Beta Cancri
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 Al Tarf is the bottom right star in the "crab" |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Cancer |
| Right ascension | 08h 16m 30.9206s[1] |
| Declination | +09° 11′ 07.961″[1] |
| Apparent magnitude (V) | 3.536 [1] |
| Characteristics | |
| Spectral type | K4III [1] |
| U−B color index | -1.77 [1] |
| B−V color index | -1.48 [1] |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | 22.94 [1] km/s |
| Proper motion (μ) | RA: -46.80 [1] mas/yr Dec.: −48.65 [1] mas/yr |
| Parallax (π) | 11.23 ± 0.97[1] mas |
| Distance | 290 ± 30 ly (89 ± 8 pc) |
| Absolute magnitude (MV) | -1.21 |
| Details | |
| Radius | 48 ± 4[2] R☉ |
| Luminosity | 660[3] L☉ |
| Surface gravity (log g) | 1.51[4] |
| Temperature | 4,039[4] K |
| Metallicity | -0.12[4] |
| Rotational velocity (v sin i) | 8[1] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Beta Cancri (β Cnc, β Cancri) is the brightest star in the constellation Cancer. It has the traditional name Tarf or Al Tarf (Altarf), certainly a derivation from Arabic الطرف aṭ-ṭarf "the eye" or طرفة aṭ-ṭarfah "the glance (of Leo)". It is approximately 290 light years from Earth.
This is an orange K-type giant with an apparent magnitude of +3.50 and absolute magnitude of -1.25 (visual). It has a faint, fourteenth magnitude companion located 29 arcseconds away.
[edit] See also
- Lists of stars in the constellation Cancer
- Class K Stars
- Barium star
[edit] References
- ^ a b c d e f g h i j k "SIMBAD query result: NSV 3973 -- Variable Star". Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HR3249. Retrieved 2010-02-23.
- ^ Nordgren, Tyler E. et al., "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal 118 (6): 3032-303
- ^ Kaler, James B.. "AL TARF (Beta Cancri)". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/altarf.html. Retrieved 2010-02-23.
- ^ a b c Cenarro, A. J.; Peletier, R. F., et al (2007). "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters" (PDF). Monthly Notices of the Royal Astronomical Society 374 (2): 664–690. arXiv:astro-ph/0611618. Bibcode 2007MNRAS.374..664C. doi:10.1111/j.1365-2966.2006.11196.x.
[edit] External links
Jim Kaler's Stars: Al Tarf
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