Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Corona Australis |
Right ascension | 18h 33m 30.18577s[1] |
Declination | −42° 18′ 45.0297″[1] |
Apparent magnitude (V) | 4.61±0.01[2] |
Characteristics | |
Spectral type | G8 III[3] |
U−B color index | +0.76[4] |
B−V color index | +1.02[4] |
Astrometry | |
Radial velocity (Rv) | −2.1±2.8[5] km/s |
Proper motion (μ) | RA: +32.046 mas/yr[1] Dec.: −20.932 mas/yr[1] |
Parallax (π) | 6.1673 ± 0.1535 mas |
Distance | 530 ± 10 ly (162 ± 4 pc) |
Absolute magnitude (MV) | −1.54[6] |
Details | |
Mass | 4.45±0.22[7] M☉ |
Radius | 29.1±1.5[8] R☉ |
Luminosity | 411+21 −19[1] L☉ |
Surface gravity (log g) | 2.50[9] cgs |
Temperature | 4,907±59[10] K |
Metallicity [Fe/H] | +0.00[1] dex |
Rotational velocity (v sin i) | 12±1[11] km/s |
Other designations | |
Database references | |
SIMBAD | data |
Theta Coronae Australis (Theta CrA), Latinized from θ Coronae Australis, is a solitary yellow-hued star[14] located in the southernconstellation Corona Australis. It has an apparent magnitude of 4.61, making it readily visible to the naked eye. Gaia DR3 parallax measurements place it 530 light years away and it is currently drifting closer with a somewhat constrained heliocentric radial velocity of −2.1 km/s. At its current distance, Theta CrA's brightness is diminished by three-tenths of a magnitudes due to interstellar dust.[15] It has an absolute magnitude of −1.54.[6]
This is an evolved red giant with a stellar classification of G8 III.[3] It has 4.45 times the mass of the Sun[7] but has expanded to 29.1 times the solar radius.[8] It radiates 411 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 4,907 K.[10] Theta CrA has a solar metallicity;[1] unlike most giant stars of this type, Theta CrA has an unusually high rate of rotation with a projected rotational velocity of 12 km/s.[11] The star may also have infrared excess, suggesting the presence of a circumstellar disk.[16] One possible explanation is that it may have engulfed a nearby giant planet, such as a hot Jupiter.[16]