Huddled tightly around a computer screen in a Nicholson Hall office, two University professors and a graduate student made a discovery that was out of this world.
The trio was working with an international team last summer to create a catalog of data collected from the Gamma-ray Burst Monitor on NASA’s Fermi gamma-ray space telescope when they found that the Crab Nebula, one of the most studied items in the sky, was dimming.
The findings were unexpected, according to Michael Cherry, Department of Physics and Astronomy chair and professor, who worked on the project with Physics and Astronomy Professor Gary Case and graduate student James Rodi.
“It was surprising because the Crab Nebula is the only source close enough and bright enough to be studied in detail,” Cherry said. “[Its energy is] so constant that we’ve used it as a calibration standard for checking our instruments.”
Cherry said his initial reaction was that they must be wrong or that the instrument was losing sensitivity, and the team began to conduct further experiments.
“We looked at the results from three other instruments and saw exactly the same results,” he said.
Case said after analyzing the data, they shared the newfound information with the rest of the collaboration. The team then joined to write the results in a paper that was submitted for publication in September.
“The results were first presented in preliminary form to a conference of X-ray astronomers in Ireland in October,” he explained. “The full results were presented at the [American Astronomical Society] meeting last week, and it is quite gratifying to see the work we had done picked by NASA to be released as a press release.”
Cherry said they have been constantly attending meetings, presenting the information and discussing the results among colleagues. The findings will also be published in the Astrophysical Journal Letters.
“It is certainly an interesting result, and we’ve been having a lot of fun with it,” he said.
The nebula is currently being monitored at the University and abroad to see how long the Crab dims before rebrightening.
“We don’t expect this will result in the Crab turning off,” he said. “At this point we are assuming this is a phenomenon that repeats itself having to do with the readjustment of the central magnetic fields. We are assuming it will go back up.”
The team came to this conclusion after examining data from the nebula’s past and noticing the energy has increased and decreased on a three-year cycle since 1999.
Cherry said the changes were only by a small percent, but the latest data shows the steepest decline has occurred within the last two years.
“We think we understand how an object like this works pretty well, but there are some things we still don’t understand,” Cherry said. “We need to find out what is going on at the central core — that’s a high priority for astrophysics.”
 
 
 
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Contact Sydni Dunn at [email protected]