Star Hop with the Big Dipper

Send questions to Heart of the Valley Astronomers

Ask people which constellation they know and nine out of ten will mention the Big Dipper. Small wonder, considering it's distinctive outline, large size, and the fact that you can see it almost all year round - thanks to its position in the Northern part of the sky. A purist would say that the Big Dipper isn't really a constellation but rather an asterism, which refers to merely a grouping of stars rather than a constellation. That is perfectly true. Yet whatever the semantics, the Big Dipper represents a group of stars that fulfill important roles - in both the romantic and pragmatic spheres of our thoughts.

The Big Dipper and Surrounding Constellations

What does the Big Dipper symbolize in the sky? That depends on who you talk to. Astronomers and many other people see the Dipper as just a part of a constellation called Ursa Major - the Big Bear. Yet a perusal of cultures reveals a wonderfully diverse collection of legends. Most of you reading this view it as a drinking cup. African-Americans in the 1800's regarded it as the drinking gourd to follow when escaping from slavery. Many medieval English saw it as a plough, a rare example of a farm instrument finding its way to the stars. And Mongolian astronomers, up through the 19th century, used a sky map which depicted the Dipper as a collection of seven old men. The list goes on.

One of the more picturesque legends is that of an old Native American interpretation; which viewed the Big Dipper as a bear (the cup portion) being pursued by three hunters who take the form of the handle stars. As they chase the bear towards the Autumn season, they succeed in wounding it, which accounts for the red plumage of the trees at this time of year. Those who don't hunt (like me) can be comforted that, despite the unwelcome attentions, the bear still continues to roam through the sky, confounding the hunters.

Get beyond the cultural nomenclatures and you'll discover that the Big Dipper is quite useful in finding your way around on Earth or in the sky. You can use the following examples (shown in the illustration) from the Big Dipper, which you can notice in the Northwest sky during Autumn evenings.

Since antiquity, we've been using the stars just to get a general sense of direction. One precise navigational facet uses a star called Polaris (or the North Star) which is directly over the North Pole of Earth. Find that, and you can see where exactly North is. The only problem with Polaris is that it's not a notably bright star - so any help that a constellation can give in locating it is pretty welcome for us. This is where the Big Dipper comes in. As you can see on the diagram, you can find Polaris just by drawing a line between the first two stars of the cup and continuing up with it. That line takes you right to the North Star. Polaris also serves as the last star in the handle of the Little Dipper. With the way they're situated, one of the Dippers can always be seen pouring into the other.

The Big Dipper also factors in finding another star. Arcturus, the 4th brightest in the sky, is an example of an ancient giant star, possessing a beautiful orange color that shows well in binoculars. By drawing a line connecting the stars (forming an arc) in the Dipper's handle, you can then "…follow the arc to Arcturus…" as a common saying in astronomy goes. Astronomers have a weakness for corny sayings like that, be warned. Arcturus is relatively close to us, only about 37 light-years away. Put it in place of the Sun in our solar system and its atmosphere's outer limit would extend about 25 times farther out than the Sun's.

Follow the arc to Arcturus