Kepler-1638 b

Kepler-1638 b is one of 1,284 exoplanets discovered (2016) by NASA’s Kepler Space Telescope, which looks for exoplanets using the transit method. This method also estimates the size of the exoplanet when it is discovered (for more information on the transit method -> http://www.exoplanetkyoto.org/study/method/). Kepler-1638 b has a radius 1.87 times that of the Earth (Molton et al. 2016) and the orbital length radius (distance from the host star, Kepler-1638) of the planet Kepler-1638 b is about 0.745 AU (Torres et al. 2016). This led to the thought that Kepler-1638 b could be a planet very similar to Earth when focusing on the size and orbital length radius.

The host star, Kepler-1638, is also considered to be similar to our Sun. Its radius is 0.95 times larger than the Sun, its mass is 0.97 times greater, and its temperature is 5,710 K, almost the same as the surface of the Sun (5,772 K.) Does Kepler-1638 have an atmosphere or a magnetic field? Could Kepler-1638 b be an Earth-like planet and have the possibility of sustaining life?

For more information about Kepler-1638 b, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/Kepler-1638_bJP.html

GJ163c

GJ 163 c is located 48.9 light-years (15.0 parsecs) from our solar system and was discovered in 2012 orbiting its host star GJ 163. The apparent magnitude of the host star is 11.8 and the absolute magnitude is 10.9. GJ 163  is about 0.4 the mass of our sun and has about 0.4 the radius. Its surface temperature is 3500 K and is a spectral M3.5 type star. The planet GJ 163 c orbits the star every 25.6 days, it’s orbital radius is 0.13 SEAU.

For more information about GJ 163 c, please visit the ExoKyoto database:

http://www.exoplanetkyoto.org/exohtml/GJ_163_cJP.html

GJ 180 c

GJ 180 c was discovered in 2014 orbiting its host star GJ 180. The apparent magnitude of the host star is 10.9 and the absolute magnitude is 25.0. GJ 180  is about 0.4 the mass of our sun and has about 0.4 the radius. Its surface temperature is 3371 K and is a spectral M2V type star. The planet GJ 180 c orbits the star every 24.3 days, it’s orbital radius is 0.13 SEAU.

For more information about GJ 180 c, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/GJ_180_cJP.html

GJ 273 b

GJ 273 b is located 12.4 light-years (3.80 parsecs) from our solar system and was discovered in 2017 orbiting its host star GJ 273. The apparent magnitude of the host star is 9.9 and the absolute magnitude is 12.0. GJ 273 is about 0.3 the mass of our sun and has about 0.3 the radius. Its surface temperature is 3382 K and is a spectral M3.5 type star. The planet GJ 273 b orbits the star every 18.6 days, it’s orbital radius is 0.09 SEAU.

GJ 273, also known as Luyten’s Star, is a red dwarf located 12.4 light years away in the Canis Minor constellation. GJ 273 is a small and dark star, slowly consuming fuel for nuclear fusion reactions; its radius and mass are both about 0.3 times smaller than the Sun’s, and its surface temperature is about 3,000 degrees C, lower than the Sun’s surface temperature of about 6,000 degrees C.

Observations of the star GJ 273 with the HARPS spectrograph over a period of 14 years, starting in 2003, revealed that it has two planets. GJ 273 b has an orbital period of about 19 days and is around three times as massive as the Earth. (The distance between the Earth and the Sun is 1 AU.) Looking at GJ 273’s size and temperature, it is possible that liquid water may exist on the surface of GJ 273 b and there could be a possibility of life.

GJ 273 b is the second closest planet to Earth that is thought to be habitable, after Proxima Centauri b. It would take only 25 years for radio communication to reach the Earth. This is why there is a project called “Sónar Calling GJ 273 b” which transmits music from Earth. The music signal, which was transmitted in October 2017 from the antennas of the EISCAT Scientific Association in Norway, will reach GJ 273 b on March 11, 2030.  It would be amazing if an intelligent creature from GJ 273 b could hear the radio waves from Earth and enjoy the music.

(文責　大山航　木村なみ)
Refrences:
(1)The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ3138, GJ3323, GJ273, GJ268, and GJ3293
N. Astudillo-Defru1,2, T. Forveille2, X. Bonfils2, D.S＇egransan1, F.Bouchy1, X. Delfosse2, C Lovis1, M. Mayor1, F. Murgas2, F. Pepel1, N.C. Santos3,4 S Udry1, A.Wunsche2
(2) http://phl.upr.edu/projects/habitable-exoplanets-catalog
(3) exokyoto
(4) https://www.sonarcalling.com/en/

For more information about GJ 273 b, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/GJ_273_bJP.html

GJ 422 b

GJ 422 b was discovered in 2014 orbiting its host star GJ 422. The apparent magnitude of the host star is 11.5 and the absolute magnitude is 25.0. GJ 682  is about 0.3 the mass of our sun and has about 0.4 the radius. Its surface temperature is 3323 K and is a spectral M3.5V type star. The planet GJ 422 b orbits the star every 26.2 days, it’s orbital radius is 0.12 SEAU.

For more information about GJ 422 b, please visit the ExoKyoto Database:

http://www.exoplanetkyoto.org/exohtml/GJ_422bJP.html