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Heavenly Skies: Meet Ursa Major, the Great Bear

By: Gene Grahek, Special to the Telegraph
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Ursa Major is Latin for “Great or Large Bear” and is one of 5 northern constellations that circle the North Star. From our location it can be seen year round rotating counterclockwise throughout the year. It contains numerous objects viewable by either binoculars, telescopes or the naked eye.

Ursa Major is best identified for the asterism, or grouping of stars known as the Big Dipper and in the United Kingdom as the Plough. Commonly mistaken for the entire constellation, the brightest 7 stars form a dipper or saucepan image. The 3 stars of the handle actually represent the bear’s tail with the remaining 4 stars of the Dipper being the bear’s upper hind quarters. The handle’s middle star, Mizar has been traditionally used as an eyesight test due to it’s proximity to the faint companion star, Alcor. See if you can spot the 2 stars, sometimes called the “Horse and Rider.” All of these stars reside in the Milky Way Galaxy about 80 light years away moving through space in the same direction.

One of the most frequently asked questions of visitors to the observatory is “where is the north star?” Instead of just pointing our laser beams at it, we teach you how it can easily be found. To do this you need to follow the 3 stars of the handle of the Big Dipper to the bowl or saucepan. Then find the 2 stars opposite the handle that make up the bowl’s outer edge. Draw a line from the outer edge of the bowl’s fainter star up through the brighter star. Continue following this line about 5 times the distance between the 2 stars. You are now at the magnitude 2.0 North Star known as Polaris.

Ursa Major contains several deep sky objects such as M101, the Pinwheel Galaxy. This face on galaxy is almost twice the size of our Milky Way Galaxy and even at 21 million light years away the center can be seen with binoculars. Two other galaxies in Ursa Major lie relatively close together at about 12 million light years away. M81, known as Bode’s Galaxy and M82, the Cigar Galaxy have actually been altered in a gravitational battle with each other and they can be viewed as faint fuzzy objects through binoculars or small telescopes.

M97 is the Owl Nebula at a mere 2,600 light years away and are the remnants of a dying star known as a planetary nebula. Early astronomers mistook theses remnants for planets as the expanding shell of gasses gave the appearance of a planet. Our sun will suffer the same fate as M97 in about 4.5 billion years. The Owl Nebula appears round with what looks to be two eyes in the center when viewed through a larger telescope.

In 1995 the National Aeronautical and Space Administration initiated Hubbl Deep Field North to search an area of darkest space outside the Milky Way Galaxy for evidence of the oldest galaxies. The Hubble Telescope took a series of 342 exposures for over 100 hours selecting an area just above where the Dipper’s handle meets the bowl. This represented an area about 1/28,000,000 of the total area of the sky. Imagine holding a grain of rice at arm’s length to represent how small of an area this was. The resulting images amazed astronomers and the public alike as they showed almost 3,000 galaxies. These galaxies are estimated to have been formed about 1,000 million years after the Big Bang.

To confirm data received in the first deep field study, Hubble searched an area in the Southern Hemisphere in 1998 and confirmed the previous images were truly representative of our early universe.

Come visit us at the Cameron Park Rotary Club Community Observatory located in Placerville to view the wonders of the night sky. For operating hours, directions and more information see www.communityobservatory.com and don’t forget to like us on Facebook.

Gene Grahek is Lead Docent for the Cameron Park Rotary Club Community Observatory.