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so hello my name is Brett Morris and I'm

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currently at NASA Goddard Space Flight

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Center normal university maryland and

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i'm going to present to you some Kepler

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data particularly on a hot Jupiter which

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I promise I will try to motivate at AB

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grad calm and a particular cool feature

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for it so you've heard this a few times

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already fortunately I don't need to give

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you too much background I'm going to try

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to put in enough against that Daniels

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talk makes a little more sense as well

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transiting exoplanets are what Kepler

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studies there was the Doppler method

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where you can see plant a planet hosting

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stars move towards you and away from you

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in spectra but then also just by looking

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at the brightness of stars that host

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exoplanets if their inclination of their

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orbit takes them in front of their star

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you can see a decrease in the brightness

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of the star over time and that's what

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Kepler does Kepler has a very high

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precision photometer the CCD on it's

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very good for measuring brightness

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changes and it measures those changes

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for 150,000 stars continuously for most

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of those stars it measures once every

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half hour forest a select group of about

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500 it measures once a minute every

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minute for the four years that it took

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continuous data so that's a lot of

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photometry and we can get out a lot of

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cool effects from them so far the last

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time I checked it was 3200 candidate

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planets so we're getting up there in the

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numbers I'm going to talk to you about

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one planet in particular it's called

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happy 7b they'll have these crazy names

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fortunately mine doesn't have too many

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numbers so happy 7b is a hot Jupiter and

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this is what the transit light curve

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looks like for happy 7b that's not a

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model that's the data and you get this

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particular transit light curve by taking

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each transit light curve the Kepler

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recorded over four years or in this set

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i'm showing about two years worth of

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data and you put them one over the other

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and overlap them and then bend down the

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data that you really been out the signal

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to noise so you get very little scatter

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in your data I didn't show a fit here

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because the fit would have just been

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right on top of the data you can't

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really see it on the scale and the shape

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of the transit light curve tells you

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everything you know about the planet

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when you're doing the transit method so

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what have we learn we know that the

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period is two point

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two days if you compare that to solar

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system planets Mercury takes 88 days to

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go around the Sun this planet takes two

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so you can imagine this one's much much

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closer it's the semi-major axis of its

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orbit which is the distance it orbits

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from its star is only four times the

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radius of the star it's nearly on top of

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the star kind of sterile so again I'm

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going to motivate this later the radius

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of the planet it's about seven percent

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of the radius of the star it's pretty

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chunky and it's its orbit takes it

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within seven degrees of edge on from us

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which is why we can see it in the

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transit method so I did not show you a

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fit overlaid onto this transit light

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curve because it would be too close but

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if you do that fit and then you subtract

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the data from the fit you get these

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residuals these leftovers let's note the

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scale of these leftovers the residuals

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are in parts per million to borrow a

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term from you chemists and so these are

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very very very fine changes in

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brightness Kepler was designed to

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measure about 10 per per million change

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in brightness because that's what you

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need to see an earth radius planet at 1a

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you which was kind of a big goal of

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Kepler there's a very questionable bump

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there it's kind of a smear in the

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residuals I'm not going to claim that

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that's a discovery of something amazing

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but I'm going to ask what might that

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bump be and we're going to talk about

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that a little bit the model that we use

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to fit this is from mandolin Eagle which

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really just considers the shadow of the

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planet on the star it doesn't consider

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too many extra fancy things so if you

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get residuals from that model cool

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things could be happening especially in

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this regime where the brightness changes

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are very small so one way that you can

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get a positive bump in like heard

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residuals is by putting a dark spot on

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your star if we imagine a big dark

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sunspot like that on our cartoon model

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and the planet begins to transit you get

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a dip in the light curve just like you

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would expect from what you just saw on

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the model but as the planet passes over

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the dark spot it's as though it didn't

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fully cover the star anymore because

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compared to your other model the star

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was darker there and so you get a big

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positive bump in your light curve for

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this cartoon model if it's a very dim

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bump you only get a smaller dark spot

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that's not as dark and you get a

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positive on

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what can cause dark spots on stars you

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probably know about sun spots those are

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common on all kinds of stars on

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particularly the sun if you've ever

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gotten to observe it through a telescope

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on earth and star spots have a few

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qualities that we can use to wonder if

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they are actually the source of this

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dark spot they only persist on the scale

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of a few weeks and they happen at more

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or less well distributed latitudes

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almost-stars and so it's probably not

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likely that our exoplanet transited over

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the same spot for four years

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continuously at the same point in its

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latitude and you can measure the

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activity of a given star using spectral

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qualities of that star and according to

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some studies this isn't a particularly

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active star so we wouldn't expect

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magnetically driven star spots to be

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quite active our referee on the paper

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that we put out mention that it could

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also be due to stellar rotation it stars

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rotate really quickly kind of like a ice

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skater with their arms getting pulled

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out the outer layers of the photosphere

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of that star might get pulled away from

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the star when that happens if you get

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pulled away from the core you cool off a

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little bit cooling off darkens the

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surface and then the planet passing over

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the darkened surface could have leftover

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residuals in your light curve but that

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would have caused a symmetric difference

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across the rotation of the star we don't

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see that we just see a little bump

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that's pretty localized so how do we

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explain a small amplitude spot that's

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very localized and always seems to cross

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the planet always seems to cross over it

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at the same time over four years there's

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a very exotic effect that's a big claim

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and so we're not claiming a discovery

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we're going to claim a maybe this is

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what it is and we say maybe it's planet

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induced stellar gravity darkening

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gravity darkening happens when the tides

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of a planet pull the layers of the star

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towards the planet kind of like the

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tides of the Moon pulled the ocean

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towards the moon except when a photo

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sphere is pulled away from it stars

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mentioned a little bit earlier getting

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pulled away means cooling down cooling

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down means getting dimmer so if there

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were a dim spot on the surface of the

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star that came from the planet pulling

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tides on the surface on the photosphere

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that dark spot would slightly lag

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the orbit of the planet just like the

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tides of the the ocean slightly lagged

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the orbit of the moon because it takes

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gas time to respond to the gravitational

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kick of the planet passing over it and

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so you would expect that if the planets

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rotating around this way

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counterclockwise or you would expect

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that the dark spot would be behind the

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planet in its orbit which means the

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viewed from down below where observer

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would be in this cartoon the planet

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would transit the dark spot in between

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the beginning of the transit event and

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the middle of the transit event which is

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where we see our spot we can predict how

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much cooler the surface of the star is

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at the center of the dark spot compared

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to the rest of the star based on how

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much dimmer that spot is so if this

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actually is what we're seeing the

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effective temperature difference between

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the center of the dark spot and the rest

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of the surface of the star has two

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tenths of a kelvin gives you an idea why

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this is a bold claim but this is kind of

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thing when that you can do when you have

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high precision photometers like Kepler

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Kepler can really give us really amazing

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signs that we haven't seen from stars

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before and a lot of stellar

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astrophysicists are having a lot of fun

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with the rebirth of their field sort of

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among younger people because Kepler is

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giving them new things to look at we can

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also then use first principles of

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photosphere physics that have been done

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by other scientists over the years to

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get an idea of how the gas in a photo

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sphere should respond to a gravitational

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kick from a planet that orbits it and if

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you measure up what we believe in the

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pressure and density of the photosphere

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of this star should be against how long

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it took the atmosphere to respond and

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create the dark spot given by that phase

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lag you can get an idea of whether or

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not the timing is consistent because the

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timing is the parameter we can best

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constrain from where that bump was in

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the anomaly and they match up to be more

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or less consistent so our timing works

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out well but this is a mega three sigma

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detection and if we want to actually

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claim anything we need to wait a little

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bit longer unfortunately there's more

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Kepler data coming in still that hasn't

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been run through the pipeline even

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though a coupler is not collecting data

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currently and so there's a little bit

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hope that this model can be continued to

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I'm going to talk to you a little bit

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about the Eclipse to we've heard it

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given a few names that we had the

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occultation word before exoplanet

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scientists have had a fun time coming

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into the field of binaries which have

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existed in astronomy for a long time and

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trying to reinvent the vocabulary and

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calling occultation solipsism clips

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things but I'm going to call the this

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particular event the secondary eclipse

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we've been talking about the transit

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event which is when the planet passes in

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front of the star which you get a nice

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big signal from but when the planet goes

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behind the star there's a very small

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effect that you can measure as well as

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the planets light gets blocked out by

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the star and the light that you're

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seeing from the planet comes from

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thermal emission from the planet and

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also from reflection of the Starlight

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off of the cloud tops essentially this

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is what that light curve looks like for

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a happy seven if you sum up the two

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years of data the planet was going

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around behind the star and then as soon

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as it passes behind the star the white

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drops down to just the solar brightness

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and then goes back up again after we

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don't have crazy bumps to claim this

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time one of the things we wanted to look

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at with this is if there's variability

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in the secondary Eclipse depth because

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variability in the depth of the

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secondary Eclipse would be variability

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in how much light is coming to you from

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the planet if you were to imagine

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looking at Earth transit or eclipse

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again and again from somewhere else the

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amount of clouds on Earth's atmosphere

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would change how bright the earth

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appeared to be clouds are very

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reflective the ocean absorbs a lot of

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light so what if the cloud tops on this

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planet we're changing what if their

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color changed kind of an interesting

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question to think about this is a

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measure of the secondary Eclipse step

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over 355 eclipses there's a lot of

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scatter not a lot of smell of anything

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interesting to talk about which you

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could expect because based on the radius

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of the planet which we constrained from

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the transit light curve and where we

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know it's semi major axis puts it away

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from its star we know how much light

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hits the planet and then we can measure

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how much light we get from the planet to

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understand how much light is being

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reflected and how much is being emitted

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if you do that you come up with a very

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low albedo albedo is the fraction of

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light that comes back to you only about

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three percent of

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light or less that hits the planet gets

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reflected to you this is blacker than

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coal it's a very dark planet so most of

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the light you see in the secondary

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Eclipse is just thermal emission because

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it's hot we can also tell how hot it is

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then by how much light is coming back

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it's about two thousand seven hundred

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Kelvin that's pretty sterile and there's

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no significant variations in how bright

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it appears to be now I'm going to try to

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motivate why I'm giving you a talk about

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this planet at a beard con I promised

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you I would so as security men sioned a

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little bit earlier hot Jupiters are some

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of the easiest planets to observe in

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transmission and emission spectroscopy

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they have big extended atmospheres that

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give us the best chance to get some

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signal and so in our efforts to get

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spectra of super earth-sized planets

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ideally in one day we need to kind of

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refine our methods on the bigger easier

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targets and since they have quick

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orbital periods they're really easy to

335
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observe again and again and again and

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beat down your signal to noise like you

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saw in the nice light curve that we had

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for this planet but then there's also

339
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the question of dynamics this planet

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orbits over the rotation axis of its

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star so if its star rotates this way the

342
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planet rotates kind of at 90 degrees to

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the inclination of everything in our

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solar system so why is it doing that how

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did it get there to form a gas giant it

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can't have formed at a distance of four

347
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stellar radii from the star something

348
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catastrophic must have happened to put

349
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it there so we can ask the question if

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there were potentially habitable

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terrestrial planets in this system they

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probably would have gotten kicked out in

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the event that put this planet where it

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is so there's an interesting question of

355
00:12:58,010 --> 00:12:55,560
dynamics to that hot Jupiters raises in

356
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terms of questions of habitability of

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extrasolar planets and I'd like to thank

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my mentors dr. Harvey Mandela professor

359
00:13:06,290 --> 00:13:04,830
Drake Deming and nasa astrobiology

360
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institute that i didn't put on here

361
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and we have a few minutes for questions

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why do you think that planet has such a

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00:13:40,400 --> 00:13:37,380
low albedo I wish I had a cool answer

364
00:13:41,960 --> 00:13:40,410
for you so one of the things you're

365
00:13:44,990 --> 00:13:41,970
seeing in the transmission spectroscopy

366
00:13:46,520 --> 00:13:45,000
is we don't know that we fully

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00:13:48,650 --> 00:13:46,530
understand the compositions of these

368
00:13:51,410 --> 00:13:48,660
atmosphere is very well yet there's

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still a huge amount of uncertainty as to

370
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what's in these atmospheres one of the

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best ideas right now as to why the

372
00:14:00,440 --> 00:13:57,720
albedo is so low is that if these

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atmospheres are very very long columns

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of gases kind of like the solar

375
00:14:06,620 --> 00:14:04,590
atmosphere if you think about the Sun

376
00:14:08,780 --> 00:14:06,630
there's just this huge column of gas and

377
00:14:10,670 --> 00:14:08,790
if the Sun weren't shining there's a

378
00:14:13,040 --> 00:14:10,680
immense column of gas that could just

379
00:14:15,110 --> 00:14:13,050
absorb lots and lots of light and so

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00:14:16,640 --> 00:14:15,120
that's kind of one of the only real

381
00:14:18,740 --> 00:14:16,650
ideas out there we don't think it's

382
00:14:20,090 --> 00:14:18,750
covered in soot or something towed to

383
00:14:22,070 --> 00:14:20,100
really make it black and even so it

384
00:14:28,040 --> 00:14:22,080
wouldn't make it that black so there's

385
00:14:29,600 --> 00:14:28,050
there's a lot of questions about that so

386
00:14:32,180 --> 00:14:29,610
I was wondering if there was a moon

387
00:14:33,350 --> 00:14:32,190
orbiting that planet like could that you

388
00:14:36,230 --> 00:14:33,360
know would you actually be able to pick

389
00:14:38,390 --> 00:14:36,240
up that signal noise as well so there's

390
00:14:40,730 --> 00:14:38,400
going to be a talk on exomoons today so

391
00:14:43,430 --> 00:14:40,740
I'm going to try not to talk over that

392
00:14:45,170 --> 00:14:43,440
speaker too much but one of the ways

393
00:14:49,280 --> 00:14:45,180
that you would see moons in transit

394
00:14:51,590 --> 00:14:49,290
Lakers input in potentially one of the

395
00:14:54,350 --> 00:14:51,600
more easier senses is by trying to

396
00:14:56,120 --> 00:14:54,360
measure when mid transit is moon's orbit

397
00:14:57,260 --> 00:14:56,130
around a planet and so you don't know if

398
00:14:58,400 --> 00:14:57,270
it's going to be on the left side or the

399
00:15:00,470 --> 00:14:58,410
right side of the planet when it

400
00:15:02,240 --> 00:15:00,480
transits and so it could kind of drag

401
00:15:03,710 --> 00:15:02,250
your light curve down early or late

402
00:15:06,320 --> 00:15:03,720
depending on which side of the planets

403
00:15:08,780 --> 00:15:06,330
it's on so that would show up as a bump

404
00:15:10,880 --> 00:15:08,790
near our ingress or egress here or a

405
00:15:12,770 --> 00:15:10,890
widening of the ingress and egress

406
00:15:15,620 --> 00:15:12,780
because this is integrated over many

407
00:15:17,180 --> 00:15:15,630
years so you just see it wider so there

408
00:15:20,690 --> 00:15:17,190
would be ways to confirm that via

409
00:15:22,190 --> 00:15:20,700
spectroscopy of this planet later but we

410
00:15:25,340 --> 00:15:22,200
don't see any evidence for that here and

411
00:15:27,470 --> 00:15:25,350
chances are you can imagine the hill

412
00:15:28,670 --> 00:15:27,480
sphere the radius around the planet at

413
00:15:31,550 --> 00:15:28,680
which things could orbit the planet

414
00:15:33,950 --> 00:15:31,560
stabili is very very small because this

415
00:15:35,450 --> 00:15:33,960
planet is nearly on top of its star so

416
00:15:37,190 --> 00:15:35,460
anything that could have been there one

417
00:15:39,290 --> 00:15:37,200
day is probably dynamically stripped

418
00:15:39,290 --> 00:15:39,300
away