Epsilon Eridani
Epsilon Eridani is a K2 class star some 10.5 light years away in the constellation of Eridanus. In addition to being one of the nearest Sun-like stars, it is the closest known star with a planetary companion, which was discovered in 2000.
Epsilon Eridani has an apparent magnitude of 3.73, making it the third closest star (outside of Alpha Centauri AB and Sirius) that can be viewed with the unaided eye.
The Star
Epsilon Eridani is a main sequence, orange-red dwarf star of spectral class K2 V[1], which is estimated to have an age around 850 million years, but may be as young as 500 million and as old as a billion years[2]. This age is indicated by it's high level of chromospheric activity, strong magnetic field, and relatively fast rotation rate of only 11 days. The star has a low metallicity, estimated with only 49 to 74 of the Sun's abundance of iron, which is typically of much older stars.
The star is smaller then our Sun, with an estimated 85 percent of the mass[3], and 84 percent of the Sun's radius[4], but even with nearly the size of the Sun, Epsilon Eridani only is 27.8 percent as luminous[5].
Planetary System
Epsilon Eridani has one confirmed planet orbiting the star, with a possible, but unconfirmed second world that possibly shepherd's Epsilon Eridani's dust disk.
Planets
Using long term radical velocity observations, scientists announced the discovery of a planet orbiting Epsilon Eridani in August of 2000[6]. The planet is believed to be a gas giant with an estimated mass 1.55 times that of Jupiter, with a mean orbital distance of 3.3 AU, taking it 6.9 years to complete one orbit[7].
A second, unconfirmed planet is believed to be possibly orbiting Epsilon Eridani some 40 AU away, this is due to computer modeling of the dust ring pattern of clumping (i.e., where a planet orbited a star three times for every two times the dust disk orbited, or five times for every three dust disk orbits)[8]. If the planet exists, it is believed to be some 30 times the mass of the Earth (or about a tenth of Jupiter's mass).
Dust Disk
Epsilon Eridani has a large dust disk made up of tiny particles of dust that orbits in a ring that generally stretches between 35 and 75 AU from the star, being densest around 60 AU. The total mass of the dust disk is estimated to be around 1000 times greater then the about of similar material in our own inner solar system. Inside of 35 AU the dust is depleted, it is believed that this is due to the formation of planets which has cleared out the dust in the region.
In 2008, using the Spitzer Space Telescope, NASA revealed that there are actually two asteroid belts in the system in addition to a cloud of dust. Made of rocky and metallic debris, the closer belt is estimated to be approximately the same distance from Epsilon Eridani as the asteroid belt in our Solar System is from the Sun, while the second belt is between the first belt and a broad, outer ring of icy bodies at 35 to 90 AUs[9].
References
- ↑ http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Epsilon+Eridani&submit=SIMBAD+search
- ↑ http://adsabs.harvard.edu/abs/2004A&A...426..601D
- ↑ http://www.chara.gsu.edu/RECONS/TOP100.posted.htm
- ↑ http://adsbit.harvard.edu/abs/1983ApJS...53..643J
- ↑ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1996ApJ...460..993S
- ↑ Hatzes, Artie P. et al. (2000). "Evidence for a Long-period Planet Orbiting Epsilon Eridani". The Astrophysical Journal 544 (2): L145–L148.
- ↑ http://hubblesite.org/newscenter/archive/releases/2006/32/text/
- ↑ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002ApJ...578L.149Q&db_key=AST&high=3da354230f12032
- ↑ http://www.spitzer.caltech.edu/Media/releases/ssc2008-19/release.shtml
