EPSILON ERIDANI

'Epsilon Eridani' (ε Eri / ε Eridani) is a notable main-sequence K2 class star in the constellation of Eridanus. It has no official proper name (called only by its Bayer designation), although Arab settlers along the East African coast occasionally applied the name 'الصادرة' ''Al-Sadirah'' "the Returning Ostriches" to the star nearly seven centuries ago.
Epsilon Eridani is the third closest star outside of the solar system visible without a telescope. It has 85% of the Sun's mass, is roughly the same size, but has only 28% of its luminosity, and is 10.522 light years distant.
Epsilon Eridani's most unusual characteristic is its extremely variable spectrum, with many emission lines. Furthermore, it has a very strong magnetic field and has been measured to rotate once every 12 days (roughly twice as fast as the Sun). The reason for this is its youth; it is only about half a billion years old. Despite this young age, however, it has relatively low metallicity, particularly in iron.
Its closest neighbour is Luyten 726-8 (UV Ceti and BL Ceti), 5.22 ly (1.60 pc) away.

Contents

Dust disk

Planetary system

See also

Footnotes and references

External links

Dust disk

In 1988, a dust disk was discovered around the star, at a similar distance as the Kuiper belt is from our Sun. Bruce Campbell and others interpreted doppler measurements as clumps in the dust ring that suggest another planet orbits the star, causing the clumps through resonance. The dust disc contains approximately 1000 times more dust than is present in the inner system around our Sun, which may mean it has about 1000 times as much cometary material as our solar system.
Within 35 AU of the star the dust is depleted, which may mean that the system has formed planets which have cleared out the dust in this region. This is consistent with currently accepted models of the inner solar system, and so there may be terrestrial planets around the star.

Planetary system

As Epsilon Eridani is one of the nearest solar-type stars to our Sun, many attempts to search for orbiting planets have been made. However, the star's high activity and variability means that finding planets with the radial velocity method is difficult, and stellar activity may mimic the presence of planets. Furthermore, the low metallicity (roughly half that of the solar system) in the system reduces the odds of planet formation. If terrestrial planets do exist, however, for liquid water to exist on the surface, the planet would have to be around 0.53 AU from the star.
There are two planets in the system, one confirmed and one unconfirmed. A 2500 day-period planet Epsilon Eridani b orbits at 3.39 AU in one of the most eccentric orbit of any extrasolar planets — 0.7. A 280 year-period low-mass planet Epsilon Eridani c orbits at 40 AU in a less eccentric orbit — 0.3.

See also

★ Epsilon Eridani in fiction

★ Tau Ceti

★ List of nearest stars

Footnotes and references

★ Magnetic Field and Rotation in Lower Main-Sequence Stars: An Empirical Time-Dependent Magnetic Bode's Relation?, Sallie Baliunas, Dmitry Sokoloff, and Willie Soon, , , Astrophysical Journal, 1996 February 1

★ Astronomers discover a nearby star system just like our own Solar System

★ A search for substellar companions to solar-type stars, Bruce Campbell, G.A.H. Walker, S. Yang, , , Astrophysical Journal, 1988

★ Structure in the ε Eridani Dusty Disk Caused by Mean Motion Resonances with a 0.3 Eccentricity Planet at Periastron, A.C. Quillen, Stephen Thorndike, , , Astrophysical Journal, 2002

★ The Dynamical Influence of a Planet at Semimajor Axis 3.4 AU on the Dust around Eridani, Sean Moran, Marc Kuchner, and Matthew Holman, , , Astrophysical Journal, 2004

External links

★ HD 22049

★ Notes for star Epsilon Eridani

★ Epsilon Eridani