There’s the Big Dipper!

Hey, sky fans!

Many years ago, late one night, I was looking out the window of the bedroom I grew up in, the one with the map I mentioned last week. The window faced north, and there was enough suburban sky over my neighbors’ house that I could see, even on bright Long Island, some of the exciting things I read about in the books I would check out from the school library and renew until the librarian Mrs. White (nee Black) told me to knock if off. I figured, from conversations with my sister and my classmates, that I was the only one who’d be reading them anyway, so I never thought I was being selfish.

One night, right around this time of year, when everyone else thought I was sleeping, I looked out and saw the Big Dipper hanging very high, upside-down, as if it was pouring soup on my neighbors’ house. I remember reading that the Big Dipper was an asterism — an unofficial and recognizable group of stars that can be part of any number of constellations—in the constellation Ursa Major, not a constellation on its own. A constellation is one of the 88 officially recognized regions that cover the entire sky with no gaps and are used for navigating the sky.

That night, it was big, bright, and unmistakable above the shingles and the big maples farther down the road. As time went on, I always looked for it out the window or when I was outside. It wasn’t always high up, but it was almost always in the sky. The few other constellations I could pick out near my house with an airport and a couple of highways off in the distance came and went, but the Big Dipper was always somewhere. As the year went on, sometimes it was off to one side or the other, and sometimes very low, almost hidden behind the houses and the trees. Sometimes, out my window, I saw a different pattern, shaped like an M. That one, I’d learn later, was the constellation Cassiopeia, the beautiful but tragically hip queen.

If you remember a few months ago, we talked about using those two constellations to find Polaris, the north star. Polaris is always in pretty much the same spot of the sky, every day, all year, day or night, while a couple of constellations seem to circle around it. The Big Dipper and Cassiopeia are on opposite sides of each other from Polaris, and are the brightest of a group of constellations that never fully set from most places in the northern hemisphere, called circumpolar constellations. The southern hemisphere, even though it has no pole star, has its own circumpolar constellations. Auriga, Draco, Lynx, Perseus, Cephus, and Ursa Minor (the little dipper—Polaris’s constellation) are also circumpolar in the north.  As the year goes by, these move from one part of the northern sky or the other, seeming to orbit Polaris.

These stories—the queen, the hunter, the very exciting triangle, the great bear, the bull, the twins, all the rest of them— travel with the constellations but aren’t tied to them. People are really great at picking out patterns and making up stories, so we have them all over the sky. I’ve never seen the Big Dipper as bear, or even part of one. To me, it’s a person, seen from overhead, with their arms stretched out to the sides. Same for Cassiopeia. As they turned and turned around Polaris, I saw kids on a merry-go-round, or fielders chasing after a badly thrown ball. Maybe it was people rushing past each other on their way to a train.

cas-umaj-all
Cassiopeia and Ursa Major Dancing around Polaris (from Stellarium)

As it happens, Ursa Major is easily one of the greatest groups of stars the sky has to offer. It’s bright and easy to find. Then, once you’ve found it, you can use to to jump off to other places in the sky, for instance Arcturus, which is probably most famous for being one of my favorite stars (more on that in another post, though). It’s also full of incredible deep sky objects, which you can see if you’re fortunate enough to have good tools. Interestingly enough, it’s also different from other constellations because its stars are part of a group of stars that are gravitationally bound and are moving through space together in what’s called the Ursa Major Moving Group. Other constellations’ stars aren’t related, but just appear to be from our seats here on Earth. Like so many other things, it’s point of view.

When you take out the recycling tonight, look up. Yeah, I always say that. This time, I mean it, though. Look up. No, way up; make your neck hurt (Note: The preceding does not advocate making your neck hurt). Almost straight up overhead to the north, you’ll see it, in great viewing position as it always is this time of year. As the year goes on, it’ll move, but it’ll always be there for you, no matter what story you like to tell.

Lately, I’ve started to see them as an old couple, who’ve lived a long happy life, spending the rest of their time dancing across the sky with each other, the smell of Sterno and pigs-in-blankets in the air around them.

Clear skies, everyone.

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