Boughn said the galaxy was discovered in the 1950s during an extensive astronomical survey of the sky. But it was not until he and two other astronomers analyzed data gathered at an Arizona observatory between May 1987 and January 1989 that they realized the galaxy was about four times longer on its diameter and 16 times larger in area than previously believed.
A scientific paper describing the findings is being published today in Science, the nation's most prestigious scientific journal. Jeffrey R. Kuhn, of Michigan State University, and Juan M. Uson, of the National Radio Astronomy Observatory in Socorro, N.M., are the co-authors.
The galaxy - which is a grouping of stars and planets that can contain billions of astronomical objects - is in the center of a cluster of galaxies known as Abell 2029. This galaxy, which is too faint to be seen by the naked eye, is in the constellation Serpens, between Bootes and Libra.
The new discovery was the byproduct of a research project designed to develop a new technique for collecting and analyzing low levels of light gathered from astronomical objects.
The scientists collected their data using a 36-inch-diameter telescope at Kitt Peak National Observatory in Tucson, Ariz. Computers were then used to process the data and generate images of the galaxy. The astronomical team then analyzed the data at Haverford, Michigan State and the National Radio Astronomy Observatory.
Two former undergraduate Haverford students, Steve Van Hook and Doug Berlin, also participated in the research, Boughn said.
Uson said the galaxy is by far the largest and brightest galaxy in the Abell 2029 cluster, which contains several thousand galaxies. He said it is about 200 times brighter than the second brightest galaxy in the cluster.
He said the galaxy gives out more than two trillion times as much light as the sun.
Until today's announcement, the largest known galaxy had been Markarian 348, about 1.3 million light-years in diameter. That galaxy was identified in 1987 by Susan Simkin of Michigan State University, Jacqueline van Gorkom and John Hibbard of the National Radio Astronomy Observatory and Hong-Jun Su of Purple Mountain Observatory in China.
Uson said the galaxy in Abell 2029 probably was formed about 10 billion years ago. He said it appears the galaxy has changed little during the past few billion years.
"It is just sitting there," he said. "No serious (astronomical) evolution is going on."
Despite increasing efforts, no scientists have been able to prove or disprove the possibility of life elsewhere in the universe, including in Abell 2029.
Kuhn said the galaxy was helping astronomers learn more about how galaxy clusters were formed. He also said the galaxy could provide clues to help astronomers solve the "dark matter problem."
Astronomers believe there is much more mass in galaxies than is detectible to astronomers on Earth. They know that these astronomical bodies are moving at enormous speeds and that there is not enough mass visible to provide the gravitational pull needed to hold them together.
Yet they remain together, leading astronomers to believe that much more mass must be present in these galaxies than is detectible.