Epsilon Eridani

ε Eridani / Ran
Location of ε Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus
Pronunciation /ˈrɑːn/
Right ascension 03h 32m 55.84496s[1]
Declination −09° 27′ 29.7312″[1]
Apparent magnitude (V) 3.736[2]
Characteristics
Spectral type K2V[3]
Apparent magnitude (B) 4.61[4]
Apparent magnitude (V) 3.73[4]
Apparent magnitude (J) 2.228±0.298[5]
Apparent magnitude (H) 1.880±0.276[5]
Apparent magnitude (K) 1.776±0.286[5]
U−B colour index +0.571[2]
B−V colour index +0.887[2]
Variable type BY Dra[4][6]
Astrometry
Radial velocity (Rv)+16.376±0.0019[7] km/s
Proper motion (μ) RA: −975.17[1] mas/yr
Dec.: 19.49[1] mas/yr
Parallax (π)311.37 ± 0.11 mas[8]
Distance10.475 ± 0.004 ly
(3.212 ± 0.001 pc)
Absolute magnitude (MV)6.19[9]
Details
Mass0.82±0.02[10][11] M☉
Radius0.735±0.005[12] R☉
Luminosity0.34[13] L☉
Surface gravity (log g)4.30±0.08[10] cgs
Temperature5,084±5.9[14] K
Metallicity [Fe/H]−0.13±0.04[15] dex
Rotation11.4 days[16]
Rotational velocity (v sin i)2.4±0.5[17] km/s
Age400–800[18] Myr
Other designations
Ran, ε Eri, 18 Eridani, BD−09°697, GJ 144, HD 22049, HIP 16537, HR 1084, SAO 130564, WDS J03330-0928, LHS 1557[4]
Database references
SIMBADThe star
planet b
planet c

Epsilon Eridani (Latinized from ε Eridani), proper name Ran,[19] is a star in the southern constellation of Eridanus. At a declination of −9.46°, it is visible from most of Earth's surface. Located at a distance 10.5 light-years (3.2 parsecs) from the Sun, it has an apparent magnitude of 3.73, making it the third-closest individual star (or star system) visible to the naked eye.

The star is estimated to be less than a billion years old.[20] This relative youth gives Epsilon Eridani a higher level of magnetic activity than the Sun, with a stellar wind 30 times as strong. The star's rotation period is 11.2 days at the equator. Epsilon Eridani is smaller and less massive than the Sun, and has a lower level of elements heavier than helium.[21] It is a main-sequence star of spectral class K2, with an effective temperature of about 5,000 K (8,500 °F), giving it an orange hue. It is a candidate member of the Ursa Major moving group of stars, which share a similar motion through the Milky Way, implying these stars shared a common origin in an open cluster.

Periodic changes in Epsilon Eridani's radial velocity have yielded evidence of a giant planet orbiting it, designated Epsilon Eridani b.[22] The discovery of the planet was initially controversial,[23] but most astronomers now regard the planet as confirmed. In 2015 the planet was given the proper name AEgir [sic].[24] The Epsilon Eridani planetary system also includes a debris disc consisting of a Kuiper belt analogue at 70 au from the star and warm dust between about 3 au and 20 au from the star.[25][26] The gap in the debris disc between 20 and 70 au implies the likely existence of outer planets in the system.

As one of the nearest Sun-like stars,[27] Epsilon Eridani has been the target of several observations in the search for extraterrestrial intelligence. Epsilon Eridani appears in science fiction stories and has been suggested as a destination for interstellar travel.[28] From Epsilon Eridani, the Sun would appear as a star in Serpens, with an apparent magnitude of 2.4.[note 1]

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  19. ^ "IAU Catalog of Star Names". Retrieved July 28, 2016.
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