Epsilon1 Arae
Star in the constellation Ara
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Epsilon1 Arae is a star in the southern constellation Ara, the Altar. Its name is a Bayer designation that is Latinized from ε1 Arae, and abbreviated Epsilon1 Ara or ε1 Ara. This star is visible to the naked eye with an apparent visual magnitude of +4.1[2] Based upon an annual parallax shift of 8.85 mas,[1] this star is approximately 368 light-years (113 parsecs) distant from the Earth. It is drifting further away with a radial velocity of +24 km/s.[5]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ara |
| Right ascension | 16h 59m 35.048s[1] |
| Declination | −53° 09′ 37.58″[1] |
| Apparent magnitude (V) | +4.068[2] |
| Characteristics | |
| Spectral type | K3 III[3] |
| U−B color index | +1.71[4] |
| B−V color index | +1.45[4] |
| Astrometry | |
| Radial velocity (Rv) | +23.85±0.03[5] km/s |
| Proper motion (μ) | RA: +1.015 mas/yr[1] Dec.: +21.455 mas/yr[1] |
| Parallax (π) | 8.8520±0.1517 mas[1] |
| Distance | 368 ± 6 ly (113 ± 2 pc) |
| Absolute magnitude (MV) | −0.79±0.16[6] |
| Details[5] | |
| Mass | 1.63±0.21 M☉ |
| Radius | 29.52±2.45 R☉ |
| Luminosity | 347+90 −71 L☉ |
| Surface gravity (log g) | 1.85±0.07 cgs |
| Temperature | 4,302±45 K |
| Metallicity [Fe/H] | −0.19±0.06 dex |
| Rotational velocity (v sin i) | 4.20±0.45 km/s |
| Age | 1.82±0.60 Gyr |
| Other designations | |
| CPD−52°10372, FK5 632, GC 22869, HD 152980, HIP 83153, HR 6295, SAO 244331, PPM 345574[7] | |
| Database references | |
| SIMBAD | data |
ε1 Arae is an evolved giant star[8] with a stellar classification of K3 III.[3] It is around 63% more massive than the Sun. At an age of about 1.8 billion years, the outer envelope of the star has expanded to almost 30 times the Sun's radius. It is radiating 347 times the luminosity of the Sun from its photosphere at an effective temperature of 4,302 K,[5] giving it the orange-hued glow of a K-type star.[9]
ε1 Arae was known as 龜一(spelled as "Guī yī", meaning: "the 1st (star) of Guī") in traditional Chinese astronomy.[10][11] Allen erroneously called it Tso Kang (左更).[12] He probably confused the constellation "Ara" with "Ari", as Tso Kang is actually in Aries.[10][11]