Luyten’s Star has a Habitable Zone Planet

Latest preprint from the HARPS observing program: The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293

GJ 273 (Gliese-Jahreiss star catalogue, number 273) is aka Luyten’s Star, an M3.5 dwarf some 12.2 light-years away.

To quote [lightly edited due to suspect grammar] the paper about the star’s planets:

GJ 273b is a super-Earth with a minimum mass of 2.89±0.26 Me (Earth masses) with an orbital period of 18.650 ± 0.006 days. Orbiting at a distance of 0.09110 ± 0.00002 AU from its parent star, it is grazing the inner edge of the conservative habitable zone (Kopparapu et al. 2013), but with an incident flux of 1.06 Se (Earth insolation) it is well within the HZ if one assumes the planet is surrounded by an atmosphere and accounts for GCM (Kopparapu et al. 2016). It has an equilibrium temperature in the range 206-293 K (using albedos of 0.75 and 0, respectively).

GJ 273c is among the least massive planets detected by radial velocities, with a minimum mass of 1.18 ± 0.16 Me. It completes one orbit in 4.7234 ± 0.0004 days. At the orbital distance of 0.036467 AU it receives almost ×7 the stellar flux received at Earth and has an equilibrium temperature within 327-462 K, and thus much too close to the star to be considered in the circumstellar habitable zone.

SO the Habitable Zone Super-Earth would have higher gravity than Earth with a similar composition. The radius would be ~1.33 Earth-radii, thus the surface gravity would be 1.63 gee. The inner planet is like Mercury in insolation terms, but Earth-like in mass.

One Reply to “Luyten’s Star has a Habitable Zone Planet”

  1. Ah, but what about rings? Frankh that is a good point, look at Jupiter and Saturn, none of the moons in the solar system have their own moons. You know we have discovered plasma, solids and gases in space but no liquids so how difficult would it be to have a liquid planet or moon, with a collision between a mostly water world could a water planet form if is in the habitable zone?

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