Kappa1 Ceti

Kappa1 Ceti
Diagram showing star positions and boundaries of the Cetus constellation and its surroundings


Location of κ1 Ceti (circled)

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 03h 19m 21.6960s[1]
Declination +03° 22′ 12.712″[1]
Apparent magnitude (V) 4.84
Characteristics
Spectral type G5Vv[2]
U−B color index +0.185[3]
B−V color index +0.674[3]
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)+19.9[5] km/s
Proper motion (μ) RA: 269.30 ± 0.24[1] mas/yr
Dec.: 93.75 ± 0.22[1] mas/yr
Parallax (π)109.41 ± 0.27[1] mas
Distance29.81 ± 0.07 ly
(9.14 ± 0.02 pc)
Absolute magnitude (MV)5.16[6]
Details
Mass1.037 ± 0.042[7] M☉
Radius0.95 ± 0.10[8] R☉
Luminosity0.85[9] L☉
Surface gravity (log g)4.51[10] cgs
Temperature5,708[10] K
Metallicity [Fe/H]+0.05[10] dex
Rotation9.2 days[9]
Rotational velocity (v sin i)4.5[9] km/s
Age300–400[11] Myr
Other designations
Kappa1 Ceti, 96 Ceti, BD+02°518, FK5 1095, GCTP 691.00, Gliese 137, HD 20630, HIP 15457, HR 996, LTT 11094, SAO 111120
Database references
SIMBADdata
ARICNSdata

Kappa1 Ceti (κ1 Cet, κ1 Ceti) is a yellow dwarf star approximately 30 light-years away[1] in the equatorial constellation of Cetus. The star was discovered to have a rapid rotation, roughly once every nine days. Though there are no extrasolar planets confirmed to be orbiting the star, Kappa1 Ceti is considered a good candidate to contain terrestrial planets (like the Earth). The system is a candidate binary star, but has not been confirmed.[12] The star should not be confused with the star Kappa2 Ceti, which is ten times as distant.

Stellar components

Kappa1 Ceti is a yellow dwarf star of the spectral type G5Ve. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[13] The star has roughly the same mass as the Sun, with 95% of the Sun's radius[8] but only 85 percent of the luminosity.[9] It is unclear whether the star is equal or is more enriched in elements heavier than hydrogen, but it is determined that the star has between 98 and 240 percent of the Sun's abundance of iron. Kappa1 Ceti is much younger than the Sun, and may only be around 800 million years old.

The rapid rotation rate of this star, approximately once every nine days, is indicative of a relatively youthful body several hundred million years in age. Due to starspots, the star varies slightly over the approximately the same period. The variations in period are thought to be caused by differential rotation at various latitudes, similar to what happens on the surface of our Sun. The star spots on Kappa1 Ceti range in latitude from 10° to 75°[9] The magnetic properties of this star make it "an excellent match for the Sun at a key point in the Earth's past".[14]

According to recent hypotheses, unusually intense stellar flares from a solar twin star could be caused by the interaction of the magnetic field of a giant planet in tight orbit with that star's own magnetic field. Some Sun-like stars of spectral class F8 to G8 have been found to undergo enormous magnetic outbursts to produce so-called superflares (coronal mass ejections) that release between 100 and 10 million times more energy than the largest flares ever observed on the sun, making them brighten briefly by up to 20 times.[15] In 1998, nine Solar twin stars (including Kappa1 Ceti) were observed to have produced superflares, on average, about once per century. None of these stars rotate particularly fast, have close binary companions, or are very young. Previously, such large flares had not been observed in solar-type main sequence stars, although they are common in a group of dim main-sequence, reddish M dwarfs known as flare stars.

The space velocity components of this star are (U, V, W) = (−22.41, −4.27, −5.32) km/s.[2] It is not known to be a member of a moving group of stars.[9]

Possible planetary system

Using the radial velocity technique, the search for substellar companions has thus far failed to find a brown dwarf or extrasolar planet in the "hot zone" orbit around Kappa1 Ceti. Given the regular eruption of superflares, however, it is unlikely that Earth-type life could survive for long on any inner terrestrial planet. The distance from the star where an Earth-type planet (with liquid water) would be stable is centered on 0.92 astronomical units from the star (between the orbital distances of Earth and Venus in the Solar system). At this distance, such a planet would have an orbital period of almost 324 days.

References

  1. 1 2 3 4 5 6 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. 1 2 Montes, D.; et al. (November 2001). "Late-type members of young stellar kinematic groups - I. Single stars". Monthly Notices of the Royal Astronomical Society 328 (1): 45–63. arXiv:astro-ph/0106537. Bibcode:2001MNRAS.328...45M. doi:10.1046/j.1365-8711.2001.04781.x.
  3. 1 2 Cousins, A. W. J. (1984). "Standardization of Broadband Photometry of Equatorial Standards". Circulars of the South African Astronomical Observatory 8: 59. Bibcode:1984SAAOC...8...59C.
  4. ↑ Kukarkin, B. V.; et al. (1981). Nachrichtenblatt der Vereinigung der Sternfreunde e.V. (Catalogue of suspected variable stars). Moscow, Academy of Sciences USSR Shternberg. Bibcode:1981NVS...C......0K.
  5. ↑ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  6. ↑ Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics 343: 222–228, Bibcode:1999A&A...343..222E
  7. ↑ Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101
  8. 1 2 Walker, Gordon A. H.; et al. (April 2007). "The Differential Rotation of κ1 Ceti as Observed by MOST". The Astrophysical Journal 659 (2): 1611–1622. arXiv:0704.2204. Bibcode:2007ApJ...659.1611W. doi:10.1086/511851.
  9. 1 2 3 4 5 6 Gaidos, E. J.; Henry, G. W.; Henry, S. M. (2000). "Spectroscopy and Photometry of Nearby Young Solar Analogs". The Astronomical Journal 120 (2): 1006–1013. Bibcode:2000AJ....120.1006G. doi:10.1086/301488.
  10. 1 2 3 Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (March 2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788.
  11. ↑ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785.
  12. ↑ Hartkopf, W. I.; McAlister, H. A. (January 1984), "Binary stars unresolved by speckle interferometry. III", Astronomical Society of the Pacific 96: 105−116, Bibcode:1984PASP...96..105H, doi:10.1086/131309
  13. ↑ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
  14. ↑ Ribas, Ignasi (February 2010), "Solar and Stellar Variability: Impact on Earth and Planets, Proceedings of the International Astronomical Union, IAU Symposium", Proceedings of the International Astronomical Union 264: 3–18, arXiv:0911.4872, Bibcode:2010IAUS..264....3R, doi:10.1017/S1743921309992298 |contribution= ignored (help)
  15. ↑ Schaefer, Bradley E.; King, Jeremy R.; Deliyannis, Constantine P. (2000). "Superflares on Ordinary Solar-Type Stars". The Astrophysical Journal 529 (2): 1026–1030. arXiv:astro-ph/9909188. Bibcode:2000ApJ...529.1026S. doi:10.1086/308325.

External links

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