Merak (star)

Merak
Location of Merak (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 11h 01m 50.47654s[1]
Declination +56° 22′ 56.7339″[1]
Apparent magnitude (V) +2.37[2]
Characteristics
Spectral type A1IVps[3]
U−B color index +0.00[2]
B−V color index -0.02[2]
Variable type Suspected
Astrometry
Radial velocity (Rv)-12.0[4] km/s
Proper motion (μ) RA: +81.43[1] mas/yr
Dec.: +33.49[1] mas/yr
Parallax (π)40.90 ± 0.16 mas[1]
Distance79.7 ± 0.3 ly
(24.45 ± 0.10 pc)
Absolute magnitude (MV)+0.61[5]
Details[6]
Mass2.56±0.03 M☉
Radius2.81 R☉
Luminosity63.5 L☉
Surface gravity (log g)3.93 cgs
Temperature9,700 K
Rotational velocity (v sin i)47±3 km/s
Age390 Myr
Other designations
Merak, Mirak,[7] β Ursae Majoris, β UMa, Beta UMa, 48 Ursae Majoris, BD+57°1302, FK5 416, GC 15145, HD 95418, HIP 53910, HR 4295, PPM 32912, SAO 27876[8]
Database references
SIMBADdata
Size comparison between the Sun, Beta Ursae Majoris, Pollux, and Arcturus.

Merak /ˈmɪəræk/, also called Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa),[9][10] is a star in the northern constellation of Ursa Major.

The apparent visual magnitude of this star is +2.37,[2] 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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  10. ^ Cite error: The named reference IAU-CSN was invoked but never defined (see the help page).