The planet (TOI-6894b) is a low-density gas giant with a radius a little larger than Saturn’s but with only ~50% of Saturn’s mass.
IIRC Saturn has very low density, was it lower than water? (IOW it would float) so this would be even lighter.
kbelder · 13h ago
I understand how they measure mass, but how do they measure an exoplanet's radius, especially to that precision?
teamonkey · 13h ago
Not sure in this specific case, but usually by measuring the brightness of the star as the planet passes in front of it, like a partial eclipse. That’s why most of the planets we have discovered are giants.
dotancohen · 13h ago
I did not read this paper, but typically the diameter can be inferred by the transit time.
nilamo · 13h ago
Sounds less like a planet, and more like a nebula.
mynegation · 15h ago
Did a quick calculation that star to planet mass ratio in this system is about 1400x. Does not seem that far from Sun to Jupiter (1047x) but probably crosses some supposed threshold.
Voloskaya · 15h ago
It's not really about the ratio.
To get a gas giant, you first need the formation of a "regular" planet through accretion of material in orbit. Once that regular planet is big enough, by capturing enough material, its' strong gravity allows it to start pulling in more and more gas, creating a gas giant.
It was believed that small stars can't possibly host those kind of gas giant, because small stars don't have enough material orbiting around them to create a planet big enough start the runaway process of gas accumulation needed to form a gas giant, because if there was enough material, the star would not have been small in the first place.
pavel_lishin · 14h ago
> To get a gas giant, you first need the formation of a "regular" planet through accretion of material in orbit. Once that regular planet is big enough, by capturing enough material, its' strong gravity allows it to start pulling in more and more gas, creating a gas giant.
That's just one theory, right? There are competing hypotheses where they form much like stars do, simply by enough gas coalescing to do the same job that the "regular" planet "seed" would.
scotty79 · 11h ago
If we can get a binary star why it's so hard to imagine that it might be so asymmetrical that the other star is not a star but just a gas giant planet instead?
karim79 · 12h ago
"which should not exist under leading planet formation theories"
Every time I read that something should not exist based on current understanding or theories, especially in the field of astronomy, I cry a bit.
IIRC Saturn has very low density, was it lower than water? (IOW it would float) so this would be even lighter.
To get a gas giant, you first need the formation of a "regular" planet through accretion of material in orbit. Once that regular planet is big enough, by capturing enough material, its' strong gravity allows it to start pulling in more and more gas, creating a gas giant.
It was believed that small stars can't possibly host those kind of gas giant, because small stars don't have enough material orbiting around them to create a planet big enough start the runaway process of gas accumulation needed to form a gas giant, because if there was enough material, the star would not have been small in the first place.
That's just one theory, right? There are competing hypotheses where they form much like stars do, simply by enough gas coalescing to do the same job that the "regular" planet "seed" would.
Every time I read that something should not exist based on current understanding or theories, especially in the field of astronomy, I cry a bit.