Sigma Andromedae, Latinized from σ Andromedae, is the Bayer designation for a single[10] star in the northern constellationofAndromeda. It has an apparent visual magnitude of +4.5,[2] which is bright enough to be seen with the naked eye from most locations. Parallax measurements made during the Gaia mission place it at a distance of about 140 light-years (43parsecs).[1] The magnitude of the star is diminished by 0.08 from extinction caused by intervening gas and dust.[11] It is drifting closer to the Sun with a radial velocity of –8 km/s.[2]
Location of σ Andromedae (circled) | |
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Andromeda |
Right ascension | 00h18m 19.65737s[1] |
Declination | +36° 47′ 06.8085″[1] |
Apparent magnitude (V) | +4.51[2] |
Characteristics | |
Evolutionary stage | main sequence[3] |
Spectral type | A2 V[4] |
U−B color index | +0.07[5] |
B−V color index | +0.05[5] |
Astrometry | |
Radial velocity (Rv) | –8.0[2] km/s |
Proper motion (μ) | RA: −65.212(153)[1] mas/yr Dec.: −42.221(124)[1] mas/yr |
Parallax (π) | 23.2542 ± 0.1809 mas[1] |
Distance | 140 ± 1 ly (43.0 ± 0.3 pc) |
Absolute magnitude (MV) | 1.33[6] |
Details | |
Mass | 2.12±0.01[3] M☉ |
Radius | 2.13[7] R☉ |
Luminosity | 21.23[7] L☉ |
Surface gravity (log g) | 4.02[6] cgs |
Temperature | 8,929[6] K |
Rotational velocity (v sin i) | 123[8] km/s |
Age | 450[7] Myr |
Other designations | |
σ And, 25 Andromedae, BD+35°44, FK5 1005, HD 1404, HIP 1473, HR 68, SAO 53798, PPM 65183[9] | |
Database references | |
SIMBAD | data |
This star has a stellar classification of A2 V,[4] which matches the spectrum of an A-type main sequence star. It is about 450 million years old[12] and is spinning rapidly with a projected rotational velocity of 123 km/s.[8] The star has 2.12[3] times the mass of the Sun and 2.13[7] times the Sun's girth. It is radiating 21[7] times the luminosity of the Sun from its photosphere at an effective temperature of 8,929 K,[6] giving it the white-hued glow of an A-type star.[13]
In the past, radial velocity variations have been reported,[14] but this remains unconfirmed.[10] The star does not show any significant photometric variations and is used as an ubvy standard star.[15]Adebris disk of warm dust around this star has been detected by Spitzer Space Telescope.[16][17] A model fit to the data yields an orbital distance of 20.3 AU from the host star with a mean temperature of 132.9 K.[7]
Sigma Andromedae is a candidate for membership in the stream of stars associated with the Ursa Major Moving Group. This is a set of stars that share a common motion through space, which suggests they originated together.[6]
InChinese, 天廄 (Tiān Jiù), meaning Celestial Stable, refers to an asterism consisting of σ Andromedae, θ Andromedae and ρ Andromedae. Consequently, the Chinese name for σ Andromedae itself is 天廄三 (Tiān Jiù sān, English: the Third Star of Celestial Stable.)[18]
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