Iota Ursae Majoris
Iota Ursae Majoris (ι Ursae Majoris, abbreviated Iota UMa, ι UMa), also named Talitha /ˈtælɪθə/, is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.14, making it visible to the naked eye and placing it among the brighter members of this constellation. Based upon parallax measurements, it is located at a distance of 47.3 light-years (14.5 parsecs) from the Sun.
Location of ι Ursae Majoris (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 08h 59m 12.45362s |
| Declination | +48° 02′ 30.5741″ |
| Apparent magnitude (V) | 3.14/10.1/10.3 |
| Characteristics | |
| Spectral type | F0IV-V + M3V + M4V |
| U−B color index | +0.08 |
| B−V color index | +0.19 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | +9.0 km/s |
| Proper motion (μ) | RA: -441.29 mas/yr Dec.: -215.32 mas/yr |
| Parallax (π) | 68.92 ± 0.16 mas |
| Distance | 47.3 ± 0.1 ly (14.51 ± 0.03 pc) |
| Absolute magnitude (MV) | +2.31 |
| Orbit | |
| Primary | ι UMa A |
| Companion | ι UMa BC |
| Period (P) | 2084 ± 15 yr |
| Semi-major axis (a) | 16.7 ± 0.3″ |
| Eccentricity (e) | 0.90 ± 0.02 |
| Inclination (i) | 54 ± 4° |
| Longitude of the node (Ω) | 134 ± 2° |
| Periastron epoch (T) | B 2029 ± 1 |
| Argument of periastron (ω) (secondary) | 23 ± 5° |
| Details | |
| ι UMa A | |
| Mass | 1.7 ± 0.1 / 1.0 ± 0.3 M☉ |
| Luminosity | 9.87 L☉ |
| Surface gravity (log g) | 4.30 ± 0.07 cgs |
| Temperature | 7260 ± 70 K |
| Rotational velocity (v sin i) | 154 km/s |
| Age | 620 Myr |
| ι UMa B | |
| Mass | 0.35 ± 0.05 M☉ |
| ι UMa C | |
| Mass | 0.30 ± 0.05 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | ι UMa |
| ι UMa A | |
| ι UMa BC | |
| ARICNS | ι UMa A |
| ι UMa B | |
| ι UMa C | |
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