Sirius things to consider

For the week ending January 29, 2011

January 31 marks the anniversary of the first time a human being saw Sirius as a binary star. That was in 1862. The story began a few years before. In the years since, some have come to believe there’s a third star.

Sirius has been recognized for millennia as the brightest star in the night sky. In 1844, German astronomer Friedrich Bessel made careful observations and determined there must be a second star. Sirius was orbiting something else, but no one could see the other object.

That changed 18 years later. American telescope maker Alvan Clark made a refractor with a lens 18.5” wide. Larger lenses gather more light, so dimmer objects can be seen more easily. They also provide higher resolution images so very close objects can be “separated” better. At the time, Clark’s new scope was the largest refractor ever.

Generally, when astronomers refer to Sirius, they’re referring to the bright star easily seen with the naked eye. When they mean to distinguish between the two now known to be there, Sirius A refers to the bright star and Sirius B to the dim one.

The Sirius pair are about 8.5 light years away from Earth. They orbit each other in 50 year periods. After more than a century of careful observations, astronomers are convinced there are just two stars there.

Legends emerged during the 20th Century, however, of beings from the Sirius star system creating the Dogon civilization in Africa. The Dogons, who had no telescopes, somehow knew about Sirius B and the 50-year orbital period. They also supposedly claimed there’s a third star in the system.

Most anthropologists today believe the Dogons learned of Sirius being a double star from some of the Caucasians who’d visited them to study them. The purported Sirius C could be just an embellishment of a storytelling people.

In any culture, it’s not hard to imagine why a star brighter than most of the planets would be important. One people, like the Dogons, may want to honor civilization’s founders while another seeks links between the appearance of the star and phenomena on Earth. A nickname for Sirius is the Dog Star, in part, because the Ancient Greeks believed the star drove dogs mad during the heat of summer.

In mid-summer, Sirius rises just before dawn. Some people still call summer’s hottest days the dog days. By modern reckoning though, Sirius is a winter star because it’s up all night in winter.

Another reason Sirius is called the Dog Star is because it’s in Canis Major, the Big Dog. You’ll find him following Orion the Hunter across the sky. I think the dog looks like a schnauzer. Those aren’t hunting dogs, but some legends say Canis Major is Orion’s hunting companion. Look for yourself and tell me what you think.

Here’s something else to ponder while you’re looking. In ancient writings, Sirius is a red star. Today, it’s bluish-white. Modern science cannot explain the color change.