The image of X-rays was dubbed Chandra Deep Field North.

Astronomers at Johns Hopkins University took a similar million-second picture with Chandra of another piece of sky near the Southern Hemisphere constellation Fornax.

With its exquisitely formed mirrors and precisely designed instruments, Chandra has been able to solve a 40-year-old X-ray astronomy problem — blurry images of X-ray sources — by clearly focusing extremely distant X-ray sources, including black holes, which emit X-rays as they tear apart nearby matter, Hornschemeier said.

"What Chandra saw were individual X-rays sources," Hornschemeier said. "Chandra's been able to pick out the point sources."

When making their million-second exposure, Penn State researchers decided to focus on a section of sky known as the Hubble Deep Field North, whose visible light rays have been intensely studied by the Hubble Space Telescope.

"If you take a penny, and you held it on a arms' length, ... the image we had isn't much bigger than Lincoln's head," said Niel Brandt, assistant professor of astronomy.

"The main thing we saw there were supermassive black holes, and we saw hundreds of those, literally," Brandt said, referring to the immense black holes at the center of galaxies. He added that the farthest supermassive black holes were roughly 100 billion light years away.

"We're trying to understand the genesis of the supermassive black holes," Brandt said. "Chandra has revealed far, far more that we've even seen before, by about a factor of 10."

However, Hornschemeier indicated that the more interesting objects in Chandra Deep Field North were the faint X-rays being emitted by much smaller black holes called stellarmass black holes.

Stellarmass black holes are not much bigger than the sun and are spread throughout galaxies that look similar to the Milky Way.

"For the first time, we're starting to observe normal galaxies," Hornschemeier said. "The supermassive black holes are exciting, shouting very loudly. They're dramatic ... If you start to listen more closely, you'll hear this whisper, and this is a whisper from more normal galaxies."

There are about 10,000 stellarmass black holes in our galaxy, Brandt said. The farthest stellarmass black holes that Chandra detected were about 7 billion light years away, he added.

"The neat thing there is we're able to study these galaxies as they were billions of years ago," Brandt said. "We're looking at galaxies that are similar to ours several billion years ago."

Some of the X-ray sources were very faint, Brandt added, sometimes giving Chandra only one photon per day to record.

"They're going deeper than ever has been done before," said Donald Schneider, professor of astronomy and astrophysics. "We're looking at the universe at a much fainter light level."

The million-second image was staggered over a period of a year-and-a-half, Hornschemeier said, which allowed the researchers to probe variability of the X-ray sources.

"The reason that it's interesting is because these stellarmass black holes are sort of the fossil record," Hornschemeier said. "What we're doing is probing back to even an earlier time."

The stellarmass black holes are formed when large, bright stars die in a supernova, she added. "They're actually the remnants of an episode star formation several million years ago."

Learning about galaxies far away can help astronomers learn more about the Milky Way galaxy. "For the normal galaxies, the general significance is that we're able to place ourselves ... in a cosmic context," Brandt said. "That is, we are able to study our galaxy — what is was like — several billion years ago."

Brandt said that these distant normal galaxies appear to be more X-ray active than the Milky Way, which could be due to more active or more numerous stellarmass black holes.

The next step, Schneider said, is to find the optical counterparts of the X-ray sources in Chandra Deep Field North. The scientists are utilizing land-based telescopes like the Keck Observatory, located on Mauna Kea, Hawaii, where Hornschemeier spent much of last week peering into the cosmos.

"That'll keep us busy for the next few years, because these objects tend to be very faint," Schneider said.