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July 26, 2010

One of the prettiest sights in the night sky is Cygnus, the swan. Its brightest stars really do look like a long-necked bird soaring gracefully through the Milky Way. The swan is high in the east at nightfall. Its brightest star, Deneb, marks its tail, with its body stretching to the right.

That region of the sky is also a pretty sight to the astronomers who work on NASA's Kepler mission. The orbiting telescope is keeping a steady eye on 150,000 stars in Cygnus and the adjoining constellation Lyra. Its goal is to find Earth-like worlds in Earth-like orbits around the stars.

Kepler measures the brightness of its target stars. If a planet passes directly in front of a star, the star's light will dip a tiny bit for a few hours. If the dip repeats itself, scientists can measure the planet's size and its distance from the star.

Kepler has already discovered several large planets in close orbits around their stars. But planets like Earth take longer, in part because it's roughly a year or so between passages in front of their stars. Kepler hasn't been in orbit long enough to confirm those types of planets. But there's no hurry: Kepler is only about a third of the way through its mission of discovery.

Look for Kepler's search area between the bright stars Deneb, the swan's tail, and Vega, which is well to its upper right this evening. Binoculars will reveal scores of Kepler's target stars. We'll have more about Deneb tomorrow.

Script by Damond Benningfield, Copyright 2010

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