Luyten b Earth-like Planet

Luyten b Earth-like Planet

Luyten b (more commonly known as GJ 273b) is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the nearby red dwarf Luyten's Star. It is one of the most Earth-like planets ever found and is the third closest potentially habitable exoplanet known, at a distance of 12.2 light-years. Only Proxima Centauri b and Ross 128 b are closer. Discovered alongside GJ 273c in June 2017, Luyten b is a Super-Earth of around 3 times the mass of Earth and receives only 6% more sunlight than Earth, making it one of the best candidates for habitability. In October 2017, the nonprofit organization METI (Messaging Extraterrestrial Intelligence) sent a message containing dozens of short musical compositions and a scientific ″tutorial″ towards the planet in hopes of contacting any potential extraterrestrial civilizations.

Luyten b is one of the most Earth-like planets ever found. The first factor in its potential habitability is its distance from the host star. With an orbital radius of about 0.0911 AU, and given the star's low luminosity, Luyten b is orbiting well within the habitable zone. This is the region around a star where temperatures are just right for liquid water to pool on a planet's surface, given sufficient atmospheric favourite. Many other factors are also in favour of Luyten b's potential habitability. It's only about 2.9 times the mass of Earth, almost certainly making it a rocky planet. The transition between rocky and gaseous planets is believed to be around 6 ME, in which planets at or above that threshold would be more akin to Mini-Neptunes. Luyten b's minimum mass falls well below the 6 ME transition, and the chances for its actual mass to exceed that limit are only around 12%. In addition to its likely terrestrial nature, Luyten b is quite close in temperature to Earth, with a Teq of 259 K. The planet is exposed to a stellar incident flux of 1.06 times that of Earth, not enough to cause a runaway greenhouse effect. While temperatures would probably be much higher on the direct star-facing side, a thick enough atmosphere would be able to distribute heat around the planet, providing life-friendly conditions to more of the planet. If Luyten b is found to be in a spin-orbit resonance with a rotation period less or close to its orbital period, then this global heat distribution effect would be more efficient.

Unlike many other potentially habitable exoplanets orbiting red dwarfs, like Proxima b and the TRAPPIST-1 planets, Luyten b has the advantage of orbiting a very quiet host. Luyten's Star has a very long rotational period of 118 days and is not prone to powerful solar flares. Strong enough flare events can strip the atmospheres of orbiting planets and eliminate their chances of habitability; a good example of this is Kepler-438b. However, with the low activity of its host, Luyten b is likely to retain an atmosphere for billions of years, potentially enabling the development of life.

It has an Earth Similarity Index (ESI) value of 0.86, which ties Luyten b with Ross 128 b as having the fourth-highest ESI of any confirmed planet.

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