Barnard’s star b (GJ 699 b)
(Imaginary picture of Barnard’s star b – GJ 699 b credit: Ryusuke Kuroki, Natsuki Hosono and Yosuke A. Yamashiki)
GJ 699 b (Barnard’s Star b) is a super-Earth located 5 light years away form our solar system and revolves around the M type star Barnard’s Star every 233 days. It is located right around the snow line of it’s host star, meaning that it is far enough from it’s host star for ice to be able to form on the surface. The surface temperature is estimated about 105 Kelvin. It was discovered by the doppler effect and the estimated mass is about 3.2 times that of the Earth.
Barnard’s Star is the second closest star to our solar system. The first being Alpha Centauri. In the 1960s, it was reported by American astronomer Peter(Piet) van de Kamp that there exists a planet orbiting Barnard’s Star, however, this theory was not confirmed by other telescopes, and was ruled out as a data error.
The planet discovered this time was different than the planet that he discovered, but it is still a huge discovery, gaining interest from around the world. GJ 699 b was finally discovered after 20 years of observation by multiple telescopes from June 1997 to November 2017.
The data taken so far suggests that there is neither a planet in close-in orbit which is typical around M-type stars. nor a planet in the habitable zone, at least a planet larger then the Earth. Unfortunately, this exoplanet cannot be deemed a “second Earth,” but there may be many new science fiction works based off this freezing super Earth.
(Author: Takanori Sasaki)
Below is the analysis of GJ 699 b from ExoKyoto.
The estimated temperature of the planet is 105 Kelvin (minus 168 ° C.), which is about the surface temperature of Jupiter’s moon Galileo, and is estimated to be an ice world on one side, according to published papers. If there is no heat source inside the planet, it would be inhospitable for human life. The radiant energy from Barnard’s Star is estimated to be 27.49 W / m2 on average, which is less than Jupiter, and about twice as much as Saturn, but because there are many infrared components (9.99% visible rays, 89.81% infrared), it may be slightly warmer than the albedo in the visible light spectrum.
Although the planetary radius is not estimated by the radial velocity method, the estimated value from ExoKyoto is about 1.37 times the radius Earth (0.12 times of Jupiter).
Since the planet has an elliptical orbit with an eccentricity of 0.32, it moves from 0.3 to 0.5 astronomical units away from it’s host star. Therefore, it might have extreme seasons. However, the snow line (the position of the asteroid belt in our solar system) is located inside the orbit, and even with the maximum greenhouse effect limit by Kopparapu it would be located outside the maximum greenhouse effect limit (in both cases 0.13 astronomical units), it is considered to be a much colder planet than previously thought.
The activity of the star is low, so even if we consider a sufficient distance from the host star, the radiation effect due to flares is likely to be small.
(Author: Yosuke A. Yamashiki)
For more information please visit our database page below:
http://www.exoplanetkyoto.org/exohtml/GJ_699_b.html
Size of GJ 699 b – Barnard’s star b
(Orbit of GJ 699 b – Barnard’s star b)
(Position of GJ699 b – Barnard’s star b)
(Position of GJ699 b – Barnard’s star b)
