Kurgan Gringioni
December 21st 06, 07:36 PM
A long time ago in a galaxy far, far away . . .
The Death Star finally got tested.
From:
http://www.sciam.com/article.cfm?chanID=sa007&articleID=A137CC64-E7F2-99DF-302F0CF971EF8913
On June 14, the Burst Alert Telescope on NASA's Swift satellite was
belted by gamma rays, the first warning that one of the most powerful
explosions in the universe was taking place as a star went through its
death throes. Within moments or hours a host of astronomers had trained
telescopes all over the world on a galaxy 1.6 billion light-years away
(relatively close in the cosmic scheme of things) toward the
constellation Indus in anticipation of an incipient supernova--the
brilliant demise of a massive star. As the flash lingered for 102
seconds, it fell into the "long" category of gamma-ray bursts typically
associated with such epic stellar explosions. But even after months of
monitoring no supernova appeared, bursting current theories for such
events and potentially revealing a new type of stellar doom.
Current understanding divides gamma-ray bursts into those that last
less than two seconds and those of longer duration. The latter occur
when a massive but young star collapses in on itself and explodes,
seeding the universe with its elemental remnants and leaving behind a
central black hole of matter so dense that no light can escape. The
former happen when an old neutron star spirals to its death in a
preexisting black hole. In addition to differences in duration, the two
types also differ in the type of energy released, with short ones
emitting a quick burst of comparatively high energy.
But GRB060614 (after the date it was discovered) fits neither category.
Its duration supported the long variety while the intensity of its
emissions more closely matched the short one. "We have lots of data on
this burst and have dedicated lots of observation time to it, and we
just can't figure out what exploded," explains astronomer Neil Gehrels
of NASA Goddard Space Flight Center, lead author of one of four papers
in the December 21 Nature examining the phenomenon. "All the data seem
to point to a new but perhaps not so uncommon kind of cosmic
explosion."
Long gamma ray bursts typically emanate from massive stars collapsing
in on themselves to form new black holes. Click on the picture for a
short animation of this form of star suicide.
In fact, observations of another gamma-ray burst (GRB060505 on May 5),
which lasted four seconds, also lacked a supernova and 1990s data from
the now-deorbited Compton Gamma Ray Observatory hint at similar
"hybrid" bursts. "Two of the six long gamma-ray bursts seen at close
distances appear to have no supernovae," notes astrophysicist Pall
Jakobsson of the University of Hertfordshire. "This may be a more
common type of explosion than we expected, possibly a new mechanism for
star death."
The Death Star finally got tested.
From:
http://www.sciam.com/article.cfm?chanID=sa007&articleID=A137CC64-E7F2-99DF-302F0CF971EF8913
On June 14, the Burst Alert Telescope on NASA's Swift satellite was
belted by gamma rays, the first warning that one of the most powerful
explosions in the universe was taking place as a star went through its
death throes. Within moments or hours a host of astronomers had trained
telescopes all over the world on a galaxy 1.6 billion light-years away
(relatively close in the cosmic scheme of things) toward the
constellation Indus in anticipation of an incipient supernova--the
brilliant demise of a massive star. As the flash lingered for 102
seconds, it fell into the "long" category of gamma-ray bursts typically
associated with such epic stellar explosions. But even after months of
monitoring no supernova appeared, bursting current theories for such
events and potentially revealing a new type of stellar doom.
Current understanding divides gamma-ray bursts into those that last
less than two seconds and those of longer duration. The latter occur
when a massive but young star collapses in on itself and explodes,
seeding the universe with its elemental remnants and leaving behind a
central black hole of matter so dense that no light can escape. The
former happen when an old neutron star spirals to its death in a
preexisting black hole. In addition to differences in duration, the two
types also differ in the type of energy released, with short ones
emitting a quick burst of comparatively high energy.
But GRB060614 (after the date it was discovered) fits neither category.
Its duration supported the long variety while the intensity of its
emissions more closely matched the short one. "We have lots of data on
this burst and have dedicated lots of observation time to it, and we
just can't figure out what exploded," explains astronomer Neil Gehrels
of NASA Goddard Space Flight Center, lead author of one of four papers
in the December 21 Nature examining the phenomenon. "All the data seem
to point to a new but perhaps not so uncommon kind of cosmic
explosion."
Long gamma ray bursts typically emanate from massive stars collapsing
in on themselves to form new black holes. Click on the picture for a
short animation of this form of star suicide.
In fact, observations of another gamma-ray burst (GRB060505 on May 5),
which lasted four seconds, also lacked a supernova and 1990s data from
the now-deorbited Compton Gamma Ray Observatory hint at similar
"hybrid" bursts. "Two of the six long gamma-ray bursts seen at close
distances appear to have no supernovae," notes astrophysicist Pall
Jakobsson of the University of Hertfordshire. "This may be a more
common type of explosion than we expected, possibly a new mechanism for
star death."