Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Octans |
Right ascension | 22h 20m 01.67970s[1] |
Declination | −80° 26′ 23.0947″[1] |
Apparent magnitude (V) | 4.58 - 5.30[2] |
Characteristics | |
Spectral type | M5III[3] |
U−B color index | +1.18[4] |
B−V color index | +1.47[4] |
Variable type | SRb[2] |
Astrometry | |
Radial velocity (Rv) | +11.70[5] km/s |
Proper motion (μ) | RA: +56.81[1] mas/yr Dec.: −43.47[1] mas/yr |
Parallax (π) | 11.22 ± 0.23 mas[1] |
Distance | 291 ± 6 ly (89 ± 2 pc) |
Absolute magnitude (MV) | +0.34[6] |
Details | |
Mass | 1.34[7] M☉ |
Radius | 112±15[8] R☉ |
Luminosity | 1,819[8] L☉ |
Surface gravity (log g) | 2.15[7] cgs |
Temperature | 3,560±264[8] K |
Other designations | |
Database references | |
SIMBAD | data |
Epsilon Octantis, Latinized from ε Octantis, is a star in the southern circumpolar constellation of Octans. It is a faintly visible to the naked eye with an apparent visual magnitude of about 5. The annual parallax shift of 11.22[1] mas yields a distance estimate of around 291 light years. It is moving further from the Sun with a radial velocity of +11.7 km/s.[5]
This is an evolved, cool red giant star with a stellar classification of class M5III.[3] It is a semiregular variable with a magnitude range of 4.58 to 5.30 and a (poorly defined) period around 55 days.[2] The star has 1.34[7] times the mass of the Sun and has expanded to around 112[8] times the Sun's radius. It is radiating 1,819[8] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,560 K.[8]
Epsilon Octantis was found to be variable on a survey of the southern sky conducted by the Bamberg observatory, which was reported in 1966.[10] In 1972, it was assigned the variable star designation BO Octantis,[11] although this is now recognised as a mistake since stars with Bayer designations are not given a separate variable star designation.[2]