Scientists using NASA's Swift satellite and several ground-basedtelescopes have detected the most distant explosion yet, a gamma-rayburst from the edge of the visible universe.
This powerful burst was detected September 4. It marks the death ofa massive star and the birth of a black hole. It comes from an era soonafter stars and galaxies first formed, about 500 million to 1 billionyears after the Big Bang.
"We designed Swift to look for faint bursts coming from the edge ofthe Universe," said Swift principal investigator Dr. Neil Gehrels ofNASA Goddard Space Flight Center in Greenbelt, Md. "Now we've got oneand it's fascinating. For the first time we can learn about individualstars from near the beginning of time. There are surely many more outthere," he added.
Only one quasar has been discovered at a greater distance. Quasarsare super-massive black holes containing the mass of billions of stars.This burst comes from a lone star. Scientists say it is puzzling how asingle star could have generated so much energy as to be seen acrossthe entire Universe. The science team has not yet determined the natureof the exploded star. A detailed analysis is forthcoming.
Scientists measure cosmic distances via redshift, the extent towhich light is "shifted" toward the red, or lower energy, part of theelectromagnetic spectrum during the light's long journey across theUniverse. The greater the distance, the higher the redshift. TheSeptember 4 burst, named GRB 050904, has a redshift of 6.29, whichtranslates to a distance of about 13 billion light-years from Earth.The Universe is thought to be 13.7 billion years old. The previous mostdistant gamma-ray burst had a redshift of 4.5. The most distant quasarknown is at a redshift of 6.4.
This burst was also very long, lasting more than 200 seconds,whereas most bursts last only about 10 seconds. The detection of thisburst confirms that massive stars mingled with the oldest quasars. Thedetection also confirms that even more distant star explosions can bestudied through combined observations of Swift and the network ofworld-class telescopes.
"This is uncharted territory," said Dr. Daniel Reichart, Universityof North Carolina (UNC), Chapel Hill, who spearheaded the distancemeasurement. "This burst smashes the old distance record by 500 millionlight-years. We are finally starting to see the remnants of some of theoldest objects in the Universe," he added.
Swift detected the burst and relayed its coordinates within minutesto scientists around the world. Reichart's team discovered theafterglow using the Southern Observatory for Astrophysical Research(SOAR) telescope atop Cerro Pachon, Chile. Over the next severalnights, the UNC team used SOAR and the Gemini South telescope, also onCerro Pachon, to calculate a redshift of greater than 6 using a lightfiltering technique. A team led by Nobuyuki Kawai of the TokyoInstitute of Technology used the Subaru Observatory on Mauna Kea,Hawaii, to confirm the distance and fine-tune the redshift measurementto 6.29, using a technique called spectroscopy.
"The earliest stars exploded eons ago, we know very little aboutthem," said Josh Haislip, a UNC team member who analyzed data fromSOAR. "One of the best ways we can study them is by watching for theirexplosions. Swift can pinpoint the location of the explosions, andtelescopes such as SOAR can study the composition of the debris tounderstand where and when these stars formed and what they were madeof," he added.
The SOAR telescope is funded by the U.S. National Optical AstronomyObservatory, Tucson, Ariz., through the National Science Foundation(NSF), Arlington, Va.; the Ministry of Science of Brazil; MichiganState University, East Lansing; and UNC. The twin Gemini Observatorytelescopes represent an international partnership funded in part by theNSF. Goddard manages the Swift mission for NASA's Science MissionDirectorate, Washington. Mission operations are conducted by Penn StateUniversity, University Park. Swift's other national laboratories,universities and international partners include the Los Alamos NationalLaboratory, N.M.; Sonoma State University, Rohnert Park, Calif.; theUnited Kingdom; and Italy.
For more information on the Internet, visit:
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