What do you
see when you look at The Great Bear? If you said the Big Dipper, you're
not alone! The Big Dipper is not a constellation, but rather an asterism:
a grouping of stars within a constellation. (The word asterism derives
from the Latin aster, meaning star.) Another example of an
asterism is The Great Square of Pegasus. The handle of the Dipper
corresponds to the Bear's tail, but I don't know of any bears with a tail
that long!
One of the ancient myths about Ursa Major involves that rascally king-of-the-gods Zeus, who seemed to have nothing better to do than cheat on his wife Hera. Zeus fell in love with the mortal Callisto, and Hera in her jealousy changed the unfortunate mortal into a bear. Understandably distraught over this turn of events, Callisto took to hiding in the woods. One day her son Arcas came looking for her, and as Callisto rose on her hind legs to greet him, young Arcas readied his bow. Zeus, who had been feeling a tad guilty about the whole affair, stepped in before yet another tragedy could occur. But rather than change Callisto back to human form (which would seem the logical choice, right?), he instead changed Arcas into a bear as well, then grabbed them both by their tails and tossed them into the safety of the sky. Perhaps their tails were stretched in the process! As a final twist to this sad tale, Hera placed them both near the north celestial pole, so they would never set and hence never rest.
It's easy to find Ursa Major on a spring night; it arches nearly overhead, above the north star Polaris. At this time of year the Dipper is upside down, pouring water on the plants to reawaken them as spring arrives. You can use the two front stars of the Dipper's bowl, a and b, to find Polaris. These two stars are called the Pointers. Also, if you follow the curve of the Dipper's handle, you come to bright yellow Arcturus, the brightest star in the Northern Hemisphere. South of the Dipper's handle are the small "C" constellations Canes Venatici and Coma Berenices. This month we will focus on Canes Venatici, the Hunting Dogs, as well.
In these more detailed views, (adapted from Norton's Sky Atlas 2000.0)
we'll take a closer look at some of the
interesting sights in Ursa Major and Canes Venatici. We're going to
go in order of right ascension, which is right to left on this map. The
vertical lines are the right ascension lines. All these objects are best
viewed with a telescope, unless otherwise noted. They can also be found
on the Interactive NGC
Catalog Online, or by following the links I have provided. The numbers
in parentheses are measurements of the object's brightness in magnitude.
M81 and M82. (6.9, 8.4) One of the most beautiful galaxy pairs in the entire sky, M81 and M82 are bright enough to be seen with binoculars. They look fantastic in just about any size telescope as well. Use a wide field eyepiece (25-30mm) to fit them both in the field of view. What makes this pair so attractive is their contrast: M81 is a face on spiral, while 82 is an edge-on irregular. More info about M81 and M82.
NGC 2976 and 3077 (10.2, 9.9) While you're in the area, check out these two faint neighbors of M81 and M82. We would recommend at least a 6 inch scope to find these faint fuzzies. Of the two, 2976 appears larger and brighter and has an edge on shape.
VY Ursa Majoris. This is a variable star that fluctuates between magnitudes 5.9 and 7.0. What's interesting about it is its color: a deep orange red. It is one of the reddest stars you will see in the night sky.
M108 and M97. (10.1, 11.2) Another lovely contrasting pair in Ursa Major is the irregular, edge-on galaxy M108 and the Owl Nebula, M97. The Owl is a large, circular planetary nebula which seems to have two ghostly holes, or eyes, peering out from it. Contrast on this object is greatly enhanced with a nebula filter. More info about M108 and M97.
NGC 3877. (12) This little galaxy is easy to find because it is just south of c Ursa Majoris, which is itself a picturesque yellow 4th magnitude star. NGC 3877 is an edge-on galaxy with uniform surface brightness. In 1998 a supernova was discovered in this galaxy! More info on NGC 3877.
NGC 4244. (10.2) I love edge-on galaxies, and NGC 4244 is one of the best. Magnitude estimates for edge-ons are more accurate, because unlike spirals and ellipticals, their brightness is not spread out over a large area. 4244 is one of the longest, thinnest galaxies I have ever viewed (its size is 16.2 x 2.5). It's fairly bright too; it should show up in a 4 1/2 inch reflector in a dark sky site.
M106. (8.3) A peculiar spiral galaxy, M106 takes an almost edge-on appearance in medium sized telescopes. Larger instruments bring out the faint details in its spiral arms. More on M106.
NGC 4485 and 4490. (12, 9.8) The closest pair of interacting galaxies in our tour. These two are an easy target, just northwest of b Canes Venatici. 4490 is the larger and brighter of the two, and it appears as a uniformly bright oval in the eyepiece. 4485 is much smaller and appears starlike.
NGC 4631 and 4627. (9.3, 12.3) Another edge-on spiral in our galaxy tour. NGC 4631 is nicknamed the Whale and the Herring Galaxy. In an 8-inch reflector it appears long and thin, with a bulge at one end. This irregularity is probably due to interactions with NGC 4627, a tiny fuzzball that will take sharp eyes to pick out. More on NGC 4631.
NGC 4656/7. Yet another player in this cosmic drama, NGC 4656/7 is heavily distorted from interactions with NGC 4631. Nicknamed the Hockey Stick Galaxy, it lies almost a degree southeast of 4631. Two bright clumps are visible with an 8 inch scope, while the material that bridges them is very tenuous, and needs a larger aperture to be clearly visible. More on NGC 4656/7.
M94. (8.2) This Messier galaxy is overlooked, as it resides in an area heavily populated by stunningly beautiful galaxies. For amateurs M94 is one of the brightest and easiest galaxies to find. It's nestled between and just north of a and b Canes Venatici, and in my opinion is much brighter than M51. Not as spectacular, but a beautiful face-on spiral none-the-less. More on M94.
NGC 5005 and 5033. (9.8, 10.1) Two more faint fuzzies, about a degree apart and southeast of a Canes Venatici. 5005 is the brighter of the two, and has an oval shape and uniform surface brightness.
M63. (8.6) The Sunflower Galaxy. A bright, nearly face-on spiral, it shows up as an oval glow in an 8-inch scope using low power. Bump up the power a bit, and some contrast is visible in the bright core as well as hints of the spiral arm structure. More on M63.
M51 and NGC 5195. (8.4, 9.6 ) The famous Whirpool Galaxy can be a tough target for amateurs. Because of its large size, M51's brightness is spread out over a wide area. The core of NGC 5195 actually appears a bit brighter to my eye because of its compactness. But under a dark sky with a 6-inch or larger scope, the beautiful, wispy spiral arms of M51 are unmatched in detail. With a 15mm eyepiece in my 8-inch f/6 reflector, I could make out a very faint star superimposed over one of the spiral arms. This is pushing the limits of vision! More on M51.
M3. (6.4) The last stop on our (mainly) galactic tour is a globular cluster, and one of the best of its kind, too! It can be a little difficult to locate, as there are no bright stars nearby. But once you do it is worth careful study. M3 is estimated to contain about half a million stars! How many can you see? More on M3.