lezboyd t1_jd9ee3t wrote
How is the planet hot enough to have such an atmosphere when it's so so distant from its host stars? Many times farther than Pluto is from the Sun.
rocketsocks t1_jda2reu wrote
The planet in question is on the borderline of being almost massive enough to be classified as a brown dwarf. Just like proto-stars and brown dwarfs, planets receive a great deal of heating from accretion and gravitational contraction. And due to the square-cube law the more massive an object is the more of this energy is released and the longer it is retained because surface area grows more slowly than volume. The result is that there is a great deal of internal heat that is retained within gas giants, especially the more massive ones.
EarthSolar t1_jda578n wrote
It’s also really, really young, at 140 million years according to Wikipedia. Jovian worlds and brown dwarfs form hot, and at young age they can be as hot as the coolest stars at ~2000-3000 Kelvins. They cool over time, but the rate is slowed from what you’d normally expect due to gravitational contraction converting planet mass’ gravitational potential energy into thermal energy as the planet shrinks down.
PineappleLemur t1_jdby2io wrote
Distance from sun doesn't mean much really..
Any planet with a thick atmosphere / high gravity will generally be hotter just from internal activity and age.
lezboyd t1_jdbyldi wrote
Maybe. But this one is 9 times more distant than the distance between Sun & Pluto, is what caught my eye.
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