Nearby exoplanet may be rich in life-giving water, study finds

There are a number of exoplanets reported now that could be *water worlds*. K2-18 b is a recent example where JWST perhaps imaged evidence for biological life on it too.


From the 22-page PDF report. "4.3. Possible Evidence of Life Our potential evidence for DMS in K2-18 b motivates consideration of possible biological activity on the planet. While the present evidence is not as strong as that for CH4 or CO2, upcoming JWST observations of K2-18 b will be able to robustly constrain the presence and abundance of DMS, as discussed in section 4.5 and earlier work (Madhusudhan et al. 2021). Here we discuss the plausibility of our DMS abundance constraints from a potential biosphere on K2-18 b in order to inform future observations and retrieval studies."

I have not seen follow up reports confirming that K2-18 b is watery and has life on it yet. Need to wait and see what happens with reporting on LHS 1140b exoplanet.

The calculated temperature for LHS 1140 b is 230 K, https://exoplanet.eu/catalog/lhs_1140_b--6561/
 
Perhaps they assigned it incorrectly to the inner planet LHS-1140 c.
LHS-1140-b-and-c.jpg


But these figures are with a 20% bump in distance on either side of the std. Hz. With no fudge, LHS 1400 b is 78% farther outside the outer Hz limit using the Temp Meth., and almost 3x beyond it using the Std. Meth. (Mag,, star clsss, etc.).

Only the Hz equation for equilibrium temperature gives it hope. It seems likely, as shown, that 1140 b is likely just outside the outer Hz limit.
 
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In looking at the article's referenced paper, I don't see where they claim it is in the HZ.


[Added: They seem to be using the Kopparapu, et. al., atmospheric modeling. Using this model places LHS -1140 b at 101%, or only 1% beyond the basic model for the outer HZ limit. But, their modeling also includes a large optimistic zone, so it, no doubt, will easily fit. I didn't include their optimistic zones.

This goes to show the large variance between the models. Time will improve these, of course.]
 
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LHS 1140 b is presented as a cold super-earth at this site, showing atmosphere and molecules detected so far, temp 230 K shown.

Yes, only the "Equilibrium Temp." places it near the middle of the HZ. This model includes a bond albedo, but I think that is all too often assumed to be some a set value, namely 0.3. Earth is 0.306, but Venus is about 2.5 times higher, Mars about 1/3 less.
 
How do they know this planet's density, which requires knowledge of its mass as well as its radius; without a moon orbiting it how could anyone get a mass?
Radial velocities reveal planetary mass. The tiny wobble of a star caused by the orbiting planet is proportional to masses of both the star and planet. The stellar mass is known from its spectrum.

Perhaps knowing the size of the planet and its temp. can allow a density estimate, which would also give some idea of its mass.
 
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Radial velocities reveal planetary mass. The tiny wobble of a star caused by the orbiting planet is proportional to masses of both the star and planet. The stellar mass is known from its spectrum.

Perhaps knowing the size of the planet and its temp. can allow a density estimate, which would also give some idea of its mass.
Thanks. My intuition would have supposed the turbulent and convective motions in the star's photosphere (such as granulation) would have prevented anyone from making a measurement at a small enough velocity to detect the mutual orbital motion around the barycenter reflected in the star.
 
Thanks. My intuition would have supposed the turbulent and convective motions in the star's photosphere (such as granulation) would have prevented anyone from making a measurement at a small enough velocity to detect the mutual orbital motion around the barycenter reflected in the star.
It’s amazing how astronomers can detect such tiny motions. These motions are seen in their spectral shifts (red and blueshifts). If one line is disturbed they have plenty more to use as they all shift equally. The Sun has over 25,000 lines.
 
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