HD29458B itself was that, perhaps, HD29458B is not
in a circular orbit around it's star,
but and ever-so-slightly eccentric orbit around a star.
I'm drawing an exaggerated version.
Normally, these things are so close to their stars
that over time, their orbits have become perfectly circularized.
Having an eccentric orbit causes you to dissipate energy as
you get closer to the star you are more in
the star's magnetic field you get squeezed as you get
further away you expand, squeezing,
expanding, squeezing, expanding, expends energy.
Expending energy like that eventually circularizes your orbit.
So of a very short amount of time, this hot Jupiter should be in circular orbits.
And indeed when we look at them they're almost all in completely circular orbits.
Now, it could've been that it used to be at a much more eccentric orbit.
In fact, we see things at much more eccentric orbit.
And it has been circularizing and it just now arrived
at circular orbit and it got heated up from that.
It's possible, but if the heat is no longer being dumped
into the interior then the planet would get smaller very quickly.
So if this is the case that means that HD209458B had to
arrive at its new circular orbit yesterday on a cosmic time scale.
It's possible, but when we started finding more and more and more
of these the probability that all of these just arrived seem pretty small.
What if it's on an eccentric orbit right now?
I said that the orbit should quickly turn circular unless one thing happens.
Unless there's a second planet out here.
We're just perturbing it the entire time.
This process, by the way, is exactly what happens on Jupiter's moons.
Jupiter is orbited by Io, Europa, Ganymede, and Callisto.
And Io is on an eccentric orbit, even though
it's very close to Jupiter and should be circular.
Why is it on eccentric orbits?
Because it's being forced by Europa, which is being forced by Ganymede, which
is being forced by Callisto and it's keeping Io on this eccen, eccentric orbit.
That squeezing and releasing, and squeezing and releasing that
I described up here for the stars is happening to
Io right now, and Io because of it is
the most volcanically active body known in the solar system.
All of that energy that's being dissipated from Io
is being spued out in the form of volcanoes.
It wouldn't take much of an extrinsicity to cause heating.
There would be enough to make HD29458b inflate and
yet, with very, very, very careful measurement, no eccentric
ever been measured and, more importantly, no hint of
a second planet in that system has ever been measured.
And third importantly, more and more of these things up here have been found,
suggesting perhaps a more common process than these sort of one off ideas.
Okay.
Here's my ugly, crude drawing of the things
that I think are important going on here.
[SOUND] In this access we have things that have not very much stellar fluxating it.
They're not very hot compared to things that are very hot.
[SOUND] On this access we have, well, we
have grouped it, grouped into three different mass ranges.
Things that are between zero point three and one Jupiter mass.
Between one and one point five, between one point five and four different masses.
So it show, it shows those three separate things.
On this axis, we have the radius between Jupiter radius to up to
one point five, up to two, and in each of these three categories.
[SOUND] Now and finally, I have in this green line what you
would have, you just clearly a radiated model that I showed you before.
And you can see it clearly [SOUND] that all
of these things are well above this green line.
But a couple of interesting things are going on that
I think you can see even from my crummy drawing here.
One is that in all three cases, [SOUND] the more flex
you get, the hotter you are, [SOUND] the more inflated you are.
More inflation, more inflation, more inflation.
That is a big hint that inflation is caused by stellar heat.
[SOUND]
There's a second really good hint which is that if you
notice these lowest massed things are much more inflated up to
one point five two [SOUND] than these which barely make it
up to one point five, and these are in the middle.
The smaller you are, the more inflated you are.
This again makes sense, if it's the inflation is caused by
stellar heating, that means a certain amount of stellar heating will get
into the interior but if the object is small, that amount
of heating will call to, cause it to puff up much bigger.
If the object is, is massive already, it won't puff up very much at all.
[SOUND] Again, very good hints on what's going on.
Neither of these things would happen if,
for example, it was caused by eccentricity.
In the case of eccentricity causing puffing up it
would simply be a function of the other planet.
What the other planet was doing.
[SOUND] You'd never get these nice correlations like this.
And these correlations look really good except maybe when I draw them.