| Epsilon Eridani b, Xi Eridani|
51 Eridani is a star in the constellation Eridanus located at RA 04 h 37 m 36.11 s and declination −02° 28′ 24.2″ with an apparent magnitude of 5.22, meaning it is just visible to the unaided eye in suburban and rural skies. Its absolute magnitude is 2.87.
51 Eridani Wikipedia
Johann Bayer gave the star its Bayer designation of c Eridani, using lower-case letters once he had exhausted all the letters of the Greek alphabet, in his 1603 star chart Uranometria. It was catalogued as 51 Eridani by John Flamsteed in 1725.
Located around 97 light-years distant, it shines with a luminosity approximately 5.38 times that of the Sun and has a surface temperature of 7199 K. A cold debris disk has been detected with a likely inner border of 82 astronomical units (AU). A yellow-white main sequence star of spectral type F0V, 51 Eridani is a member of the Beta Pictoris moving group and hence thought to be around 23 million years old. Somewhat more luminous than it should be for its surface temperature, 51 Eridani has also been classified as spectrum F0IV—a type corresponding to ageing stars that have used up their core hydrogen fuel and become subgiants—however in this case it is a phenomenon of very young stars 5 to 30 million years old that have yet to settle on the main sequence.
The star is significant as the host sun to one of the first planets to have been directly imaged in wide-orbit, and the first detected by the Gemini Planet Imager.
51 Eridani b is a young Jupiter-like planet and was photographed, in near-infrared light on December 21, 2014. The study, led by Bruce Macintosh, a professor of physics at Stanford University and confirmed by Christian Marois found that methane and water were abundant in the atmosphere of the planet and its mass was only slightly larger than Jupiter’s. It is the smallest exoplanet directly imaged to date.