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]

Rho²

The location of ρ2 Arae (circled)
Observation data Epoch J2000      Equinox J2000
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 mas[1]
Distance	520 ± 30 ly (159 ± 10 pc)
Absolute magnitude (MV)	−0.47[6]
Details
Mass	3.42 ± 0.10[7] M☉
Luminosity	238[7] L☉
Temperature	10,520[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
SIMBAD	data

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