ϑ Ursae Majoris

Theta Ursae Majoris is a bright (3.2m) main-sequence star over 2 billion years old with 2.5 times the Sun's radius; it's 44 light years away. Theta has a 13.5 magnitude dwarf companion with a very slow orbit.

Place beta UMa on your extreme eastern edge; move one binocular field southwest: Theta UMa.

Two more binaries are more accessible here: phi UMa and 21 UMa:
      phi UMa (Otto Struve 208): 5.3, 5.4; 296, 0.4" with an orbit of 105.6 years.
      21 UMa (Struve 1346) has a yellow primary and blue companion, AB: 7.7, 8.6; 314, 5.7".


Placing theta UMa on your southern edge move two fields north to 23 UMa. This bright (5.5m) star is a pleasant binary (Struve 1351) with colour contrast, white and pale blue, AB: 3.7, 9.2; 269, 23.2".

If you centre 23 UMa and move one field north and very slightly west, you'll encounter the two sigma stars, 1 and 2; these represent the ears of the great bear.
     Sigma2 is a yellow-white subgiant and a fine binary (Struve 1306)AB: 4.9, 8.9; 349, 4.3"; the orbit has been estimated to be 1067 years.

Just to the east half a binocular field are two superb Messier objects, M81 and M82 seen side by side (or rather top to bottom).

Click on M81 for details on these two galaxies.

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1999-2014 by Richard Dibon-Smith.