most titanic explosions in the universe take the form of gamma-ray
bursts. These bright bursts of energy appear from random regions
in space and typically last a few seconds. United States Air
Force Vela satellites first discovered them in the 1960s.
Since then, numerous theories of their origins have been proposed,
but the causes of gamma-ray bursts remain unknown.
Hubble Space Telescope has helped astronomers trace these
bursts back to distant galaxies. The principal limitation
in understanding the bursts was the difficulty in pinpointing
their direction in the sky. Unlike visible light, gamma rays
are exceedingly difficult to observe with a telescope, and
the burst's short duration exacerbates the problem.
has teamed up with several observatories, including X-ray
satellites, to collect information on bursts. Among the most
energetic was the gamma-ray burst labeled GRB971214, detected
Dec. 14, 1997. Astronomers measured the distance to a faint
galaxy from which the burst originated. Using the Italian/Dutch
satellite BeppoSAX, astronomers pinpointed the direction of
the burst, which permitted follow-up observations with the
world's most powerful telescopes. These follow-up observations
tracked the burst's "afterglow" in radio waves and X-ray,
visible, and infrared light. While gamma-ray bursts last only
a few seconds, their afterglows can be studied for several
months. By analyzing these afterglows, astronomers have discovered
that the bursts do not originate within our own galaxy, the
Milky Way, but rather are associated with extremely distant
Hubble telescope images of GRB971214 confirmed the association
of the burst's afterglow with a faint galaxy.
still don't understand the origins of bursts. Theories suggest
they happen where vigorous star formation takes place. Gamma-ray
bursts may be created by the mergers of a pair of neutron
stars or black holes or a hypernova, a theorized type of exceptionally
violent exploding star.
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