Pi Arietis

Pi Arietis is a multiple star system in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from π Arietis, and abbreviated Pi Ari or π Ari. Based upon parallax measurements made during the Hipparcos mission, this system is approximately 800 light-years (250 parsecs) distant from Earth,^[2] and has an apparent visual magnitude of 5.314.^[3] This is bright enough to be faintly seen with the naked eye. The position of this system near the ecliptic means it is subject to lunar occultation.^[9]

π Arietis

Location of π Arietis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aries[1]
Right ascension	02h 49m 17.55924s[2]
Declination	+17° 27′ 51.5168″[2]
Apparent magnitude (V)	5.314[3]
Characteristics
Spectral type	B6 V + A0 V + F8 V[4]
U−B color index	−0.47[5]
B−V color index	−0.06[5]
Astrometry
Radial velocity (Rv)	+8.8±0.9[6] km/s
Proper motion (μ)	RA: +2.60 mas/yr[2] Dec.: −14.10 mas/yr[2]
Parallax (π)	4.18±0.69 mas[2]
Distance	approx. 800 ly (approx. 240 pc)
Absolute magnitude (MV)	−1.56[1]
Details
Mass	4.4+0.55 −0.51[3] M☉
Luminosity	538[1] L☉
Surface gravity (log g)	4.5±0.25[3] cgs
Temperature	16,000±1,000[3] K
Rotational velocity (v sin i)	70[7] km/s
Age	13+9 −6[3] Myr
Other designations
π Ari, 42 Arietis, NSV 944, BD+16°355, GC 3378, HD 17543, HIP 13165, HR 836, SAO 93127, PPM 118581[8]
Database references
SIMBAD	data

The primary member of this system is an intermediate-mass,^[3] B-type main sequence star with a stellar classification of B6 V. It is a close, single-lined^[10] spectroscopic binary with an orbital period of 3.854 days, an eccentricity of 0.04, and a combined visual magnitude of 5.30. At an angular separation of 3.28 arcseconds is a magnitude 8.46 A-type main sequence star with a classification of A0 Vp. Finally, a fourth member of the system is a magnitude 11.0 F-type main sequence star with a classification of F8V at an angular separation of 25.2 arcseconds from the primary.^[4]

Name

This star, along with δ Ari, ε Ari, ζ Ari, and ρ³ Ari, were Al Bīrūnī's Al Buṭain (ألبطين), the dual of Al Baṭn, the Belly.^[11] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Buṭain were the title for five stars : δ Ari as Botein, π Ari as Al Buṭain I, ρ³ Ari as Al Buṭain II, ε Ari as Al Buṭain III dan ζ Ari as Al Buṭain IV.^[12]

In Chinese, 左更 (Zuǒ Gēng), meaning Official in Charge of the Forest, refers to an asterism consisting of π Arietis, ν Arietis, μ Arietis, ο Arietis and σ Arietis.^[13] Consequently, the Chinese name for π Arietis itself is 左更五 (Zuǒ Gēng wu, English: the Fifth Star of Official in Charge of the Forest.)^[14]