The Big and Little Dippers

It is nice to know there are readers for this column, I know because several of them have asked my why, so far, I've skipped two important constellations: the Big and Little Dippers.

Aside from a very short mention in an earlier column that the dippers are asterisms (a distinctive group of stars) and not official constellations I have sort of ignored them. One reason is they are very low in the northern sky at this time of the year and not very prominent. You will need a very flat, very clear (no trees or houses) horizon to find them. And the Little Dipper contains some faint stars, faint enough that many people have never seen the figure.

The Big and Little Dippers are part of the constellations Ursa Major, the Great Bear and Ursa Minor, the Small Bear respectively. Some civilizations saw the Bid Dipper stars as a wagon or a plow (as it is called in Great Britain only they spell it Plough). The Persians, the Greeks, and even the American Indians mention them as bears in their histories. There is even a mention in the Bible, although it is mistranslated as Arcturus in Job 9:9 in the King James. Newer translations have made the correction.

Both dippers are circumpolar, which means they never set beneath the horizon and are visible at all times of the year. Actually, from our latitude the star at the end of the Big Dipper's handle does set for a short time, but we can still see enough of the figure to make it out. Right now the Big Dipper is low in the north in the early evening. In May it will be much higher in the northern sky.

The two outer stars of the Big Dipper's "cup" can be used as pointers to find the North Star.

Just find the pointers, draw a line from bottom to top and continue on to find Polaris, the North Star, the end star in the handle of the Little Dipper. In springtime, the arc of the handle of the Big Dipper can be used to find the bright star Arcturus. Just follow the arc or, "arc to Arcturus" in the constellation Bootes (a subject for a future column).

The second star in the handle of the Big Dipper is called Mizar. If you have good eyesight, and a dark place, you can see it is a double star. The fainter companion is called Alcor. In the ancient Arab culture they were called the Horse and Rider and were used as a way to measure the eyesight of its soldiers. If they could see them, they had good eyesight.

Mizar and Alcor are not really double stars. They are about a quarter of a light year apart. Nonetheless, they do move through space together. For all those who received telescopes for Christmas, Alcor and Mizar are a good place to start. Through a telescope, you will see that Mizar itself is a double star!

There will be more about these two later in the spring when they are higher in the sky and it is warm enough to go outside and have a look.

Next time, The Mighty Hunter.