AAS: estimate that half of sunlike stars have habitable planets

[notFritzArgelander]

https://aasnova.org/2020/11/17/around-h ... le-worlds/

[ThinkerX]

that might be a little optimistic, even with the 'potential' tag. Age of the star and orbital eccentricity need to be factored in. Alas, the data becomes sparse right when the calculation gets interesting.

[helicon]

Hard to imagine that half of the sun-like stars in the galaxy would harbor habitable worlds. So far, planets with liquid water and significant oxygen atmospheres have been scarce to nonexistent, but I suppose it is a matter of not being able to identify those signatures yet.

[notFritzArgelander]

Hard to imagine that half of the sun-like stars in the galaxy would harbor habitable worlds. So far, planets with liquid water and significant oxygen atmospheres have been scarce to nonexistent, but I suppose it is a matter of not being able to identify those signatures yet.

Either that or the estimate is flawed. I don't have much confidence in it.

[notFritzArgelander]

OK, I've looked at the paper and this is basically a Bayesian update of the Drake equation based on Kepler data. If anything has been learned from the exoplanet searches it is that there are many devils lurking in the dynamical details of planet systems. This work ignores that and simply seeks to estimate the number of planets in "the habitable zone". So it ignores the differences in dynamics that make a difference between Mars, Earth and Venus for instance. All three would count as habitable for the purposes of this work.

https://arxiv.org/abs/2010.14812

We present occurrence rates for rocky planets in the habitable zones (HZ) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η⊕ as the HZ occurrence of planets with radius between 0.5 and 1.5 R⊕ orbiting stars with effective temperatures between 4800 K and 6300 K. We find that η⊕ for the conservative HZ is between 0.37+0.48−0.21 (errors reflect 68\% credible intervals) and 0.60+0.90−0.36 planets per star, while the optimistic HZ occurrence is between 0.58+0.73−0.33 and 0.88+1.28−0.51 planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates using both a Poisson likelihood Bayesian analysis and Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is about 6 pc away, and there are about 4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.