Beta Circini

Beta Circini, Latinized from β Circini, is an A-type main sequence star and is the second-brightest star in the constellation of Circinus.^[2] It has an apparent visual magnitude of approximately 4.069,^[2] which is bright enough to be viewed with the naked eye. Based upon an annual parallax shift of 35.8 mas as seen from the Earth, it is located 91 light years from the Sun.

β Circini

Location of β Circini (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Circinus
Right ascension	15h 17m 30.84945s[1]
Declination	−58° 48′ 04.3453″[1]
Apparent magnitude (V)	4.069[2]
Characteristics
Spectral type	A3 Va[2]
U−B color index	+0.09[3]
B−V color index	+0.09[3]
Astrometry
Radial velocity (Rv)	9.6±2[2] km/s
Proper motion (μ)	RA: −97.182[1] mas/yr Dec.: −136.055[1] mas/yr
Parallax (π)	35.8205±0.2515 mas[1]
Distance	91.1 ± 0.6 ly (27.9 ± 0.2 pc)
Absolute magnitude (MV)	+1.64[4]
Details
Mass	1.96+0.03 −0.01[5] M☉
Radius	1.92[6] R☉
Luminosity	19[4] L☉
Surface gravity (log g)	4.281[7] cgs
Temperature	8676±33[5] K
Metallicity [Fe/H]	0.16[4] dex
Rotational velocity (v sin i)	59[3] km/s
Age	370–500[5] Myr
Other designations
β Cir, Beta Circini, Beta Cir, CPD−58 5875, FK5 561, GC 20526, GJ 580.1, GJ 9516, HD 135379, HIP 74824, HR 5670, PPM 343590, SAO 242384.[2]
Database references
SIMBAD	data

With a stellar classification of A3 Va,^[2] this is an main-sequence star fusing atoms of hydrogen into helium at its core. It is between 370 and 500 million years old^[5] with around 1.9^[6] times the Sun's radius. The star is radiating 19^[4] times the Sun's luminosity from its photosphere at an effective temperature of 8,676 K.^[5] It has one known sub-stellar companion.

Substellar companion

Beta Circini b is a distant brown dwarf companion orbiting the host star at a distance of 6,656 AU. It was detected as a proper motion companion to Beta Circini in 2015 by L.C. Smith and collaborators. Using BHAC15 isochrones, its mass is estimated at 0.056 M_☉, or 59 M_J. It has a stellar classification of L1 and a temperature of 2,084 K (1,811 °C).^[5]

The β Circini planetary system^[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	58.7±7.3 MJ	6,656	—	—	—	—