Epsilon1 Arae
 The location of ε1 Arae (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Ara |
| Right ascension | 16h 59m 35.04880s |
| Declination | –53° 09′ 37.5713″ |
| Apparent magnitude (V) | +4.068 |
| Characteristics | |
| Spectral type | K3 III |
| U−B color index | +1.71 |
| B−V color index | +1.45 |
| Astrometry | |
| Radial velocity (Rv) | +23.1 km/s |
| Proper motion (μ) |
RA: +2.16 mas/yr Dec.: +22.04 mas/yr |
| Parallax (π) | 9.04 ± 0.27mas |
| Distance | 360 ± 10 ly (111 ± 3 pc) |
| Absolute magnitude (MV) | –0.79 ± 0.16 |
| Details | |
| Mass | 1.74 ± 0.24 M☉ |
| Radius | 33.7 ± 3.4 R☉ |
| Surface gravity (log g) | 1.80 cgs |
| Temperature | 4,176 K |
| Metallicity [Fe/H] | 0.08 ± 0.05 dex |
| Age | 1.70 ± 0.57 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon1 Arae (ε1 Ara, ε1 Arae) is the Bayer designation for a star in the constellation Ara, the Altar. It is visible to the naked eye with an apparent visual magnitude of +4.1 Based upon an annual parallax shift of 9.04 mas, this star is around 360 light-years (110 parsecs) distant from the Earth.
ε1 Arae is an evolved giant star with a stellar classification of K3 III. It is around 74% more massive than the Sun. At an age of about 1.7 billion years, the outer envelope of the star has expanded to almost 34 times the Sun's radius. It is radiating energy into space at an effective temperature of 4,176 K, giving it the orange-hued glow of a K-type star.
ε1 Arae was known as 龜一 (meaning: "the 1st (star) of Guī") in traditional Chinese astronomy. Allen erroneously called it as Tso Kang (左更). He probably confused constellation "Ara" with "Ari". Tso Kang was lain in Aries.
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