A

David

Darling

Ursa Major

Ursa Major

Ursa Major, with the stars of the Big Dipper (Plough) labeled. Photo by David Cleave.


Ursa Major constellation

Ursa Major. © 2003 Torsten Bronger.


Ursa Major (abbreviation: UMa), the Great Bear, is a very large and prominent northern constellation, located west of Lyra and north of Leo and Leo Minor.

 

Ursa Major is well-known in most world cultures and associated with a number of myths. It was one of the constellations catalogued by the Greek astronomer Ptolemy in the secondnd century. In Greek mythology, it is associated with Callisto, a nymph who was turned into a bear by Zeus' jealous wife Hera.

 

Ursa Major is a good starting point to find other stars and constellations in the sky. A line through the Pointers, Alpha Ursae Majoris (Dubhe) and Beta UMa (Merak), leads north to the pole star, Polaris, and south toward Regulus. Capella in Auriga can be found by following a line from Delta UMa to Alpha UMa. Likewise, a line from Delta UMa to Beta UMa and beyond, leads to Alpha Gem.

 

See below for details of the constellation's brightest stars and interesting deep sky objects.

 


The Big Dipper

Ursa Major contains the famous asterism known as the Big Dipper (or, in Britain, the Plough), which is made from the stars Alpha, Beta, Gamma, Delta, Epsilon, Zeta and Eta UMa. The five middle stars are all moving through space together as part of a loosely-bound group known as the Ursa Major Moving Cluster. Alkaid (Eta, leftmost star in diagram below) and Dubhe (Alpha), however, are moving in their own directions, ultimately dooming the Dipper's shape.

 

Big Dipper changes over time
How the Big Dipper's shape will change over the next 100,000 years.

 


SU Ursae Majoris

SU Ursae Majoris (SU UMa) is the prototype SU Ursae Majoris star. It is located,inear the tip of the nose of the Great Bear, about 3 degrees northwest of Omicron UMa. The unusual variability of SU UMa was first noted in 1908 by the Russian astronomer L. Ceraski. SU UMa shows normal U Geminorum-type outbursts every 11–17 days and super-outbursts every 153–260 days; its range is from magnitude 15 at minimum to a peak magnitude of 10.8 at super-outburst. Since the defining features of SU UMa stars are a narrow outburst, a super-outburst, and a super-hump, it is strange that for a period of nearly three years in the early 1980s the prototype itself did not exhibit such behavior. Thus, it was questioned whether this variable even belonged to the category named after it! Another absence of super-outburst activity happened between April 1990 and July 1991.

 


Ursa Major Moving Cluster

The Ursa Major Moving Cluster is a loose group of stars, widely scattered about the sky, with similar space velocities (about 14 kilometers per second in the direction of eastern Sagittarius). It includes five of the seven major members of the Big Dipper – Merak (Beta), Phad (Gamma), Megrez (Delta), Alioth (Epsilon), and Mizar (Zeta) – as well as Alphekka (Alpha Coronae Borealis) and Sirius (Alpha Canis Majoris). With its center located about 75 light-years from us, about half the distance of the Hyades, it is the nearest star cluster to the Sun. Its proximity and size (some 30 light-years long by 18 light-years wide) mean that it covers an enormous portion of the sky.

 


Ursa Major Groups

The Ursa Major Groups are a large spur of spiral galaxies on one side of the Virgo Cluster stretching across 20 million light-years. There are probably two main groups: Ursa Major North (around NGC 3631, 3953, and M109) and Ursa Major South (around NGC 3726, 3938 and 4051).

 

Stars in Ursa Major brighter than magnitude 4.0
Star Visual mag. Abs. mag. Spectral type Distance (lt-yr) R.A. (h m s) Dec. (° ' ")
Epsilon (Alioth) 1.76 -0.22 A0VpCr 81 12 54 02 +55 57 35
Alpha (Dubhe) 1.81 -1.09 F7Va 124 11 03 44 +61 45 03
Eta (Alkaid) 1.85 -0.60 B3V 101 13 47 32 +49 18 48
Zeta (Mizar) 2.23 0.33 A1VpSrSi
+A1m
78 13 23 06 +54 55 31
Beta (Merak) 2.34 0.41 A1V 79 11 01 50 +56 22 56
Gamma (Phekda) 2.41 0.36 A0Ve 84 11 53 50 +53 41 41
Psi 3.01 -0.27 K1III 147 11 09 40 +44 29 54
Mu (Tania Australis) 3.06 -1.35 M0III 249 10 22 20 +41 29 58
Iota (Talita) 3.12 2.29 A7IV 48 08 59 12 +48 02 29
Theta 3.17 2.52 F6IV 44 09 32 51 +51 40 38
Delta (Megrez) 3.32 1.33 A3V 81 12 15 26 +57 01 57
Omicron (Muscida) 3.35 -0.41 G4II 184 08 30 16 +60 43 05
Lambda (Tania Borealis) 3.45 0.37 A2IV 134 10 17 06 +42 54 52
Nu (Alula Borealis) 3.49 -2.07 K3IIIBa0.3 421 11 18 29 +33 05 39
Kappa (Al Kaprah) 3.57 -2.00 A1Vn 423 09 03 38 +47 09 23
h 3.65 1.82 F0IV 76 09 31 32 +63 03 42
Chi (Alkafzah) 3.69 -0.21 K0III 196 11 46 03 +47 46 45
Upsilon 3.78v 1.04 F0IV 115 09 50 59 +59 02 19
10 3.96 2.88 F5V 54 09 00 38 +41 46 57

 

Other objects of interest
Name Type of object Notes
Owl Nebula planetary nebula See main entry
M81 (NGC 3031) galaxy See main entry
M82 (NGC 3034) galaxy See main entry
M101 (NGC 5457) galaxy See main entry
M108 (NGC 3556) galaxy Nearly edge-on type Sc spiral. Distance 45 million light-years;
magnitude 10.0; diameter 8' × 1'; R.A. 11h 11.5m, Dec. +55° 40'
M109 (NGC 3992) galaxy A type SBc barred spiral that looks like a "theta" in the sky. Distance
55 million light-years; magnitude 9.8; diameter 7' × 4'; R.A. 11h 57.6m,
Dec. +53° 23'
Ambartsumian's Knot galaxy See main entry
47 Ursae Majoris star with exoplanet See main entry

 

Constellations
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