Merak (star)
Merak /ˈmɪəræk/, also called Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa), is a star in the northern constellation of Ursa Major.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 11h 01m 50.47654s |
| Declination | +56° 22′ 56.7339″ |
| Apparent magnitude (V) | +2.37 |
| Characteristics | |
| Spectral type | A1IVps |
| U−B color index | +0.00 |
| B−V color index | -0.02 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | -12.0 km/s |
| Proper motion (μ) | RA: +81.43 mas/yr Dec.: +33.49 mas/yr |
| Parallax (π) | 40.90 ± 0.16 mas |
| Distance | 79.7 ± 0.3 ly (24.45 ± 0.10 pc) |
| Absolute magnitude (MV) | +0.61 |
| Details | |
| Mass | 2.7 M☉ |
| Radius | 3.021 ± 0.038 R☉ |
| Luminosity | 63.015 ± 1.307 L☉ |
| Surface gravity (log g) | 3.83 cgs |
| Temperature | 9377 ± 75 K |
| Rotational velocity (v sin i) | 46 km/s |
| Age | 500 ± 100 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The apparent visual magnitude of this star is +2.37, which means it is readily visible to the naked eye. It is more familiar to northern hemisphere observers as one of the "pointer stars" in the Big Dipper, or the Plough (UK), which is a prominent asterism of seven stars that forms part of the larger constellation. Extending an imaginary straight line from this star through the nearby Alpha Ursae Majoris (Dubhe) extends to Polaris, the north star.
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