Astronomy:Rho2 Arae

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Short description
Star in the constellation Ara
Rho2
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
Cercle rouge 100%.svg
The location of ρ2 Arae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ara
Right ascension  16h 58m 17.94161s[1]
Declination –50° 38′ 28.2691″[1]
Apparent magnitude (V) 5.54[2]
Characteristics
Spectral type B9 IV[3] or B9 V[4]
B−V color index +0.02[2]
Astrometry
Radial velocity (Rv)–44.0[5] km/s
Proper motion (μ) RA: –8.05[1] mas/yr
Dec.: –38.68[1] mas/yr
Parallax (π)6.28 ± 0.38[1] mas
Distance520 ± 30 ly
(159 ± 10 pc)
Absolute magnitude (MV)−0.47[6]
Details
Mass3.42 ± 0.10[7] M
Luminosity238[7] L
Temperature10,520[7] K
Rotational velocity (v sin i)302[7] km/s
Other designations
ρ2 Ara, CD–50° 10924, FK5 1444, HD 152824, HIP 83057, HR 6289, SAO 244313.[8]
Database references
SIMBADdata

Rho2 Arae is the Bayer designation for a star in the southern constellation of Ara. It received this designation when the star was catalogued by Bode in his Uranographia. This is a rather dim naked eye star with an apparent visual magnitude of 5.54.[2] Based upon an annual parallax shift of just 6.28 mas, it is around 520 light-years (160 parsecs) distant from the Sun, give or take a 30 light-year margin of error.[1]

The spectrum of this star matches a stellar classification of B9 IV[3] or B9 V.[4] The IV luminosity class would indicate the star is in the subgiant stage, while a V class means it is a main sequence star like the Sun. In the latter case, it is close to entering the subgiant stage at an estimated 93% of the way through its lifespan on the main sequence.[7]

Rho2 Arae has more than three times the mass of the Sun and shines with 238 times the Sun's luminosity.[7] This energy is being radiated into space from the outer atmosphere at an effective temperature of 10,520 K,[7] giving it the blue-white hue of a B-type star.[9] It is spinning rapidly with a projected rotational velocity of 302 km/s.[7]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V. 
  2. 2.0 2.1 2.2 Corben, P. M.; Stoy, R. H. (1968), "Photoelectric Magnitudes and Colours for Bright Southern Stars", Monthly Notes of the Astronomical Society of Southern Africa 27: 11, Bibcode1968MNSSA..27...11C. 
  3. 3.0 3.1 Hiltner, W. A.; Garrison, R. F.; Schild, R. E. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal 157: 313, doi:10.1086/150069, Bibcode1969ApJ...157..313H. 
  4. 4.0 4.1 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode1978mcts.book.....H. 
  5. Wielen, R. et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg (Astronomisches Rechen-Institut Heidelberg) 35 (35): 1, Bibcode1999VeARI..35....1W. 
  6. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode2012AstL...38..331A. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics 537: A120, doi:10.1051/0004-6361/201117691, Bibcode2012A&A...537A.120Z 
  8. "rho02 Ara". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=rho02+Ara. 
  9. "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16.