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you

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[Music]

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okay hello everyone my name is Jake

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Hansen and I'm here to share some work

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that I've been doing with Steve -

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regarding disintegrating planets and

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hopefully it's not too confusing that

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Owens talk was about hydrodynamic escape

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from normal planets and these are

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disintegrating planets much lower mass

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regime but still exhibiting hydrodynamic

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escape and I think there is some overlap

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but I haven't been able to think about

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the details of exactly how they overlap

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so hopefully it doesn't confuse you

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hopefully it's enlightening to some

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bones research ok ok so why care about

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integrating planets at all the reason

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that disintegrating planets are

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important is because it's one of the few

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ways that we can get simultaneous mass

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and Composition constraints

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observational about planets the

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distribution of planet composition of

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the function of mass is ultimately

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what's going to constrain which

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planetary processes are possible so

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things relevant for life such as abiotic

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outgassing and tectonic activity are

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going to be constrained by planetary

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compositions so we're going to have and

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we're going to need to have a handle on

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the distribution of composition if we

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want to constrain the abiotic signature

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so in other words how I'm viewing this

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problem is we're getting Starlight

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passing through an atmosphere that we

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hope is from a planet teeming with life

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and the spectral signatures of that life

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are imprinted in the spectrum and we

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catch it with JWST but we need to be

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able to separate that from a abiotic

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world that also has spectral signatures

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in its atmosphere and that's going to

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depend on the compositions of the planet

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through the distribution of composition

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how you actually can get a composition

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is actually a very involved process the

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first step is to understand how these

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planets are disintegrating which is

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through Parker winds which is a steady

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state mass loss hydrodynamic mass loss

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and then we're going to use the per

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queuing formalism to constrain what

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properties are allowed so the mere

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existence of a steady state parker wind

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actually puts some constraints on what

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mass planet you can have as well as the

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mean molecular weight for that planet's

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atmosphere so this is different than

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other forms of escape

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that are not steady states this project

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is all through the lens of steady state

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and then once we have the mass we can

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calculate the velocity structure of the

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wind so ultimately these winds are

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accelerated beyond the escape velocity

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of the planet and so the velocity

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structure tells you when the wind will

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escape and then we're also going to

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couple the velocity structure to a

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mineral condensation code so that's

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really the unique portion of this

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project is going to be coupling the

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hydrodynamic escapes from my parker

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winds to a condensation code that tells

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you how gas vapor condenses into dust

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and that's ultimately well ultimately

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what you want to compare to spectra from

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JWST but unfortunately for you all this

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project is just focused on the first

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portion of this project so what can you

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learn about planets that are hydro

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dynamically losing mass via Parker winds

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it's a little bit more about integrating

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planets you may be surprised to know

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that there's only four known

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disintegrating planetary systems three

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around M stars and one around a white

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dwarf observations tell us that these

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planets are extremely low mass there's

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upper limits on their masses they're hot

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rocky and ultra short orbits so periods

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of order of one day you can back out the

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mass loss rates from the transit depths

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and people have calculated that it's

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about one earth mass per GigE or mass

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loss rate so for a low mass mercury mass

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planet the mass loss rates are quite

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substantial and the general thinking is

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just these planets are too hot to hold

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on to the material so surface materials

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being vaporized this is different than

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losing an atmosphere and that vaporized

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material then forms an atmosphere which

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is kicked off as for how they're

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actually detected there's two big

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telltale signs that you're looking at

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it's integrating planet the first is

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variable transit depth you can see this

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is a periodic signal but it varies in

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depth and the second is an asymmetric

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transit profile so you can see the

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ingress is a much steeper gradient than

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the egress and that's due to the diffuse

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portion of the tail taking a long time

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to exit the face of the star so I've

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mentioned Parker winds a few times a

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little bit of historical context they

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were originally developed by Eugene

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Parker to describe the solar wind so

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it's the exact same physics

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from solar wind physics but now we're

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applying them to exoplanet so we're you

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know 40 50 years 60 years behind but

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we're there now and Cayman told me that

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if I put too many equations he would

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personally kick me off the stage but I

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slimmed it down and these are the basics

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all that you really need to know is that

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it's a force equation where gravity and

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pressure is trying to balance if the

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right-hand side of that top equation 0

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that's hydrostatic equilibrium if you

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allow for a nonzero acceleration then

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you'll get the potential for a parker

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winds the only other piece of

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information you need are a law for

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conservation of mass and an equation of

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state which we have some a polytope here

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and then the results we'll see how many

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is too many here the results is that you

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get the wind velocity as a function of

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distance so that's really what we're

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after this dimensionless variable psy is

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velocity and distance is it mentioned

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this where you'll see and then we also

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have the June's parameter which is the

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ratio of the gravitational potential

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energy to the thermal energy and that

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kind of characterizes the likelihood of

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of planets have this wind that was

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abstract if we were to imagine putting

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mercury in a radiation environment of

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2100 Kelvin we could ask ourself what

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would happen to our beloved mercury and

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basically you can see that winds can

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develop and about eight mercury radii

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away the wind would reach escape

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velocity so mercury would undergo mass

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loss what you don't see in this plot

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that's very important is that the mean

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molecular weight of the atmosphere is

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incredibly fine-tuned for this plot this

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is a six hydrogen mass atmosphere if I

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try to do the same thing for five or

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seven there's no Parker wind solution

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and so the generalization of that is

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that there's two different regimes for

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Parker winds to you have to operate

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between them in the upper regime so you

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can see this is planet mass and

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atmospheric mean molecular weight and

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the upper regime your planet is too

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massive or cold for your wind to

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overcome gravity in these shaded regions

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those are different temperatures that

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would have a Parker wind solutions you

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can see for mercury if you knew the mass

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then you could calculate there's a very

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small mean molecular weight that would

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allow for a study state Parker wind to

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develop and these are for different

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temperatures and the lower regime is

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of the more subtle one in this regime

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the you can think of as too little mass

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for wins but I think it's easier to

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think of it as having too much thermal

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energy for wins to hold their shape so a

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parker wind is a subsonic to supersonic

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wind and if you start your surface lots

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velocity supersonic there's no solution

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that kind of keeps that structure

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propagating outward your your equation

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blows up and you basically don't have a

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wind so that's not to say these planets

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can't lose mass they probably are losing

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mass through non steady state means but

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it is there is a lower limit for steady

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state Parker wins and so the

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implications of that are that these

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Parker winds are extremely fine tuned if

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you want to assume steady state mass

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loss you have to be in a very small

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parameter space what you would expect

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instead is for a periodic or sporadic

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mass loss corresponding to brief periods

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of time in the Parker wind regime and

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the process itself may be self regulated

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or throttled so you can imagine building

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up an atmosphere slowly heating your

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surface temperature until eventually you

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reach the point where you're in the

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steady state mass loss regime all of a

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sudden you get these bulk ejection

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events and then you cool down and get

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back to where you started originally and

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so it's my tip of the hat towards the

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alien mega-structure stars perhaps this

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is it but I would like to share this

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quote with you from a BuzzFeed article

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it says no amount of extreme mass so far

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has figured out what is going on with

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star named pic4 6 - 85 - and I kind of

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laughed a sext I thought it sounds

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childish and I thought wait that's

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basically exactly exactly what it is so

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anyways a few applications of this we

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can look at something like 55 Cancri E

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you see it's a super earth very hot 2000

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Kelvin the period is less than a day and

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high density so it fits the bill for

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what a disintegrating planet should be

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but if you plot the mass if you plot the

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mass of 55 Cancri you can see that there

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is absolutely no reasonable temperature

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so the green line is 3000 Kelvin surface

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the blue is 1300 you can see there's no

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solution that comes in contact with the

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mass of almost 10 earth mass it's just

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too massive of a planet

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so if we try to lower the mass of the

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planet so this is the point eight five

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earth-mass planet Trappist 1b this

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planet if it were a two thousand Kelvin

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it could it would have a solution for

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Parker winds but the problem is that

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it's at 400 kelvins

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this planet is just too cold and ideally

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I would like to show you something in

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the other regime of this to a planet

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that's too small or too hot for a Parker

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wind but the problem is that if you get

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planets that are that low of mass we

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have no way of detecting them to begin

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with unless so disintegrating so

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basically I have two examples for

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planets that are too massive or too cold

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but no examples for too hot or too light

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because they're impossible to detect but

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we do have these known disintegrating

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planets these are low-mass planets that

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exhibit almost steady state mass loss

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and I say almost because each period

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they are continuously losing mass but

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those small variations in transit depths

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show that it's not perfectly hydro it's

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not a perfectly steady state system so

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this plot now these these colors regions

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show the solution space for those

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different planets so I said there were

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four but two of them have the same

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effective temperature so here I'm taking

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the surface temperature to be the

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effective temperature and you can see

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this is the allowed solution space and

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even without knowing the molecular

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00:10:26,000 --> 00:10:24,000
weight of these planet's atmosphere you

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can put a constraint on their mass just

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by assuming that the mean molecular

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weight of the atmosphere is somewhere

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less than 60 if you were to get better

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constraints on the mean molecular

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weights of this atmosphere you could put

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very tight constraints on the allowed

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mass for these planets but without the

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mean molecular weight constraint you can

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still concern them to be somewhere

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between 10 to the negative 3 earth mass

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and one or it's not so the upper limit

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obviously is not that surprising you

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need a very small mass planet to be able

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to eject to end but the lower limit is

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somewhat counterintuitive and that's

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basically because I think the wind can't

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hold its shape so anyways the part that

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00:11:03,380 --> 00:11:01,380
would be nice to tell you more about is

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the mineral condensation portion so I

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can give you a small teaser for that and

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basically what you do is you assume your

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planetary parameters so you assume your

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surface temperature and stoichiometric

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composition and then you calculate the

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velocity profile of your wind so your

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wind profile depends on your

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our mass and surface temperature and

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then you will compute two relevant time

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scales the first is basically the time

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scale for gas to condense onto grains

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and the second is the time for the win

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the time scale for the wind to diffuse

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if you set these two time scales equal

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you can calculate what's called the

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freeze-out radius which is defined as

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the point beyond which the wind is

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moving too fast for your particles to

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condense and so that will be the final

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distance at which you're actively

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condensing minerals and then what what

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the plan is is to iteratively condense

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from the surface out to this freeze-out

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radius and compute your mineral

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abundances and then compare that to

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observed spectrum and in theory you can

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go the other way but obviously this

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isn't the portion that we worked out in

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all the detail so in summary

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compositional constraints are very

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important because we're going to need

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them to put constraints on the abiotic

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signatures of planets disintegrating

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planets allow simultaneous mass and

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compositional constraints which is very

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important and the main results from this

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00:12:26,449 --> 00:12:22,799
soccer that parker winds are very

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fine-tuned solution space and a periodic

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or throttled mass loss is probably more

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likely where you pass in and out of this

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regime where you're capable of launching

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steady-state winds and for the known

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planets the mass constraints that we

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would put on them are somewhere between

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10 to the negative 3 and 1's mass i just

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like to quickly thank Steve for his help

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as well as my adviser Sarah Walker in

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the rest of our group for their help and

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advice and if you have any questions

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please email me at Jake Hansen asu.edu

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thanks Jake we have about three minutes

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for questions

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00:13:07,080 --> 00:13:05,260
Wanda hi Jake I am so sorry that I did

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not mention this previously I see you

353
00:13:17,100 --> 00:13:12,180
almost every day but you do realize that

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wd1 145 and the body that's orbiting it

355
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and what you're calling a disintegrating

356
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planet is on a nearly circular orbit

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that passes through the white door Roche

358
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radius at least twice during orbit right

359
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that's wise disintegrating but Parker

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wind treatment that is applicable to the

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other planets I don't think you should

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include the WD one one four five rocky

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body with it okay alright I do yeah the

364
00:13:49,470 --> 00:13:46,120
this treatment is just for a given

365
00:13:51,210 --> 00:13:49,480
surface temperature and so I guess for

366
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the point of my argument it's just a

367
00:13:55,740 --> 00:13:53,620
theoretical planet in that system would

368
00:13:57,180 --> 00:13:55,750
have this math constraint and that

369
00:13:59,400 --> 00:13:57,190
system is also complicated because

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there's the six different bodies and so

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I would say the be known disintegrating

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planets the canonical ones that I'm

373
00:14:09,870 --> 00:14:07,660
thinking about are the three around the

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00:14:11,940 --> 00:14:09,880
M stars okay good yeah the white dwarf

375
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is a little ratchet in this whole mess

376
00:14:15,810 --> 00:14:14,080
right no but they're the reason why

377
00:14:17,130 --> 00:14:15,820
they're just integrating right cuz it's

378
00:14:18,510 --> 00:14:17,140
passing through the roof yeah and that

379
00:14:22,710 --> 00:14:18,520
is not the case for any of the other sir

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00:14:25,440 --> 00:14:22,720
okay hi Russell dietrich University of

381
00:14:28,410 --> 00:14:25,450
Washington I was curious if the Parker

382
00:14:30,030 --> 00:14:28,420
wind if it's ever if the mass loss is

383
00:14:33,210 --> 00:14:30,040
ever really strong enough that you would

384
00:14:36,630 --> 00:14:33,220
get some change in the orbit of the

385
00:14:38,190 --> 00:14:36,640
planet do you see or orbital be K would

386
00:14:40,200 --> 00:14:38,200
you expect orbital decay or anything

387
00:14:42,210 --> 00:14:40,210
like that well unfortunately don't have

388
00:14:45,540 --> 00:14:42,220
many of these systems but there was the

389
00:14:47,430 --> 00:14:45,550
2014 wrap-up or at all papers there

390
00:14:48,990 --> 00:14:47,440
seems to be a feedback mechanism where

391
00:14:51,330 --> 00:14:49,000
you see the depth of the transit on a

392
00:14:52,620 --> 00:14:51,340
year average is getting shallower and

393
00:14:54,450 --> 00:14:52,630
shallower and so that seems to imply

394
00:14:57,090 --> 00:14:54,460
that this planet is losing so much mass

395
00:14:59,220 --> 00:14:57,100
that the feedback from the mass loss has

396
00:15:00,990 --> 00:14:59,230
affected the mass of the planet itself

397
00:15:03,270 --> 00:15:01,000
in a way that dictates the mass loss

398
00:15:04,950 --> 00:15:03,280
again so you can see a feedback process

399
00:15:07,580 --> 00:15:04,960
that the amount of mass is oozing is

400
00:15:10,970 --> 00:15:07,590
actively affecting its future mass loss

401
00:15:12,380 --> 00:15:10,980
but that's the only case that had some

402
00:15:16,519 --> 00:15:12,390
sort of feedback mechanism

403
00:15:18,380 --> 00:15:16,529
thanks we have time for one more hi Bill

404
00:15:21,820 --> 00:15:18,390
diamond from the SETI Institute just a

405
00:15:25,790 --> 00:15:21,830
question on the graph you had with the

406
00:15:27,680 --> 00:15:25,800
various light curve depths because they

407
00:15:30,440 --> 00:15:27,690
did seem quite random but they didn't

408
00:15:32,990 --> 00:15:30,450
seem to me to indicate a trend toward

409
00:15:34,400 --> 00:15:33,000
you know suggesting continual mass loss

410
00:15:35,390 --> 00:15:34,410
they seemed kind of all over the place

411
00:15:38,660 --> 00:15:35,400
mm-hmm

412
00:15:40,280 --> 00:15:38,670
so I think that what's the point that

413
00:15:41,810 --> 00:15:40,290
I'm trying to make with the steady state

414
00:15:43,490 --> 00:15:41,820
mass off of those planets is the fact

415
00:15:45,769 --> 00:15:43,500
that they're continuously losing mass

416
00:15:48,710 --> 00:15:45,779
puts them in and around the steady-state

417
00:15:50,480 --> 00:15:48,720
regime and so when I talk about the

418
00:15:53,600 --> 00:15:50,490
throttle to a periodic mass loss what

419
00:15:56,720 --> 00:15:53,610
I'm thinking of as planets that are far

420
00:15:58,400 --> 00:15:56,730
from the regime of losing mass via

421
00:16:00,380 --> 00:15:58,410
Parker wins and then they enter the

422
00:16:02,240 --> 00:16:00,390
regime briefly only to lose an

423
00:16:04,160 --> 00:16:02,250
atmosphere and then go back to being far

424
00:16:05,840 --> 00:16:04,170
from the regime and so I picture these

425
00:16:08,090 --> 00:16:05,850
planets as at least being close to the

426
00:16:11,390 --> 00:16:08,100
steady-state regime and the fact that

427
00:16:13,010 --> 00:16:11,400
they're variable the depth of the

428
00:16:14,990 --> 00:16:13,020
transit is variable I take to mean that

429
00:16:16,700 --> 00:16:15,000
obviously the surface temperature those

430
00:16:18,170 --> 00:16:16,710
planets isn't fixed and you do get

431
00:16:19,700 --> 00:16:18,180
fluctuations in the amount of mass

432
00:16:21,770 --> 00:16:19,710
you're actually losing but they're very