The Bear Crawl

1/22/06 – 1/29/06

By C. Zaitz

Have you noticed the Big Dipper in the northern sky this winter? Look for seven bright stars in the shape of a pot with a long handle. Around 9 pm the Dipper is almost “standing” on its handle in the northwest. The Big Dipper is a well known collection of stars, though it is not an official constellation. The Big Dipper is the nickname for the group of stars that to us looks like a water dipper, but it reminded people living a long time ago of a great bear crawling around the sky. In a very dark sky when the dimmer stars are visible, you can trace the faint outline of an ursine being. Ursa Major is the Latin name given to the shape, and our English word “ursine” comes from the Latin word for bear; ursa. The entire constellation is much larger than the seven stars of the Big Dipper, but in our modern light-polluted skies, the Big Dipper stands out as the other stars of the constellations are washed out.

If you see the Big Dipper around 9pm, look for the two top stars- the two stars farthest from the handle of the dipper. These are nicknamed the “Pointer Stars.” Trace a line in the sky with your finger; begin with the eastern or right top star, pass through the star next to it on the left and keep going... the next star you find will be the North Star. Don’t be surprised if it looks faint to you- it is not a very bright star as seen by earthlings. But it does lie almost directly above the north pole of the earth, and therefore is famous for its helpfulness in finding north. Once you’ve found the North Star, you’ve found the end star in the handle of the Little Dipper, otherwise known as the Little Bear, Ursa Minor.

The cool part about the Big and Little Dippers is that they both dance around the North Star over the course of the evening and over the course of the year. The nightly motion is due to the rotation of the earth, which is what causes day and night. Over the course of one evening you can watch the Big and Little Dippers rotate part way around the North Star so that by morning the Big Dipper will be high up in the northern sky, on top of the Little Dipper, rather than beside it. The yearly motion is the crawl of the bear around the sky. If you went outside at 10pm every night you would notice over the course of a season that the Big Dipper (Ursa Major) would be crawling around the sky in slow motion. This motion is caused by the orbit of the earth around the sun. It’s almost like a giant clock in the sky, though the bear’s crawl is counterclockwise. Through the rest of the winter and into the spring, you can watch the bear climb higher in the sky night after night, until by nearly summer it will be high over the North Star at 10pm.

As long as you’re out stargazing, you can peek over at Mars and Saturn dancing across the early evening sky from east to west, and if you prefer to do your stargazing in the morning, you’ll see Jupiter shining in the pre-dawn sky in the southeast.


Until next week, my friends, enjoy the view!