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On many a late night in Hugel Science Center, Lyle Hoffman, professor and head of physics, looks for clues to the origin of the universe.
He is contemplating reams of data on clouds of neutral hydrogen that float seemingly at random between the galaxies. Observing faint emission is best done late at night to avoid radio frequency interference and electronic noise, he explains.
“It’s always a thrill to discover new things,” says Hoffman, part of a team of researchers – one of only two members from small colleges – participating in the Arecibo L-band Feed Array survey of the extragalactic sky. One of the goals of the survey is to identify clouds of neutral hydrogen that have not coalesced to form stars.
“This survey gets after some very fundamental things that happened in the universe,” says Hoffman, who joined Lafayette’s faculty in 1983. “We’re looking at how stars were formed.”
He is examining data gathered by the 1,000-foot-wide Arecibo radio telescope in Puerto Rico and parceled out to participating researchers.
“I think the fact that this is something I took part in makes the subject more personal to my students,” he says.
This summer, he worked on the project with Ibrahima Bah ’06 (Bronx, N.Y.), a double major in physics and mathematics, through Lafayette’s EXCEL Scholars program.
Hoffman began using the Arecibo telescope to track and measure neutral hydrogen in the Virgo Cluster of galaxies as a Cornell graduate student in 1980. He also has conducted research on the origins of hydrogen clouds in the universe.
“There are several hypotheses,” he explains. “One thing in particular that we’d like to know is whether this is gas that was thrown from the disk of the Milky Way and is now falling back in. On the other hand, it may never have been there before and is falling in for the first time.”
Another possibility, says Hoffman, is that as galaxies pass each other in space, gravitational tides of hydrogen can be pulled from the smaller galaxy by the larger galaxy’s greater gravitational pull.
One clue, he says, may be dwarf irregular galaxies, which are examples of delayed formation. Dwarf irregular galaxies took longer to form than the giant spiral galaxies, he says, and perhaps the loose hydrogen might come from dwarf irregular galaxies that are still forming.
“Figuring out how galaxies form has been a difficult problem,” says Hoffman. “There are lots of intricate processes. Galaxy formation is the single longest outstanding problem in how the Big Bang evolved.”
Hoffman mapped several hydrogen clouds, several of which are smaller and of less density than those scientists had observed previously.
Physics graduate Silas Beane ’88, assistant professor of physics at the University of New Hampshire, arrived at Lafayette as an undergraduate about the same time that Hoffman joined the faculty.
“He was extremely dedicated and patient,” said Beane, who works in an area of physics to which Hoffman introduced him. “I remember that, at first, he was very hard to understand. Now I realize how hard it is for young faculty members to communicate with beginning undergraduates. I spent countless hours in his office.”
Not all of that time was spent on physics.
“We also talked a great deal about music,” said Beane. “We both play piano.”
Hoffman recently published an article in The Astronomical Journal with several coauthors, including physics graduate Nathan Carle ’99. In addition to Bah, more recent student collaborators have included electrical and computer engineeringgraduate Salman Mujahid ’04 and Ajay Hirani ’04, who graduated as a double major in physics and mathematics.
This region, by the way, is a perfectly lousy place to point a radio telescope at the sky, says Hoffman.
“Everywhere on the East Coast is terrible,” he explains. “The main difficulty is man-made interference, things like cell phones and aeronautical radar. That’s why the premier radio telescopes tend to be in out-of-the-way places.”
Some work can be done online or with electronic tape sent by the observatory. But when Hoffman needs large blocks of telescope time, he flies to Puerto Rico.