Dubhe (Alpha Ursae Majoris)
The second brightest star in the constellation Ursa
Major; it lies at the front of the Big
Dipper's bowl and with Merak (Beta UMa)
makes the famed Pointers. Its name comes from the Arabic phrase thur
al Dubbal Akbar, "the back of the Great Bear." Unlike the
middle five stars of the Big Dipper, Dubhe is not part of the Ursa
Major Moving Cluster, and as a giant K star
with a temperature of 4,500 K, it is much cooler than its A-type constellation
neighbors, more evolved (in the core helium-burning stage), and noticeably
orange in color. Dubhe is orbited every 44 years at a distance of about
23 AU by a warmer, much dimmer, and less massive class F
star. Over 400 times farther away is another F star that also has a
companion (with a 6-day period), making Dubhe a quadruple system.
| visual magnitude |
1.81 |
| absolute magnitude |
-1.09 |
| spectral type |
K0III + F0V |
| luminosity |
300 Lsun |
| radius |
30 Rsun |
| distance |
124 light-years |
| position |
R.A. 11h 03m 43.7s,
Dec. +61° 45' 03" |
Related category
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