Pi Arae, Latinized from π Arae, is the Bayer designation for a star in the southern constellation of Ara. It is faintly visible to the naked eye with an apparent visual magnitude of +5.25.[2] Based upon an annual parallax shift of 46.30 mas as seen from Earth,[1] it is located 70 light years from the Sun. It is most likely moving closer to the Sun with a radial velocity of −3 km/s.[4]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ara |
| Right ascension | 17h 38m 05.51512s[1] |
| Declination | –54° 30′ 01.5643″[1] |
| Apparent magnitude (V) | +5.25[2] |
| Characteristics | |
| Spectral type | A5 IV-V[3] |
| B−V color index | +0.20[2] |
| Astrometry | |
| Radial velocity (Rv) | −3.3±3.1[4] km/s |
| Proper motion (μ) | RA: +128.19[1] mas/yr Dec.: +62.16[1] mas/yr |
| Parallax (π) | 46.30 ± 0.19 mas[1] |
| Distance | 70.4 ± 0.3 ly (21.60 ± 0.09 pc) |
| Absolute magnitude (MV) | +2.01[5] |
| Details | |
| Mass | 1.73[6] M☉ |
| Radius | 1.90[7] R☉ |
| Luminosity | 13.3[5] L☉ |
| Surface gravity (log g) | 4.36[6] cgs |
| Temperature | 8,215±279[6] K |
| Metallicity [Fe/H] | +0.13[5] dex |
| Rotational velocity (v sin i) | 54.1±0.4[8] km/s |
| Age | 319[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The stellar classification of this star is A5 IV-V,[3] indicating the spectrum displays the hybrid features of both a main sequence and a more evolved subgiant star. Pi Arae is an estimated 319[6] million years old and is spinning with a projected rotational velocity of 54.1 km/s.[8] The star has 1.73[6] times the mass of the Sun and 1.90[7] times the Sun's radius. It is radiating 13.3[5] times the Sun's luminosity from its photosphere at an effective temperature of about 8,215 K.[6]
Pi Arae displays an excess emission of infrared radiation, which may be explained by circumstellar dust.[10] 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.[11]
Located 55 arc minutes to the north of Pi Arae is the globular cluster NGC 6397.[12]
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