W Ursae Majoris

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W Ursae Majoris
Observation data
Epoch J2000
Constellation
(pronunciation)
Ursa Major
Right ascension 09h 43m 45.5s
Declination +55° 57′ 09″
Apparent magnitude (V) 7.75–8.48
Characteristics
Spectral type F8Vp / F8Vp
U-B color index 0.08
B-V color index 0.66
Variable type W Ursae Majoris
Astrometry
Radial velocity (Rv) -46 km/s
Proper motion (μ) RA: 15.55 mas/yr
Dec.: -27.35 mas/yr
Parallax (π) 20.17 ± 1.05 mas
Distance 162 ly (50 pc)
Details
Mass 0.99/0.62 M
Radius 1.14/0.83 R
Luminosity 1.45/1.0 L
Temperature ? K
Metallicity ?
Rotation ?
Age ? years
Other designations
BD +56°1400, HD 83950, SAO 27364, ADS 7494, CCDM 09438+5557, HIP 47727.

W Ursae Majoris (W UMa) is a variable star in the constellation Ursa Major. It is an eclipsing contact binary whose two component stars share a common outer layer, and is the prototype of a class of contact binary variables known as W Ursae Majoris variables. Unlike with normal eclipsing binaries, the contact nature makes it impossible to tell when an eclipse of one component by the other starts or ends precisely. During an eclipse its apparent magnitude ranges between 7.75 and 8.48 over a period of 8 hours. Because the two components share their outer layers, they have the same stellar classification, and are classified as yellow F-type main sequence dwarfs.


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