Exoplanet Discoveries and Updates

[AstroChara]

The Perpetua projects can be relocated to Gl752Ab. The important thing is having the potential resources to build infrastructure.

Well, I think some asteroids and maybe a few small rocky planets (+ an ice giant for fuel?) are enough. Easier to utilize than giant planets and enough for most purposes unless you're >S2, really.

[AstroChara]

Exploring Whether Super-Puffs Can Be Explained as Ringed Exoplanets
(link)
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.

[AstroChara]

More planets!
TESS announced several new planets, including its first Earth-sized habitable zone planet at TOI-700, and a circumbinary planet at TOI-1338. Both are outside the Inner Sphere.

In addition, several planets have been found by reanalyzing old data, including Gliese 229 Ac (the Dustbuilders' system) and Gliese 180 d. Both are more massive than 7 Earth masses, however, and are very likely to be sub-Neptunes.

[stevebowers]

We already have GL229Ab in the Dustbuilders article, so GL229Ac can be accomodated quite easily. This is quite a tight binary for multiple planets, suggesting that binary planetary systems are not particularly rare.

[AstroChara]

We already have GL229Ab in the Dustbuilders article, so GL229Ac can be accomodated quite easily. This is quite a tight binary for multiple planets, suggesting that binary planetary systems are not particularly rare.

Researchers were unable to find Gliese 229 Ab in the 2019 paper. Seeing that it basically does nothing to the article we could easily move Tessera elsewhere. Ideally not as a moon though, we've had too many of that.

[AstroChara]

Researchers were unable to find Gliese 229 Ab in the 2019 paper. Seeing that it basically does nothing to the article we could easily move Tessera elsewhere. Ideally not as a moon though, we've had too many of that.

Ah, sorry. It seems Gliese 229 Ab has merely been demoted to an unconfirmed planet. We'll see whether if it's a real planet or not later.

[AstroChara]

Coherent low-frequency radio emission was detected on the quiescent M4.5 star GJ 1151. I don't know the exact details nor how it actually works, but it is analogous to the interactions between Jupiter's magnetosphere and its moons. Therefore, some researchers suggested that this may be evidence of an orbiting planet.

Details about this world are almost nonexistent right now, but we do know that
- Its orbital period is somewhere between 1-5 days
- Its minimum mass is no more massive than 5.6 Earth masses

Next, scientists are trying to confirm the planet through radial velocity, which should give us much more precise values for the orbital period and minimum mass.

[stevebowers]

Excellent! A new method of detecting planets!
...perhaps.

[AstroChara]

Excellent! A new method of detecting planets!
...perhaps.

It might not give you precise numbers, but at least you know where to look.
 
GJ 1151 is pretty close; it's roughly 26.2 light-years away from us, so this discovery is interesting in my book. The period of 1-5 days is, judging from the star spectrum, too close to be habitable, but that's not really what I signed up for 

[Will the Wanderer]

Astronomer, you seem like the right person to ask this. Water worlds, or giant liquid worlds like described here are news to me. Are these a relatively new idea or have they been around? Has the OA delved into these much?