A Closer Orion Nebula

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• 8 of 1995
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The stars that speckle the night sky are anything but eternal. Like people, they're born, they live, and they die. The best-known birthplace of new stars is the Orion Nebula, a cloud of gas and dust that's bright enough to see with the unaided eye. Orion is high in the south in mid to late evening.

Two recent studies have found that the nebula is nearly three hundred light-years closer to us than astronomers had thought.

One study, by astronomers at the University of California at Berkeley, measured the parallax of one of the nebula's stars.

Parallax is a tiny shift in a star's apparent position in the sky. It's caused by the back-and-forth swing in Earth's position as it orbits the Sun. It's like holding out a finger and viewing it with one eye, then the other. The finger appears to move a little compared to the background of more-distant objects. Measuring how much it moves tells you the finger's distance -- and the same thing works with stars: Measuring a star's parallax reveals its distance from Earth.

The Berkeley astronomers used an array of radio telescopes from New Hampshire to Hawaii to pinpoint the parallax of a young star in the nebula. They found that the star is just 1,270 light-years from Earth, with an uncertainty of just a few dozen light-years. That makes it the most precise measurement ever made of the distance to the Orion Nebula -- a nursery for newborn stars.

We'll have more about Orion tomorrow.

Script by Ken Croswell, Copyright 2007

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