:47,410 --> 00:50:44,240
being exact integer ratios of one

1077
00:50:50,800 --> 00:50:47,420
another so how does this happen it seems

1078
00:50:53,320 --> 00:50:50,810
like a bit of a coincidence so what we

1079
00:50:56,170 --> 00:50:53,330
believe happens is that if the planets

1080
00:50:58,720 --> 00:50:56,180
are born far from the star and they go

1081
00:51:01,900 --> 00:50:58,730
through this migration process to come

1082
00:51:04,570 --> 00:51:01,910
further in if you have multiple planets

1083
00:51:07,150 --> 00:51:04,580
doing this and their gravity pulls on

1084
00:51:09,760 --> 00:51:07,160
one another they can end up locked in

1085
00:51:12,010 --> 00:51:09,770
these resonance positions so as they

1086
00:51:14,410 --> 00:51:12,020
both migrate in their orbits at some

1087
00:51:17,650 --> 00:51:14,420
point will sync up to exact ratios and

1088
00:51:19,930 --> 00:51:17,660
this turns out to be very stable so once

1089
00:51:22,180 --> 00:51:19,940
you hit this sweet spot you tend to stay

1090
00:51:24,520 --> 00:51:22,190
there and then the planets continue to

1091
00:51:26,950 --> 00:51:24,530
migrate in with these exact ratios as

1092
00:51:31,030 --> 00:51:26,960
their orbit and you might be like

1093
00:51:33,100 --> 00:51:31,040
walking but so what the point is that if

1094
00:51:35,470 --> 00:51:33,110
that happened to these planets that

1095
00:51:37,990 --> 00:51:35,480
means the planet started here further

1096
00:51:42,070 --> 00:51:38,000
away from the star behind the ice line

1097
00:51:45,450 --> 00:51:42,080
and then ended up here this would mean

1098
00:51:48,220 --> 00:51:45,460
that they formed with a lot of ice and

1099
00:51:50,830 --> 00:51:48,230
so maybe as they moved closer to the

1100
00:51:55,510 --> 00:51:50,840
star this may have melted to become a

1101
00:51:57,670 --> 00:51:55,520
global ocean so our other option instead

1102
00:51:59,830 --> 00:51:57,680
of a lava world it could be that the

1103
00:52:01,960 --> 00:51:59,840
Trappist one planets have a huge amount

1104
00:52:06,940 --> 00:52:01,970
of water and they're actually water

1105
00:52:09,640 --> 00:52:06,950
worlds with no exposed land at all so

1106
00:52:11,890 --> 00:52:09,650
this is a beautiful graphic by NASA and

1107
00:52:17,620 --> 00:52:11,900
if we go below the atmosphere this is

1108
00:52:20,050 --> 00:52:17,630
how we might picture a water world so

1109
00:52:22,589 --> 00:52:20,060
this then brings us to the obvious

1110
00:52:25,829 --> 00:52:22,599
question on water world's habitable

1111
00:52:28,019 --> 00:52:25,839
I mean water and life are intricately

1112
00:52:30,479 --> 00:52:28,029
asserted are associated on earth so is

1113
00:52:33,089 --> 00:52:30,489
more water and better for life

1114
00:52:35,099 --> 00:52:33,099
well the shorter answer is we don't know

1115
00:52:37,109 --> 00:52:35,109
we've got no analog in our solar system

1116
00:52:40,799 --> 00:52:37,119
to go and explore which has a surface

1117
00:52:43,829 --> 00:52:40,809
global ocean however we have some reason

1118
00:52:47,549 --> 00:52:43,839
to be slightly skeptical and it comes

1119
00:52:49,349 --> 00:52:47,559
down to the carbon dioxide in our air so

1120
00:52:50,940 --> 00:52:49,359
if we didn't have an atmosphere the

1121
00:52:53,670 --> 00:52:50,950
global temperature of the earth would be

1122
00:52:56,009 --> 00:52:53,680
-5 Celsius below the freezing point of

1123
00:52:57,450 --> 00:52:56,019
water however because we have an

1124
00:52:59,969 --> 00:52:57,460
atmosphere and it contains these

1125
00:53:02,009 --> 00:52:59,979
greenhouse gases we're able to trap heat

1126
00:53:05,519 --> 00:53:02,019
effectively and brings our global

1127
00:53:08,190 --> 00:53:05,529
temperature to about 15 Celsius and

1128
00:53:11,009 --> 00:53:08,200
exactly how warm our planet gets can be

1129
00:53:12,839 --> 00:53:11,019
controlled by geology through what we

1130
00:53:15,630 --> 00:53:12,849
call the carbon cycle or sometimes the

1131
00:53:18,089 --> 00:53:15,640
carbon silicate cycle so here carbon

1132
00:53:20,130 --> 00:53:18,099
dioxide in the air dissolves in

1133
00:53:22,650 --> 00:53:20,140
rainwater comes down as slightly acidic

1134
00:53:25,019 --> 00:53:22,660
rain it reacts with the rocks and forms

1135
00:53:26,789 --> 00:53:25,029
of solids this gets swept into the ocean

1136
00:53:29,309 --> 00:53:26,799
and it eventually gets returned to the

1137
00:53:31,380 --> 00:53:29,319
atmosphere through volcanoes now the

1138
00:53:34,049 --> 00:53:31,390
process is very slow so it doesn't

1139
00:53:37,559 --> 00:53:34,059
really protect us against man-made

1140
00:53:40,259 --> 00:53:37,569
increase in greenhouse gases but it does

1141
00:53:43,559 --> 00:53:40,269
protect us over at slower moving changes

1142
00:53:45,930 --> 00:53:43,569
for example in its early years the Sun

1143
00:53:48,239 --> 00:53:45,940
would have been much cooler and during

1144
00:53:50,339 --> 00:53:48,249
this time the our earth should have been

1145
00:53:52,319 --> 00:53:50,349
too cold for life but we have evidence

1146
00:53:54,900 --> 00:53:52,329
that it wasn't and one of the

1147
00:53:57,269 --> 00:53:54,910
possibilities is that this process was

1148
00:53:59,969 --> 00:53:57,279
able to change the amount of greenhouse

1149
00:54:02,190 --> 00:53:59,979
gases in our atmosphere so if the planet

1150
00:54:04,049 --> 00:54:02,200
was colder this reaction with the rocks

1151
00:54:06,690 --> 00:54:04,059
would have slowed down because chemical

1152
00:54:08,009 --> 00:54:06,700
reactions slowed when it's colder but we

1153
00:54:09,870 --> 00:54:08,019
still would have been spitting out

1154
00:54:11,880 --> 00:54:09,880
carbon dioxide into the atmosphere so

1155
00:54:13,859 --> 00:54:11,890
the amount of greenhouse gas in the

1156
00:54:16,469 --> 00:54:13,869
atmosphere would have risen and given us

1157
00:54:18,839 --> 00:54:16,479
a thicker thermal blanket and this

1158
00:54:22,769 --> 00:54:18,849
allows us to have a lot more time in

1159
00:54:26,599 --> 00:54:22,779
which life can develop on earth but in

1160
00:54:29,910 --> 00:54:26,609
Eveland so if you have a global ocean

1161
00:54:33,660 --> 00:54:29,920
can you have any kind of carbon silicate

1162
00:54:35,340 --> 00:54:33,670
cycle so could a Waterworld actually

1163
00:54:37,290 --> 00:54:35,350
regulate its temperature

1164
00:54:39,990 --> 00:54:37,300
if it couldn't it has two main effects

1165
00:54:42,780 --> 00:54:40,000
the first is your habitable zone which I

1166
00:54:45,750 --> 00:54:42,790
presented as a broadband shrinks to a

1167
00:54:48,090 --> 00:54:45,760
narrow point because the reason ours is

1168
00:54:50,520 --> 00:54:48,100
a broadband is that our carbon cycle can

1169
00:54:52,440 --> 00:54:50,530
adjust slightly our atmosphere to allow

1170
00:54:55,110 --> 00:54:52,450
us to manage in slightly warmer areas

1171
00:54:57,210 --> 00:54:55,120
and slightly colder areas if there's no

1172
00:54:59,490 --> 00:54:57,220
way of adjusting the thermostat of the

1173
00:55:03,090 --> 00:54:59,500
planet the radiation you receive from

1174
00:55:04,740 --> 00:55:03,100
your star needs to be bang-on perfect so

1175
00:55:08,430 --> 00:55:04,750
you get a very narrow band for that

1176
00:55:11,310 --> 00:55:08,440
habitable zone secondly because you

1177
00:55:13,350 --> 00:55:11,320
can't buffer against the star increasing

1178
00:55:16,860 --> 00:55:13,360
in luminosity you have a much shorter

1179
00:55:19,620 --> 00:55:16,870
time for life to be able to develop so

1180
00:55:22,800 --> 00:55:19,630
does that mean it's curtains for any

1181
00:55:25,740 --> 00:55:22,810
water wells well not necessarily it may

1182
00:55:28,140 --> 00:55:25,750
depend on ocean depth for example if the

1183
00:55:30,390 --> 00:55:28,150
ocean is shallow enough you can still

1184
00:55:32,970 --> 00:55:30,400
have a carbon silicon cycle with the

1185
00:55:35,340 --> 00:55:32,980
ocean bottom it's not as good because

1186
00:55:38,370 --> 00:55:35,350
the ocean changes temperature much more

1187
00:55:41,040 --> 00:55:38,380
slowly than the atmosphere birds maybe

1188
00:55:43,140 --> 00:55:41,050
not impossible if the ocean gets very

1189
00:55:45,120 --> 00:55:43,150
deep then the chances are the pressure

1190
00:55:48,000 --> 00:55:45,130
of that ocean floor will rise so much

1191
00:55:50,460 --> 00:55:48,010
your form Isis and these Isis will

1192
00:55:52,710 --> 00:55:50,470
completely seal off your rocky core from

1193
00:55:57,600 --> 00:55:52,720
your ocean and so it won't be able to

1194
00:55:59,280 --> 00:55:57,610
produce any kind of thermostat at all so

1195
00:56:02,280 --> 00:55:59,290
this always leads to the question of can

1196
00:56:04,440 --> 00:56:02,290
we go and check these planets out well

1197
00:56:07,050 --> 00:56:04,450
our closest exoplanet is the one

1198
00:56:10,550 --> 00:56:07,060
orbiting Proxima Centauri this is our

1199
00:56:13,860 --> 00:56:10,560
nearest star so is our nearest possible

1200
00:56:16,770 --> 00:56:13,870
exoplanets and it's four light-years

1201
00:56:18,450 --> 00:56:16,780
away now our fastest spacecraft is

1202
00:56:19,830 --> 00:56:18,460
Voyager one which is currently at the

1203
00:56:21,960 --> 00:56:19,840
edge of our solar system

1204
00:56:24,480 --> 00:56:21,970
if forager one was pointing in the right

1205
00:56:26,550 --> 00:56:24,490
direction which isn't it would still

1206
00:56:29,700 --> 00:56:26,560
take it 75 thousand years

1207
00:56:32,130 --> 00:56:29,710
is to reach Proxima Centauri B now there

1208
00:56:33,930 --> 00:56:32,140
are some other ideas in the pipeline for

1209
00:56:36,480 --> 00:56:33,940
instance this project star shots which

1210
00:56:38,850 --> 00:56:36,490
is an idea where we could use lasers to

1211
00:56:42,000 --> 00:56:38,860
send very very very light spacecraft

1212
00:56:43,800 --> 00:56:42,010
great distances reasonably quickly but

1213
00:56:45,650 --> 00:56:43,810
as futuristic technology and we don't

1214
00:56:49,710 --> 00:56:45,660
know yet whether it's at all feasible

1215
00:56:51,270 --> 00:56:49,720
however all is not lost there are a

1216
00:56:53,130 --> 00:56:51,280
couple of really or more a couple

1217
00:56:55,290 --> 00:56:53,140
several really exciting missions coming

1218
00:56:58,140 --> 00:56:55,300
up that are going to tell us a lot more

1219
00:57:00,960 --> 00:56:58,150
about these exoplanets so as the planet

1220
00:57:02,970 --> 00:57:00,970
transits across the star surface some of

1221
00:57:05,910 --> 00:57:02,980
our starlight is going to pass through

1222
00:57:10,110 --> 00:57:05,920
the planet's atmosphere if we can spot

1223
00:57:12,450 --> 00:57:10,120
that then we will see a fingerprint that

1224
00:57:14,030 --> 00:57:12,460
marks out the gases at the atmosphere so

1225
00:57:16,290 --> 00:57:14,040
the light passes through the atmosphere

1226
00:57:18,360 --> 00:57:16,300
particular molecules in the atmosphere

1227
00:57:20,670 --> 00:57:18,370
will absorb certain parts of the light

1228
00:57:23,040 --> 00:57:20,680
spectrum and so they'll be missing when

1229
00:57:25,800 --> 00:57:23,050
we observe them on earth and based on

1230
00:57:27,500 --> 00:57:25,810
those missing light waves we can tell

1231
00:57:29,940 --> 00:57:27,510
what gases might be in the atmosphere

1232
00:57:33,060 --> 00:57:29,950
and this gives us our first hint that

1233
00:57:37,440 --> 00:57:33,070
geological processes and maybe even a

1234
00:57:38,910 --> 00:57:37,450
whiff of life so obviously in a space

1235
00:57:40,410 --> 00:57:38,920
telescope I have to mention that one of

1236
00:57:42,240 --> 00:57:40,420
the major instruments that we'll be

1237
00:57:45,870 --> 00:57:42,250
looking for this is a course at James

1238
00:57:47,940 --> 00:57:45,880
Webb which is due to launch in 2019 but

1239
00:57:49,830 --> 00:57:47,950
there's also ESA is the European Space

1240
00:57:52,790 --> 00:57:49,840
Agency's aerial mission which is

1241
00:57:56,030 --> 00:57:52,800
hopefully to go up in 2026

1242
00:57:58,260 --> 00:57:56,040
so this is going to be very exciting and

1243
00:58:02,460 --> 00:57:58,270
just to end on an utterly shameless

1244
00:58:04,950 --> 00:58:02,470
pitch as Frank mentioned my book comes

1245
00:58:06,930 --> 00:58:04,960
out today officially in the US it is

1246
00:58:09,060 --> 00:58:06,940
full of truly awful planets I mean there

1247
00:58:10,980 --> 00:58:09,070
are the hot Jupiters there are Tatooine

1248
00:58:13,080 --> 00:58:10,990
worlds around two stars there are rogue

1249
00:58:15,960 --> 00:58:13,090
worlds that have no star at all there

1250
00:58:17,970 --> 00:58:15,970
are planets with seas of lava and tar so

1251
00:58:19,920 --> 00:58:17,980
really whatever your favorite way to die

1252
00:58:23,460 --> 00:58:19,930
horribly is you'll probably find it in

1253
00:58:25,560 --> 00:58:23,470
the pages of my book so if you're at all

1254
00:58:28,740 --> 00:58:25,570
interested I've put some little cards

1255
00:58:32,850 --> 00:58:28,750
here just to remind you please grab one

1256
00:58:47,630 --> 00:58:32,860
and thank you very much

1257
00:59:00,150 --> 00:58:58,109
questions alright so I'm sure we have a

1258
00:59:04,890 --> 00:59:00,160
few questions I see in the green back

1259
00:59:08,099 --> 00:59:04,900
there now that was you all these

1260
00:59:10,799 --> 00:59:08,109
terrible planets Oh what about ours

1261
00:59:14,069 --> 00:59:10,809
which is you know sort of so coddling

1262
00:59:16,190 --> 00:59:14,079
almost what is your knee-jerk reaction

1263
00:59:19,770 --> 00:59:16,200
when people talk about like a Gaia

1264
00:59:21,930 --> 00:59:19,780
hypothesis where it's like a system

1265
00:59:22,680 --> 00:59:21,940
working together to maintain this

1266
00:59:25,799 --> 00:59:22,690
balance

1267
00:59:29,010 --> 00:59:25,809
nothing wearing it yeah one giant

1268
00:59:31,079 --> 00:59:29,020
tortoise okay so I'm gonna repeat the

1269
00:59:33,030 --> 00:59:31,089
question for the online audience so the

1270
00:59:36,390 --> 00:59:33,040
question is what is your opinion on the

1271
00:59:38,280 --> 00:59:36,400
Gaia hypothesis considers a planet as

1272
01:00:06,870 --> 00:59:38,290
sort of being an entire organism and

1273
01:00:10,260 --> 01:00:06,880
such and the question is where is the

1274
01:00:12,390 --> 01:00:10,270
bottleneck is it that life is very hard

1275
01:00:14,280 --> 01:00:12,400
to start maybe you never get a planet

1276
01:00:18,720 --> 01:00:14,290
with the right organics to start life

1277
01:00:22,530 --> 01:00:18,730
maybe life develops but in fact it dies

1278
01:00:23,970 --> 01:00:22,540
really quickly or maybe that you can

1279
01:00:25,650 --> 01:00:23,980
develop life quite easily and actually

1280
01:00:26,970 --> 01:00:25,660
it thrives but it just never becomes

1281
01:00:29,039 --> 01:00:26,980
intelligent life because it's not

1282
01:00:33,299 --> 01:00:29,049
selected for those sort of options and

1283
01:00:35,280 --> 01:00:33,309
one hypothesis put forward by Charlie

1284
01:00:38,520 --> 01:00:35,290
lineweaver was actually what he calls

1285
01:00:40,829 --> 01:00:38,530
the Gaya bottleneck where he says that

1286
01:00:42,210 --> 01:00:40,839
you have to not only form life you have

1287
01:00:44,160 --> 01:00:42,220
to form it fast enough

1288
01:00:46,410 --> 01:00:44,170
that it can actually change your

1289
01:00:49,680 --> 01:00:46,420
planet's environment to self sustain

1290
01:00:52,109 --> 01:00:49,690
itself and so that's the idea that in

1291
01:00:54,450 --> 01:00:52,119
the early stages of our earth the carbon

1292
01:00:57,030 --> 01:00:54,460
cycle that I mentioned before was not

1293
01:00:58,740 --> 01:00:57,040
sufficient to actually protect our

1294
01:01:00,900 --> 01:00:58,750
it's atmosphere and keep it temperate

1295
01:01:44,650 --> 01:01:00,910
enough but because we were able to form

1296
01:01:48,950 --> 01:01:47,059
obviously the aliens are trying to drown

1297
01:01:53,120 --> 01:01:48,960
out her talk and she's revealing too

1298
01:01:54,890 --> 01:01:53,130
many secrets folks those of you who've

1299
01:02:00,230 --> 01:01:54,900
been here know this has absolutely never

1300
01:02:03,289 --> 01:02:00,240
happened before in my 17 years we've

1301
01:02:08,420 --> 01:02:03,299
never had that kind of noise let's see

1302
01:02:11,029 --> 01:02:08,430
so yes I will also note that we just had

1303
01:02:13,339 --> 01:02:11,039
some major work done on the auditorium

1304
01:02:15,559 --> 01:02:13,349
honor if you noticed the projectors are

1305
01:02:18,829 --> 01:02:15,569
4k and other things and the audio system

1306
01:02:22,250 --> 01:02:18,839
was updated a little bit so I apologize

1307
01:02:25,609 --> 01:02:22,260
we are this is the first live event to

1308
01:02:28,430 --> 01:02:25,619
test out the system in detail so you can

1309
01:02:30,740 --> 01:02:28,440
see that it is being tested out okay so

1310
01:02:32,960 --> 01:02:30,750
back to what you were saying so even

1311
01:02:35,950 --> 01:02:32,970
though I obviously external forces tried

1312
01:02:39,109 --> 01:02:35,960
to stop me answering this question I

1313
01:02:41,299 --> 01:02:39,119
would say that I would consider life as

1314
01:02:43,220 --> 01:02:41,309
to be definitely part of the planets I

1315
01:02:44,420 --> 01:02:43,230
think when we talk about origins of life

1316
01:02:45,620 --> 01:02:44,430
we also have to talk about plant

1317
01:02:59,240 --> 01:02:45,630
information and they are intricately

1318
01:03:01,339 --> 01:02:59,250
connected yes okay yes so the question

1319
01:03:03,499 --> 01:03:01,349
was on there's the cellar type of

1320
01:03:05,240 --> 01:03:03,509
Trappist one is that what the root

1321
01:03:08,870 --> 01:03:05,250
you're asking about yes this is a red

1322
01:03:29,930 --> 01:03:08,880
dwarf yeah it is a red dwarf red dwarfs

1323
01:03:34,940 --> 01:03:29,940
are interesting they're good why is it

1324
01:03:41,270 --> 01:03:39,230
so yeah a Trappist one red dwarfs have

1325
01:03:43,760 --> 01:03:41,280
pros and cons one of the pros is that

1326
01:03:46,070 --> 01:03:43,770
being very small and dim stars is much

1327
01:03:49,160 --> 01:03:46,080
easier to find planets circling them and

1328
01:03:51,320 --> 01:03:49,170
indeed Kepler's successor test is going

1329
01:03:54,620 --> 01:03:51,330
to be focusing on red dwarfs for exactly

1330
01:03:56,780 --> 01:03:54,630
this reason however they're also

1331
01:03:59,240 --> 01:03:56,790
extremely rambunctious when they're

1332
01:04:02,300 --> 01:03:59,250
young and they are prone to a lot of

1333
01:04:04,550 --> 01:04:02,310
stellar flares and it is possible that a

1334
01:04:06,770 --> 01:04:04,560
planets around red dwarfs may become

1335
01:04:08,840 --> 01:04:06,780
sterilized because during this early

1336
01:04:10,250 --> 01:04:08,850
phase and the star's evolution it just

1337
01:04:12,260 --> 01:04:10,260
might have nuked everything that might

1338
01:04:13,940 --> 01:04:12,270
be developing on the planets at the

1339
01:04:15,830 --> 01:04:13,950
moment we just don't know the

1340
01:04:18,290 --> 01:04:15,840
interesting thing about Trappist one is

1341
01:04:20,450 --> 01:04:18,300
if they genuinely did this migration it

1342
01:04:22,160 --> 01:04:20,460
might just have saved them because they

1343
01:04:24,560 --> 01:04:22,170
would have started further away from the

1344
01:04:27,790 --> 01:04:24,570
star when the star was younger and maybe

1345
01:04:30,380 --> 01:04:27,800
that it would have got over its and

1346
01:04:34,910 --> 01:04:30,390
awkward adolescent stage by the time the

1347
01:04:45,080 --> 01:04:34,920
planet started approaching it all the

1348
01:04:46,970 --> 01:04:45,090
way in the very back row there okay so

1349
01:04:49,160 --> 01:04:46,980
do you anticipate any technology that

1350
01:04:52,700 --> 01:04:49,170
will allow us to see not just exoplanets

1351
01:04:54,020 --> 01:04:52,710
but also exomoons I guess start his

1352
01:04:57,380 --> 01:04:54,030
answer and see if everything cuts off

1353
01:04:59,540 --> 01:04:57,390
again yes absolutely so renie heller who

1354
01:05:02,270 --> 01:04:59,550
is an expert on EXO moon formation in

1355
01:05:04,820 --> 01:05:02,280
germany told me that he feels that

1356
01:05:07,580 --> 01:05:04,830
exomoons is where exoplanets was at the

1357
01:05:09,980 --> 01:05:07,590
start of the 1990s we are on the brink

1358
01:05:11,750 --> 01:05:09,990
and indeed their active search is

1359
01:05:15,109 --> 01:05:11,760
currently going on for EXO meals

1360
01:05:17,240 --> 01:05:15,119
one of them is called HEC which I forgot

1361
01:05:20,900 --> 01:05:17,250
what it stands for but it's using Kepler

1362
01:05:22,790 --> 01:05:20,910
to look for moons and the PI on that is

1363
01:05:25,340 --> 01:05:22,800
David kipping at Columbia University and

1364
01:05:28,400 --> 01:05:25,350
currently Kepler is sensitive enough to

1365
01:05:30,320 --> 01:05:28,410
find a very very large moon in fact

1366
01:05:33,290 --> 01:05:30,330
slightly larger than we believe would

1367
01:05:35,960 --> 01:05:33,300
form around a gas giants but could

1368
01:05:38,560 --> 01:05:35,970
potentially be captured now of course if

1369
01:05:40,810 --> 01:05:38,570
we find that earth sized moons exist

1370
01:05:43,400 --> 01:05:40,820
then we have a lot more real estate

1371
01:05:45,620 --> 01:05:43,410
because our gas giants are mobbed with

1372
01:05:46,340 --> 01:05:45,630
meals so if you imagine a gas giant in

1373
01:05:49,370 --> 01:05:46,350
the habit

1374
01:05:51,560 --> 01:05:49,380
then it's not habitable but it might

1375
01:05:53,570 --> 01:05:51,570
have a whole bunch of moons that are now

1376
01:05:55,040 --> 01:05:53,580
it's a slightly interesting game when

1377
01:05:57,380 --> 01:05:55,050
you start looking at exomoons and

1378
01:05:59,930 --> 01:05:57,390
habitability in particular they get

1379
01:06:02,540 --> 01:05:59,940
multiple sources of heat because they

1380
01:06:04,790 --> 01:06:02,550
get the star but they also get heat

1381
01:06:07,400 --> 01:06:04,800
coming from the planet so that may mean

1382
01:06:09,980 --> 01:06:07,410
that if the planet is in the ideal spot

1383
01:06:12,950 --> 01:06:09,990
to support liquid water its moons may

1384
01:06:16,820 --> 01:06:12,960
potentially be too hot so it might be

1385
01:06:18,890 --> 01:06:16,830
your ideal Endor or a walk filled moon

1386
01:06:20,900 --> 01:06:18,900
would actually left live slightly

1387
01:06:22,520 --> 01:06:20,910
outside the habitable zone with the

1388
01:06:38,150 --> 01:06:22,530
planet providing that additional source

1389
01:06:43,400 --> 01:06:41,120
so what can we learn if we are able to

1390
01:06:45,259 --> 01:06:43,410
travel to Mars and explore it what shall

1391
01:06:48,650 --> 01:06:45,269
we learn that will enhance our knowledge

1392
01:06:50,539 --> 01:06:48,660
on this subject so I think probably what

1393
01:06:56,359 --> 01:06:50,549
most people would love to find is life

1394
01:06:58,460 --> 01:06:56,369
of any kind or even idea where is

1395
01:07:00,799 --> 01:06:58,470
everyone but one of the questions might

1396
01:07:04,069 --> 01:07:00,809
be does life just never start anywhere I

1397
01:07:07,009 --> 01:07:04,079
mean that's possible right if we were to

1398
01:07:09,079 --> 01:07:07,019
find a second genesis of life that would

1399
01:07:11,839 --> 01:07:09,089
probably imply that actually life is

1400
01:07:13,630 --> 01:07:11,849
pretty easy to kick-start now Mars isn't

1401
01:07:16,039 --> 01:07:13,640
necessarily the best place for that

1402
01:07:18,440 --> 01:07:16,049
because it's sufficiently close to the

1403
01:07:20,630 --> 01:07:18,450
earth that we can share material indeed

1404
01:07:22,160 --> 01:07:20,640
there isn't some theories that it's just

1405
01:07:25,220 --> 01:07:22,170
about possible life originated on Mars

1406
01:07:26,870 --> 01:07:25,230
and then came across to earth we never

1407
01:07:29,509 --> 01:07:26,880
found any evidence for life on Mars so

1408
01:07:32,870 --> 01:07:29,519
far and we're maybe more interesting

1409
01:07:34,819 --> 01:07:32,880
area might be Europe so as a moon of

1410
01:07:37,910 --> 01:07:34,829
Jupiter it has these deep subsurface

1411
01:07:39,680 --> 01:07:37,920
oceans if we were able to find evidence

1412
01:07:41,240 --> 01:07:39,690
of life on those I think we could be

1413
01:07:43,279 --> 01:07:41,250
more certain to say this was an

1414
01:07:45,740 --> 01:07:43,289
independent genesis of life and

1415
01:07:59,529 --> 01:07:45,750
therefore life is at least easy to start

1416
01:08:01,700 --> 01:07:59,539
if not continue the hot Jupiters

1417
01:08:06,260 --> 01:08:01,710
eventually lose our atmosphere by being

1418
01:08:10,509 --> 01:08:06,270
so close and why isn't our Jupiter hot

1419
01:08:10,509 --> 01:08:10,519
[Music]

1420
01:08:15,319 --> 01:08:13,460
that the Stars gravitational field

1421
01:08:17,510 --> 01:08:15,329
starts to penetrate that atmosphere and

1422
01:08:19,760 --> 01:08:17,520
literally starts siphoning it off we

1423
01:08:21,950 --> 01:08:19,770
call that a rich loop in flow and we've

1424
01:08:24,470 --> 01:08:21,960
also seen evidence of some hot Jupiters

1425
01:08:29,599 --> 01:08:24,480
rapidly using their answers so certainly

1426
01:08:31,999 --> 01:08:29,609
for some of them if they're close yes is

1427
01:08:35,629 --> 01:08:32,009
a big mystery so the idea of migration

1428
01:08:37,910 --> 01:08:35,639
was not actually invented when we found

1429
01:08:40,669 --> 01:08:37,920
hot Jupiters indeed the idea of been

1430
01:08:42,680 --> 01:08:40,679
around since the 1980s and we knew that

1431
01:08:44,809 --> 01:08:42,690
it was possible that this migration

1432
01:08:46,490 --> 01:08:44,819
process could occur but we look to our

1433
01:08:48,800 --> 01:08:46,500
own solar system didn't see any evidence

1434
01:08:49,760 --> 01:08:48,810
of strong migration and therefore is

1435
01:08:51,980 --> 01:08:49,770
assumed

1436
01:08:54,320 --> 01:08:51,990
either didn't happen or it just wasn't a

1437
01:08:56,420 --> 01:08:54,330
major player now we've discovered all

1438
01:08:59,570 --> 01:08:56,430
these exoplanets we realize it's a major

1439
01:09:02,510 --> 01:08:59,580
sculptor of exoplanet systems so then

1440
01:09:04,130 --> 01:09:02,520
the question comes I'll be weird so what

1441
01:09:06,170 --> 01:09:04,140
people think happened with our gas

1442
01:09:08,599 --> 01:09:06,180
giants is that jupiter was formed and

1443
01:09:10,309 --> 01:09:08,609
indeed it did start migrating and it

1444
01:09:12,200 --> 01:09:10,319
started to munch its way towards the

1445
01:09:14,599 --> 01:09:12,210
inner solar system which would have not

1446
01:09:16,970 --> 01:09:14,609
look good for earth but as it was doing

1447
01:09:19,880 --> 01:09:16,980
so saturn formed and caught up with it

1448
01:09:21,950 --> 01:09:19,890
as it started its own migration and at

1449
01:09:24,470 --> 01:09:21,960
that point the gravitational pull of the

1450
01:09:28,010 --> 01:09:24,480
two planets together caused a u-turn

1451
01:09:29,510 --> 01:09:28,020
that we call the grand tack model after

1452
01:09:31,370 --> 01:09:29,520
the sailing turn we turn the boat around

1453
01:09:34,070 --> 01:09:31,380
so the two planets moved in together

1454
01:09:36,920 --> 01:09:34,080
they actually do the u-turn around about

1455
01:09:39,079 --> 01:09:36,930
the position of Mars and moved out and

1456
01:09:41,870 --> 01:09:39,089
it's one of the explanations we have for

1457
01:09:43,190 --> 01:09:41,880
why Mars is so small because naively we

1458
01:09:45,260 --> 01:09:43,200
would have thought further away from the

1459
01:09:47,180 --> 01:09:45,270
star where the star's gravity is a

1460
01:09:49,250 --> 01:09:47,190
little bit weaker you should actually be

1461
01:09:51,650 --> 01:09:49,260
able to build a blog of planets but

1462
01:09:53,120 --> 01:09:51,660
instead we have a real squiffy one it's

1463
01:09:54,170 --> 01:09:53,130
possible that it was Jupiter just

1464
01:09:55,490 --> 01:09:54,180
marched right in there

1465
01:09:59,690 --> 01:09:55,500
eat up all the building material and

1466
01:10:01,220 --> 01:09:59,700
then left now whether this is common we

1467
01:10:03,380 --> 01:10:01,230
don't know yet because it's harder to

1468
01:10:05,630 --> 01:10:03,390
see planets at Jupiter's distance around

1469
01:10:07,430 --> 01:10:05,640
other stars as we start to see more

1470
01:10:08,960 --> 01:10:07,440
planets that are further out and get a

1471
01:10:10,940 --> 01:10:08,970
more complete picture of planetary

1472
01:10:14,360 --> 01:10:10,950
systems I think we'll get a better idea

1473
01:10:16,280 --> 01:10:14,370
about whether this grand tak system is

1474
01:10:20,060 --> 01:10:16,290
common or whether actually we have a

1475
01:10:22,640 --> 01:10:20,070
very unique system question in the

1476
01:10:25,910 --> 01:10:22,650
center there and there's kind of a

1477
01:10:27,740 --> 01:10:25,920
follow up is the word migration it

1478
01:10:29,470 --> 01:10:27,750
indicates that it's still moving could

1479
01:10:34,520 --> 01:10:29,480
these could these hot Jupiters

1480
01:10:37,280 --> 01:10:34,530
eventually go in actually hit the star

1481
01:10:38,870 --> 01:10:37,290
that they're that they're of form so

1482
01:10:41,120 --> 01:10:38,880
this is my creative process

1483
01:10:49,910 --> 01:10:41,130
can this migrating process end with the

1484
01:10:55,350 --> 01:10:51,140
[Music]

1485
01:10:58,530 --> 01:10:55,360
gasps disk circling about 10 million

1486
01:11:02,160 --> 01:10:58,540
years the star vaporizes its planet

1487
01:11:04,709 --> 01:11:02,170
migration due to the gaseous stops there

1488
01:11:07,260 --> 01:11:04,719
is also normally a gap at the disk edge

1489
01:11:09,689 --> 01:11:07,270
so the planet could go up to that gap

1490
01:11:12,959 --> 01:11:09,699
just before it reaches a star also stop

1491
01:11:14,700 --> 01:11:12,969
because there's no gas that site so in

1492
01:11:17,459 --> 01:11:14,710
terms of gas drip and migration you

1493
01:11:18,839 --> 01:11:17,469
shouldn't throw the whole planet into

1494
01:11:21,510 --> 01:11:18,849
the star there should be some kind of

1495
01:11:23,899 --> 01:11:21,520
stopping mechanism now exactly what

1496
01:11:26,910 --> 01:11:23,909
stops the planets we're not certain

1497
01:11:29,160 --> 01:11:26,920
because we don't see planets all exactly

1498
01:11:30,180 --> 01:11:29,170
the same distance which would suggest it

1499
01:11:32,790 --> 01:11:30,190
was just stopping at the disk edge

1500
01:11:34,830 --> 01:11:32,800
instead we see hot and warm Jupiter's

1501
01:11:36,569 --> 01:11:34,840
that obviously seemed to have migrated

1502
01:11:38,879 --> 01:11:36,579
but stopped at different distances and

1503
01:11:40,919 --> 01:11:38,889
we're still not entirely sure why that

1504
01:11:43,350 --> 01:11:40,929
happens there's different ideas for

1505
01:11:45,180 --> 01:11:43,360
these plant traps that can cause for

1506
01:11:47,640 --> 01:11:45,190
instance sharp density gradients at the

1507
01:11:50,669 --> 01:11:47,650
ice line that can slow a planet down and

1508
01:11:51,959 --> 01:11:50,679
hold it for a bit and also see the gas

1509
01:11:54,479 --> 01:11:51,969
disc can evaporate at slightly different

1510
01:11:57,720 --> 01:11:54,489
times and in job effectively beaching

1511
01:11:59,280 --> 01:11:57,730
the planets but for the hot Jupiters we

1512
01:12:06,720 --> 01:11:59,290
found now because the gas disc is no

1513
01:12:10,080 --> 01:12:06,730
longer when you make comments or

1514
01:12:12,870 --> 01:12:10,090
observations about orbits on distant

1515
01:12:14,850 --> 01:12:12,880
worlds it seems to me we're making the

1516
01:12:17,790 --> 01:12:14,860
assumption that we'll use an earth time

1517
01:12:20,729 --> 01:12:17,800
but a time is relative is it possible

1518
01:12:22,620 --> 01:12:20,739
that time is very different on these

1519
01:12:25,439 --> 01:12:22,630
different worlds and has it completely

1520
01:12:27,950 --> 01:12:25,449
different I don't know if a second is

1521
01:12:56,430 --> 01:12:27,960
ten times longer than is here whatever

1522
01:13:02,220 --> 01:13:00,630
so we see everything in a time yeah it's

1523
01:13:12,350 --> 01:13:02,230
we're all measuring it from our point of

1524
01:13:16,320 --> 01:13:12,360
view measurements in other solar systems

1525
01:13:19,290 --> 01:13:16,330
is there a minimum distance from the

1526
01:13:28,410 --> 01:13:19,300
star and a maximum distance is that is

1527
01:13:31,820 --> 01:13:28,420
that kind of area from on the planet

1528
01:13:36,900 --> 01:13:31,830
from the star and a maximum distance is

1529
01:13:38,880 --> 01:13:36,910
that area where planets forms of systems

1530
01:13:40,229 --> 01:13:38,890
is there a minimum distance from the

1531
01:13:43,950 --> 01:13:40,239
star or a maximum distance from a star

1532
01:13:46,260 --> 01:13:43,960
for planets so the prototype disk is

1533
01:13:48,630 --> 01:13:46,270
perfectly between one three percent of

1534
01:13:56,040 --> 01:13:48,640
the mass of the star and for that build

1535
01:13:57,630 --> 01:13:56,050
up process from it does not control

1536
01:13:59,459 --> 01:13:57,640
where the plants ultimately end up

1537
01:14:01,290 --> 01:13:59,469
because the addition to this gas

1538
01:14:02,250 --> 01:14:01,300
migration which would incur system

1539
01:14:05,660 --> 01:14:02,260
within that disk

1540
01:14:07,950 --> 01:14:05,670
there's also specially so if you have

1541
01:14:10,200 --> 01:14:07,960
multiple clients in their system they

1542
01:14:12,570 --> 01:14:10,210
can gravitationally pinboard each other

1543
01:14:13,920 --> 01:14:12,580
out the system so in our own solar

1544
01:14:16,380 --> 01:14:13,930
system we see evidence for that

1545
01:14:19,229 --> 01:14:16,390
happening in small objects so for

1546
01:14:21,330 --> 01:14:19,239
example our long-range comets come from

1547
01:14:23,760 --> 01:14:21,340
an area we call the Oort cloud which is

1548
01:14:25,470 --> 01:14:23,770
a huge distance away from us and it's

1549
01:14:27,660 --> 01:14:25,480
thought that objects there couldn't

1550
01:14:29,370 --> 01:14:27,670
possibly afford that they must have

1551
01:14:31,260 --> 01:14:29,380
formed much closer where our normal

1552
01:14:33,360 --> 01:14:31,270
planets are and then being scattered

1553
01:14:35,700 --> 01:14:33,370
gravitationally by planets like Jupiter

1554
01:14:37,979 --> 01:14:35,710
Saturn in this kind of gravitational

1555
01:14:40,050 --> 01:14:37,989
pinball game and when we look at

1556
01:14:42,930 --> 01:14:40,060
extrasolar planets we do sometimes see

1557
01:14:44,850 --> 01:14:42,940
planets that are far more distance then

1558
01:14:48,060 --> 01:14:44,860
there should have been a decent amount

1559
01:14:51,060 --> 01:14:48,070
of gas and dust in existence and we

1560
01:14:52,380 --> 01:14:51,070
genuinely believe that that is beyond

1561
01:14:53,970 --> 01:14:52,390
the edge where we expect planet

1562
01:14:56,100 --> 01:14:53,980
formation and they probably didn't form

1563
01:14:58,950 --> 01:14:56,110
there but it's a scattering event lob

1564
01:15:01,620 --> 01:14:58,960
them further out so as a result we don't

1565
01:15:03,930 --> 01:15:01,630
have a hard edge to where we expect to

1566
01:15:06,660 --> 01:15:03,940
see a planet not because we believe it

1567
01:15:22,300 --> 01:15:06,670
could have formed infinitely far but

1568
01:15:26,960 --> 01:15:24,560
protection of the earth and what we are

1569
01:15:30,350 --> 01:15:26,970
doing to it I mean I think it's so

1570
01:15:32,870 --> 01:15:30,360
crucial to do all right so the question

1571
01:15:34,910 --> 01:15:32,880
was since you're studying all these

1572
01:15:37,610 --> 01:15:34,920
thoughts how do you feel about the

1573
01:15:41,300 --> 01:15:37,620
protection of our own planet how we

1574
01:15:46,490 --> 01:15:41,310
might be treating it I believe it's a

1575
01:15:51,050 --> 01:15:46,500
controversial statement and the reason

1576
01:15:54,860 --> 01:15:51,060
is it got hold of one of the things I

1577
01:15:57,620 --> 01:15:54,870
hate so much with this idea in

1578
01:15:59,840 --> 01:15:57,630
understand that you saw a planet so

1579
01:16:02,510 --> 01:15:59,850
we're not remotely earth-like once more

1580
01:16:04,700 --> 01:16:02,520
they were incredible distances away so

1581
01:16:06,800 --> 01:16:04,710
much so that the only way possible and

1582
01:16:09,340 --> 01:16:06,810
ending that movie was it go so

1583
01:16:14,300 --> 01:16:09,350
completely crazy

1584
01:16:16,520 --> 01:16:14,310
I think that tells you that even if life

1585
01:16:18,680 --> 01:16:16,530
is common in the universe even if there

1586
01:16:20,360 --> 01:16:18,690
are no bottlenecks even if the Fermi

1587
01:16:23,000 --> 01:16:20,370
paradox is not a thing and you can

1588
01:16:25,790 --> 01:16:23,010
develop life for all these worlds we may

1589
01:16:27,860 --> 01:16:25,800
never ever reach it and that means as

1590
01:16:33,680 --> 01:16:27,870
far as we're concerned we've only got