Theta Arae

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Theta Arae
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
Cercle rouge 100%.svg

The location of θ Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 18h 06m 37.87129s[1]
Declination –50° 05′ 29.3125″[1]
Apparent magnitude (V) +3.67[2]
Spectral type B2 Ib[3]
U−B color index –0.870[2]
B−V color index –0.109[2]
Radial velocity (Rv) +3.4[4] km/s
Proper motion (μ) RA: –8.27[1] mas/yr
Dec.: –8.70[1] mas/yr
Parallax (π) 4.01 ± 0.15[1] mas
Distance 810 ± 30 ly
(249 ± 9 pc)
Mass 8.9 ± 0.1[5] M
Radius 20.1[6] R
Surface gravity (log g) 2.70[7] cgs
Temperature 17,231 ± 231[6] K
Rotational velocity (v sin i) 95[8] km/s
Age 28.2 ± 4.7[5] Myr
Other designations
CD −50° 11720, FK5 1471, HD 165024, HIP 88714, HR 6743, SAO 245242.[9]

Theta Arae (θ Ara, θ Arae) is the Bayer designation for a star in the constellation Ara. It has an apparent visual magnitude of +3.67,[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 4.01 mas,[1] Theta Arae is 810 light-years (250 parsecs) distant from the Earth.

This is a supergiant star with a stellar classification of B2 Ib.[3] It has nearly nine[5] times the mass of the Sun and is over 20[6] times the Sun's radius. The outer atmosphere of this star has an effective temperature of 17,231 K;[6] much hotter than the surface of the Sun. At this heat, the star shines with the characteristic blue-white hue of a B-type star.[10]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168. 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, 
  4. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W. 
  5. ^ a b c Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x. 
  6. ^ a b c d Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601. 
  7. ^ Fraser, M.; et al. (May 2010), "Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants", Monthly Notices of the Royal Astronomical Society, 404 (3): 1306–1320, arXiv:1001.3337Freely accessible, Bibcode:2010MNRAS.404.1306F, doi:10.1111/j.1365-2966.2010.16392.x. 
  8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B. 
  9. ^ "tet Ara -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2010-07-30. 
  10. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 

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