Astronomy:Theta Geminorum
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Gemini |
| Right ascension | 06h 52m 47.33887s[1] |
| Declination | +33° 57′ 40.5175″[1] |
| Apparent magnitude (V) | 3.59[2] |
| Characteristics | |
| Spectral type | A2 IV[3] |
| U−B color index | +0.13[2] |
| B−V color index | +0.10[2] |
| Astrometry | |
| Radial velocity (Rv) | +21[4] km/s |
| Proper motion (μ) | RA: −1.66[1] mas/yr Dec.: −47.31[1] mas/yr |
| Parallax (π) | 17.25 ± 0.19[1] mas |
| Distance | 189 ± 2 ly (58.0 ± 0.6 pc) |
| Absolute magnitude (MV) | −0.18[5] |
| Details | |
| Mass | 1.80[6] M☉ |
| Radius | 5.1[7] R☉ |
| Luminosity | 93[8] L☉ |
| Surface gravity (log g) | 3.40±0.14[6] cgs |
| Temperature | 8,502±289[6] K |
| Rotational velocity (v sin i) | 133[9] km/s |
| Age | 252[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Theta Geminorum (θ Gem, θ Geminorum) is a single[11] star in the northern zodiac constellation of Gemini. It is visual to the naked eye with an apparent visual magnitude of 3.59.[2] Based upon an annual parallax shift of 17.25 mas,[1] it is about 189 light years distant from the Sun.
This is an evolving A-type subgiant star with a stellar classification of A2 IV.[3] It has 1.80[6] times the mass of the Sun and radiates 93[8] times the solar luminosity. The measured angular diameter is 0.82±0.03 mas.[12] At an estimated distance of this star, this yields a physical size of about 5.1 times the radius of the Sun.[7] It is around 252 million years old and has a projected rotational velocity of 133[9] km/s. This rotation rate is giving the star an oblate shape, with an equatorial bulge that is 11% larger than the polar radius.[13]
The Washington Visual Double Star Catalog lists five visual companions within 100″; the closest and brightest such companion is the magnitude 8.6 θ Geminorum E at an angular separation of 2.4″ along a position angle of 295°, as of 2010.[14]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V.
- ↑ 2.0 2.1 2.2 2.3 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M.
- ↑ 3.0 3.1 Abt, Helmut A.; Morrell, Nidia I. (1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement 99: 135, doi:10.1086/192182, Bibcode: 1995ApJS...99..135A.
- ↑ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, 30, University of Toronto: International Astronomical Union, p. 57, Bibcode: 1967IAUS...30...57E.
- ↑ Huang, W. et al. (2012), "A catalogue of Paschen-line profiles in standard stars", Astronomy & Astrophysics 547: A62, doi:10.1051/0004-6361/201219804, Bibcode: 2012A&A...547A..62H.
- ↑ 6.0 6.1 6.2 6.3 6.4 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D.
- ↑ 7.0 7.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41. The radius (R*) is given by:
- [math]\displaystyle{ \begin{align} 2\cdot R_* & = \frac{(58.0\cdot 0.82\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 10.2\cdot R_{\bigodot} \end{align} }[/math]
- ↑ 8.0 8.1 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M.
- ↑ 9.0 9.1 Royer, F. et al. (October 2012), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, doi:10.1051/0004-6361:20020943, Bibcode: 2002A&A...393..897R.
- ↑ "tet Gem". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tet+Gem.
- ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
- ↑ Richichi, A. et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R.
- ↑ van Belle, Gerard T., Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode: 2012A&ARv..20...51V.
- ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M.
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