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January 16, 2011

Winter nights abound with some of the brightest stars in the sky: Rigel and Betelgeuse in Orion, Aldebaran in Taurus, and Procyon in Canis Minor, the little dog, to name but a few. Yet it takes only a brief glance at the sky to pick out the brightest of them all: Sirius, the leading light of Canis Major, the big dog. It shines in the southeast in early evening, and scoots low across the south during the night.

Sirius looks so bright in part because it is fairly bright as stars go -- a couple of dozen times brighter than the Sun.

But it also shines brightly because it's just 8.6 light-years away. Only four other stars systems are closer.

By astronomical standards, that's just down the block. By human standards, though, that gap is pretty much incomprehensible -- it's far beyond any ordinary concept of "far away."

To put it in everyday terms, the distance to Sirius is about 50 trillion miles -- a five followed by 13 zeroes. To look at it another way, the farthest that any human has ever journeyed is to the Moon. A one-way trip to Sirius would be equivalent to a hundred million round trips to the Moon. At the speed of the fastest probe ever launched from Earth, it would take you about 150,000 years to get to Sirius.

And even if you could streak toward Sirius at the speed of light -- a zippy 186,000 miles per second -- it would take 8.6 years to get there -- hence the star's distance: 8.6 light-years.

Script by Damond Benningfield, Copyright 2010

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