Phil Harrington’s binocular universe: The Big Dipper, part two

Ready to return to the sky’s most famous star pattern, the Big Dipper? Last month, we visited several deep-sky sights lying near the bowl. This time out, we’ll tour the Dipper’s crooked three-star handle.

The Big Dipper is not a constellation by itself, but rather part of Ursa Major the Great Bear. The Dipper’s bowl forms the Bear’s back and belly, while artists often portray the three stars in the Dipper’s handle — Alioth, Mizar, and Alkaid — as its long tail. But bears don’t have long tails.

A better explanation comes from a Native American legend that depicts the tail stars as three hunters chasing the bear. In fact, if you look carefully, you can see that the hunter in the middle is carrying a pot to cook the bear in after they catch it.

The “pot” is the star Alcor. With Mizar, they form one of the sky’s best-known
double-star teams. They make a fun naked-eye test and are an easy target for even the smallest binoculars. Mizar shines at 2nd magnitude, while Alcor glows at 4th.

They may look like a physical pair, but Alcor and Mizar are actually frauds. Mizar lies 78 light-years from us, while Alcor is 81 light-years away. Mizar turns out to be a true close-set binary star, but you’ll need a telescope to see its companion.

Don’t confuse that for a third, fainter star that forms a tiny triangle with Alcor and Mizar. Although this star is not physically related to either, it holds an interesting footnote in astronomical history. In 1722, German mathematician Johann Liebknecht thought he saw this star move against the background from 1 night to the next. He concluded it was not a star, but a new planet. In his excitement, he christened it Sidus Ludoviciana (“Ludwig’s Star”) after Ludwig V, then king of Germany. It quickly became apparent that Liebknecht was mistaken, but the star is still called Sidus Ludoviciana.

Now, let’s go hunting for bigger game. From Mizar, trace a zigzag of four faint stars eastward, away from the curving handle. At the fourth star, hook a little to the northeast, toward a diamond of four fainter stars. Can you see a faint smudge next to the diamond’s eastern point? That’s the famous spiral galaxy M101 — a challenging target for small telescopes, let alone binoculars. Even with averted vision, M101 probably will seem little more than a dim glow, but ponder what you are looking at — a system of billions of stars. The light from these stars left 27 million years ago, long before our earliest ancestors evolved on the grassy savannahs of eastern Africa.

If M101 proves a little too tough, try your luck with a brighter galaxy. Aim toward Alkaid, the star at the end of the Dipper’s handle. Look half a field to Alkaid’s west-southwest for a 4th-magnitude star, and then, from there, move an equal distance farther south to a pentagon of dimmer suns. If you look carefully just inside the pentagon’s eastern corner, you might spot a dim glow. That’s M51, the beautiful Whirlpool Galaxy.

Through 70mm and larger binoculars, you might notice M51 appears a little lopsided. You aren’t looking at just one galaxy, but two. Charles Messier missed M51’s companion, so you won’t find it in his catalog. We know it today as NGC 5195, its listing in the New General Catalogue. NGC 5195 glows at about 10th magnitude.

Let’s wrap things up with a reminder. In the March issue, I mentioned how Saturn was near M44, the Beehive Cluster in Cancer. The pair continues to form a pretty sight through binoculars. As a bonus, the crescent Moon joins them May 31. All three will fit nicely into the same binocular view as the sky darkens after sunset.

Come on back next month. We’ll visit the sky’s strongman, who has a few celestial surprises of his own. Till then, remember: Two eyes are better than one.