Epsilon Eridani

Epsilon Eridani (ε Eri, ε Eridani) is a star in the southern constellation Eridanus, just south of the celestial equator. It can be seen from most of Earth's surface. 

It is 10.5 light years (ly) away, and has an apparent magnitude of 3.73. It is the third closest individual star or star system visible to the unaided eye.

Epsilon Eridani was the closest star known to host a planet until the unconfirmed discovery of Alpha Centauri Bb. Its age is less than a billion years. Because of its youth, Epsilon Eridani has a more active magnetic field than the present-day Sun. Its stellar wind is 30 times as strong. Its rotation period is 11.2 days at the equator. The star is smaller and less massive than the Sun, and has a lower level of metal elements. It is a main-sequence star of spectral class K2, which means that energy generated at the core through nuclear fusion of hydrogen is emitted from the surface at a temperature of about 5,000 K, giving it an orange hue.

Its planet, Epsilon Eridani b, was announced in 2000.Hatzes, Artie P. et al 2000, Evidence for a long-period planet orbiting ε Eridani. The Astrophysical Journal 544 (2): L145–L148.  The planet orbits in about 7 years. It is about 3.4 astronomical units (AU) away from its star.1 AU is the mean distance between the Earth and the Sun. 

The system includes two belts of rocky asteroids: one at about 3 AU and a second at about 20 AU, whose structure may be maintained by a hypothetical second planet, Epsilon Eridani c.Aguilar, David A.; Pulliam, Christine 2008. Solar System's young twin has two asteroid belts, Harvard-Smithsonian Center for Astrophysics.  Epsilon Eridani has an extensive outer debris disk of remnant planetesimals left over from the system's formation. Backman D. et al 2008. Epsilon Eridani's planetary debris disk: structure and dynamics based on Spitzer and CSO observations. The Astrophysical Journal 690 (2): 1522–1538. 

Epsilon Eridani may be a member of the Ursa Major Moving Group of stars that share a similar motion through the Milky Way. This suggests they share a common origin in an open star cluster. Its nearest neighbor, the binary star system Luyten 726-8, will have a close encounter with Epsilon Eridani in about 31,500 years when they will be separated by about 0.93 ly.Potemine, Igor Yu.  2010. Transit of Luyten 726-8 within 1 ly from Epsilon Eridani.  

Epsilon Eridani has been the target of SETI searches. Epsilon Eridani appears in science fiction stories and has been suggested as a destination for interstellar travel. Boyle, Alan 2009. The case for Pluto: how a little planet made a big difference. Hoboken, New Jersey: Wiley, 191.

 References 

Category:Stars