Alpha Caeli

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α Caeli
Caelum constellation map.png
Alpha Caeli is at lower center.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Caelum
Right ascension 04h 40m 33.7125s
Declination −41° 51′ 49.509″[1]
Apparent magnitude (V) 4.456
Right ascension 04h 40m 34.0s
Declination −41° 51′ 51″[2]
Apparent magnitude (V) 12.5[2]
Spectral type F2V[3]
U−B color index +0.01[4]
B−V color index +0.34[4]
Spectral type M0.5[2]
Radial velocity (Rv)–0.6 ± 0.9[5] km/s
Proper motion (μ) RA: –141.18[1] mas/yr
Dec.: –74.95[1] mas/yr
Parallax (π)49.67 ± 0.53 mas[1]
Distance65.7 ± 0.7 ly
(20.1 ± 0.2 pc)
Absolute magnitude (MV)3.39[6]
Radial velocity (Rv)−0.6 ± 0.9[2] km/s
Proper motion (μ) RA: −147[2] mas/yr
Dec.: −78[2] mas/yr
Mass1.48[7] M
Radius1.3[8] R
Surface gravity (log g)4.01[3] cgs
Temperature6,991[3] K
Metallicity [Fe/H]−0.10[3] dex
Rotational velocity (v sin i)47.8±2.4[9] km/s
Age0.9 (0.7–1.3)[7] Gyr
Mass0.3[10] M
Temperature3,800[10] K
Other designations
A: CCDM J04406-4152A, CD−42°1587, CPD−42°513, FK5 1129, GC 5708, Gl 174.1 A, GJ 9164 A, HD 29875, HIP 21770, HR 1502, IDS 04373-4203 A, SAO 216926.[11]
B: CCDM J04406-4152B, CD−42°1587B, CPD−42°513B, Gl 174.1 B, GJ 9164 B, IDS 04373-4203 B.[2]
Database references

Alpha Caeli (α Cae, α Caeli) is a double star system in the constellation Caelum.

Physical Properties[edit]


Alpha Caeli A is an F-type main sequence star with a stellar classification of F2V and an apparent magnitude of +4.44. It has 1.48 times the mass of the Sun[7] and 1.3 times the solar radius.[8] The projected rotational velocity at the stellar equator is 47.8 km/s.[9] It is suspected of being a Delta Scuti variable star.[12]

Companion + Orbit[edit]

The companion is a spectral class M0.5V red dwarf star with absolute magnitude 9.80.[13] It is a UV Ceti variable star that undergoes random increases in luminosity.[14] This star is currently separated from the primary by an angle of 6.6 arcseconds, which indicates an orbit with a semimajor axis whose expected value is 206 AU.[15]


Alpha Caeli is approximately 65.7 light years from Earth and is an estimated 900 million years old. The space velocity components of this system are U = 10, V = 6 and W = -10 km/s. It is orbiting the Milky Way galaxy at an average distance of 8.006 kpc from the core and with an orbital eccentricity of 0.07. This orbit lies close to the galactic plane, and the system travels no more than 0.05 kpc above or below this plane.[7] Alpha Caeli is probably a member of the Ursa Major moving group of stars that have similar kinematic properties and probably originated from the same star cluster.[16]


  1. ^ a b c d Perryman, M. A. C.; et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. ^ a b c d e f g GJ 174.1 B -- Flare Star, database entry, SIMBAD. Accessed on line November 5, 2009.
  3. ^ a b c d Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  4. ^ a b Johnson, H. L.; Iriarte, B.; Mitchell, R. I.; Wisniewskj, W. Z. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: Academic Press. Bibcode:1967IAUS...30...57E.
  6. ^ Reiners, Ansgar (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics, 446 (1): 267–277, arXiv:astro-ph/0509399, Bibcode:2006A&A...446..267R, doi:10.1051/0004-6361:20053911, S2CID 8642707
  7. ^ a b c d Holmberg, J.; et al. (November 2007). "The Geneva-Copenhagen survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk". Astronomy and Astrophysics. 475 (2): 519–537. arXiv:0707.1891. Bibcode:2007A&A...475..519H. doi:10.1051/0004-6361:20077221. S2CID 119054949. See the entry for HIP 21770 in the VizieR table with CDS ID V/117A Archived 2016-03-03 at the Wayback Machine.
  8. ^ a b Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics". Astronomy and Astrophysics. 367 (2): 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451. S2CID 425754.
  9. ^ a b Reiners, Ansgar; Schmitt, Jürgen H. M. M. (December 2003), "Differential rotation in rapidly rotating F-stars", Astronomy and Astrophysics, 412 (3): 813−819, arXiv:astro-ph/0309616, Bibcode:2003A&A...412..813R, doi:10.1051/0004-6361:20034255, S2CID 16900202.
  10. ^ a b Alpha Cae, Stars, Jim Kaler. Accessed on line November 5, 2009.
  11. ^ * alf Cae -- Star in double system, database entry, SIMBAD. Accessed on line November 4, 2009.
  12. ^ Petit, M. (November 1977). "Etoiles Proches Suspectees de Variabilite". Information Bulletin on Variable Stars. 1362: 1–3. Bibcode:1977IBVS.1362....1P.
  13. ^ Hawley, Suzanne L.; Gizis, John E.; Reid, Neill I. (April 1997). "Erratum: The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity". Astronomical Journal. 113: 1458. Bibcode:1997AJ....113.1458H. doi:10.1086/118363.
  14. ^ Gershberg, R. E.; et al. (November 1999). "Catalogue and bibliography of the UV Cet-type flare stars and related objects in the solar vicinity". Astronomy and Astrophysics Supplement. 139 (3): 555–558. Bibcode:1999A&AS..139..555G. doi:10.1051/aas:1999407.
  15. ^ Poveda, A.; et al. (April 1994). "Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems". Revista Mexicana de Astronomía y Astrofísica. 28 (1): 43–89. Bibcode:1994RMxAA..28...43P.
  16. ^ King, Jeremy R.; et al. (April 2003). "Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group". The Astronomical Journal. 125 (4): 1980–2017. Bibcode:2003AJ....125.1980K. doi:10.1086/368241.