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
Component A B
Right ascension 04h 40m 04h 40m
  33.7125s 34.0s
Declination –41° 51′[1] −41° 51′[2]
  49.509″ 51″
Apparent magnitude (V) 4.456 12.5[2]
Spectral type F2V[3] M0.5[2]
U-B color index +0.01[4]
B-V color index +0.34[4]
Radial velocity (Rv) –0.6 ± 0.9[5] km/s −0.6 ± 0.9[2] km/s
Proper motion:  
RA α cos δ)  –141.18[1] mas/yr  −147[2] mas/yr 
Dec. δ)  –74.95[1] mas/yr  −78[2] mas/yr 
Parallax (π) 49.67 ± 0.53[1] mas
Distance 65.7 ± 0.7 ly
(20.1 ± 0.2 pc)
Absolute magnitude (MV) 3.39[6]
Mass 1.48[7] M 0.3[8] M
Radius 1.3[9] R
Surface gravity (log g) 4.01[3]
Temperature 6,991[3] K 3800[8] K
Metallicity \begin{smallmatrix}\left[\frac{M}{H}\right]\ =\ -0.10\end{smallmatrix}[3]
Rotational velocity (v sin i) 47.8 ± 2.4[10]km/s
Age 0.9 (0.7–1.3) × 109[7]y
Database references
SIMBAD data data
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]

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

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.[9] The projected rotational velocity at the stellar equator is 47.8 km/s.[10] It is suspected of being a Delta Scuti variable star.[12]

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. 
  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). Bibcode:1966CoLPL...4...99J. 
  5. ^ Evans, D. S. (June 20–24, 1966). "Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30". University of Toronto: Academic Press. Bibcode:1967IAUS...30...57E.  |chapter= ignored (help)
  6. ^ Reiners, A. (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. 
  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.  See the entry for HIP 21770 in the VizieR table with CDS ID V/117A.
  8. ^ a b Alpha Cae, Stars, Jim Kaler. Accessed on line November 5, 2009.
  9. ^ 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. 
  10. ^ a b Reiners, A.; Schmitt, J. 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. 
  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 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.