A bubble in space: Abell 39 marks the death of a star like the sun. Wind from the aging central star pushes into the surrounding interstellar gas, building up a dense shell that glows blue in this image. After 36 years of travel, the Voyager spacecraft is just now reaching the edge of the sun's own wind-blown bubble. WIYN/NOAO/NSF hide caption

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This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. AP hide caption

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Has Voyager 1 Left The Solar System?

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Will we need to tread lightly, in deference to the locals, when finally do make it to Mars? Pat Rawlings/SAIC/NASA hide caption

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On its way to Jupiter, the Galileo spacecraft looked back and captured this remarkable view of Earth and the moon. The image was taken from a distance of about 3.9 million miles. NASA hide caption

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An artist's impression of a gamma-ray burst, a powerful jet of energy lasting from less than a second to several minutes. The most powerful events in the universe, they are thought to be mostly associated with the explosion of stars that collapse into black holes. A. Roquette/ESO hide caption

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Venus on the eastern limb of the Sun captured by TRACE satellite. NASA hide caption

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The Venus Transit: Who Cares?

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