 A colour photo of the R Coronae Australis region in the southern Milky Way. | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 | |
|---|---|
| Constellation | Corona Australis |
| Right ascension | 19h 01m 53.6503s[1] |
| Declination | −36° 57′ 07.87″[1] |
| Apparent magnitude (V) | +11.91 |
| Characteristics | |
| Spectral type | B5IIIpe[2] |
| Variable type | INSA[3] |
| Astrometry | |
| 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 mas[5] |
| Distance | 152.9+8.1 −7.3[6] pc |
| Absolute magnitude (MV) | −0.30[7] |
| Orbit | |
| Period (P) | 45±2[8] yr |
| Semi-major axis (a) | 0.1968±0.0045[8]" (27-28 AU[6]) |
| Eccentricity (e) | 0.4[6] |
| Inclination (i) | 70[6]° |
| Details | |
| A | |
| Mass | 3.5[7] M☉ |
| Radius | 6.2[7] R☉ |
| Luminosity | 132[7] L☉ |
| Temperature | 9,550[7] K |
| Age | 1+1 −0.5[6] Myr |
| B | |
| Mass | 0.3 - 0.55[6] M☉ |
| Surface gravity (log g) | 3.45±0.06[6] cgs |
| Temperature | 3,650 - 3,870[6] K |
| Other designations | |
| CD−37°13027,HIP 93449, Wray 15-1887 | |
| Database references | |
| SIMBAD | data |
R Coronae Australis (R CrA) is avariable binary system in theconstellationCorona Australis.[2][8] It has varied between magnitudes 10 and 14.36.[10] A smallreflection/emission nebulaNGC 6729 extends from the star towards SE. It is also the brightest feature of theCoronet Cluster, therefore sometimes called R CrA Cluster.
This star is moving toward the Solar System with aradial velocity of36 km s−1. It was previously believed that in roughly 222,000 years, this system could have approached within 1.77light-years (0.54parsecs) of the Sun. However, the estimate had a considerablemargin of error in it.[11] 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 ± 31light-years (34.0 ± 9.5parsecs).[5] Examination of other objects known to be in the same star-forming region gives a distance of152.9+8.1
−7.3 pc, suggesting an error in the Gaia parallax for R CrA itself.[6]
Johann Friedrich Julius Schmidt discovered that R Coronae Australis is a variable star, in 1865. It appeared with itsvariable star designation inAnnie Jump Cannon's 1907 workSecond Catalogue of Variable Stars.[12]
A companion to the star was proposed in 2019 with a mass between 0.1 and 1Solar masses, depending on the characteristics of the stellar environment, orbiting the primary in 43–47 years.[8] The companion was later directly observed to be ared dwarf with a mass between 0.3 M☉ and 0.55 M☉.[6] It has also been proposed that the primary component is itself a closebinary.[7]
