Epsilon Reticuli

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Epsilon Reticuli
Diagram showing star positions and boundaries of the Reticulum constellation and its surroundings
Cercle rouge 100%.svg

Location of ε Reticuli (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Reticulum
Right ascension 4h 16m 29.029s[1]
Declination –59° 18′ 07.76″[1]
Apparent magnitude (V) 4.44[2] / 12.5
Spectral type K2 IV[3] / D
U−B color index +1.07[2]
B−V color index +1.08[2]
Radial velocity (Rv) +29.3[4] km/s
Proper motion (μ) RA: –47.53 ± 0.17[1] mas/yr
Dec.: –167.58 ± 0.17[1] mas/yr
Parallax (π) 54.83 ± 0.15[1] mas
Distance 59.5 ± 0.2 ly
(18.24 ± 0.05 pc)
Absolute magnitude (MV) 0.87[5]
Surface gravity (log g) 3.3[6] cgs
Temperature 4,749[6] K
Metallicity [Fe/H] +0.22[6] dex
Rotational velocity (v sin i) 2.80[7] km/s
Age 10[3] Gyr
Other designations
ε Reticuli, ε Ret, Epsilon Ret, GJ 9153, HD 27442, HIP 19921, HR 1355, SAO 233463.[8]
Database references

Epsilon Reticuli (Epsilon Ret, ε Reticuli, ε Ret) is a double star approximately 59 light-years away in the constellation of Reticulum. The primary component is an orange subgiant, while the secondary is a white dwarf. The two stars share a common motion through space and hence most likely form a binary star system.[3] The brighter star should be easily visible without optical aid under dark skies in the southern hemisphere. In 2000, an extrasolar planet was confirmed to be orbiting the primary star in the system.

Star system[edit]

The primary component is a subgiant star with a stellar classification of K2 IV.[3] The fusing of hydrogen in its core is coming to an end and it is in the process of expanding as a red giant. (The NStars project gave it a classification of K2 III, which would make it a giant star.)[9]

The secondary component is a white dwarf star located at a separation of at least 240 AU from the primary.[3] It has a surface temperature between 9000 and 17000 K.

Planetary system[edit]

The inner solar system superimposed behind the orbits of the planet Epsilon Reticuli b (and several others).

On December 11, 2000, a team of astronomers announced the discovery of a planet Epsilon Reticuli b.[10] With a minimum mass of 1.17 that of Jupiter, the planet moves around Epsilon Reticuli with an average separation of 1.16 AUs. The eccentricity of the planet is extremely low (at 0.06), and it completes an orbit every 418 days (or 1.13 years).

Stability analysis shows that the planet's Lagrangian points would be stable enough to host Earth-sized planets, though as yet no trojan planets have been detected in this system.[11]

The Epsilon Reticuli planetary system[7]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b >1.56 ± 0.14 MJ 1.271 ± 0.073 428.1 ± 1.1 0.060 ± 0.043


  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  3. ^ a b c d e Chauvin, G.; Lagrange, A.-M.; Udry, S.; Mayor, M. (2007), "Characterization of the long-period companions of the exoplanet host stars: HD 196885, HD 1237 and HD 27442", Astronomy and Astrophysics, 475 (2): 723–727, arXiv:0710.5918Freely accessible, Bibcode:2007A&A...475..723C, doi:10.1051/0004-6361:20067046. 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  5. ^ Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics, 343: 222–228, Bibcode:1999A&A...343..222E. 
  6. ^ a b c Randich, S.; et al. (August 1999), "Lithium in population I subgiants", Astronomy and Astrophysics, 348: 487–500, Bibcode:1999A&A...348..487R. 
  7. ^ a b Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493Freely accessible. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. 
  8. ^ "eps Ret -- Star in double system", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-05-23. 
  9. ^ Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770Freely accessible, Bibcode:2006AJ....132..161G, doi:10.1086/504637. 
  10. ^ Butler, R. P.; et al. (2001). "Two New Planets from the Anglo-Australian Planet Search". The Astrophysical Journal. 555 (1): 410–417. Bibcode:2001ApJ...555..410B. doi:10.1086/321467. 
  11. ^ Schwarz; Dvorak, R.; Süli, Á.; Érdi, B. (2007). "Survey of the stability region of hypothetical habitable Trojan planets" (PDF). Astronomy and Astrophysics. 474 (3): 1023–1029. Bibcode:2007A&A...474.1023S. doi:10.1051/0004-6361:20077994. 

External links[edit]

Coordinates: Sky map 04h 16m 29.03s, −59° 18′ 07.76″