Jimmy Westlake: Canis Major — the Great Overdog
December 15, 2014
Steamboat Springs — American poet Robert Frost was a poet of the stars. Take, for example, his short poem about the winter constellation of "Canis Major," Orion's big hunting dog in the stars:
“The great Overdog
That Heavenly beast
With a star in one eye
Gives a leap in the east.
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He dances upright
All the way to the west
And never once drops
On his forefeet to rest.
I’m a poor underdog,
But tonight I will bark
With the great Overdog
That romps through the dark!”
What a thrill it is to see the Great Overdog poke his nose up over our mountains as he gives his leap in the east. His nose is marked by no less than the brightest star visible in our night sky, the dazzling white superstar Sirius, also nicknamed the Dog Star.
When Sirius suddenly pops up over the mountain, it’s as if a miniature sun has risen, casting faint, flickering shadows over the snowy ground. When seen low on the horizon, Sirius seems to twinkle and flash with every color of the rainbow.
Sirius is the sixth-closest star to our solar system, shining only 8.6 light-years away. The bright star that we see, Sirius A, is accompanied by a fainter companion star that we can't see without a powerful telescope. Called Sirius B, or "the Pup," it was only the second white dwarf star to be discovered, back in the year 1862, though its most unusual nature wasn't revealed until decades later.
Astronomer Arthur Eddington summed it up in 1927: "We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the Companion of Sirius, when it was decoded, ran: 'I am composed of material 3,000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox.' What reply can one make to such a message? The reply which most of us made in 1914 was — 'Shut up. Don’t talk nonsense.'"
Just south of Sirius is the beautiful star cluster called M41. It is faintly visible to the unaided eye on a clear, dark night, but with just a simple pair of binoculars, M41 is resolved into a jewel box of diamonds and sapphires. It's hard to believe that the glittering starlight from this cluster of stars began its journey to Earth 2,200 years ago.
You can locate the rising point of Sirius by following a line through the three stars of Orion's belt down to the southeast horizon. You'll know when Sirius is about to the crest the mountain peaks when you spot the fainter star Mirzam, rising in the same location. Mirzam means "the Announcer," so named because it trumpets the arrival of the Dog Star, Sirius.
Sirius rises at about 8 p.m. Christmas Eve and about 30 minutes earlier, or 7:30 p.m., on New Year’s Eve.
Why not step outside with your family this holiday season and bark with "the Great Overdog that romps through the dark?"
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. Check out Westlake’s new "2015 Cosmic Calendar" of sky events on his website at http://www.jwestlake.com. It features 12 of his best astrophotographs and a day-by day listing of cool celestial events that you and your family can enjoy watching in 2015.
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