What is Epsilon Eridani?
'''Epsilon Eridani''' ('''ε Eri''', '''ε Eridani''') is a star in the southern constellation [[Eridanus (constellation)|Eridanus]], just south of the [[celestial equator]]. It can be seen from most of Earth's surface. It is 10.5 [[light year]]s (ly) away, and has an [[apparent magnitude]] of 3.73. It is the [[List of nearest stars|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&nbsp;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|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&nbsp;[[Kelvin|K]], giving it an orange [[hue]]. Its planet, [[Epsilon Eridani b]], was announced in 2000.<ref>Hatzes, Artie P. ''et al'' 2000, Evidence for a long-period planet orbiting ε Eridani. ''The Astrophysical Journal'' '''544''' (2): L145–L148. [http://iopscience.iop.org/1538-4357/544/2/L145/]</ref> The planet orbits in about 7 years. It is about 3.4 [[astronomical unit]]s (AU) away from its star.<ref>1 AU is the mean distance between the Earth and the Sun.</ref> The system includes two belts of rocky [[asteroid]]s: one at about 3&nbsp;AU and a second at about 20&nbsp;AU, whose structure may be maintained by a hypothetical second planet, Epsilon Eridani c.<ref>Aguilar, David A.; Pulliam, Christine 2008. Solar System's young twin has two asteroid belts, Harvard-Smithsonian Center for Astrophysics. [http://www.cfa.harvard.edu/news/2008-22]</ref> Epsilon Eridani has an extensive outer [[debris]] disk of remnant [[planetesimal]]s left over f