Astronomy:Eta Cancri
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 32m 42.49600s[1] |
| Declination | 20° 26′ 28.1865″[1] |
| Apparent magnitude (V) | 5.34[2] |
| Characteristics | |
| Spectral type | K3 III[2] |
| U−B color index | +1.40[2] |
| B−V color index | +1.25[2] |
| Astrometry | |
| Radial velocity (Rv) | +22.46[3] km/s |
| Proper motion (μ) | RA: −46.33[1] mas/yr Dec.: −44.31[1] mas/yr |
| Parallax (π) | 10.93 ± 0.40[1] mas |
| Distance | 300 ± 10 ly (91 ± 3 pc) |
| Absolute magnitude (MV) | +0.44[4] |
| Details | |
| Mass | 1.51[5] M☉ |
| Radius | 17[6] R☉ |
| Luminosity | 87[5] L☉ |
| Surface gravity (log g) | 2.1[6] cgs |
| Temperature | 4,415±57[5] K |
| Metallicity [Fe/H] | 0.07±0.21[4] dex |
| Rotational velocity (v sin i) | 2.7[6] km/s |
| Age | 3.92[5] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Cancri, Latinized from η Cancri, is a single,[8] orange-hued star in the zodiac constellation of Cancer. It is a faint star but visible to the naked eye with an apparent visual magnitude of 5.34.[2] The annual parallax shift of 10.93[1] mas as seen from Earth yields a distance estimate of 155 light years from the Sun. It is moving further away with a radial velocity of +22 km/s.[3]
A stellar classification of K3 III[2] for Eta Cancri indicates that, at the estimated age of 3.9 billion years old,[5] it has left the main sequence and become an evolved giant star. The spectrum shows unusually strong absorption lines of cyanogen.[2] It has 1.5[5] times the mass of the Sun and has expanded to 17[6] times the Sun's radius. The star is radiating 87[5] times the Sun's luminosity from its photosphere at an effective temperature of around 4,415 K.[5]
In Chinese astronomy, Ghost (Chinese: 鬼宿; pinyin: Guǐ Xiù) refers to an asterism consisting of Theta Cancri, Eta Cancri, Gamma Cancri and Delta Cancri.[9] Eta Cancri itself is the second star of Ghost (Chinese: 鬼宿二; pinyin: Guǐ Xiù èr), following the designation from its determinative star (θ Cnc) from east to west.
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. Vizier catalog entry
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 McClure, R. D. (February 1970). "A photometric investigation of strong-cyanogen stars". Astronomical Journal 75: 41–52. doi:10.1086/110938. Bibcode: 1970AJ.....75...41M.
- ↑ 3.0 3.1 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
- ↑ 4.0 4.1 Luck, R. Earle; Heiter, Ulrike (June 2007), "Giants in the Local Region", The Astronomical Journal 133 (6): 2464–2486, doi:10.1086/513194, Bibcode: 2007AJ....133.2464L
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 23, doi:10.1088/0004-6256/150/3/88, 88, Bibcode: 2015AJ....150...88L.
- ↑ 6.0 6.1 6.2 6.3 Massarotti, Alessandro et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal 135 (1): 209–231, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M
- ↑ "* eta Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+eta+Cnc.
- ↑ 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.
- ↑ 陳久金 (2005). Zhōngguó Xīngzuò Shénhuà. 台灣古籍出版有限公司. p. 394. ISBN 978-986-7332-25-7. https://books.google.com/books?id=0Vex0rYzdu8C&pg=394.
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