Eta Cancri

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]

Eta Cancri
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[1] mas
Distance300 ± 10 ly
(91 ± 3 pc)
Absolute magnitude (MV)+0.44[4]
Details
Mass1.51[5] M☉
Radius17[6] R☉
Luminosity87[5] L☉
Surface gravity (log g)2.1[6] cgs
Temperature4,415±57[5] K
Metallicity [Fe/H]0.07±0.21[4] dex
Rotational velocity (v sin i)2.7[6] km/s
Age3.92[5] Gyr
Other designations
η Cnc, 33 Cnc, BD+20° 2109, FK5 321, GC 11687, HD 72292, HIP 41909, HR 3366, SAO 80243[7]
Database references
SIMBADdata

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. 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. Vizier catalog entry
  2. 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.
  3. 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
  4. 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
  5. 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, 88.
  6. 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
  7. "* eta Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-10-07.
  8. 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.
  9. 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.
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