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Epsilon Eridani
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Epsilon Eridani Observation data
Epoch J2000
Constellation Eridanus
Right ascension 3h 32m 55.8s
Declination -9° 27' 29.7"
Apparent magnitude (V) 3.73
Characteristics
Spectral type K2V
U-B color index 0.59
B-V color index 0.88
V-R color index 0.50
R-I color index 0.42
Variable type BY Draconis
Astrometry
Radial velocity (Rv) 15 km/s
Proper motion (μ) RA: -976.44 mas/yr
Dec.: 17.97 mas/yr
Parallax (π) 310.75 ± 0.85 mas
Distance 10.5 ± 0.03 ly
(3.218 ± 0.009 pc)
Absolute magnitude (MV) 6.192
Details
Mass 0.85 M☉
Radius 0.84 R☉
Surface gravity (log g) 4.57[1]
Luminosity 0.28 L☉
Temperature 5,100 K
Metallicity 49–65% Sun
Rotation 11.1 days
Age 5 × 108 years
Database references
SIMBAD data
ARICNS data
Other designations
18 Eri, HD 22049, HR 1084, BD-09°697, GCTP 742.00, WDS 03330-0928, SAO 130564, LHS 1557
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.[citation needed]
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
[hide]
* 1 Dust disk
* 2 Planetary system
* 3 See also
* 4 Footnotes and references
* 5 External links
[edit] 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.
[edit] 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.
Companion
(In order from star) ↓ Mass
(MJ) ↓ Orbital period
(days) ↓ Semimajor axis
(AU) ↓ Eccentricity ↓
b 1.55 ± 0.24 2502 ± 10 3.39 ± 0.36 0.702 ± 0.039
c ~0.1 ~102200 ~40 ~0.3
[edit] See also
* Epsilon Eridani in fiction
* Tau Ceti
* List of nearest stars
[edit] Footnotes and references
1. ^ Zhao, G.; Chen, Y. Q.; Qiu, H. M.; Li, Z. W. (2002). "Chemical Abundances of 15 Extrasolar Planet Host Stars". The Astronomical Journal 124 (4): 2224-2232. Retrieved on 2007-06-01.
* Sallie Baliunas, Dmitry Sokoloff, and Willie Soon (1996 February 1). "Magnetic Field and Rotation in Lower Main-Sequence Stars: An Empirical Time-Dependent Magnetic Bode's Relation?". Astrophysical Journal 457 (Number 2, Part 2): L99 – L102.
* Astronomers discover a nearby star system just like our own Solar System. JAC/UCLA. Retrieved on 24 March, 2005.
* Bruce Campbell, G.A.H. Walker, S. Yang (1988). "A search for substellar companions to solar-type stars". Astrophysical Journal 331 (Part 1): 902 – 921.
* A.C. Quillen, Stephen Thorndike (2002). "Structure in the ε Eridani Dusty Disk Caused by Mean Motion Resonances with a 0.3 Eccentricity Planet at Periastron". Astrophysical Journal 578 (2): L149 – L142.
* Sean Moran, Marc Kuchner, and Matthew Holman (2004). "The Dynamical Influence of a Planet at Semimajor Axis 3.4 AU on the Dust around Eridani". Astrophysical Journal 612: 1163 – 1170.
[edit] External links
* HD 22049. SIMBAD. Retrieved on 13 April, 2006.
* Notes for star Epsilon Eridani. The Extrasolar Planets Encyclopaedia. Retrieved on 13 April, 2006.
* Epsilon Eridani. SolStation. Retrieved on 13 April, 2006.
[hide]
v • d • e
Epsilon Eridani System
Star Epsilon Eridani
Planets b · c
Retrieved from "http://en.wikipedia.org/wiki/Epsilon_Eridani"
Categories: All articles with unsourced statements | Articles with unsourced statements since February 2007 | Bayer objects | Eridanus constellation | Extrasolar planets | HD and HDE objects | Orange dwarfs
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