Epsilon Leonis

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Epsilon Leonis
Diagram showing star positions and boundaries of the Leo constellation and its surroundings
Cercle rouge 100%.svg
Location of ε Leonis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 09h 45m 51.07330s[1]
Declination 23° 46′ 27.3208″[1]
Apparent magnitude (V) 2.98[2]
Spectral type G1 II[3]
U−B color index +0.47[2]
B−V color index +0.808[4]
Variable type suspected[5]
Radial velocity (Rv)4.86 ± 0.33[4] km/s
Proper motion (μ) RA: –45.61[1] mas/yr
Dec.: –9.21[1] mas/yr
Parallax (π)13.22 ± 0.15[1] mas
Distance247 ± 3 ly
(75.6 ± 0.9 pc)
Absolute magnitude (MV)–1.49[6]
Mass4.01[6] M
Radius21[4] R
Luminosity288[4] L
Surface gravity (log g)2.2[4] cgs
Temperature5,248[4] K
Metallicity [Fe/H]–0.28[4] dex
Rotational velocity (v sin i)8.1[4] km/s
Age162[6] Myr
Other designations
Algenubi, ε Leo, 17 Leo, BD +24°2129, FK5 367, GC 13443, HD 84441, HIP 47908, HR 3873, SAO 81004
Database references

Epsilon Leonis (ε Leo, ε Leonis) is the fifth-brightest star in the constellation Leo, consistent with its Bayer designation Epsilon. The star has the traditional names Ras Elased (Australis), Asad Australis and Algenubi, all of which derive from the Arabic رأس الأسد الجنوبي rās al-’asad al-janūbī, which means "the southern (star) of the lion's head"; australis is Latin for "southern".[citation needed]


Epsilon Leonis has a stellar classification of G1 II, with the luminosity class of II indicating that, at an age of 162 million years,[6] it has evolved into a bright giant. It is much larger and brighter than the Sun with a luminosity 288 times and a radius 21 times solar.[4] Consequently, its absolute magnitude is actually –1.49,[6] making it one of the more luminous stars in the constellation, significantly more than its alpha star, Regulus. Algenubi's apparent brightness, though, is only 2.98.[2] Given its distance of about 247 light-years (76 parsecs), the star is more than three times the distance from the Sun than Regulus. At this distance, the visual magnitude of Epsilon Leonis is reduced by 0.03 as a result of extinction caused by intervening gas and dust.[6]

Algenubi exhibits the characteristics of a Cepheid-like variable, changing by an amplitude of 0.3 magnitude every few days.[7][8] It has around four times the mass of the Sun and a projected rotational velocity of 8.1 km s−1.[4] Based upon its iron abundance, the metallicity of this star's outer atmosphere is only around 52% of the Sun's. That is, the abundance of elements other than hydrogen and helium is about half that in the Sun.[4]

See also[edit]


  1. ^ a b c d e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Note: see VizieR catalogue I/311.
  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. ^ "eps Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-05-10.
  4. ^ a b c d e f g h i j k Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
  5. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  6. ^ a b c d e f Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (August 2008), "Stellar parameters and elemental abundances of late-G giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781
  7. ^ Andrievsky, S. M. (July 1998), "BA II lines as luminosity indicators: s-Cepheids and non-variable supergiants", Astronomische Nachrichten, 319 (4): 239–240, Bibcode:1998AN....319..239A, doi:10.1002/asna.2123190405
  8. ^ Kaler, James B., "ALGENUBI (Epsilon Leonis)", Stars, University of Illinois, retrieved 2010-05-10