Pi Arae

Pi Arae is a star in the southern constellation of Ara. Its name is a Bayer designation that is Latinized from π Arae, and abbreviated Pi Ara or π Ara. This star is faintly visible to the naked eye with an apparent visual magnitude of +5.25.^[3] Based upon an annual parallax shift of 24.38 mas as seen from Earth,^[2] it is located 134 light-years (41 pc) from the Sun. It is moving closer to the Sun with a radial velocity of −2 km/s.^[2]

Pi Arae

Location of π Arae (dot within red circle)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Ara[1]
Right ascension	17h 38m 05.515s[2]
Declination	−54° 30′ 01.56″[2]
Apparent magnitude (V)	+5.25[3]
Characteristics
Spectral type	A5 IV-V[4]
B−V color index	+0.20[3]
Astrometry
Radial velocity (Rv)	−2.11±0.22[2] km/s
Proper motion (μ)	RA: −50.775 mas/yr[2] Dec.: −149.745 mas/yr[2]
Parallax (π)	24.3817±0.0805 mas[2]
Distance	133.8 ± 0.4 ly (41.0 ± 0.1 pc)
Absolute magnitude (MV)	+2.01[1]
Details
Mass	1.73[5] M☉
Radius	1.90[6] R☉
Luminosity	13.3[1] L☉
Surface gravity (log g)	4.36[5] cgs
Temperature	8,215±279[5] K
Metallicity [Fe/H]	+0.13[1] dex
Rotational velocity (v sin i)	54.1±0.4[7] km/s
Age	319[5] Myr
Other designations
π Ara, CPD−54°8403, GC 23862, GJ 683, HD 159492, HIP 86305, HR 6549, SAO 244896, PPM 346165[8]
Database references
SIMBAD	data

The stellar classification of this star is A5 IV-V,^[4] indicating the spectrum displays the hybrid features of both a main sequence and a more evolved subgiant star. Pi Arae is an estimated 319^[5] million years old and is spinning with a projected rotational velocity of 54.1 km/s.^[7] The star has 1.73^[5] times the mass of the Sun and 1.90^[6] times the Sun's radius. It is radiating 13.3^[1] times the Sun's luminosity from its photosphere at an effective temperature of about 8,215 K.^[5]

Pi Arae displays an excess emission of infrared radiation, which may be explained by circumstellar dust.^[9] The thermal emission matches a two component model, consisting of an inner disk of warm crystalline silicate dust and an outer colder disk of dirty ice. The inner disk has a temperature of 173 K and is orbiting roughly 9.1 AU from the host star. The outer disk is 77 K and orbits at a distance of about 117.3 AU. The small size of some of the dust grains indicate the inner disk may have formed relatively recently from collisions between orbiting planetesimals.^[10]

Located 55 arc minutes to the north of Pi Arae is the globular cluster NGC 6397.^[11]