A team of international
researchers announced today the detection of the farthest space explosion ever
recorded, breaking the previous record by 500 million light-years.
Known as gamma-ray bursts
(GRBs), the eruptions are giant flares of energetic gamma-rays that can last
from less than a second to several minutes. They were accidentally discovered
in 1967 by sentry satellites monitoring for breeches of the nuclear test ban
treaty.
GRBs signal the explosion
of very massive stars that have collapsed into black holes and are the most
explosive events to happen in the Universe since the Big Bang.
"It's luminosity is such
that within a few minutes it must have released 300 times more energy than the
Sun will release during its entire life of 10,000 million years," said
Guido Chincarini, a researcher from the INAF-Osservatorio Astronomico di Brera
and leader of the Italian team.
Astronomers believe short
GRBs that can last for only fractions of a second are generated when two
massive objects, like black
holes or neutron stars or even whole galaxies, collide, releasing
tremendous amounts of radiation in the process.
The longer bursts, which
can last for several minutes, are thought to be the final energetic emissions
of massive stars that first undergo tremendous explosions called supernovas before
condensing into black holes.
Researchers calculate
cosmic distances by measuring the extent to which light from distant stars are
"shifted" towards the red part of the electromagnetic spectrum. The
higher the redshift, the greater the distance.
The new GRB has a redshift
of 6.29, meaning that it occurred when the universe was less than a billion
years old. The previous most distant GRB had a redshift of 4.5.
"This is uncharted
territory," said Daniel Reichart, an astronomer from the University of
North Carolina and the leader of the US team. "We are finally starting to
see the remnants of some of the oldest objects in the universe."
GRB 050904, as the new GRB
is called, was detected by a joint US/UK/Italian telescope project called Swift.
Launched last winter, Swift is designed to automatically detect the first flash
of a GRB. Follow-up observations
recorded the event in other wavelengths of light.
"We designed Swift to
look for faint bursts coming from the edge of the universe," said Neil
Gehrels, the Swift principal investigator from NASA Goddard Space Flight
Center. "Now we've got one and it's fascinating. For the first time we can
learn about individual stars from near the beginning of time."
Once a flash is detected,
Swift notifies astronomers worldwide via e-mail, websites and even text
messages to mobile phones.
During a time when new
galaxies and stars were still being born, distant GRBs like the one recently
detected were already ancient and in their final death throes. Astronomers can
therefore use GRB's to better understand physical conditions of the very early
universe and the evolution of stars.
advertisement
