For the week including January 1, 2010

M101 Larger Illustration

SHARING STARS

I’ve been glad to hear from some readers that they send this column to family members in the military to give them a touch of home. At this time, while we celebrate here, it’s also good to remember the men and women we care for who are serving in dangerous places half-way around the world. So, to those of you overseas, please keep safe. Our thoughts are with you and if you look to the northern sky tonight, know that we will be looking at those same stars. No matter the separating distance, the stars can bring us a bit closer together.

In the northern hemisphere, there are stars that can be seen year round everywhere on the planet. They are gathered around Polaris, the North Star. So, the constellations we’ll use for our remotely shared view will be those of the Bears, Ursa Major and Ursa Minor, otherwise known as the Big and Little Dippers.

The Big Dipper: The Big Dipper is an asterism, a group of stars that form a familiar shape. It’s part of the larger constellation of Ursa Major, the Greater Bear. The stars of the Big Dipper are not fixed in place and, as stars go, they’re moving apart fairly quickly. If you stick around for another 25,000 years, you’ll see a marked change in their positions. Certainly worth waiting for... Star groups like these are called open clusters and the Big Dipper is the closest one to the Earth.

The Little Dipper: This is really the constellation Ursa Minor, named the Lesser Bear because of its resemblance to a bear cub. Well, OK, maybe I don’t think it does either. The Little Dipper has the North Star at the end of its handle. A quick way to find it is to use the two stars that form the far edge of the Big Dipper’s bowl. Follow these stars straight outward and you will come to Polaris, a star that looks brighter than any of the stars around it.

For SPC Sean Durbin and the folks in the 301st, the Dippers will be situated differently at sunset. At latitudes closer to the Equator, these constellations will be nearer the horizon. But because the Earth’s rotation causes the stars we see in the sky to wheel counter-clockwise around Polaris, you’ll be able to find both Dippers as the evening goes by.

And for those with access to a good telescope, try looking for the magnificent galaxy, M101. Twenty-two million light years away and spanning a distance of 170,000 light years, M101 is one of the largest Grand Design spiral galaxies visible from Earth. Shown in the Hubble Space Telescope photograph at upper right in our illustration, this galaxy appears so large in the sky that astronomers discovered it “gradually” over many years. The bright knots of star forming regions in its outer arms were originally thought to be separate objects, distinct from the galaxy’s bright core. You can see this effect for yourself with a telescope under low power. The galaxy is so big that there appears to be a significant amount of empty space surrounding its central region.

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