Pi4 Orionis

Pi⁴ Orionis (π⁴ Ori, π⁴ Orionis) is a binary star system in the western part of the Orion constellation. It is visible to the naked eye with an apparent visual magnitude of 3.7.^[2] Based upon an annual parallax shift of 3.1 mass,^[1] it is located roughly 1,050 light-years from the Sun.

For other stars with this Bayer designation, see Pi Orionis.

π⁴ Orionis

Location of π4 Orionis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Orion
Right ascension	04h 51m 12.36472s[1]
Declination	+05° 36′ 18.3723″[1]
Apparent magnitude (V)	3.685[2]
Characteristics
Spectral type	B2 III[3]
U−B color index	−0.797[2]
B−V color index	−0.180[2]
Astrometry
Radial velocity (Rv)	23.3[4] km/s
Proper motion (μ)	RA: −2.21[1] mas/yr Dec.: +0.85[1] mas/yr
Parallax (π)	3.10±0.18 mas[1]
Distance	1,050 ± 60 ly (320 ± 20 pc)
Orbit[5]
Period (P)	9.5191 d
Eccentricity (e)	0.03
Periastron epoch (T)	2,418,275.65±10.0
Argument of periastron (ω) (secondary)	165°
Semi-amplitude (K1) (primary)	25.8 km/s
Details
π4 Ori A
Mass	10.95±0.97[6] M☉
Radius	9.1[7] R☉
Luminosity	19,726[6] L☉
Surface gravity (log g)	3.59[8] cgs
Temperature	21,874±126[7] K
Metallicity [Fe/H]	−0.31[8] dex
Rotational velocity (v sin i)	38[9] km/s
Age	15.4±1.0[10] Myr
Other designations
π4 Ori, 3 Orionis, BD+05°745, FK5 179, HD 30836, HIP 22549, HR 1552, SAO 112142[11]
Database references
SIMBAD	data

This is a spectroscopic binary star system with an orbital period of 9.5 days and an eccentricity of 0.03.^[5] The primary component is a B-type star with a stellar classification of B2 III.^[3] The stellar spectrum of π⁴ Ori A shows a strong depletion of the element boron.^[12] It has nearly 11^[6] times the mass of the Sun and nine times the Sun's radius.^[7] The star is 15.4^[10] million years old and has a projected rotational velocity of 38 km/s.^[9] It shines with 19,726^[6] times the solar luminosity from its outer atmosphere at an effective temperature of 21,874 K.^[7]