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so hi I'm Brett McGuire I'm going to be

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the session chair this morning for

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astrochemistry and for exoplanets so

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since I thought we'd probably be

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starting a little bit late I put

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together a kind of short warm-up talk

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here and it's just going to touch on a

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few different topics in astrochemistry

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and in exoplanets it's not meant to be

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comprehensive you're going to get the

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details and the people that are giving

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the talks today and it may not actually

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talk about everything that are going to

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be in the talks today it's just supposed

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to get you thinking about the topic that

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we're going to be discussing I don't

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really plan to stop for questions at the

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end but that doesn't mean that you

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shouldn't stop to either ask questions

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or more importantly give commentary

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along the way if there's any experts in

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the room that want to add something to a

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particular topic that would be fine so

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just getting started here in the

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beginning there was hydrogen and helium

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from the big bang and a smattering of a

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few other less interesting things like

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boron and lithium that hydrogen helium

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formed into the first stars and then

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these stars eventually spat out more

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complicated things so here's a periodic

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table I got off of Wikipedia that tells

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you it's actually really nicely

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color-coded right the different things

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that came out of the Big Bang things

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that are produced in large stars or have

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to be made in supernovae and then of

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course the the fun things down here that

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we make in labs so we really had to go

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through a first generation of processing

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and stars to get anything more

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complicated than hydrogen and helium

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eventually we started looking for things

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even more complicated than that up until

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the 1930s so I guess this reference here

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is 1937 the prevailing wisdom was that

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there was nothing other than atoms and

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their ions in space because it was just

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going to be too harsh there's too much

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UV radiation there's too much high

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energy stuff coming out of these stars

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for molecules to exist and people that

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we're looking for molecules were kind of

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shunned to the edges

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of of the field so there were some folks

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that said screw you we're going to look

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for them anyways so this is a spectrum

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taken with them out wilson observatory I

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there of CH the first molecule detected

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in space so the spectrums from 1941 1937

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was when the assignments were made but

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there weren't any pretty spectra in the

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papers so I couldn't show you those and

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then so this timeline there over the the

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next few years they picked up a few more

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some very simple ones cnc h plus and OH

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h and then astrochemistry as a field was

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really born here between 1963 and 1980

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this is when radio astronomy came to the

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forefront all of these small molecules

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here were being detected primarily in

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electronic transitions using visible and

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infrared telescopes it's kind of a

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challenging way to find molecules

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because you have to have a background

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light source to absorb against so you

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have to have molecules between you and

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the star and you have to know what that

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star spectrum looks like so that you can

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register what those dips in the spectra

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are with radio telescopes you can look

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for the emission for molecules that are

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rotating and tumbling over in space and

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I have a very unique spectra a unique

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spectra not a very unique spectra so

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there were 59 more molecules detected in

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this space and then since then we've

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we've gotten I put this slide together

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two years ago so 110 so now we're up to

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this number should be like 120 or 130

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where we're nearing the 200 mark for

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molecules detected in space so what is

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astrochemistry then well I call it the

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study of molecules in space where they

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are how they got there and what they are

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doing all right so chemistry does occur

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in space it's very different from the

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chemistry that occurs here on earth

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because you're in a vacuum you're at low

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temperatures most of the time and the

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time between collisions for molecules is

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very small so you can get exciting

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energetic exotic species that don't last

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for any amount of time on earth that

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have very long lifetimes in space so

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they can hang out and do interesting

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things so how do you build up some

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molecular complexity in the is M

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for a while I on molecule chemistry will

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dominate and what that means is that you

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have one neutral molecule and one eye on

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right space is a very good vacuum so

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it's very hard for molecules to find

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each other to react if you have one

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that's charged that can induce just a

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little bit of a dipole and the other

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molecule and pull an attractive force

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together so that they're more likely to

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find each other and react all right i am

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molecule reactions also have the benefit

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of being largely exothermic and

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kinetically favorable so they go fast

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and they release energy they don't take

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energy input so it's very good for the

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cold vacuum regions of space so you can

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see here you start with H 3 plus alright

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and then you can just start using H 3

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plus to transfer charge all the way up

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the line now this can build up

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long-chain hydrocarbons up to about h c

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9n all right so that's just a long

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linear chain molecules and it can do

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some organic chemistry you can get up to

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about methanol efficiently in the gas

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phase but at that point these ion

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molecule reactions drop off and you

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really can't make anything more complex

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than that what you have to do then is

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turn to these ice surfaces all right so

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you take a dust screen you freeze out

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molecules onto the surface and now

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you've concentrated all of your rare

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reactants into one place and you have a

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third body that grain surface to take

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away some of the energy so you can start

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piecing together more complex things you

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take methanol you bring a cosmic ray in

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you break it up into a methyl under an o

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H and now you just start clicking blocks

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together like legos to build up more

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complicated structures and then these

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Isis can be desorbed into the gas phase

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and detected that way so astrochemistry

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you're going to hear about some

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different talks today from the different

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disciplines is laboratory astrophysics

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these are the people that measure the

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spectra of molecules in the lab measure

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how they react with one another the

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rates and the thermodynamics there's the

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observational astronomers that go out

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and look for the molecules tell us which

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ones are there how many are there how

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excited are they and then astro chemical

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modelers that try to take the

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information from both of these groups

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pieced them together and say well you

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have this soup of molecules what can you

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make next what does this tell us about

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the chemistry

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in the region so we're also going to

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talk about exoplanets today and

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molecules have been found in the

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birthplace of exoplanets these

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protoplanetary disks this is HL tau an

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image from oma that came out last year

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the most complex molecules seemed to

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date there is methanol just came out in

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a paper a couple months ago methyl

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cyanide was out earlier than that and

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we've also seen things like formaldehyde

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and water can't see anything more

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complicated in that yet just because

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there's not a lot of those molecules

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there they're very faint and hard to

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detect but the molecules still play an

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important role in these disks there was

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a paper out just about a month ago or so

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showing that if you take the small

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little dust grains that are coated in

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ice you can actually start

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conglomerating them together not as a

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large icy chunk like a comet but

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sintered like a sintered glass crucible

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so that they have little connecting

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bridges of Isis between them and this

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allows them to aggregate into larger and

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larger structures now this hasn't been

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proven yet this is a you know a

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theoretical paper modeling paper that

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came out but it's a very good theory for

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how you can overcome the barrier between

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small icy dust grains and rocks

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planetesimals that will chunk together

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to make these exoplanets so speaking of

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exoplanets this was as of two days ago

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when I went and got this pot from the

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exoplanet database Kepler one of the

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main observatories that's been

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contributing to the detection of

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exoplanets there are thousands of them

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here this is a plot of orbital period so

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how long it takes them to orbit their

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star and the mass of the planet and then

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this I just picked the size of the dot

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to give the size relative to the radius

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of the actual planet alright so we have

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a lot of these relatively large planets

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over here that are on Jupiter mass but

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we're starting to fill in the smaller

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mass more earth-like more earth-like

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radius planets just give a brief

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overview of a couple of different ways

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that these can be detected you know we

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can hope to do some direct imaging but

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it's kind of really really hard planets

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are not bright they're hard to see

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they're far away and they tend to be

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embedded in

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dust from that forming disk and it's

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really hard to see through a dusty dusty

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gas disk to look at these planets

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directly so we can play some tricks the

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one that is used as we'll see in a

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second another slide most commonly is

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this transit photometry so you just put

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the planet in front of a star and look

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for the dip as that planet blocks some

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of the light this is what Kepler does

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and it's really good at detecting

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planets that are relatively large or

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that are small but they have a small

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star so you can see the dip it that

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comes along with them the only downside

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to this is that if you have a planet

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that takes three years to orbit your

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star you only get one dip every three

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years so you have to get lucky and be

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observing it at that point and then if

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you want reproducibility you have to

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wait another three years this is really

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good for short period planets but it's a

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little harder for the longer ones but

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we're starting to see them and the last

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one that I'll mention is radial velocity

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measurements so this is where you take a

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star here that you're looking at and as

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it as it moves relative to the earth the

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light that we see from it is going to be

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Doppler shifted all right red and blue

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but it has a planet perturbing that

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movement a little bit that's going to

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perturb that Doppler shift that we see

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and you can pull out a planet's

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perturbation of its own host star by

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looking at changes in the Doppler shift

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and here's I think my last slide because

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I am right on time to be done just a

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graph of the different ways that these

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planets have been detected over the last

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decade and a half two decades there

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you'll see that this huge bump in the

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number that we've detected from transit

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photometry that's do pretty much

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exclusively to the Kepler telescope

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which has been out hunting planets for a

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very long time now close second well

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distant second I don't know is the

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radial velocity and then there's a

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little bit here for direct imaging and

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there's a few other I don't want to say

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niche but niche detection methods which

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maybe we'll hear about today and maybe

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we won't oh very last thing exoplanet

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atmospheres if you are doing transit

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photometry you are actually capable if

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you're lucky of getting an absorption

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spectrum of that

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planetary atmosphere as it passes in

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front of the star so here's one the red

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is a model black are the data points

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showing the absorption of CO CO 2 water

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in the intern exoplanet atmosphere as it

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transited in front of its host star

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presumably over many many many averages

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of that data I think that is it yes