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Ursa Major is a large sprawling constellation, the third largest in fact. It's mainly known as the home of the Big Dipper, certainly the best known asterism in all the heavens. The constellation offers a number of objects, some well known, others rather obscure, and one star that has recently been in the news as having at least one "temperate" planet circling about it. The stars are fairly bright, and widely dispersed. The Big Dipper/Plough covers only half of the breadth, and the constellation extends much farther south, with its most southerly star, xi Ursae Majoris (Alula Australis), as far south as Leo and Cancer. The Big Dipper is one of the most distinctive asterisms in the sky. The familiar and easy to spot bowl and handle of the Big Dipper are composed of bright stars that are visible even from the city. It is part of the constellation of Ursa Major, the Big Bear. The second star from the end of the handle of the Big Dipper, Mizar (Zeta Ursa Majoris), is an interesting multiple star system made up of four stars. To the keen unaided eye, two stars can be seen, the brighter 2nd magnitude Mizar, and a fainter 4th magnitude nearby star, Alcor. They are separated by about 11.8 minutes of arc, and being able to detect the two as separate is considered a test of good eyesight. However, Alcor is not part of the Mizar multiple star system. Mizar, at a distance of 78 light years from the Sun, and Alcor at 81 light years, while appearing to be a double star, are actually only an optical double. An optical double star is not a true double star where the components are gravitationally bound together and orbit around each other, but rather a chance alignment along our line of sight. However, Mizar and Alcor are members of the nearest star cluster to the sun, the Ursa Major moving cluster, Collinder 285. The components of the Mizar multiple star system are Mizar A (Zeta 1 Ursa Majoris at magnitude 2.27) and Mizar B (Zeta 2 Ursa Majoris at magnitude 3.95), located 14.42 arc seconds away. Each of these stars is in turn a binary star, however the companions are so close to their primaries they can only be detected by spectroscopy. When examining the field near to Mizar and Alcor in a telescope, four stars can easily be seen. The brightest is Mizar at magnitude 2.27. Alcor is about 12 arc minutes away at magnitude 4. Closer to Mizar at just 15 arc seconds away is Mizar B, the 4th magnitude companion. Between Mizar and Alcor is a fourth star, Sidus Ludoviciana, shining at magnitude 8, which is a field star that is not even part of the Ursa Major cluster. M101 (NGC5457) 
M101 (NGC5457) is a large (29'x27') fairly bright (mag. 7.9) galaxy. Located 5.5° NNE of Alkaid (the tip star of the Big Dipper's handle) it appears dimmer than it's magnitude rating implies. A good 8-10" telescope should begin to see hints of spiral structure and bright knots. M101 is a large magnitude 8 galaxy. Photographically it is quite spectacular, however it has low surface brightness, making it difficult to observe in small instruments. It was discovered by P. Mechain in 1781 and catalogued by Messier in March the same year. Its distance is estimated at about 24 million light years. The diameter is approximately 90,000 light years and the total mass is estimated to be the eqivalent of 16 billion suns - about 10% of the mass of the Milky Way.
NGC4605 
NGC4605 is an edge on spiral galaxy located 5.5° northeast of Megrez (Delta Ursae Majoris, the star at the junction of Dipper's bowl and handle). Dreyer describes it as bright, large, very much elongated (in p.a. 118°), and with a little, gradual brightening toward the middle. M40 
M40 is not a deepsky object, but a double star found 1.4° NE of Megrez (Delta Ursae Majoris). It forms a nice triangle with the mag. 12.7 galaxy NGC 4290 (visible in a 6") and the star 70 Ursae Majoris. NGC4088, NGC4026, NGC4085 
Three brightish spiral galaxies lie a degree apart from each other, and about 3.5° SSE of Phecda (Gamma Ursae Majoris). M109 (NGC3992) 
Often overlooked barred Spiral Galaxy M109 (NGC3992) in Ursa Major. Located .5° SE of Phecda, the south-easten bowl star of the Big Dipper, it shines at mag 10.6. It measures 8'x5' minutes in size. M109 is a type SBc barred spiral galaxy. M109 is around 40 to 50 million light-years away in a loose galaxy grouping which includes M108 and possibly M106. NGC3941 
NGC3941 is a spiral galaxy located in southeastern Ursa Major. It sits on a line between the mag. 3.7 Alula Borealis (Nu Ursae Majoris, 8° separation) and the mag. 2.8 Cor Caroli (Alpha Canum Venaticorum, 12.5° separation). Described as very bright (mag. 11), fairly large (3.5'x2.3'), round, with a mag. 9 star involved. The "star" is actually a stellar nucleus, just visible at higher power in an 8". The mag. 6.5 SAO62754 lies 31' to the ESE. NGC3877 
NGC3877 is one of three major galaxies, and several minor ones, in an area of sky covering 1.5° of sky. It sits 17' south of the star Chi Ursae Majoris, just south of the bowl of the Dipper. Dreyer describes it as bright (mag. 11.9), large (5.5'x1.3'), and moderately elongated (in p.a. 37°). NGC3893 
NGC3893 sits 1° NNE of Chi Ursae Majoris. The description reads bright (mag. 10.9), fairly large (4.4'x2.7'), round, and much brighter toward the middle. Increasing aperture helps brighten the middle, as well as produce a mottled appearance. Its very small (1.4'x1.0'), faint (mag. 13.9) companion, NGC3896 sits 5' to the southeast. NGC3893 makes a good jumping off point for three small faint galaxies. NGC3938 (mag. 13, 1.5') lies 31' to the east and is the easiest. NGC3932 is more difficult (mag. 15, 1.1'x0.5') and lies another 15' SSE. NGC3906 may be the most difficult of all (brighter at mag. 13.8, but larger too at 1.9'x1.7') and lies 20' southeast of NGC3893. NGC3949 lies 1.3° east of Chi Ursae Majoris, and is the third bright galaxy of the group. Dreyer says it is quite bright (mag.11.6), fairly large (2.9'x1.6'), pretty much elongated (p.a. 120°), and brightening gradually toward the middle. NGC3675 
NGC3675 is a spiral galaxy located in the central portion of the constellation, 3.1° ESE of Psi Ursae Majoris (mag. 4) and 36' east of 56 Ursae Majoris (mag. 5). The NGC description reads: Very bright (mag. 10.9), quite large (5.9'x3.1'), very much elongated (in p.a. 0°), and brightening very suddenly to a much brighter, stellar nucleus. Many stars lie to the west. M97 (NGC3587) 
M97 (NGC3587) is a rather faint (mag. 11.2) planetary nebula located 2.3° ESE from Merak, the southwestern star of the Big Dipper's bowl. Dreyer optimistically describes it as very bright. He also calls it large (3'), round, posessing a bright middle and gaps. These gaps form the "eyes" of the Owl Nebula. They require dark skies, and a good 10" telescope and larger telescopes may reveal some stars against the nebulosity. The Owl nebula is just visible in a 4-inch as a pale gray oval. M108 (NGC3556) 
M108 (NGC3556) lies .8° NW. M108 is considered bright (mag. 10.7), quite large (8.7'x2.3'), very elongated (PA 79°) and condensed. Countless galaxies fainter than mag. 15 inhabit this image. M108 is a type Sc spiral galaxy. Almost edge-on, it shows little or no bulge and no noticeably strong center, being a motley collection of features often referred to, in classic understatement, as very dusty. The spiral structure is not very clearly delineated, unsurprisingly. M108 is around 40 to 50 million light-years away in a loose galaxy grouping which includes M109 and possibly M106. NGC3184 
NGC3184 is a spiral galaxy located in southwestern Ursa Major, just north of Leo Minor. The nearest "bright" star is Tania Australis (Mu Ursae Majoris), 46' to the east. Dreyer's description reads fairly bright (mag. 10.5), very large (7.4'x7.0'), round, and brightening only very gradually toward the middle. Several other galaxies inhabit this image, the most significant of them is NGC3179. lying 19' south of NGC3184, it shines at mag. 14.1 and covers 1.8'x0.5'. It's small size compensates a little for its dimness. NGC3079 
NGC3079 (Best 93) is the primary galaxy to view in this group of three. Indeed, below 8" will hardly stand a chance seeing more than one. They lie in western Ursa Major, 2.1°rees northeast of the mag. 4.6 Phi Ursae Majoris. Dreyer describes NGC3079 as very bright (mag. 10.6), large (7.5'x1'), and moderately elongated (Dreyer says the position angle is 135 °, others give 165°). This edge-on galaxy has a radial velocity of 1100 km per second, which translates to a distance of some 55 million light-years. The other galaxies are the very faint NGC3073 (mag. 13.7, 1.3'x1.2', and 11' west of the southern tip of NGC3079) and the even fainter MCG9-17-9 (mag.14.8, 0.8'x0.3', and 7' west of the northern tip of NGC3079). NGC3077 
NGC3077 (Best 94) is a galactic companion to M81 (M81 lies 47' to the northwest). Dreyer's description reads quite bright (mag. 10.8), quite large (5.3'x4.4'), much brighter toward the middle, and then the peculiar comment "round with ray." A 12" class instrument might catch the "ray" with averted vision, as well as the nearly stellar nucleus. M81 (NGC3031) & M82 (NGC3034)   
M81 (NGC3031) & M82 (NGC3034) are a pair of bright (mags. 7.9 & 9.2) galaxies located 10° NW of Dubhe, the northwestern star of the bowl of the Big Dipper. Separated by .5°, they make a beautiful pair. M81 is a classic spiral (size 27'x14'). M82 (size 11'x4') looks a little strange, even when viewed visually through a telescope. M81 is one of the easiest and most rewarding galaxies to observe for the amateur astronomer on the northern hemisphere, because with its total visual brightness of about 6.8 magnitude. NGC2841 
NGC2841 is a spiral galaxy located in western Ursa Major, 1.8° WSW of Theta Ursae Majoris. Dreyer describes it as very bright, large, and very much elongated (p.a. 147°). Like so many other galaxies, Dreyer says this one brightens very suddenly toward the middle. There is a mag. 10 star involved on the northwestern edge. With the right equipment (a 13") one can see a stellar nucleus and mottled arms. |