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Megrez

Megrez
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings

Location of Megrez (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 12h 15m 25.56063s[1]
Declination +57° 01′ 57.4156″[1]
Apparent magnitude (V) +3.312[2]
Characteristics
Spectral type A3 V[3]
U−B color index +0.067[2]
B−V color index +0.075[2]
Astrometry
Radial velocity (Rv)-20.2[4] km/s
Proper motion (μ) RA: +104.11[1] mas/yr
Dec.: 7.30[1] mas/yr
Parallax (π)40.51 ± 0.15 mas[1]
Distance80.5 ± 0.3 ly
(24.69 ± 0.09 pc)
Absolute magnitude (MV)+1.39[5]
Details
Mass1.63[6] M☉
Radius1.4[7] R☉
Luminosity14[7] L☉
Surface gravity (log g)4.49[7] cgs
Temperature9,480±570[7] K
Rotational velocity (v sin i)233[8] km/s
Age0.3[9] Gyr
Other designations
Megrez, δ Ursae Majoris, δ UMa, Delta UMa, 69 Ursae Majoris, BD+57 1363, CCDM J12155+5702A, FK5 456, GC 16736, HD 106591, HIP 59774, HR 4660, IDS 12105+5735 A, PPM 33469, SAO 28315, WDS J12154+5702A.[10]
Database references
SIMBADdata

Megrez /ˈmiːɡrɛz/, also called Delta Ursae Majoris (δ Ursae Majoris, abbreviated Delta UMa, δ UMa),[11][12] is a star in the northern constellation of Ursa Major. With an apparent magnitude of +3.3,[2] it is the dimmest of the seven stars in the Big Dipper asterism. Parallax measurements yield a distance estimate of 80.5 light-years (24.7 parsecs) from the Sun.[1]

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  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  12. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
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