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]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 mas[1] |
| 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 |
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
edit- ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
- ^ a b c d e f g McClure, R. D. (February 1970). "A photometric investigation of strong-cyanogen stars". Astronomical Journal. 75: 41–52. Bibcode:1970AJ.....75...41M. doi:10.1086/110938.
- ^ a b 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, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304
- ^ a b Luck, R. Earle; Heiter, Ulrike (June 2007), "Giants in the Local Region", The Astronomical Journal, 133 (6): 2464–2486, Bibcode:2007AJ....133.2464L, doi:10.1086/513194
- ^ a b c d e f g h Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
- ^ a b c d 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, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
- ^ "* eta Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-10-07.
- ^ 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
- ^ 陳久金 (2005). Zhōngguó Xīngzuò Shénhuà 中國星座神話 [Chinese Constellation Mythology]. 台灣古籍出版有限公司. p. 394. ISBN 978-986-7332-25-7.