Tau Andromedae

Not to be confused with T Andromedae.

Tau Andromedae, Latinized from τ Andromedae, is the Bayer designation for a single^[9] star in the northern constellation of Andromeda. It has an apparent visual magnitude of +4.94,^[2] which is bright enough to be viewed from dark suburban skies. From parallax measurements made during the Gaia mission, the distance to this star can be estimated as roughly 680 light-years (210 parsecs) from Earth. The brightness of this star is diminished by 0.24 in magnitude due to extinction caused by intervening gas and dust.^[3] It is drifting closer to the Sun with a radial velocity of −14 km/s.^[4]

Tau Andromedae

Location of τ Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	01h 40m 34.81619s[1]
Declination	+40° 34′ 37.3397″[1]
Apparent magnitude (V)	+4.94[2]
Characteristics
Spectral type	B5 III[3]
U−B color index	−0.41[2]
B−V color index	−0.09[2]
Astrometry
Radial velocity (Rv)	−13.9±2.6[4] km/s
Proper motion (μ)	RA: 17.889(178)[1] mas/yr Dec.: −20.981(95)[1] mas/yr
Parallax (π)	4.7804 ± 0.1304 mas[1]
Distance	680 ± 20 ly (209 ± 6 pc)
Details
Luminosity	851[5] L☉
Surface gravity (log g)	3.357±0.020[6] cgs
Temperature	12,680±100[6] K
Rotational velocity (v sin i)	74±13[6] km/s
Age	217[7] Myr
Other designations
τ And, 53 And, BD+39 378, HD 10205, HIP 7818, HR 477, SAO 37418, PPM 44297[8]
Database references
SIMBAD	data

The spectrum of this star matches a stellar classification of B5 III,^[3] with the luminosity class of III indicating that this is a giant star. It is radiating about 851 times the luminosity of the Sun^[5] from its photosphere at an effective temperature of 12,670 K.^[6] The star is an estimated 217^[7] million years old and is spinning with a high projected rotational velocity of ~74 km/s.^[6]

Naming

In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of τ Andromedae, γ Andromedae, φ Persei, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, the Chinese name for τ Andromedae itself is 天大將軍七 (Tiān Dà Jiāng Jūn qī, English: the Seventh Star of Heaven's Great General.).^[10]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
3. van Belle, Gerard T.; von Braun, Kaspar (April 2009), "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars", The Astrophysical Journal, 694 (2): 1085–1098, arXiv:0901.1206, Bibcode:2009ApJ...694.1085V, doi:10.1088/0004-637X/694/2/1085, S2CID 18370219.
4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
5. van Belle, G. T.; et al. (May 2008), "The Palomar Testbed Interferometer Calibrator Catalog", The Astrophysical Journal Supplement Series, 176 (1): 276–292, arXiv:0711.4194, Bibcode:2008ApJS..176..276V, doi:10.1086/526548, S2CID 10713221.
6. Huang, Wenjin; et al. (October 2010), "A Stellar Rotation Census of B Stars: From ZAMS to TAMS", Astrophysical Journal, 722 (1): 605–619, arXiv:1008.1761, Bibcode:2010ApJ...722..605H, doi:10.1088/0004-637X/722/1/605, ISSN 0004-637X, S2CID 118532653.
7. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982.
8. "* tau And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-24.
9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
10. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日

External links

• Image Tau Andromedae