4 Ursae Majoris

This article is about π2 Ursae Majoris. For other stars with this Bayer designation, see π Ursae Majoris.
Pi2 Ursae Majoris
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings

Location of π2 Ursae Majoris (circled) near the center
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 08h 40m 12.81767s[1]
Declination +64° 19′ 40.5700″[1]
Apparent magnitude (V) +4.620[2]
Characteristics
Spectral type K2 III[3]
U−B color index +1.193[2]
B−V color index +1.159[2]
Astrometry
Radial velocity (Rv)+14.62[4] km/s
Proper motion (μ) RA: −60.05[1] mas/yr
Dec.: +26.40[1] mas/yr
Parallax (π)12.74 ± 0.26 mas[1]
Distance256 ± 5 ly
(78 ± 2 pc)
Absolute magnitude (MV)0.150[3]
Details
Mass1.234 ± 0.15[5] M☉
Radius18.79±0.38[6] R☉
Luminosity112.4±10.0[6] L☉
Surface gravity (log g)1.8 ± 0.15[5] cgs
Temperature4336±99[6] K
Metallicity [Fe/H]-0.25 ± 0.04[5] dex
Rotational velocity (v sin i)8[7] km/s
Age4.18 ± 1.95[3] Gyr
Other designations
π2 Ursae Majoris, π2 UMa, Pi2 UMa, 4 Ursae Majoris, BD+64°698, FK5 2677, GC 11850, HD 73108, HIP 42527, HR 3403, PPM 16713, SAO 14616
Database references
SIMBADdata

4 Ursae Majoris (sometimes abbreviated 4 UMa) is the Flamsteed designation of a star in the northern circumpolar constellation of Ursa Major. It also bears the Bayer designation of Pi2 Ursae Majoris (Pi2 UMa, π2 Ursae Majoris, π2 UMa) and is traditionally named Muscida. With an apparent visual magnitude of +4.6,[2] this star is visible from suburban or darker skies based upon the Bortle Dark-Sky Scale. From parallax measurements made during the Hipparcos mission, this star is at a distance of 256 light-years (78 parsecs) from Earth.[1] As of 2011, one extrasolar planet has been confirmed to be orbiting the star.

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