Sigma Octantis
Sigma Octantis is a solitary star in the Octans constellation that forms the pole star of the Southern Hemisphere. Its name is also written as σ Octantis, abbreviated as Sigma Oct or σ Oct, and it is officially named Polaris Australis (/poʊˈlɛərɪs ɔːˈstreɪlɪs/). The star is positioned one degree away from the southern celestial pole of the Southern Hemisphere, lying in nearly opposite direction to the North Star on the celestial sphere.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Octans |
| Right ascension | 21h 08m 46.86357s |
| Declination | −88° 57′ 23.3983″ |
| Apparent magnitude (V) | 5.47 |
| Characteristics | |
| Spectral type | F0 IV |
| U−B color index | +0.13 |
| B−V color index | +0.26 |
| Variable type | δ Sct |
| Astrometry | |
| Radial velocity (Rv) | +11.9 km/s |
| Proper motion (μ) | RA: +26.323 mas/yr Dec.: +4.721 mas/yr |
| Parallax (π) | 11.1005 ± 0.0616 mas |
| Distance | 294 ± 2 ly (90.1 ± 0.5 pc) |
| Absolute magnitude (MV) | 0.86±0.09 |
| Details | |
| Mass | 1.59 M☉ |
| Radius | 4.4 R☉ |
| Luminosity | 44 L☉ |
| Surface gravity (log g) | 3.71 cgs |
| Temperature | 7,415±252 K |
| Metallicity [Fe/H] | −0.5 dex |
| Rotational velocity (v sin i) | 145 km/s |
| Age | 912 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Located approximately 294 light-years from Earth, it is classified as a subgiant with a spectral type of F0 III. Sigma Octantis has an apparent magnitude of 5.5, but is slightly variable and is classified as a Delta Scuti variable.
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