Astronomy:3 Equulei
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Equuleus |
| Right ascension | 21h 04m 34.65147s[1] |
| Declination | +5° 30′ 10.3032″[1] |
| Apparent magnitude (V) | 5.593[2] |
| Characteristics | |
| Spectral type | K5 III[3] |
| U−B color index | +1.934[2] |
| B−V color index | +1.651[2] |
| Astrometry | |
| Radial velocity (Rv) | –15.26 ± 0.2[4] km/s |
| Proper motion (μ) | RA: +13.15[1] mas/yr Dec.: +0.66[1] mas/yr |
| Parallax (π) | 4.24 ± 0.42[1] mas |
| Distance | 770 ± 80 ly (240 ± 20 pc) |
| Absolute magnitude (MV) | –1.02[5] |
| Details | |
| Radius | 63[6] R☉ |
| Luminosity | 949[7] L☉ |
| Temperature | 3,893[8] K |
| Rotational velocity (v sin i) | 4.6[7] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
3 Equulei is a single[3] star located in the small northern constellation of Equuleus. It is faintly visible to the naked eye at an apparent visual magnitude of 5.6.[2] Based upon an annual parallax shift of 4.24 mas,[1] 3 Equulei is roughly 770 light-years (240 parsecs) distant from Earth, give or take an 80 light-year margin of error. At that distance, the apparent brightness of the star is diminished by 0.15 in visual magnitude because of extinction from interstellar gas and dust.[4]
3 Equulei has been referred to in some sources as ζ (Zeta) Equulei, although it was not given that designation by Bayer.[10]
Properties
3 Equulei is an evolved giant star with a stellar classification of K5 III.[3] The measured angular diameter of this star, after correction for limb darkening, is 2.44 ± 0.03 mas.[11] At the estimated distance of Delta Ophiuchi,[1] this yields a physical size of about 63 times the radius of the Sun.[6] It is radiating an estimated 949[7] times the luminosity of the Sun from this expanded outer envelope at an effective temperature of 3,893 K.[8] At this heat, it shines with the orange-hued glow of a K-type star.[12]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 van Leeuwen, F. (November 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 Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode: 1984SAAOC...8...59C.
- ↑ 3.0 3.1 3.2 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.
- ↑ 4.0 4.1 Famaey, B. et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics 430 (1): 165–186, doi:10.1051/0004-6361:20041272, Bibcode: 2005A&A...430..165F.
- ↑ Ryon, Jenna; Shetrone, Matthew D.; Smith, Graeme H. (August 2009), "Comparing the Ca ii H and K Emission Lines in Red Giant Stars", Publications of the Astronomical Society of the Pacific 121 (882): 842–856, doi:10.1086/605456, Bibcode: 2009PASP..121..842R.
- ↑ 6.0 6.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 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{(240\cdot 2.44\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 126\cdot R_{\bigodot} \end{align} }[/math]
- ↑ 7.0 7.1 7.2 Henry, Gregory W. et al. (September 2000), "Photometric Variability in a Sample of 187 G and K Giants", The Astrophysical Journal Supplement Series 130 (1): 201–225, doi:10.1086/317346, Bibcode: 2000ApJS..130..201H.
- ↑ 8.0 8.1 Soubiran, C.; Le Campion, J.-F.; Cayrel de Strobel, G.; Caillo, A. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics 515: A111, doi:10.1051/0004-6361/201014247, Bibcode: 2010A&A...515A.111S.
- ↑ "* 3 Equ". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+3+Equ.
- ↑ 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.
- ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (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
- ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-07-21.
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