By David Ward
A sure sign of spring for stargazers is the Big Dipper rising in the northeast. Look for it standing on its handle as soon as the sky gets dark. Follow the curve of the handle down and to the right towards a bright orange-looking star low in the east.
Arcturus is its name and you may notice that it sounds a little like our word arctic. Indeed, they both come from the same Greek root word Arktos, which means bear. Arctic literally means “realm of the bears” and Arcturus means “guardian of the bears.” The bears are Ursa Major and Minor, which we see as the Big and Little Dippers. Ancient people somehow envisioned that the star Arcturus kept the two bears in their orbits around the North Star.
Does Arcturus look bright to you? It should, because it is the fourth-brightest star in the sky. The only one that we can see from this latitude that is brighter is Sirius, that brilliant one below and to the left of Orion.
Arcturus is bright because it is close to us. At only 222,000,000,000,000 miles distant it is not our next door neighbor, but just down the block a bit you might say. It is an old star, billions of years older than our sun, and has swelled up into a red giant star, but not nearly so large as Betelgeuse in Orion, another orange reddish-looking star.
An unusual aspect of Arcturus is that it is moving rapidly across the background of other stars from our perspective. You cannot see the movement yourself – the distances are too vast and our lives are too short. Imagine that our sun is riding on a huge merry-go-round, cruising along at 500,000 miles per hour tugging the earth and the other planets along with it. All the stars we see in the sky are flying along with us, and if we could fast-forward a few million years into the future, they would all still be with us. Their exact positions in relation to each other would be somewhat different, however.
Arcturus is doing something completely different. It is “dropping” in from “above” (up and down really have no meaning in scales this large) and is flying by us at right angles to our motion through the galaxy. Four thousand years from now it will reach its closest approach to earth. If you can manage to hang on for that long, look for it to be a little brighter. One million years from now it will be out of sight, headed for a different part of our galaxy.
Why is it doing this? Some astronomers speculate that Arcturus was actually born in another smaller galaxy which fell into our own galaxy billions of years ago. We too are in a long, long fall into yet another even larger galaxy.
Arcturus is the brightest star in the constellation Bootes, often portrayed as a herdsman or driver of oxen. Many legends are associated with this grouping of stars but perhaps the most famous is that he is the guy that invented the plow. Nowadays that does not sound like such a big deal. Why isn’t the guy who invented the smart phone up there?
Back then it was so amazing that Ceres, goddess of agriculture, placed him in the sky to honor his great achievement. By the way, did you ever wonder where the name of that stuff you pour milk on and eat in the morning for breakfast came from?
Closer to home, there are planets up above that will dazzle you. Look for Venus in the west just after sunset in the evening twilight. If you are lucky you might even spot Mercury nearby too. You will probably need binoculars to tease the innermost planet out of the twilight glow. If you are up late, Jupiter will be rising in the east, a bright steady yellowish light that does not twinkle like the stars. Before dawn, Mars and Saturn are visible in the east. Mars is getting brighter, building towards a spectacular show this summer.
Worried about that fall into another galaxy? Do not lose too much sleep over it. That crash will happen billions of years from now and I do not imagine any of us will be around to feel the jolt.