Binary star system in the constellation Leo
Eta Leonis Location of η Leo (circled)
Observation dataEpoch J2000 Equinox J2000 Constellation Leo Right ascension 10h 07m 19.9519s [ 1] Declination +16° 45′ 45.592″[ 1] Apparent magnitude (V)3.486[ 2] Characteristics Evolutionary stage Blue supergiant (blue loop )[ 3] Spectral type A0 Ib[ 2] U−Bcolor index −0.206[ 2] B−Vcolor index −0.026[ 2] Astrometry Radial velocity (Rv )1.40[ 4] km/s Proper motion (μ)RA: −2.80[ 1] mas /yr Dec.: −1.82[ 1] mas /yr Parallax (π)2.57± 0.16 mas [ 1] Distance 1,270 ± 80 ly pc ) Absolute magnitude (MV )−5.54[ 3] Details Mass 10[ 5] M ☉ Radius 47[ 3] R ☉ Luminosity 19,000[ 5] L ☉ Surface gravity (log g )2.00[ 5] cgs Temperature 9,600[ 2] K Metallicity −0.04[ 3] Rotational velocity (v sin i )2[ 2] Age 25[ 5] Myr Other designations η Leo ,30 Leonis ,HR 3975,BD +17°2171,HD 87737,FK5 379,HIP 49583,SAO 98955,GC 13899Database references SIMBAD data
Eta Leonis (η Leo, η Leonis) is a third-magnitudeblue supergiant star in theconstellation Leo , aboutlight years
WithRegulus ,γ Leonis (Algieba), andζ Leonis (Adhafera), it formed the Arabiclunar mansion Al Jabhah , the forehead (of the lion).[ 6] Al Jabhah to this star specifically,[ 7] Algieba for γ Leonis has the same etymology.[ 8]
Eta Leonis is a bluesupergiant with thestellar classification A0Ib. Since 1943, thespectrum of this star has served as one of the stable anchor points by which other stars are classified.[ 9] apparent magnitude is 3.5, making it a relatively dim star to the naked eye, it is nearly 20,000 times moreluminous than the Sun, with anabsolute magnitude of -5.60. TheHipparcos astrometric data has estimated the distance of Eta Leonis to be roughly 390parsecs fromEarth , or 1,270light years away. It is believed to be in ablue loop phase.[ 3]
Eta Leonis is apparently amultiple star system , but the number of components and their separation is uncertain.[ 10]
^a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction".Astronomy and Astrophysics .474 (2):653– 664.arXiv :0708.1752 Bibcode :2007A&A...474..653V .doi :10.1051/0004-6361:20078357 .S2CID 18759600 . ^a b c d e f Firnstein, M.; Przybilla, N. (2012). "Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters".Astronomy & Astrophysics .543 : A80.arXiv :1207.0308 Bibcode :2012A&A...543A..80F .doi :10.1051/0004-6361/201219034 .S2CID 54725386 . ^a b c d e Przybilla, N.; Butler, K.; Becker, S. R.; Kudritzki, R. P. (2006). "Quantitative spectroscopy of BA-type supergiants".Astronomy and Astrophysics .445 (3): 1099.arXiv :astro-ph/0509669 Bibcode :2006A&A...445.1099P .doi :10.1051/0004-6361:20053832 .S2CID 118953817 . ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system".Astronomy Letters .32 (11):759– 771.arXiv :1606.08053 Bibcode :2006AstL...32..759G .doi :10.1134/S1063773706110065 .S2CID 119231169 . ^a b c d Tanrıverdi, Taner (2013). "Elemental abundances of the supergiant stars σ Cygnus and η Leonis".New Astronomy .25 : 50.arXiv :1512.04557 Bibcode :2013NewA...25...50T .doi :10.1016/j.newast.2013.03.013 .S2CID 118525375 . ^ Allen, R. H. (1899),Star Names: Their Lore and Meaning ^ Rhoads, Jack W. (November 15, 1971),Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF) , Jet Propulsion Laboratory, California Institute of Technology. ^ Ridpath, Ian ."Star Tales - Leo" . Retrieved28 July 2025 .^ Garrison, R. F. (December 1993). "Anchor Points for the MK System of Spectral Classification".Bulletin of the American Astronomical Society .25 : 1319.Bibcode :1993AAS...183.1710G . ^ Mason, Brian D. (1996). "ICCD Speckle Observations of Binary Stars.XV.An Investigation of Lunar Occultation Systems".The Astronomical Journal .112 : 2260.Bibcode :1996AJ....112.2260M .doi :10.1086/118179 .
