Sigma2 Ursae Majoris

Sigma² Ursae Majoris

Location of σ2 Ursae Majoris (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Ursa Major
Right ascension	09h 10m 23.2s
Declination	+67° 08' 05"
Apparent magnitude (V)	4.85 + 8.16
Characteristics
Spectral type	F7IV-V+K2V
Astrometry
Distance	66.7 ± 0.8 ly (20.5 ± 0.3 pc)
Other designations
σ2 Ursae Majoris, σ2 UMa, Sigma2 UMa, 13 Ursae Majoris, BD+67 577, GC 12619, HD 78154, HIP 45038, HR 3616, PPM 16933, SAO 14788, WDS J09104+6708AB .
Database references
SIMBAD	The system
	A
	B

Sigma² Ursae Majoris (Sigma² UMa, σ² Ursae Majoris, σ² UMa) is a binary star approximately 66.7 light years from Earth. The primary component, is a yellow-white F-type subgiant with an apparent magnitude of +4.85. The companion is an orange K-type main sequence dwarf with an apparent magnitude of +8.16. The two stars have a semi-major axis on the sky of 6 arcseconds and have an orbital period of 1067 years. There is a third component, Sigma² Ursae Majoris C, 205 arcseconds from the primary which is thought to be a line-of-sight co-incidence.

Naming

In Chinese, 三師 (Sān Shī), meaning Three Top Instructors, refers to an asterism consisting of σ² Ursae Majoris and ρ Ursae Majoris. Consequently, σ² Ursae Majoris itself is known as 三師三 (Sān Shī sān, English: the Third Star of Three Top Instructors.).