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Alpha Caeli

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Alpha Caeli (α Cae, α Caeli) is the brightest star in the constellation Caelum. It is in fact a binary star, made up of a F-type star of magnitude 4.46 and a red dwarf of magnitude 12.5. They are separated by 6.6" in the sky. Parallax measurements by the Gaia spacecraft imply a distance of 20.4 pc (67 ly) to Alpha Caeli. A debris disk has been detected around the primary component of the system.

α Caeli
Location of α Caeli in Caelum (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Caelum
A
Right ascension 04h 40m 33.7125s[1]
Declination −41° 51′ 49.5045″[1]
Apparent magnitude (V) 4.456[2] (4.44–4.47[3])
B
Right ascension 04h 40m 34.17s[4]
Declination −41° 51′ 54.7″[4]
Apparent magnitude (V) 12.5[5]
Characteristics
A
Evolutionary stage F-type main-sequence star
Spectral type F2V[6]
Apparent magnitude (U) 4.79[1]
Apparent magnitude (B) 4.79[1]
Apparent magnitude (R) 4.11[1]
Apparent magnitude (G) 4.35[1]
Apparent magnitude (I) 3.9[1]
Apparent magnitude (J) 3.944±0.354[1]
Apparent magnitude (H) 3.654±0.292[1]
Apparent magnitude (K) 3.724±0.324[1]
U−B color index 0.01[7]
B−V color index +0.34[2]
Variable type suspected Delta Scuti[8]
B
Evolutionary stage Red dwarf
Spectral type M0.5V[6]
Variable type Flare star[9]
Astrometry
A
Radial velocity (Rv)0.65±0.3[10] km/s
Proper motion (μ) RA: –139.843 mas/yr[10]
Dec.: –75.677 mas/yr[10]
Parallax (π)49.062 ± 0.00937 mas[10]
Distance66.48 ± 0.01 ly
(20.382 ± 0.004 pc)[10]
Absolute magnitude (MV)2.93±0.01[11]
B
Radial velocity (Rv)−0.6±0.9[4] km/s
Proper motion (μ) RA: −147[4] mas/yr
Dec.: −78[4] mas/yr
Absolute magnitude (MV)9.8[12]
Orbit[5]
PrimaryA
CompanionB
Period (P)460,000 days
(1,260 years)
Semi-major axis (a)133.1 AU
Details
A
Mass1.54[13] M☉
Radius1.546[14] R☉
Luminosity5.156[14] L☉
Surface gravity (log g)4.12[10] cgs
Temperature7,002[14] K
Metallicity [Fe/H]−0.06±0.06[13] dex
Rotation1.4[15] days
Rotational velocity (v sin i)47[16] km/s
Age1.5[13] Gyr
B
Radius0.45[17][a] R☉
Temperature3,355[17] K
Position (relative to A)[18]
ComponentB
Epoch of observation2008
Angular distance6.6″
Other designations
Gliese 174.1, Gaia DR2 4815660547961306112, Gaia DR3 4815660547961306112, GJ 9164, HD 29875, HIP 21770, HR 1502, PPM 308904, WDS J04406-4152A, TIC 77263680, TYC 7589-1693-1, GSC 07589-01693, IRAS 04389-4157, 2MASS J04403374-4151495, WISE J044033.59-415150.2
Database references
SIMBADA
B

Physical properties

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Primary

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The primary component (α Caeli A) has a spectral classification of F2V,[6] meaning that it is a main sequence star, currently fusing hydrogen into helium at its core. It is estimated to be 1.5 billion years old, has 50% more mass[13] and has 1.55 times the Sun's radius.[14] Its photoshpere, which is emitting 5 times the solar luminosity, has an effective temperature of 7000 K,[14] so it is hotter than the Sun and has a white hue, typical of early F-type stars.[19] α Caeli A is a rapid rotator, spinning at its own axis at a projected rotational velocity of 47 km/s.[16]

The star is suspected of being a Delta Scuti variable star.[8] The variation in the brightness is of 0.03 magnitudes.[3] It was first suspected to be a variable star by M. Petit in 1979.[20]

It presents a significant infrared excess at the 100 μm wavelength, which indicates that it is surrounded by a debris disk. The disk extends up to a radius of 46 AU from the star and has a temperature of 60 Kelvin (-213 °C). Its mass is estimated to be about 1/11000 times Earth's mass (ME), and was equivalent to about 1/7100 ME when α Caeli was only 1 million years old.[13]

Companion + Orbit

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The companion (α Caeli B) is a red dwarf star, with spectral class of M0.5V[6] and absolute magnitude 9.80.[12] It is a flare star that undergoes random increases in luminosity.[9] This star was separated from the primary by an angle of 6.6 arcseconds in 2008,[18] but this separation changes over time.[15] They are physically separated by 133 astronomical units and take 1,300 years to fully orbit each other.[5]

Because of the small angular separation and faintness (12.5m) of the companion, Alpha Caeli B is hard to be seen by a small telescope.[15]

Motion

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Alpha Caeli is approximately 66.5 light years from Earth[10] and is an estimated 1.5 billion years old.[13] 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 Galactic Center 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.[11] 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.[21]

The nearest star to Alpha Caeli is LHS 1678, a stellar system formed by a red dwarf star, which is orbited by three exoplanets smaller than Earth, and a possible brown dwarf star.[22][23]

Notes

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  1. ^ Labelled GJ 9164/Wo 9164 in the reference

References

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  1. ^ a b c d e f g h i j "Alpha Caeli". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved June 1, 2024.
  2. ^ a b Ducati, J. R. (2002-01-01). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D. Alpha Caeli's database entry at VizieR.
  3. ^ a b "VSX : Detail for NSV 16147". AAVSO. Retrieved 2024-06-02.
  4. ^ a b c d e "alf Cae b". SIMBAD. Centre de données astronomiques de Strasbourg.
  5. ^ a b c Rodriguez, David R.; Duchêne, Gaspard; Tom, Henry; Kennedy, Grant M.; Matthews, Brenda; Greaves, Jane; Butner, Harold (2015-05-01). "Stellar multiplicity and debris discs: an unbiased sample". Monthly Notices of the Royal Astronomical Society. 449 (3): 3160–3170. arXiv:1503.01320. Bibcode:2015MNRAS.449.3160R. doi:10.1093/mnras/stv483. ISSN 0035-8711. Alpha Caeli's database entry at VizieR.
  6. ^ a b c d Tamazian, V. S.; Malkov, O. Yu. (2014-12-01). "Catalog of Binary UV Ceti Type Flare Stars". Acta Astronomica. 64 (4): 359–369. Bibcode:2014AcA....64..359T. ISSN 0001-5237. Alpha Caeli's database entry at VizieR.
  7. ^ Renson, P.; Manfroid, J. (2009-05-01). "Catalogue of Ap, HgMn and Am stars". Astronomy and Astrophysics. 498 (3): 961–966. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788. ISSN 0004-6361. Alpha Caeli's database entry at VizieR.
  8. ^ a b Hoffleit, D.; Warren Jr., W. H. (1995-11-01). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR Online Data Catalog. 5050: V/50. Bibcode:1995yCat.5050....0H. Alpha Caeli's database entry at VizieR.
  9. ^ a b 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.
  10. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  11. ^ a b 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. Alpha Caeli's database entry at the VizieR.
  12. ^ a b 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.
  13. ^ a b c d e f Gáspár, András; Rieke, George H.; Ballering, Nicholas (2016-08-01). "The Correlation between Metallicity and Debris Disk Mass". The Astrophysical Journal. 826 (2): 171. arXiv:1604.07403. Bibcode:2016ApJ...826..171G. doi:10.3847/0004-637X/826/2/171. ISSN 0004-637X. Alpha Caeli's database entry at VizieR.
  14. ^ a b c d e Schofield, Mathew; Chaplin, William J.; Huber, Daniel; Campante, Tiago L.; Davies, Guy R.; Miglio, Andrea; Ball, Warrick H.; Appourchaux, Thierry; Basu, Sarbani; Bedding, Timothy R.; Christensen-Dalsgaard, Jørgen; Creevey, Orlagh; García, Rafael A.; Handberg, Rasmus; Kawaler, Steven D. (2019-03-01). "The Asteroseismic Target List for Solar-like Oscillators Observed in 2 minute Cadence with the Transiting Exoplanet Survey Satellite". The Astrophysical Journal Supplement Series. 241 (1): 12. arXiv:1901.10148. Bibcode:2019ApJS..241...12S. doi:10.3847/1538-4365/ab04f5. ISSN 0067-0049. Alpha Caeli's database entry at VizieR.
  15. ^ a b c Alpha Cae, Stars, Jim Kaler. Accessed on line June 2, 2024.
  16. ^ a b Mizusawa, Trisha F.; Rebull, Luisa M.; Stauffer, John R.; Bryden, Geoffrey; Meyer, Michael; Song, Inseok (2012-11-01). "Exploring the Effects of Stellar Rotation and Wind Clearing: Debris Disks around F Stars". The Astronomical Journal. 144 (5): 135. arXiv:1208.6248. Bibcode:2012AJ....144..135M. doi:10.1088/0004-6256/144/5/135. ISSN 0004-6256. Alpha Caeli's database entry at VizieR.
  17. ^ a b Johnson, H. M.; Wright, C. D. (1983-11-01). "Predicted infrared brightness of stars within 25 parsecs of the sun". The Astrophysical Journal Supplement Series. 53: 643–711. Bibcode:1983ApJS...53..643J. doi:10.1086/190905. ISSN 0067-0049.
  18. ^ a b Eggleton, P. P.; Tokovinin, A. A. (2008-09-01). "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. ISSN 0035-8711. Alpha Caeli's database entry at VizieR.
  19. ^ "The Colour of Stars". Australia National Telescope Facility. 6 March 2024. Retrieved 2024-05-27.
  20. ^ Petit, M. (November 1977). "Etoiles Proches Suspectees de Variabilite". Information Bulletin on Variable Stars. 1362: 1–3. Bibcode:1977IBVS.1362....1P.
  21. ^ 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.
  22. ^ "★ Alpha Caeli". Stellar Catalog. Retrieved 2024-04-25.
  23. ^ "★ LHS 1678". Stellar Catalog. Retrieved 2024-04-25.
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