Epsilon Leonis
Star in the constellation Leo
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Epsilon Leonis (ε Leo, ε Leonis) is the fifth-brightest star in the constellation Leo, consistent with its Bayer designation Epsilon. It is known as Algenubi or Ras Elased Australis. Both names mean "the southern star of the lion's head". Australis is Latin for "southern" and Genubi is Arabic for "south".
 | |
| 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] |
| Characteristics | |
| Evolutionary stage | Red-giant branch[3] |
| Spectral type | G1 IIIa[4] |
| U−B color index | +0.47[2] |
| B−V color index | +0.808[5] |
| Variable type | suspected[6] |
| Astrometry | |
| Radial velocity (Rv) | 4.86 ± 0.33[5] km/s |
| Proper motion (μ) | RA: –45.61[1] mas/yr Dec.: –9.21[1] mas/yr |
| Parallax (π) | 13.22±0.15 mas[1] |
| Distance | 247 ± 3 ly (75.6 ± 0.9 pc) |
| Absolute magnitude (MV) | –1.49[7] |
| Details | |
| Mass | 3.71±0.04[8] M☉ |
| Radius | 21.03+0.31 −0.32[8] R☉ |
| Luminosity | 282±13[9] L☉ |
| Surface gravity (log g) | 2.36±0.05[9] cgs |
| Temperature | 5,314±17[9] K |
| Metallicity [Fe/H] | −0.03±0.11[9] dex |
| Rotational velocity (v sin i) | 8.1[5] km/s |
| Age | 210±0[8] Myr |
| Other designations | |
| Algenubi, Ras Elased Australis,[10] ε Leo, 17 Leo, BD+24°2129, FK5 367, GC 13443, HD 84441, HIP 47908, HR 3873, SAO 81004[11] | |
| Database references | |
| SIMBAD | data |
Properties
Epsilon Leonis has a stellar classification of G1 III,[4] with the luminosity class of III indicating that, it has evolved into a giant star. It is currently on the red-giant branch stage of evolution[3] and is much larger and brighter than the Sun, with a luminosity 282 times[9] and a radius 21 times solar.[8] Consequently, its absolute magnitude is actually –1.49,[7] making it one of the more luminous stars in the constellation, significantly more than Regulus. Its 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.[7]
Epsilon Leonis exhibits the characteristics of a Cepheid-like variable, changing by an amplitude of 0.3 magnitude every few days.[12][10] It has around four times the mass of the Sun and a projected rotational velocity of 8.1 km s−1.[5] 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.[5]