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October 19, 2010

Galactic beauty in the Big Dipper

On clear, dry nights - the kind we often see at this time of year in Maryland - it's nice to look upBig Dipper and see familiar constellations. One of the most familiar, of course, is the Big Dipper. The big rectanglular bowl and long, curved handle are easy to pick out in the northern sky at any time of year.

The Big Dipper constellation is also known as Ursa Major, the "Big Bear." The Greeks saw a bear in the pattern, and so did some native North American tribes. The Dipper also has much to offer backyard stargazers.

Galaxy NGC 3982For example, the star at the bend of the dipper's handle - Mizar - is actually a double star. Its companion is Alcor. They're sometimes used as a test of visual acuity. People with the sharpest eyesight may be able to see two stars there without magnification. For the rest of us, binoculars can easily separate the pair. 

The two stars on the side of the bowl farthest from the handle point to the North Star - Polaris - which stands five dipper-heights from the top of the bowl.

You can also use the dipper's handle to find the bright star Arcturus. As the old memory aid says, just "follow the arc [of the handle outward] to Arcturus." Let your eyes trace the handle's arc, continuing beyond the end to the first bright star you come to. That's Arcturus, the third-brightest star in the night sky.

But there's lots we can't see. And there's a striking new image out from astronomers using the Hubble Space Telescope to prove the point. It's a photo of a beautiful spiral galaxy, called NGC 3982. The galaxy is in Ursa Major, 68 million light-years from Earth. 

About a third the size of our own Milky Way galaxy, NGC 3982  is 30,000 light-years across, which means it takes 30,000 Earth years for light to travel from one side of the spiral to the other. NGC 3982 is located in a cluster of galaxies, called the M109 Group, located on the lefthand corner of the dipper base.

Here's more on the new Hubble image.

(PHOTOS: Top: NASA. Bottom: NASA/ESA/Hubble Heritage Team/STScI/AURA)

Posted by Frank Roylance at 10:37 AM | | Comments (1)
Categories: Sky Watching


Great information and photos. Astronomer Alan Dressler writes in "Voyage to the Great Attractor" that the bowl of the Big Dipper (Ursa Major) frames about one million galaxies--not stars--but galaxies! This is just stunning to think about.

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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