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Ultra Hot Jupiters


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Okay, apparently today is now National Hot Jupiter Day, because there have been FIVE studies characterizing various planets of this category. 

All jokes aside, four of today’s papers dealt with a new category of planet: Ultra Hot Jupiters or Extremely Irradiated Hot Jupiters. These are the absolute hottest gas giants in existence, with dayside temperatures in excess of 2,000 K. Some of the most notable examples include WASP-12b, WASP-33b, and Kelt-9b. The four papers studied HAT-P-7b, WASP-121b, and WASP-103b. One of the studies was about atmospheric characteristics of UHJs. 

https://arxiv.org/abs/1805.00424

https://arxiv.org/abs/1805.00096

https://arxiv.org/abs/1805.00038

https://arxiv.org/abs/1805.00029

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Great balls of fire :D Still... are hot gas giants the norm, or their sheer number is just the effect of observation bias? I hope they are fairly rare - because migration of a gas giant into low solar(?) orbit is bound to cause mayhem  and destruction among smaller, rocky planets of the inner system.

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2 hours ago, Scotius said:

Great balls of fire :D Still... are hot gas giants the norm, or their sheer number is just the effect of observation bias? I hope they are fairly rare - because migration of a gas giant into low solar(?) orbit is bound to cause mayhem  and destruction among smaller, rocky planets of the inner system.

observation bias an huge planet very close to the star is way easier to detect either with transit or wobble. 
Think about it, an planet very close to the star with an random inclination has an very high chance of eclipsing the star, out at earth orbit this is very unlikely 
 

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I read a number of papers about hot Jupiters at arxiv.org when made myself a Kepler 7b analogue in Kopernicus, and from what I recall the answer is a little of both.  There is some observation bias, because large exoplanets orbiting close to their star are easier to detect with our current methods.  But even allowing for this bias, hot Jupiters appear to be more common than we initially expected.

The migration of giant planets through the inner system might not be as destructive one may think though, since simulations have shown that the protoplanetary disk can re-form behind them as they pass.  A side effect of this migration is that the inner system would be water-rich, and any rocky planets would likely be water worlds with oceans hundreds of kilometers deep.  There are also a few known hot Jupiters in systems that also include terrestial planets.  I'm away from my home computer right now, but later tonight I can cite some references if anybody wants (I kept notes).

Edited by JetJaguar
Punctuation.
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5 minutes ago, wumpus said:

How much can you heat a Jupiter before it becomes a star?  And does it really count as a star if it requires external heating to maintain criticallity?

You can't do that. It can be as hot or hotter than a star I suppose, but it has to have a certain mass to sustain fusion in its core. And that's around 14 x the mass of Jupiter (But that's only for Deuterium fusion), up to around ~80 Jupiter masses or so. Above that, and you have a legitimate star.

Edited by Spaceception
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