Arcturus


The two stars that I seem to mention the most are Arcturus and Spica. Since I wrote about Spica last month, I thought it was time to tell you about Arcturus. You know the drill: find the Big Dipper and follow the arc of its handle to Arcturus.

The fourth-brightest star in the sky is a red giant. It’s 25 times the diameter of our sun and radiates 100 times the light of our sun. The orange color signifies that with a temperature of 7,300 degrees it’s several thousand degrees cooler than our sun. All of this is due to its old age of 7-8 billion years.

What’s interesting about Arcturus is that it’s moving at a tremendous rate of speed perpendicular to the disc of the Milky Way. It’s highly unusual for an object to do that rather than orbiting in the disc. It’s moving with a group of old stars known as the Arcturus Stream. In about 4,000 years it will be closest to us before it begins to move away.

Arcturus is part of the constellation Boötes the Herdsman, a kite shaped form with Arcturus near the bottom as a foot.  Boötes is the guardian of the Great Bear, Ursa Major, which contains the Big Dipper asterism.

It’s one of the few stars mentioned in the Bible.  You can find it in Job 9:9 and Job 38:32. Because of its position in the sky, Arcturus is visible all year.  Currently it’s high in the southwest.

Saturn’s rings and three moons, galaxies, globular clusters and shooting stars! So, go out on a clear night and enjoy what we have and protect it for future generations by avoiding light pollution.

Happy Thanksgiving!

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