Astronomy:4 Sagittarii
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagittarius[1] |
| Right ascension | 17h 59m 47.55646s[2] |
| Declination | −23° 48′ 58.0130″[2] |
| Apparent magnitude (V) | 4.74[1] |
| Characteristics | |
| Spectral type | B9V[3] |
| U−B color index | −0.03[4] |
| B−V color index | -0.05[4] |
| Astrometry | |
| Radial velocity (Rv) | 64.33±1.32[2] km/s |
| Proper motion (μ) | RA: −0.900[2] mas/yr Dec.: −51.149[2] mas/yr |
| Parallax (π) | 7.9879 ± 0.3689[2] mas |
| Distance | 410 ± 20 ly (125 ± 6 pc) |
| Absolute magnitude (MV) | −0.77[1] |
| Details | |
| Mass | 3.23[5] M☉ |
| Radius | 5.53[5][lower-alpha 1] R☉ |
| Luminosity | 240[5] L☉ |
| Temperature | 9,661[5] K |
| Rotational velocity (v sin i) | 149[5] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
4 Sagittarii, also named Tianyue,[7] is a suspected astrometric binary[8] star system in the zodiac constellation of Sagittarius, located approximately 410 light-years away based on parallax.[2] It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 4.74.[1] The system is moving away from the Earth with a heliocentric radial velocity of +64 km/s.[2]
The visible component is a B-type main-sequence star with a stellar classification of B9 V.[3] It has a high rate of spin, displaying a projected rotational velocity of 149 km/s.[5] This is giving it an oblate shape with an equatorial bulge that is an estimated 14% larger than the polar radius.[9] 4 Sagittarii has 3.23 times the mass of the Sun and is radiating 240 times the Sun's luminosity from its photosphere at an effective temperature of 9,661 K.[5]
In Chinese astronomy, this star is part of the constellation Tiān Yuè (天籥, Celestial Keyhole). The IAU Working Group on Star Names adopted the name Tianyue for this star on 13 August 2026, after this Chinese constellation.[7]
Notes
- ↑ Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:
References
- ↑ 1.0 1.1 1.2 1.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. Vizier catalog entry
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 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.
- ↑ 3.0 3.1 Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H 5050. Bibcode: 1995yCat.5050....0H.
- ↑ 4.0 4.1 Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers 42 (2): 443. Bibcode: 2014JAVSO..42..443M.Vizier catalog entry
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars". Astronomy & Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. Bibcode: 2012A&A...537A.120Z. Vizier catalog entry
- ↑ "4 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=4+Sgr.
- ↑ 7.0 7.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/.
- ↑ Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. doi:10.1111/j.1365-2966.2008.13596.x. Bibcode: 2008MNRAS.389..869E.
- ↑ van Belle, Gerard T. (March 2012). "Interferometric observations of rapidly rotating stars". The Astronomy and Astrophysics Review 20 (1). doi:10.1007/s00159-012-0051-2. Bibcode: 2012A&ARv..20...51V.
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