51 Eridani b is a "Jupiter-like" planet that orbits the young F0 V star

51 Eridani 51 Eridani is a star in the constellation Eridanus. It has an apparent magnitude of 5.22, meaning it is just visible to the unaided eye in suburban and rural skies. The primary star's absolute magnitude is 2.87. There is also a binary st ...

, in the constellation Eridanus. It is 96 light years away from the solar system, and it is approximately 20 million years old.

Discovery

51 Eridani b was announced in August 2015, but was discovered in December 2014 using the

Gemini Planet Imager The Gemini Planet Imager (GPI) is a high contrast imaging instrument that was built for the Gemini South Telescope in Chile. The instrument achieves high contrast at small angular separations, allowing for the direct imaging and integral field spec ...

, an international project led by the

Kavli Institute for Particle Astrophysics and Cosmology The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) is an independent joint laboratory of Stanford University and the SLAC National Accelerator Laboratory, founded in 2003 by a gift by Fred Kavli and The Kavli Foundation. It is h ...

. 51 Eridani b is the first exoplanet discovered by the Gemini Planet Imager. The Gemini Planet Imager was specifically created to discern and evaluate dim, newer planets orbiting bright stars through “direct imaging.” Direct imaging allows astronomers to use adaptive optics to sharpen the resolution of the image of a target star, then obstruct its starlight. Any residual incoming light is then scrutinized, and the brightest spots suggest a possible planet. Prior to the discovery of 51 Eridani b, each of the directly imaged worlds previously discovered had been gas giants many times the mass of Jupiter.

Physical characteristics

The planet has a mass at least 2.6, but not more than 11. Its radius is about 1.11 times the radius of Jupiter. It orbits 11.1 AU from its host star, and has an orbital period of roughly 10,000 days. The average temperature is 807 K, which is substantially hotter than the 130 K average temperature of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

, the planet in the Solar System of closest size.

Atmosphere

'51 Eridani b' has relatively low C/O molar ratio of 0.38. The planet has the second strongest methane signature of any

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

, after

GJ 504 b Gliese 504 b (often shortened to GJ 504 b) is considered by NASA to be a Jovian planet and it is located in the system of the solar analog 59 Virginis (GJ 504),In spite of names of some exoplanets, derived from theirs host stars Flamsteed designa ...

. This methane signature, along with the low luminosity of the object, should produce additional clues as to how 51 Eridani b was formed. Astronomers also detected the presence of water in the planet's spectrum. Atmospheric modeling favors a low surface gravity and a partly cloudy atmosphere.

References

{{DEFAULTSORT:51 Eridani b Eridanus (constellation) Exoplanets discovered in 2014 Exoplanets detected by direct imaging Exoplanets detected by astrometry