Navigating by the stars is not very common in these days of GPS-enabled cellphones, but if you want to enjoy the sky from an unfamiliar location, it is often useful to be able to orient yourself without relying on the omnipresent technological gadgets. In this case, by orient yourself, I simply mean to be able to tell which way is north just by finding a few easy-to-spot reference points in the sky.
The most obvious star to use to find north is Polaris (the north star). But Polaris isn’t very bright, and without some reliable pointers, it would be quite unremarkable. It is, after all, only the 50th-brightest star in the sky.
Many of you know about the two stars at the dipper end of the Big Dipper (Duhbe and Merak – part of the constellation Ursa Major) that point toward Polaris. But if you venture out right after dark to find the Dipper, you will see that it is near the western horizon, and if it isn’t already obscured by trees or mountains from your location, it soon will be. The Dipper being low and hard to find just goes along with the changing of the seasons.
Fortunately, there is an equally recognizable constellation that is now rising that will help you find north – Cassiopeia. This is the W-shaped constellation that is almost directly opposite Polaris from the Big Dipper. The points of the “W” aim toward Polaris.
If Durango were slightly farther north, both the Big Dipper and Cassiopeia would be truly circumpolar, meaning they never set. But even from our latitude, their motion in the sky gives the impression more of circling Polaris in a counterclockwise direction than of rising in the east and setting in the west. As Cassiopeia circles Polaris, it will be alternately oriented like a “W,” a “3,” an “M” and finally an “E,” depending on the season and time of night.
For the next six months, while Ursa Major is low on the horizon to the north, Cassiopeia will be high and easily visible. These two constellations take turns being a night guide.
So for the next few months, if you are lost in the wilderness and need to find north without the Big Dipper – and there aren’t any mossy trees around – find Cassiopeia. (And you’ll get extra credit for a correct spelling.)
The bright star Arcturus, which has been mentioned in previous columns about color and magnitude, is setting in the west. Vega and the Summer Triangle, while still overhead, have now moved toward the west and will be gone from view in not too many weeks.
Cassiopeia is two to three fist-widths up from the horizon, and a similar angular distance to the right of Polaris. The points of the “W” are pointing left, (like a “3”) toward Polaris. At 3 a.m., Cassiopeia will be very high in the sky, and the points will be aiming downward in more of an “M” configuration. Still pointing toward Polaris though.
Cassiopeia is a great constellation to view through binoculars. It falls right along the center of the Milky Way and contains numerous open clusters, including the Messier objects M52 and M103. This rich star field also includes nebulosities (glowing gases) that show up usually only in long-exposure photographs. Some of these nebulae, such as the Bubble Nebula (NGC 7635), and the Pacman Nebula (NGC 281), have been named much more recently than Cassiopeia.
Charles Hakes is an assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory.