The universe clearly works weekends, delivering the closest, and one of the brightest, gamma-ray bursts yet on Saturday, March 29, at 6:37 a.m. EST.
The burst, signaling the birth of a black hole, was detected in the constellation Leo by the MIT-built High-Energy Transient Explorer (HETE). For more than 30 seconds, the burst outshone the entire universe in gamma rays, and its afterglow was still 10 trillion times brighter than the sun two hours later. This was the brightest burst yet detected by HETE and is in the top 1 percent of all bursts in terms of its brightness.
Within seconds, HETE nailed down a location and subsequently relayed the coordinates to the astronomy community, allowing hundreds of scientists and amateur astronomers to join the observation, from Australia to Finland and across the ocean to America. Observations continue to pour in as scientists attempt to unravel what caused the burst. The region is still too bright to determine the galaxy from which this burst originated. Observations with the Hubble Space Telescope are expected soon.
"This was our biggest one ever," said George Ricker, senior research scientist at MIT's Center for Space Research and principal investigator for the HETE mission. "With scores of observations now completed and more on the way, we should get a rather clear picture of what triggered this burst."
Gamma-ray bursts are the most powerful explosions seen in the universe today. Scientists say that these bursts are likely caused by the death of a massive star, which implodes to form a black hole. Yet they occur randomly and few last more than a minute, making them hard to study.
HETE detects the fleeting gamma-ray and X-ray portions of these bursts. Its prompt localization enables scientists to study the burst afterglow, which can linger from days to weeks in optical light and radio waves. Most bursts originate in the early universe, traveling upwards of 10 billion years at light speed to reach us.
The burst on March 29 was named GRB 030329. Both the burst and its afterglow were brilliant. The burst itself poured out a thousand trillion trillion times the gamma rays seen in a solar flare. At its peak, the afterglow may well have been visible to the naked eye. When measured over an hour after the burst, the GRB 030329 afterglow was about as bright as a 12th magnitude star. This means it was only about 100 times dimmer than what can be seen with the naked eye, and was readily visible with backyard telescopes.
The burst originated approximately two billion light years from Earth, which is relatively close. (The GRB 030329 redshift measurement was 0.168, making this the closest classical GRB with a redshift measurement.) "Few amateur astronomers are treated to an event that originated billions of light years away," said Ricker.
Bruce Peterson and Paul Price of the Research School of Astronomy and Astrophysics at the Australian National University first identified the burst afterglow. The location was quickly confirmed by an automated telescope at Japan's RIKEN science institute. Finnish amateur astronomers provided even tighter constraints on the properties of the afterglow. The multitude of observations enables a thorough study of the burst environment.
Gamma-ray burst hunters are greatly aided by three new developments: fast triggers from orbiting detectors; fast relays to observers worldwide via the Gamma-ray burst Coordinates Network (GCN); and fast responses from ground-based robotic telescopes. HETE is the first satellite to provide and distribute accurate burst locations within seconds.
The GCN, developed and maintained at NASA Goddard Space Flight Center in Greenbelt, Md., serves as a gamma-ray burst hub. Via its control center at MIT, HETE signals the GCN, which sends out "phone calls" and e-mail messages to scientists and amateurs worldwide. The GCN web site also posts scientific information from the astronomers making observations.
HETE was built by MIT as a mission of opportunity under the NASA Explorer Program, a collaboration among U.S. universities, Los Alamos National Laboratory, and scientists and organizations in Brazil, France, India, Italy and Japan.
To track the progress of GRB 030329, refer to http://space.mit.edu/HETE.
The HETE spacecraft, on an extended mission until 2004, was built by MIT under the NASA Explorer Program. The HETE program is a collaboration among MIT; NASA; Los Alamos National Laboratory, New Mexico; France's Centre National d'Etudes Spatiales (CNES), Centre d'Etude Spatiale des Rayonnements (CESR) and Ecole Nationale Superieure de l'Aeronautique et de l'Espace (Sup'Aero); and Japan's Institute of Physical and Chemical Research (RIKEN). The science team includes members from the University of California (Berkeley and Santa Cruz) and the University of Chicago, as well as from Brazil, India and Italy.
At MIT, the HETE team includes Ricker, Geoffrey Crew, John Doty, Roland Vanderspek, Joel Villasenor, Nat Butler, Allyn Dullighan, Glen Monnelly, Gregory Prigozhin, Steve Kissel, Alan Levine, Francois Martel and Fred Miller; at Los Alamos National Laboratory, team members are Edward E. Fenimore, Mark Galassi and Tanya Tavenner; at the University of California at Berkeley, team members are Kevin Hurley and J. Garrett Jernigan; at the University of California at Santa Cruz, Stanford E. Woosley; at the University of Chicago, team members are Don Lamb, Carlo Graziani and Tim Donaghy; and the NASA project scientist at Goddard Space Flight Center is Thomas L. Cline.