Andrew Yee[_1_]
January 7th 08, 09:32 PM
Media Relations
Caltech
Contact:
Kathy Svitil, (626) 395-8022
January 2, 2008
LIGO Sheds Light on Cosmic Event
PASADENA, Calif. -- An analysis by the international LIGO (Laser
Interferometer Gravitational-Wave Observatory) Scientific Collaboration has
excluded one previously leading explanation for the origin of an intense
gamma-ray burst that occurred last winter. Gamma-ray bursts are among the
most violent and energetic events in the universe, and scientists have only
recently begun to understand their origins.
The LIGO project, which is funded by the National Science Foundation, was
designed and is operated by the California Institute of Technology and the
Massachusetts Institute of Technology for the purpose of detecting cosmic
gravitational waves and for the development of gravitational-wave
observations as an astronomical tool. Research is carried out by the LIGO
Scientific Collaboration, a group of 580 scientists at universities around
the United States and in 11 foreign countries. The LIGO Scientific
Collaboration interferometer network includes the GEO600 interferometer,
located in Hannover, Germany, funded by the Max-Plank-Gesellschaft/Science
and Technologies Facilities Council and designed and operated by scientists
from the Max Planck Institute for Gravitational Physics and partners in the
United Kingdom.
Each of the L-shaped LIGO interferometers (including the 2-km and 4-km
detectors in Hanford, Washington, and a 4-km instrument in Livingston,
Louisiana) uses a laser split into two beams that travel back and forth down
long arms, each of which is a beam tube from which the air has been
evacuated. The beams are used to monitor the distance between precisely
configured mirrors. According to Albert Einstein's 1916 general theory of
relativity, the relative distance between the mirrors will change very
slightly when a gravitational wave -- a distortion in space-time, produced
by massive accelerating objects, that propagates outward through the
universe -- passes by. The interferometer is constructed in such a way that
it can detect a change of less than a thousandth the diameter of an atomic
nucleus in the lengths of the arms relative to each other.
On February 1, 2007, the Konus-Wind, Integral, Messenger, and Swift
gamma-ray satellites measured a short but intense outburst of energetic
gamma rays originating in the direction of M31, the Andromeda galaxy,
located 2.5 million light-years away. The majority of such short (less than
two seconds in duration) gamma-ray bursts (GRBs) are thought to emanate from
the merger and coalescence of two massive but compact objects, such as
neutron stars or black-hole systems. They can also come from astronomical
objects known as soft gamma-ray repeaters, which are less common than binary
coalescence events and emit less energetic gamma rays.
During the intense blast of gamma rays, known as GRB070201, the 4-km and
2-km gravitational-wave interferometers at the Hanford facility were in
science mode and collecting data. They did not, however, measure any
gravitational waves in the aftermath of the burst.
That non-detection was itself significant.
The burst had occurred along a line of sight that was consistent with it
originating from one of Andromeda's spiral arms, and a binary coalescence
event -- the merger of two neutron stars or black holes, for example -- was
considered among the most likely explanations. Such a monumental cosmic
event occurring in a nearby galaxy should have generated gravitational waves
that would be easily measured by the ultrasensitive LIGO detectors. The
absence of a gravitational-wave signal meant GRB070201 could not have
originated in this way in Andromeda. Other causes for the event, such as a
soft gamma-ray repeater or a binary merger from a much further distance, are
now the most likely contenders.
LIGO's contribution to the study of GRB070201 marks a milestone for the
project, says Caltech's Jay Marx, LIGO's executive director: "Having
achieved its design goals two years ago, LIGO is now producing significant
scientific results. The nondetection of a signal from GRB070201 is an
important step toward a very productive synergy between gravitational-wave
and other astronomical communities that will contribute to our understanding
of the most energetic events in the cosmos."
"This is the first time that the field of gravitational-wave physics has
made a significant contribution to the gamma-ray astronomical community, by
searching for GRBs in a way that electromagnetic observations cannot," adds
David Reitze, a professor of physics at the University of Florida and
spokesperson for the LIGO Collaboration.
Up until now, Reitze says, astronomers studying GRBs relied solely on data
obtained from telescopes conducting visible, infrared, radio, X-ray, and
gamma-ray observations. Gravitational waves offer a new window into the
nature of these events.
"We are still baffled by short GRBs. The LIGO observation gives a
tantalizing hint that some short GRBs are caused by soft gamma repeaters. It
is an important step forward," says Neil Gehrels, the lead scientist of the
Swift mission at NASA's Goddard Space Flight Center.
"This result is not only a breakthrough in connecting observations in the
electromagnetic spectrum to gravitational-wave searches, but also in the
constructive integration of teams of complementary expertise. Our findings
imply that multimessenger astronomy will become a reality within the next
decade, opening a wonderful opportunity to gain insight on some of the most
elusive phenomena of the universe," says Szabolcs Mka, an assistant
professor of physics at Columbia University.
The next major construction milestone for LIGO will be the Advanced LIGO
Project, which is expected to start in 2008. But Advanced LIGO, which will
utilize the infrastructure of LIGO, will be 10 times more sensitive.
Advanced LIGO will incorporate advanced designs and technologies for mirrors
and lasers that have been developed by the GEO project and have allowed the
GEO detector to achieve enough sensitivity to participate in this discovery
despite its smaller size.
The increased sensitivity will be important because it will allow scientists
to detect cataclysmic events such as black hole and neutron star collisions
at 10-times-greater distances.
Related Links
* LIGO
http://www.ligo.caltech.edu/
* GEO
http://www.geo600.uni-hannover.de/
Caltech
Contact:
Kathy Svitil, (626) 395-8022
January 2, 2008
LIGO Sheds Light on Cosmic Event
PASADENA, Calif. -- An analysis by the international LIGO (Laser
Interferometer Gravitational-Wave Observatory) Scientific Collaboration has
excluded one previously leading explanation for the origin of an intense
gamma-ray burst that occurred last winter. Gamma-ray bursts are among the
most violent and energetic events in the universe, and scientists have only
recently begun to understand their origins.
The LIGO project, which is funded by the National Science Foundation, was
designed and is operated by the California Institute of Technology and the
Massachusetts Institute of Technology for the purpose of detecting cosmic
gravitational waves and for the development of gravitational-wave
observations as an astronomical tool. Research is carried out by the LIGO
Scientific Collaboration, a group of 580 scientists at universities around
the United States and in 11 foreign countries. The LIGO Scientific
Collaboration interferometer network includes the GEO600 interferometer,
located in Hannover, Germany, funded by the Max-Plank-Gesellschaft/Science
and Technologies Facilities Council and designed and operated by scientists
from the Max Planck Institute for Gravitational Physics and partners in the
United Kingdom.
Each of the L-shaped LIGO interferometers (including the 2-km and 4-km
detectors in Hanford, Washington, and a 4-km instrument in Livingston,
Louisiana) uses a laser split into two beams that travel back and forth down
long arms, each of which is a beam tube from which the air has been
evacuated. The beams are used to monitor the distance between precisely
configured mirrors. According to Albert Einstein's 1916 general theory of
relativity, the relative distance between the mirrors will change very
slightly when a gravitational wave -- a distortion in space-time, produced
by massive accelerating objects, that propagates outward through the
universe -- passes by. The interferometer is constructed in such a way that
it can detect a change of less than a thousandth the diameter of an atomic
nucleus in the lengths of the arms relative to each other.
On February 1, 2007, the Konus-Wind, Integral, Messenger, and Swift
gamma-ray satellites measured a short but intense outburst of energetic
gamma rays originating in the direction of M31, the Andromeda galaxy,
located 2.5 million light-years away. The majority of such short (less than
two seconds in duration) gamma-ray bursts (GRBs) are thought to emanate from
the merger and coalescence of two massive but compact objects, such as
neutron stars or black-hole systems. They can also come from astronomical
objects known as soft gamma-ray repeaters, which are less common than binary
coalescence events and emit less energetic gamma rays.
During the intense blast of gamma rays, known as GRB070201, the 4-km and
2-km gravitational-wave interferometers at the Hanford facility were in
science mode and collecting data. They did not, however, measure any
gravitational waves in the aftermath of the burst.
That non-detection was itself significant.
The burst had occurred along a line of sight that was consistent with it
originating from one of Andromeda's spiral arms, and a binary coalescence
event -- the merger of two neutron stars or black holes, for example -- was
considered among the most likely explanations. Such a monumental cosmic
event occurring in a nearby galaxy should have generated gravitational waves
that would be easily measured by the ultrasensitive LIGO detectors. The
absence of a gravitational-wave signal meant GRB070201 could not have
originated in this way in Andromeda. Other causes for the event, such as a
soft gamma-ray repeater or a binary merger from a much further distance, are
now the most likely contenders.
LIGO's contribution to the study of GRB070201 marks a milestone for the
project, says Caltech's Jay Marx, LIGO's executive director: "Having
achieved its design goals two years ago, LIGO is now producing significant
scientific results. The nondetection of a signal from GRB070201 is an
important step toward a very productive synergy between gravitational-wave
and other astronomical communities that will contribute to our understanding
of the most energetic events in the cosmos."
"This is the first time that the field of gravitational-wave physics has
made a significant contribution to the gamma-ray astronomical community, by
searching for GRBs in a way that electromagnetic observations cannot," adds
David Reitze, a professor of physics at the University of Florida and
spokesperson for the LIGO Collaboration.
Up until now, Reitze says, astronomers studying GRBs relied solely on data
obtained from telescopes conducting visible, infrared, radio, X-ray, and
gamma-ray observations. Gravitational waves offer a new window into the
nature of these events.
"We are still baffled by short GRBs. The LIGO observation gives a
tantalizing hint that some short GRBs are caused by soft gamma repeaters. It
is an important step forward," says Neil Gehrels, the lead scientist of the
Swift mission at NASA's Goddard Space Flight Center.
"This result is not only a breakthrough in connecting observations in the
electromagnetic spectrum to gravitational-wave searches, but also in the
constructive integration of teams of complementary expertise. Our findings
imply that multimessenger astronomy will become a reality within the next
decade, opening a wonderful opportunity to gain insight on some of the most
elusive phenomena of the universe," says Szabolcs Mka, an assistant
professor of physics at Columbia University.
The next major construction milestone for LIGO will be the Advanced LIGO
Project, which is expected to start in 2008. But Advanced LIGO, which will
utilize the infrastructure of LIGO, will be 10 times more sensitive.
Advanced LIGO will incorporate advanced designs and technologies for mirrors
and lasers that have been developed by the GEO project and have allowed the
GEO detector to achieve enough sensitivity to participate in this discovery
despite its smaller size.
The increased sensitivity will be important because it will allow scientists
to detect cataclysmic events such as black hole and neutron star collisions
at 10-times-greater distances.
Related Links
* LIGO
http://www.ligo.caltech.edu/
* GEO
http://www.geo600.uni-hannover.de/