Pi Arae
Star in the constellation Ara
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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]
 | |
| Observation data Epoch J2000 Equinox 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]