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The Carnivorous Cosmos

August 27, 2009
Harriet Witt
The star that we’re orbiting is on a journey of its own. It’s transporting its family of planets—including the one we live on—around the core of the Milky Way Galaxy. Each of our orbits around the galaxy is a galactic year, and during this galactic year, our planet orbits the sun 225 million times.

Our galaxy, a spiraling mass of billions of stars, is shaped like an oval serving platter with a central bulge. Earth is located about two-thirds of the way out from the central bulging core.

On summer evenings, when the moon isn’t too bright, you can easily see our galaxy’s core and the platter-like disk in which other galaxy stars orbit. At the end of twilight, face where the sun set, and make a quarter-turn to the left toward the south. Now look up.

If the sky is clear and dark, you’ll notice a swath of light extending from the southern sky upward, over the top of your head to the north. This light comes from billions of stars that are too far away to see individually. The southern portion of this swath is thicker and brighter because it’s the center—the massive, bulging core of our home galaxy.

Just because our galaxy has the same name as a candy bar doesn’t mean it’s sweet. In fact, it appears to be cannibalizing its neighbors. Its neighborhood is called the Local Group of galaxies and it contains the Andromeda Galaxy, which you can see on fall and winter evenings if the sky is dark, and some others you can see only if you’re south of Earth’s equator.

Recently, astronomers discovered another member of our Local Group, a dwarf galaxy closer to us than any other, but hard to see because it’s behind the bright, bulging core of our galaxy. It became visible in telescopes only when astronomers “subtracted” the light of the stars in between the two galaxies Now astronomers are able to see this little galaxy, and it’s shape implies that it’s being torn apart and gobbled up by our Milky Way. It will be completely consumed within another 100 million years.

Meanwhile, another group of astronomers discovered 175 stars orbiting the fringes of our galaxy in a peculiar pattern indicating that they were captured from neighboring dwarf galaxies gobbled up by our own Milky Way long ago. All of this gobbling makes you wonder: Is anything eating us?

It turns out that our galaxy and most of our neighboring galaxies are being pulled toward an unknown object that’s been dubbed the Great Attractor, which is located in the lower west-southwest sky just after sunset. It’s attracting our galaxy toward it at more than 1.5 million miles per hour.

It is now thought that the hungry Great Attractor is probably a supercluster, containing many clusters of maybe hundreds of galaxies each—or something bigger.

Harriet’s class, Making Friends With the Night Sky, will be held on four Thursday evenings, beginning Oct. 1. To register, call Maui Community College at 984-3231. For more information, visit Harriet’s Website: 

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Harriet Witt

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