Upsilon Ursae Majoris
Upsilon Ursae Majoris, Latinized from υ Ursae Majoris, is a binary star in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of +3.79. Based upon an annual parallax shift of 13.24 mas, it is located roughly 246 light-years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 50m 59.35700s |
| Declination | +59° 02′ 19.4486″ |
| Apparent magnitude (V) | 3.68 – 3.86 |
| Characteristics | |
| Spectral type | F2 IV |
| U−B color index | +0.09 |
| B−V color index | +0.29 |
| Variable type | δ Sct |
| Astrometry | |
| Radial velocity (Rv) | 27.3±4.1 km/s |
| Proper motion (μ) | RA: +42.97 mas/yr Dec.: −23.62 mas/yr |
| Parallax (π) | 28.06 ± 0.20 mas |
| Distance | 116.2 ± 0.8 ly (35.6 ± 0.3 pc) |
| Absolute magnitude (MV) | +1.11 |
| Details | |
| υ UMa A | |
| Mass | 1.57 or 2.20 M☉ |
| Radius | 2.79±0.40 R☉ |
| Luminosity | 29.5 L☉ |
| Surface gravity (log g) | 3.79±0.14 cgs |
| Temperature | 7,211±245 K |
| Rotation | 1.2±0.30 d |
| Rotational velocity (v sin i) | 124.2 km/s |
| Age | 1.168 Gyr |
| υ UMa B | |
| Mass | 0.44 M☉ |
| Other designations | |
| A: 29 Ursae Majoris, BD+59°1268, FK5 368, HD 84999, HIP 48319, HR 3888, SAO 27401 | |
| Database references | |
| SIMBAD | data |
The primary member of the system, component A, is an F-type subgiant star. It is a Delta Scuti variable with a period of 0.1327 day and an amplitude of 0.050 magnitude. With an estimated age of 1.168 billion years, it is spinning rapidly with a projected rotational velocity of 124.2 km/s and a rotation period of 1.2 days. The star has about 1.57 times the mass of the Sun and 2.79 times the Sun's radius. (De Rosa and colleagues give a mass estimate of 2.2 times the Sun's mass.) It is radiating around 29.5 times the solar luminosity from its outer atmosphere at an effective temperature of 7,211 K.
The companion, component B, is a magnitude +11.0 star. As of 2008, it has an angular separation of 11.78 arcseconds along a position angle of 295.4°. This corresponds to a projected separation of 419.8 AU. It has a mass around 40% that of the Sun.