Nasa : 2007-11-19

A growing black hole, called a quasar, can be seen at the center of a faraway galaxy in this artist's concept. Using NASA's Spitzer and Chandra Space Telescopes, astronomers discovered swarms of similar quasars hiding in dusty galaxies in the distant universe.

The new-found quasars belong to a long-lost population that had been theorized to be buried inside dusty, distant galaxies, but were never actually seen. While some quasars are easy to detect because they are oriented in such a way that their X-rays point toward Earth, others are oriented with their surrounding doughnut-clouds blocking the X-rays from our point of view. In addition, dust and gas in the galaxy itself can block the X-rays.

Astronomers had observed the most energetic of this dusty, or obscured, bunch before, but the "masses," or more typical members of the population, remained missing. Using data from Spitzer and Chandra, scientists uncovered many of these lost quasars in the bellies of massive galaxies between 9 and 11 billion light-years away. Because the galaxies were also busy making stars, the scientists now believe most massive galaxies spent their adolescence building stars and black holes simultaneously.

Image Credit: NASA/JPL-Caltech