R Coronae Australis

R Coronae Australis (R CrA) is a variable binary system in the constellation Corona Australis.[2][6] It has varied between magnitudes 10 and 14.36.[7] A small reflection/emission nebula NGC 6729 extends from the star towards SE.

R Coronae Australis
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Corona Australis
Right ascension 19h 01m 53.6503s[1]
Declination −36° 57′ 07.87″[1]
Apparent magnitude (V) +11.91
Spectral type B5IIIpe[2]
Variable type INSA[3]
Radial velocity (Rv)-36.0 ± 4.9[4] km/s
Proper motion (μ) RA: 1.582[5] mas/yr
Dec.: -30.835[5] mas/yr
Parallax (π)10.5361 ± 0.6971[5] mas
Distance310 ± 20 ly
(95 ± 6 pc)
Mass3.5 M
Age1-3 million
0.3 million years
PrimaryR Coronae Australis A
CompanionR Coronae Australis B
Period (P)45±2 yr
Semi-major axis (a)0.1968±0.0045
Other designations
CD−37° 13027, HIP 93449, Wray 15-1887
Database references

This star is moving toward the Solar System with a radial velocity of 36 km s−1. It was previously believed that in roughly 222,000 years, this system could have approached within 1.77 light-years (0.54 parsecs) of the Sun. However, the estimate had a considerable margin of error in it.[8] With the release of Gaia DR2, the star was determined to be 4 times further from the Sun than initially believed, constraining the approach to only 111 ± 31 light-years (34.0 ± 9.5 parsecs).[5]

A companion to the star was detected in 2019 with a mass between 0.1 and 1 Solar masses, depending on the characteristics of the stellar environment, orbiting the primary in 43–47 years.[6]

A colour photo of the R Coronae Australis region in the southern Milky Way.


  1. ^ a b van Leeuwen, F. (13 August 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ a b "R Coronae Australis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 29 June 2014.
  3. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  5. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  6. ^ a b c Cugno, G.; Quanz, S. P.; Launhardt, R.; Musso Barcucci, A.; Brems, S. S.; Cheetham, A.; Godoy, N.; Kennedy, G. M.; Henning, T.; Müller, A.; Olofsson, J.; Pepe, F.; Quirrenbach, A.; Reffert, S.; Rickman, E. L.; Ségransan, D. (3 April 2019). "ISPY – NaCo Imaging Survey for Planets around Young stars". Astronomy & Astrophysics. 624: A29. arXiv:1902.04092. doi:10.1051/0004-6361/201935142. S2CID 102491664.
  7. ^ BSJ (14 June 2010). "R Coronae Australis". AAVSO Website. American Association of Variable Star Observers. Retrieved 29 June 2014.
  8. ^ Dybczyński, P. A. (April 2006), "Simulating observable comets. III. Real stellar perturbers of the Oort cloud and their output", Astronomy and Astrophysics, 449 (3): 1233–1242, Bibcode:2006A&A...449.1233D, doi:10.1051/0004-6361:20054284