A long time ago, in a galaxy far, far away, thousands of stars that were clustered into several groups blew up at almost the same time.

The result: a galaxy with the consistency of Swiss cheese.

For the past several months, undergraduate Nicholas Bond (junior-astronomy and astrophysics), in collaboration with researchers from Penn State and the University of California-Santa Cruz, has been detecting and measuring the presence of the "superbubbles" in the galaxy 7 billion light years away.

Bond, who has done astronomical research since the summer after his freshman year, recently traveled to San Diego to present his findings at the 197th Meeting of the American Astronomical Society, where many other astronomical researchers from all around the world presented their work.

A superbubble is the result of thousands of large stars exploding, explained Christopher Churchill, research associate for the Department of Astronomy and Astrophysics at Penn State.

"Galaxies are systems of stars. Not only are these stars in the galaxies, but stars are made of gas," he said. The stars responsible for the explosions leading to the superbubbles are 20 to 50 times more massive than our sun and have relatively short life spans.

"When just one of them explodes, it releases more energy in one second than our sun releases in its lifetime," Churchill said.

When 1,000 to 10,000 of these stars explode within a short time, they effectively push away all of the surrounding interstellar gas--the same gas that is used to make stars. The gas is pushed farther and faster as the explosion expands, creating the outer rim of the spherically shaped superbubble.

"All this gas has piled up because it can only move so fast in the interstellar medium of the galaxies," Churchill said. "The bubble is hot and has relatively no gas in it."

The superbubbles are about 10,000 trillion miles in diameter. The galaxy in which they reside is about 30 times bigger than the superbubbles, said Jane Charlton, associate professor of astrophysics and astronomy.

"We think we're seeing several bubbles," Churchill said, later estimating the number of bubbles to be six or seven. This implies anywhere from 6,000 to 70,000 massive clustered stars exploded to create the superbubbles.

The stars all died at roughly the same time, meaning the stars were born at roughly the same time, Charlton said.

Churchill said that some 8 billion years ago, "Some event happened in this galaxy to make lots of stars in small pockets."

One likely scenario is that the galaxy merged with a smaller satellite galaxy, creating pockets of gas closer to the edge of the galaxy.

"A pocket of gas is a place in the galaxy that is more dense than the rest of the galaxy," Charlton said. From these dense areas of gas come clusters of the massive stars.

"It's the big (stars) we're interested in," she said. "They sort of sweep up stuff around them," creating the shell of the superbubbles.

Some evidence supports this theory. "The specific region of the galaxy we're studying is not all that close to the center of the galaxy," Charlton said. The fact that the superbubbles exist closer to the rim of the galaxy appears to show that the original pockets of gas were created from an incoming galaxy.

Bond seemed to support the meshing galaxies idea. "You get superbubbles when galaxies collide," he said. "They (superbubbles) expand for about 50 million years."

The superbubbles could expand too much, creating what Bond called a blowout. "That's when the superbubble escapes the gravitational pull of the galaxy. They become non-spherical," he said, adding the superbubbles could later fragment.

Bond and others detected the distant superbubbles by taking advantage of quasar located behind the galaxy.

"A typical quasar's luminosity is somewhere in the order of 1018 suns," Churchill said, describing the quasar as a cosmic flashlight.

"That light that's traveling from the quasars to the earth goes through the galaxy," he said.

As the quasar light passes through the galaxy on its way to the earth, the gas in the galaxy absorbs some frequencies of the light, creating an absorption spectrum that can be measured on earth.

"The gas puts its fingerprints into the light," Churchill said. "We can see with great detail the movement of the gas in the galaxy."

From the complicated graphs and lines of the absorption spectrum, the researchers deduced the presence of the expanding superbubbles in the distant galaxy.

Although superbubbles have been detected in nearby galaxies and our own Milky Way, this is some of the first evidence for superbubbles in such far away galaxies, Bond said. Since light from the galaxy takes so long to reach earth, the researchers are actually looking at the activity of a distant galaxy from the distant past.

"It shows high red shift galaxies are going though the same thing galaxies go through now, 'high red shift' meaning galaxies very far away," Bond said. "Superbubbles so far have only been observed in low red shift galaxies."

Churchill said the formation of the superbubbles took place when the universe was about half of its age. "It hasn't been clear than 7 billion years ago galaxies do what they do today," he said. "What were galaxies doing when the universe was half its age? People don't know."

Now that they think superbubbles have formed in the faraway galaxy, "It says that the galaxies are doing something similar to what they're going today," Churchill said.

The research also shows that the ancient galaxies were far from idle.

"This seems to imply that they're more active," Bond said of the very old galaxies.

With the new absorption spectrum evidence of superbubbles in faraway galaxies, the astronomy world is one step closer to finding out what happened in the universe billions of years ago, Charlton said.

"It's been challenging to make these specific connections between the ancient and present universe," she said. But the secret lies in measuring more absorption spectrums, she adds.

"If we can crack this code, we can map the whole evolution of the universe."