Mu2 Boötis

For other stars with this Bayer designation, see Mu Boötis.

Mu² Boötis is a binary star in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from μ² Boötis, and abbreviated Mu² Boo or μ² Boo. Based on parallax measurements, these stars are located at a distance of approximately 120 light-years from the Sun.

Mu² Boötis

Location of μ2 Boötis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Boötes
A
Right ascension	15h 24m 30.86726s[1]
Declination	+37° 20′ 50.2761″[1]
Apparent magnitude (V)	6.98[2]
B
Right ascension	15h 24m 30.89704s[3]
Declination	+37° 20′ 52.5550″[3]
Apparent magnitude (V)	7.63[2]
Characteristics
Spectral type	F9V + G0V[4]
U−B color index	+0.13[5]
B−V color index	+0.59[5]
Astrometry
A
Proper motion (μ)	RA: −139.142[1] mas/yr Dec.: +90.281[1] mas/yr
Parallax (π)	27.2223±0.0168 mas[1]
Distance	119.81 ± 0.07 ly (36.73 ± 0.02 pc)
B
Proper motion (μ)	RA: −152.149[3] mas/yr Dec.: +89.593[3] mas/yr
Parallax (π)	27.2126±0.0181 mas[3]
Distance	119.85 ± 0.08 ly (36.75 ± 0.02 pc)
Orbit[4]
Primary	A
Companion	B
Period (P)	265 yr
Semi-major axis (a)	1.46″
Eccentricity (e)	0.585
Inclination (i)	135.5°
Longitude of the node (Ω)	174°
Periastron epoch (T)	1864.9
Argument of periastron (ω) (secondary)	338°
Details
A
Mass	1.24[4] M☉
Radius	1.23[1] R☉
Luminosity	1.75[1] L☉
Surface gravity (log g)	4.3[4] cgs
Temperature	6,000[4] K
Rotational velocity (v sin i)	5[4] km/s
Age	5.6[1] Gyr
B
Mass	1.05[4] M☉
Radius	1.09[3] R☉
Luminosity	1.06[3] L☉
Surface gravity (log g)	4.4[4] cgs
Temperature	5,900[4] K
Rotational velocity (v sin i)	9[4] km/s
Age	11.3[3] Gyr
Other designations
51 Boo B, BD+37°2637, GC 20725, GJ 3904, HD 137392, HIP 75415, HR 5734, SAO 64687
Database references
SIMBAD	data

The components of μ² Boötis have apparent magnitudes of +7.0 and +7.6.^[2] They have similar spectral types, F9V and G0V respectively, and complete one orbit about their common centre of mass every 260 years.^[4]

The system μ¹ Boötis is at a similar distance and share similar proper motions with μ², but has a significantly different chemical composition, so they are not gravitationally bound.^[4]