Kapteyn's Star
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Pictor |
| Right ascension | 05h 11m 40.58112s[1] |
| Declination | -45° 01′ 06.2899″[1] |
| Apparent magnitude (V) | 8.853[2] |
| Characteristics | |
| Spectral type | sdM1[2] |
| U−B color index | +1.21[3] |
| B−V color index | +1.57[3] |
| Variable type | BY Dra[4] |
| Astrometry | |
| Radial velocity (Rv) | +245.2[5] km/s |
| Proper motion (μ) | RA: +6,505.08[1] mas/yr Dec.: -5,730.84[1] mas/yr |
| Parallax (π) | 255.66 ± 0.91[1] mas |
| Distance | 12.76 ± 0.05 ly (3.91 ± 0.01 pc) |
| Details | |
| Mass | 0.274[6] M☉ |
| Radius | 0.293[6] R☉ |
| Surface gravity (log g) | 4.96[6] |
| Temperature | 3,570[6] K |
| Metallicity [Fe/H] | –0.99 ± 0.04[7] dex |
| Rotational velocity (v sin i) | 9.15[8] km/s |
| Age | ~10 Gyr[6] years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Kapteyn's Star is a class M1 red dwarf star about 13 light years from Earth in the southern constellation of Pictor. With a magnitude of nearly 9 it is visible through binoculars or a telescope.[3]
Contents |
[edit] History
The star now known as Kapteyn's Star was originally cataloged by the Dutch astronomer, Jacobus Kapteyn, in 1898.[9] While he was reviewing star charts and photographic plates he noted the star's very high proper motion of more than 8 arc seconds per year. Later, the star became referred to as Kapteyn's Star, in honor of its discoverer.[10] At that time, it had the highest proper motion of any star known, dethroning Groombridge 1830. With the discovery of Barnard's Star in 1916,[11] Kapteyn's Star dropped to second place, where it remains.[6][10]
[edit] Characteristics
Based upon parallax measurements, Kapteyn's Star is at a distance of 12.76 light-years (3.91 parsecs) from the Earth.[1] It came within 7.00 light-years (2.15 parsecs) of the Sun about 10,800 years ago and has been moving away since that time.[12] The star is between one quarter and one third the size and mass of the Sun and much cooler at about 3500°K, with some disagreement in the exact measurements between different observers.[6] The stellar classification is sdM1,[2] which indicates that it is a subdwarf star with a luminosity lower than that of a main sequence star at the same spectral type of M1. The abundance of elements other than hydrogen and helium, what astronomers term the metallicity, is about 14% of the abundance in the Sun.[7][13] It is a variable star of the BY Draconis type with the identifier VZ Pictoris. This means that the luminosity of the star changes because of magnetic activity in the chromosphere coupled with rotation moving the resulting star spots into and out of the line of sight with respect to the Earth.[4]
Kapteyn's Star is distinctive in a number of other regards: it has a high radial velocity,[10] orbits the Milky Way retrograde,[6] and is the nearest known halo star to the Sun.[14] It is a member of a moving group of stars that share a common trajectory through space, named the Kapteyn moving group.[15] Based upon their element abundances, these stars may once have been members of the Omega Centauri, a globular cluster that is thought to be the remnant of a dwarf galaxy that merged with the Milky Way. During this process, the stars in the group, including Kapteyn's Star, may have been stripped away as tidal debris.[16][6][17]
[edit] See also
[edit] References
- ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
- ^ a b c Koen, C. et al. (April 2010), "UBV(RI)C JHK observations of Hipparcos-selected nearby stars", Monthly Notices of the Royal Astronomical Society 403 (4): 1949–1968, Bibcode 2010MNRAS.403.1949K, doi:10.1111/j.1365-2966.2009.16182.x
- ^ a b c d "V* VZ Pic -- Variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NAME+Kapteyn%27s+star, retrieved 2009-10-14.
- ^ a b "VZ Pic", General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia, http://www.sai.msu.su/groups/cluster/gcvs/cgi-bin/search.cgi?search=VZ+pic, retrieved 2009-10-14
- ^ Nordström, B. et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics 418 (3): 989–1019, arXiv:astro-ph/0405198, Bibcode 2004A&A...418..989N, doi:10.1051/0004-6361:20035959
- ^ a b c d e f g h i Kotoneva, E. et al. (2005), "A study of Kapteyn's star", Astronomy & Astrophysics 438 (3): 957–962, Bibcode 2005A&A...438..957K, doi:10.1051/0004-6361:20042287.
- ^ a b Woolf, Vincent M.; Wallerstein, George (January 2005), "Metallicity measurements using atomic lines in M and K dwarf stars", Monthly Notices of the Royal Astronomical Society 356 (3): 963–968, Bibcode 2005MNRAS.356..963W, doi:10.1111/j.1365-2966.2004.08515.x
- ^ Houdebine, E. R. (September 2010), "Observation and modelling of main-sequence star chromospheres - XIV. Rotation of dM1 stars", Monthly Notices of the Royal Astronomical Society 407 (3): 1657–1673, Bibcode 2010MNRAS.407.1657H, doi:10.1111/j.1365-2966.2010.16827.x
- ^ Kapteyn, J. C. (1898), "Stern mit grösster bislang bekannter Eigenbewegung", Astronomische Nachrichten 145 (9–10): 159–160, Bibcode 1897AN....145..159K, doi:10.1002/asna.18981450906.
- ^ a b c Kaler, James B. (2002), "Kapteyn's Star", The Hundred Greatest Stars, Copernicus Books, pp. 108–109.
- ^ Barnard, E. E. (1916), "A small star with large proper motion", Astronomical Journal 29 (695): 181, Bibcode 1916AJ.....29..181B, doi:10.1086/104156.
- ^ Bobylev, Vadim V. (March 2010), "Searching for Stars Closely Encountering with the Solar System", Astronomy Letters 36 (3): 220–226, arXiv:1003.2160, Bibcode 2010AstL...36..220B, doi:10.1134/S1063773710030060.
- ^ The abundance is given by taking the metallicity to the power of 10. From Woolf and Wallerstein (2005), [M/H] ≈ –0.86 dex. Thus:
- 10–0.86 = 0.138
- ^ Woolf, V. M.; Wallerstein, G. (2004), "Chemical abundance analysis of Kapteyn's Star", Monthly Notices of the Royal Astronomical Society 350 (2): 575–579, Bibcode 2004MNRAS.350..575W, doi:10.1111/j.1365-2966.2004.07671.x.
- ^ Eggen, O. J. (December 1996), "The Ross 451 Group of Halo Stars", Astronomical Journal 112: 2661, Bibcode 1996AJ....112.2661E
- ^ Wylie-de Boer, Elizabeth; Freeman, Ken; Williams, Mary (February 2010), "Evidence of Tidal Debris from ω Cen in the Kapteyn Group", The Astronomical Journal 139 (2): 636–645, Bibcode 2010AJ....139..636W, doi:10.1088/0004-6256/139/2/636
- ^ "Backward star ain't from round here", New Scientist, November 4, 2009, http://www.newscientist.com/article/mg20427334.100-backward-star-aint-from-round-here.html
[edit] Additional reading
- Luyten, W. J. (1927), "Note on the magnitude and spectrum of Kapteyn's star", Harvard College Observatory Bulletin 843: 3–4, Bibcode 1927BHarO.843....3L.
- MacConnell, D. J. (1973), "The spectrum and colors of Kapteyn's star", Bulletin of the American Astrnomical Society 5: 346, Bibcode 1973BAAS....5..346M.
- Murdin, Paul, ed. (2001), "Kapteyn's Star", Encyclopedia of Astronomy and Astrophysics, Bristol: Institute of Physics Publishing, doi:10.1888/0333750888/5156.
- Wing, R. F.; Dean, C. A.; MacConnell, D. J. (1976), "The temperature, luminosity, and spectrum of Kapteyn's star", The Astrophysical Journal 205: 186–193, Bibcode 1976ApJ...205..186W, doi:10.1086/154263.
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