An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time

SUPERNOVA 1987a

This Hubble Space Telescope image shows the remnant of a supernova a star that blew itself to pieces. We first saw the light of the explosion on Earth in 1987, and this image was taken in 1994. The remnant of the explosion itself is the blob of stuff in the center; the rings are regions of material ejected by the star earlier in its death throes. They have been "lit up" by the energy of the explosion. The inset at the bottom shows the expansion of the exploded material in the center from 1994 through 1996. Even after 7 to 9 years after the star exploded, the remnant is seen to expand at almost 10 million kilometers per hour. Supernovae are nature's way of making and recycling some of the heavier elements that make up the universe. (Courtesy of C. Pun & R. Kirshner, the Space Telescope Science Institute, and NASA)

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