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Exoplanet Discoveries and Updates
#32
Exploring Whether Super-Puffs Can Be Explained as Ringed Exoplanets
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21 Nov 2019

Some exoplanets with both measured mass and radius turn out to be too light for their size - densities measuring lower than 0.3 g/cm^3. For comparison, the density of Saturn, the least dense planet in the Solar System, is roughly 0.7 g/cm^3. But Saturn also has something that's very light, but also very big, surrounding it. Yep, rings.

This paper explores whether if these anomalously low densities can be explained by the presence of an optically thick ring around the planet.
Based on the abstract (and only the abstract, ha), this hypothesis cannot explain all of them:
- Unless if their ring material consists of porous materials, it is difficult to explain Kepler-51b, 51c, 51d, and 79d - these four are, to put simply, too large.
- Kepler-18d, 223d, and 223e are likely tidally-locked, and so would not have stable rings.
- There are promising candidates: Kepler 87c and 177c, but it is difficult to test them. It would be easier to test Kepler-18d, 223d, and 223e (the tidally-locked gang).
Finally, the paper concludes HIP 41378 f, mentioning it to be a promising candidate for future observations.

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I note that the planet Kepler-47d is also pretty large. At 19 Earth masses and 7.04 Earth radii with a semi-major axis of 0.7 AU putting it beyond the tidal-lock zone, it might be a good candidate for a ringed planet.
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RE: Exoplanet Discoveries and Updates - by The Astronomer - 12-07-2019, 02:16 PM

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