I have a late night assignment for night owls this week. If you can handle the late hour and the January cold, there’s something really special waiting for you in the heavens that will make braving the cold and loss of sleep worth it.
In the midnight hour, direct your view to the southern half of the sky. That’s where Orion the Hunter and his gang of other brilliant stars and constellations are holding court. They’re my favorite set of constellations, centered around the mighty hunter that reminds me, and a lot of other people, of a giant hourglass. Orion’s most striking feature is his belt, made up of three bright stars in a near perfect row. I’ll have a lot more to tell you about Orion in the coming weeks of Starwatch.
If you extend Orion’s belt with your mind’s eye to the lower left, you’ll run right into a seriously bright star. That’s Sirius, the brightest star in the entire night sky and the brightest star in the constellation Canis Major, Orion’s loyal hunting dog. In fact, one of Sirius’s nicknames is the “Dog Star.” You won’t find any brighter star than Sirius in any part of the night sky or at any other time of the year around here.
What’s unique about Sirius this time of year is that the brightest star in the night sky reaches its highest point in the sky at around midnight to help kick off the new year. On New Year’s Day, Sirius was exactly at its highest point right at midnight, but it’s still pretty close to that this week. Just about all of the stars in the sky arc across the sky, rising in the east and setting in the west, crossing over an imaginary line called the meridian. The meridian bisects the sky, running from the north compass point on the horizon to the south compass point on the horizon, passing right through the overhead zenith. At midnight Sirius will be transiting the meridian, and at its highest point will be a little less then a third of the way from the southern horizon to overhead zenith.
The reason Sirius is such a bright shiner is that it’s is one of the closer stars to us, at least relatively speaking. Sirius is roughly 8.5 light years away, which works out to roughly 50 trillion miles. Believe it or not, that’s considered down the block astronomically, and is one of the Sun’s closest celestial neighbors. Most stars you see up there, even with the naked eye, are much farther away, some hundreds, even thousands of light years away.
Astronomically Sirius is well over a million miles in diameter, roughly 1.5 times that of our sun, and is almost twice as hot as our home star. It also kicks out more than 25 times the light and energy of the sun. It’s far from being one of the biggest stars in our home Milky Way Galaxy, but if you put it in place of the sun in our solar system Sirius would basically fry us all. So just as well that Sirius is 50 trillion miles away. I don’t have strong enough sun block for the Dog Star.
To me, one of the coolest things about stargazing is that these stars are so far away that we don’t see them as they are now. Since Sirius is over eight light years away, you’re seeing what it looked like in 2007, when George W. Bush was still president and the iPhone was first introduced by Apple. It’s taken that long for the light from Sirius to reach our eyes on planet Earth. That’s actually chickenfeed compared to other bright stars close to Sirius in the sky. The bright star Betelgeuse next door in the constellation Orion is better than 600 light years away. The light we see from that gargantuan star this week left that star in the late 1300s, or around the start of the Italian renaissance.
Enjoy the highest and brightest star in the midnight hour, along with all of the other bright shiners around Sirius.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications available at bookstores at http://www.adventurepublications.net
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