Zeta Arae
 Location of ζ Arae (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Ara |
| Right ascension | 16h 58m 37.21217s |
| Declination | –55° 59′ 24.5203″ |
| Apparent magnitude (V) | 3.13 |
| Characteristics | |
| Spectral type | K3 III |
| U−B color index | +1.96 |
| B−V color index | +1.60 |
| Astrometry | |
| Radial velocity (Rv) | –6.0 km/s |
| Proper motion (μ) |
RA: –17.80 mas/yr Dec.: –36.67 mas/yr |
| Parallax (π) | 6.71 ± 0.19mas |
| Distance | 490 ± 10 ly (149 ± 4 pc) |
| Absolute magnitude (MV) | –3.95 |
| Details | |
| Mass | 7-8 M☉ |
| Radius | 114 R☉ |
| Luminosity | 3,800 L☉ |
| Surface gravity (log g) | 1.20 cgs |
| Temperature | 4,246 K |
| Metallicity [Fe/H] | –0.40 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Zeta Arae (ζ Ara, ζ Arae) is a star in the southern constellation Ara. It is sometimes called by the name Tseen Yin, together with δ Arae. The apparent visual magnitude of this star is 3.1, which can be seen from suburban skies in the southern hemisphere. From the parallax measurements, it is located at a distance of 490 light-years (150 parsecs) from Earth.
The spectrum of this star matches a stellar classification of K3 III. The luminosity class of 'III' indicates this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. It is radiating energy from its outer atmosphere at an effective temperature of 4,246 K which is what gives it the orange hue of a K-type star. This star displays an excess of infrared emission that may indicate circumstellar matter.
In Chinese, 杵 (Guī), meaning Tortoise, refers to an asterism consisting of ζ Arae, ε1 Arae, γ Arae, δ Arae and η Arae. Consequently, ζ Arae itself is known as 龜五 (Guī wǔ, English: the Fifth Star of Tortoise.)
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