W Ursae Majoris
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 43m 45.5s |
| Declination | +55° 57′ 09″ |
| Apparent magnitude (V) | 7.75–8.48 |
| Spectral 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) |
| Physical Characteristics | |
| 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 | |
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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