Astronomy:Alpha Tucanae
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Tucana |
| Right ascension | 22h 18m 30.11244s[1] |
| Declination | −60° 15′ 34.6664″[1] |
| Apparent magnitude (V) | 2.86[2] |
| Characteristics | |
| Spectral type | K3 III[3] |
| U−B color index | +1.54[2] |
| B−V color index | +1.39[2] |
| Astrometry | |
| Radial velocity (Rv) | +45.8[4] km/s |
| Proper motion (μ) | RA: −77.000[1] mas/yr Dec.: −32.823[1] mas/yr |
| Parallax (π) | 17.7324 ± 0.3290[1] mas |
| Distance | 184 ± 3 ly (56 ± 1 pc) |
| Absolute magnitude (MV) | −1.05[5] |
| Absolute bolometric magnitude (Mbol) | −1.97[5] |
| Orbit[6] | |
| Period (P) | 4197.7 days |
| Eccentricity (e) | 0.39 |
| Periastron epoch (T) | 18666.4 |
| Argument of periastron (ω) (secondary) | 48.5° |
| Semi-amplitude (K1) (primary) | 7.2 km/s |
| Details | |
| Mass | 2.5 - 3[7] M☉ |
| Radius | 37.3[8] R☉ |
| Luminosity | 424[7] L☉ |
| Temperature | 4310[8] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Tucanae (α Tuc, α Tucanae), also named Lang-Exster,[10] is a binary star system in the southern circumpolar constellation of Tucana. With an apparent visual magnitude of 2.86,[2] it can be seen with the naked eye from the Southern Hemisphere. Using parallax measurements, the distance to this system can be estimated as 184 light-years (56 parsecs). A cool star with a surface temperature of 4300 K, it is 424 times as luminous as the sun and 37 times its diameter. It is 2.5 to 3 times as massive. It is unclear what stage of evolution the star is in.[7]
This is a spectroscopic binary, which means that the two stars have not been individually resolved using a telescope, but the presence of the companion has been inferred from measuring changes in the spectrum of the primary. The orbital period of the binary system is 4197.7 days (11.5 years).[6] The primary component has a stellar classification of K3 III,[3] which indicates it is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence. It has the characteristic orange hue of a K-type star.
The IAU Working Group on Star Names approved the name Lang-Exster for this star system on 19 September 2024 and it is now so entered in the IAU Catalog of Star Names.[10] "Lang" is a Malay and Indonesian word meaning hornbill, and "Exster" is a Dutch word meaning magpie; both were historically used as names for the constellation Tucana. Since this star is a binary system it is given a double name;[10] the names can refer individually to the two components.[11]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 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
- ↑ 3.0 3.1 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode: 1975mcts.book.....H
- ↑ Buscombe, W.; Kennedy, P. M. (1968), "Stellar radial velocities from coudé spectrograms", Monthly Notices of the Royal Astronomical Society 139 (3): 341–346, doi:10.1093/mnras/139.3.341, Bibcode: 1968MNRAS.139..341B
- ↑ 5.0 5.1 Pasquini, L.; de Medeiros, J. R.; Girardi, L. (2000). "Ca II activity and rotation in F-K evolved stars". Astronomy and Astrophysics 361: 1011–1022. Bibcode: 2000A&A...361.1011P.
- ↑ 6.0 6.1 Pourbaix, D. et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics 424: 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P
- ↑ 7.0 7.1 7.2 Kaler, Jim. "Alpha Tucanae". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/alphatuc.html. Retrieved 19 October 2013.
- ↑ 8.0 8.1 Wood, Brian E.; Müller, Hans-Reinhard; Harper, Graham M. (2016-09-23), "Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars" (in en), The Astrophysical Journal 829 (2): 74, doi:10.3847/0004-637X/829/2/74, ISSN 0004-637X, Bibcode: 2016ApJ...829...74W
- ↑ "alf Tuc -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alpha+Tucanae, retrieved 2012-01-20
- ↑ 10.0 10.1 10.2 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/.
- ↑ "Lang-Exster". IAU Working Group on Star Names. https://xing.fmi.uni-jena.de/mediawiki/index.php/Lang-Exster.
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