Four hundred years after Galileo Galilei pointed the first telescope at the stars, astronomers devised instruments that could look beyond what optical telescopes reveal. The Chandra X-Ray Observatory, launched on July 23, 1999, aboard the space shuttle Columbia, is a highly sophisticated descendant of the early X-ray instruments. Orbiting 85,000 miles above Earth and operated by the Smithsonian’s Astrophysical Observatory in Cambridge, Massachusetts, the telescope is designed to detect X-ray emissions from extraordinarily hot regions of the universe. Over nearly two decades, Chandra has revealed a universe of violent and extreme environments. With it, scientists have studied intense gravitational and magnetic fields around black holes, supernova shock waves, and titanic collisions between clusters of galaxies.
Text adapted from Chandra’s Cosmos: Dark Matter, Black Holes, and Other Wonders Revealed by NASA’s Premier X-ray Observatory by Wallace H. Tucker, to be published on March 28, 2017, by Smithsonian Books.
Chandra’s First Light
The target for Chandra’s first observation, made 17 years ago, was Cassiopeia A, the remnants of a supernova. Cas A, a strong source of X-rays, had been observed by every previous X-ray telescope, so the quality of Chandra’s image would be a test of just how good this new telescope was.
Scientists and engineers who had worked on the telescope for more than a decade crowded in front of a computer monitor. At 8:40 p.m. on August 26, 1999, there it was: a dazzling image of the remains of a star that had exploded 10,000 light-years away. It was the best X-ray image ever made of an object outside our solar system. The team quickly noticed a tiny bright dot in the middle of the remnant. In its first look, Chandra had discovered what no previous telescope had found: the neutron star left over from the explosion that had produced Cas A three and a half centuries earlier.