Eta Leonis

Eta Leonis (η Leo, η Leonis) is a third-magnitude blue supergiant star in the constellation Leo, about 1,270 light years away.

Eta Leonis

Location of η Leo (circled)
Observation data Epoch 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−B color index	−0.206[2]
B−V color 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 (390 ± 20 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] km/s
Age	25[5] Myr
Other designations
η Leo, 30 Leonis, HR 3975, BD+17°2171, HD 87737, FK5 379, HIP 49583, SAO 98955, GC 13899
Database references
SIMBAD	data

Nomenclature

With Regulus, γ Leonis (Algieba), and ζ Leonis (Adhafera), it formed the Arabic lunar mansion Al Jabhah, the forehead (of the lion).^[6] Some sources apply the name Al Jabhah to this star specifically,^[7] though the name Algieba for γ Leonis has the same etymology.^[8]

Properties

Eta Leonis is a blue supergiant with the stellar classification A0Ib. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.^[9] Though its apparent magnitude is 3.5, making it a relatively dim star to the naked eye, it is nearly 20,000 times more luminous than the Sun, with an absolute magnitude of -5.60. The Hipparcos astrometric data has estimated the distance of Eta Leonis to be roughly 390 parsecs from Earth, or 1,270 light years away. It is believed to be in a blue loop phase.^[3]

Eta Leonis is apparently a multiple star system, but the number of components and their separation is uncertain.^[10]