Sigma Ursae Majoris
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The Bayer designation Sigma Ursae Majoris (σ UMa / σ Ursae Majoris) is shared by two star systems, σ¹ Ursae Majoris and σ² Ursae Majoris, in the constellation Ursa Major. They are separated by 0.33° on the sky.
[edit] σ¹ Ursae Majoris
| Observation data Equinox J2000.0 |
|
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 08m 23.6s |
| Declination | +66° 52' 24" |
| Apparent magnitude (V) | +5.15 |
| Distance | 500 ± 45 ly (153 ± 14 pc) |
| Spectral type | K5III |
| Other designations | |
Sigma-1 Ursae Majoris is an orange K-type giant with an apparent magnitude of +5.15. It is approximately 500 light years from Earth.
[edit] σ² Ursae Majoris
| Observation data Equinox J2000.0 |
|
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 10m 23.2s |
| Declination | +67° 08' 05" |
| Apparent magnitude (V) | 4.85 + 8.16 |
| Distance | 66.7 ± 0.8 ly (20.5 ± 0.3 pc) |
| Spectral type | F7IV-V+K2V |
| Other designations | |
Sigma-2 Ursae Majoris is a binary star approximately 66.7 light years from Earth. The primary component, Sigma-2 Ursae Majoris A, is a yellow-white F-type subgiant with an apparent magnitude of +4.85. The companion, Sigma-2 Ursae Majoris B, 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, Sigma-2 Ursae Majoris C, 205 arcseconds from the primary which is thought to be a line-of-sight co-incidence.
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