Researchers are “in the midst of a heated debate” over whether the planets orbiting the 70% of stars classed as red dwarfs are habitable. For one thing, do they have an atmosphere. The question, of course, affects calculations of habitable planets. One researcher is disappointed to report findings that suggest maybe not:
[Laura] Kreidberg, who is also at the CfA, has been in the daily habit of checking for new results from NASA’s Transiting Exoplanet Survey Satellite (TESS), a space-based observatory hunting for nearby planets that “transit” their host stars—flitting across the faces of those stellar hosts and casting shadows toward our solar system. Among TESS’s first discoveries was the rocky world LHS 3844 b, located just under 49 light-years away, and Kreidberg quickly recognized that it was in an ideal position to test the atmospheric-retention capabilities of red dwarf exoplanets.Adam Mann, “Scientists mull the implications of an airless alien planet” at Scientific American
Kreidberg’s team estimated that the promising planet had temperatures of –273 degrees Celsius on the night side and 767 degrees C on the day side, which implies little or no atmosphere to moderate it.
So don’t found your Air BnB on catering to aliens just yet.
Most known terrestrial planets orbit small stars with radii less than 60 per cent of that of the Sun1,2. Theoretical models predict that these planets are more vulnerable to atmospheric loss than their counterparts orbiting Sun-like stars3,4,5,6. To determine whether a thick atmosphere has survived on a small planet, one approach is to search for signatures of atmospheric heat redistribution in its thermal phase curve7,8,9,10. Previous phase curve observations of the super-Earth 55 Cancri e (1.9 Earth radii) showed that its peak brightness is offset from the substellar point (latitude and longitude of 0 degrees)—possibly indicative of atmospheric circulation11. Here we report a phase curve measurement for the smaller, cooler exoplanet LHS 3844b, a 1.3-Earth-radii world in an 11-hour orbit around the small nearby star LHS 3844. The observed phase variation is symmetric and has a large amplitude, implying a dayside brightness temperature of 1,040 ± 40 kelvin and a nightside temperature consistent with zero kelvin (at one standard deviation). Thick atmospheres with surface pressures above 10 bar are ruled out by the data (at three standard deviations), and less-massive atmospheres are susceptible to erosion by stellar wind. The data are well fitted by a bare-rock model with a low Bond albedo (lower than 0.2 at two standard deviations). These results support theoretical predictions that hot terrestrial planets orbiting small stars may not retain substantial atmospheres. (paywall)
See also: Researchers: Toxic Gases Would Slow Emergence Of Life On Exoplanets
Recent Finding: The “Water World” Exoplanets Are Not Habitable Ocean Planets
and (hope never dies)
Researcher: Why Finding Extraterrestrial Life “Now Seems Inevitable,” Maybe Soon
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