Beta Muscae

Beta Muscae, Latinized from β Muscae, is a binary star in the southern circumpolar constellation of Musca. With a combined apparent visual magnitude of 3.07,^[2] it is the second brightest star (or star system) in the constellation. Judging by the parallax results, it is located at a distance of roughly 340 ± 13 light-years (105 ± 4 parsecs) from the Earth.^[1]

Beta Muscae

Location of β Musca (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Musca
Right ascension	12h 46m 16.80410s[1]
Declination	−68° 06′ 29.2164″[1]
Apparent magnitude (V)	3.05 (3.51 + 4.01)[2]
Characteristics
Spectral type	B2 V + B3 V[2]
U−B color index	−0.766[3]
B−V color index	−0.198[3]
Astrometry
Radial velocity (Rv)	+42[4] km/s
Proper motion (μ)	RA: −41.97[1] mas/yr Dec.: −8.89[1] mas/yr
Parallax (π)	9.55±0.41 mas[1]
Distance	340 ± 10 ly (105 ± 4 pc)
Absolute magnitude (MV)	−2.06[5]
Orbit[6]
Period (P)	194.28 yr
Semi-major axis (a)	0.969″
Eccentricity (e)	0.598
Inclination (i)	37.1°
Longitude of the node (Ω)	349.4°
Periastron epoch (T)	1857.50
Argument of periastron (ω) (secondary)	209.0°
Details
β Mus A
Mass	7.35[7] M☉
Luminosity	1,892[5] L☉
Age	15.1±1.2[8] Myr
β Mus B
Mass	6.40[7] M☉
Other designations
β Mus, CPD−67 2064, HD 110879, HIP 62322, HR 4844, SAO 252019[9]
Database references
SIMBAD	data

This is a binary star system with a period of about 194 years at an orbital eccentricity of 0.6.^[6] As of 2007, the two stars had an angular separation of 1.206 arcseconds at a position angle of 35°.^[7] The components are main sequence stars of similar size and appearance. The primary component, β Muscae A, has an apparent magnitude of 3.51, a stellar classification of B2 V,^[2] and about 7.35 times the Sun's mass.^[7] The secondary component, β Muscae B, has an apparent magnitude of 4.01, a stellar classification of B3 V,^[2] and is about 6.40 times the mass of the Sun.^[7]

This is a confirmed member of the Scorpius–Centaurus association,^[2][7] which is a group of stars with similar ages, locations, and trajectories through space, implying that they formed together in the same molecular cloud. Beta Muscae is considered a runaway star system as it has a high peculiar velocity of 43.9 km s⁻¹ relative to the normal galactic rotation. Runaway stars can be produced through several means, such as through an encounter with another binary star system. Binary systems form a relatively small fraction of the total population of runaway stars.^[10]