IBEX

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Our solar system sits inside a protective bubble -- a volume of space dominated by the Sun's magnetic field. It blocks radiation from other stars, and pushes aside the gas and dust that permeate the space between stars.

A new NASA spacecraft will probe the edges of the bubble, looking for the extent of the Sun's influence. The mission is called IBEX -- the Interstellar Boundary Explorer. It's scheduled for launch soon from a base in the Pacific.

The bubble is known as the heliosphere. It's filled with the solar wind -- electrically charged particles from the Sun. Guided by the Sun's magnetic field, the particles race outward at millions of miles an hour. They prevent the gas and dust that's found between stars from pushing into the inner solar system. The bubble also blocks harmful cosmic rays that come from exploding stars and distant galaxies.

Two spacecraft have flown through the inner edge of the magnetic bubble, about nine billion miles out -- a hundred times the distance between Earth and the Sun. More about that tomorrow.

But they haven't mapped the whole magnetosphere, which is contoured by the Sun's flight through the galaxy. It's squeezed inward in the direction of the Sun's motion, and stretched into a long tail in the opposite direction.

IBEX will snap images of the magnetosphere's boundary all around the solar system. It'll provide the best map to date of the region where the solar system ends and interstellar space begins.

Script by Damond Benningfield, Copyright 2008

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