Capping four decades of research

For Riccardo Giacconi, who led the Chandra study, the new findings cap a four-decade quest for answers.

In 1962, Giacconi and others realized that no matter where one points a telescope, X-rays filled the skies above Earth's atmosphere. Back then, instruments could not resolve whether these X-rays permeated the universe evenly or if they came from individual sources. As data rolled in, the case grew for the latter in the 1980s and 90s.

The new findings are the strongest confirmation yet that, in fact, X-rays from distant sources are generated by individual galaxies presumed to have supermassive black holes at their centers.

"For me these observations were the fulfillment of a dream," said Giacconi, who researchers called "the Granddaddy" of the effort.

More than just black holes: A quasar

Another discovery in the Chandra data was an ancient "type II quasar," by far the most distant ever found, that was shrouded in gas and dust. Tananbaum said the researchers found high concentrations of iron in the quasar, which provides a glimpse of the chemical makeup of the early universe.

"The discovery of this object, some 12 billion light-years away, is a key to understanding how dense clouds of gas form galaxies, with massive black holes at their centers," said Colin Norman of Johns Hopkins, who worked with Giacconi and others on the study.

Astronomers think quasars are powered by massive black holes. A type II quasar is surrounded by, or buried in, an occluding cloud of gas and dust that reduces its brightness in visible light, so they can only be studied well in X-rays.

Norman said the gas and dust is likely the material that feeds the voracious black hole.

"The thinking is that these may be quasars in the early stages of their evolution," Norman said. "As the quasar matures, the extremely powerful radiation it emits disperses the shroud of gas and dust. We're very eager to get a sense of how prevalent they are, and to compare that to type I quasars."

An answer may come fast. The findings reported Tuesday represent a first run at just a portion of the more than more than 500 hours of observations made over the course of more than a year, and Tananbaum and others said other astronomers were already clamoring to get their hands on the data. More detailed findings are pending throughout the year, including the possibility of many more quasars in the far corners of the cosmos.

Tananbaum said the observations will explain more than just black holes.

Researchers now have a wealth of data about galaxies and galaxy clusters, and what they looked like when the universe was less than half its current age. Such information will improve understanding of how and when the universe began and evolved.

"For the first time, we are able to use X-rays to look back to a time when normal galaxies were several billion years younger," said Ann Hornshemeier, a Penn State graduate student who led the other study. "In essence, it is like seeing galaxies similar to our own Milky Way at much earlier times in their lives."

Hornshemeier said the study also revealed a handful of galaxies that contain smaller X-ray emitting objects called stellar black holes. If the studied patch of sky is representative of the entire universe, Hornshemeier said there could be as many as 300 billion stellar black holes lurking out there.

These black holes typically have the mass of a few Sun-sized stars and are thought to be spread throughout our own galaxy. Finding them in distant galaxies provides a glimpse of what our own Milky Way might have looked like in its early years, she said.

One particular galaxy that looks like a younger version of our own, but is seen as it was 5 billion years ago, is two or three times more luminous in X-rays than the Milky Way, Hornshemeier said.

Data for the studies were also provided by the European Southern Observatory, the Hobby-Eberly telescope in Texas and the Keck Observatory atop Mauna Kea in Hawaii.