GRB 990123
Encyclopedia
GRB 990123 is a gamma-ray burst that occurred on January 23, 1999. It was the first GRB for which a simultaneous optical flash was detected. GRB 990123 is one of the most distant distinct landmarks in our map of the universe.
Astronomers first managed to obtain a visible-light image of a GRB as it occurred on January 23, 1999, using the ROTSE-I
telescope in Los Alamos, New Mexico. The ROTSE-I was operated by a team under Dr. Carl Akerlof of the University of Michigan
and included members from Los Alamos National Laboratory
and Lawrence Livermore National Laboratory
. The robotic telescope was fully automated, responding to signals from NASA's BATSE instrument aboard the Compton Gamma Ray Observatory within seconds, without human intervention. In the dark hours of the morning of January 23, 1999, the Compton satellite recorded a gamma-ray burst that lasted for about a minute and a half. There was a peak of gamma and X-ray emission 25 seconds after the event was first detected, followed by a somewhat smaller peak 40 seconds after the beginning of the event. The emission then fizzled out in a series of small peaks over the next 50 seconds, and eight minutes after the event had faded to a hundredth of its maximum brightness. The burst was so strong that it ranked in the top 2% of all bursts detected.
Compton reported the burst to its ground control facility at NASA Goddard Space Flight Center
in Maryland
the moment it began, and Goddard immediately sent the data out over the "gamma-ray Burst Coordinates Network (GCN)". While Compton, as mentioned, could not provide precise locations of bursts, the location was good enough for the wide-field ROTSE-I. The camera array automatically focused on the region of the sky and obtained an image of the burst 22 seconds after it was detected by Compton, with subsequent images obtained every 25 seconds after that.
ROTSE-I could image cosmic objects as faint as magnitude
16, and GRB hunters had expected the visible component of a GRB to be very faint. Instead, the visible component reached magnitude 9. It was so bright that it could have been seen by an amateur astronomer with good binoculars
. The object that produced it increased in brightness by a factor of 4,000 in less than a minute.
Because ROTSE-I operated automatically (while its creators slept) the news of ROTSE-I's accomplishment didn't make it out on the networks until later in the day, and in the meantime other observatories were focusing on the event, by then designated "GRB 990123".
The BeppoSAX
satellite had also seen the burst, and pinned down its location to within a few arcminutes
. This data was sent out, and four hours after the burst the area was imaged with the 1.52 meter (60 inch) Schmidt camera at Palomar Mountain
in California
. The image revealed a magnitude 18 optical transient that wasn't on archive images of the same area.
The next night, the fading object, by now down to magnitude 20, was imaged by the Keck telescope, and the 2.6 meter Nordic Optical Telescope
in the Canary Islands
. The observations revealed absorption lines with a redshift of 1.6, implying a distance of 9 billion light-years.
The Hubble Space Telescope
performed observations on the location of GRB 990123, sixteen days after the event. It had faded by more than a factor of three million in that time. The Hubble was able to pick up the traces of a faint galaxy
, whose blue color suggested it was forming new stars at a rapid rate.
Astronomers first managed to obtain a visible-light image of a GRB as it occurred on January 23, 1999, using the ROTSE-I
Robotic Optical Transient Search Experiment
The Robotic Optical Transient Search Experiment is an multi-telescope experiment designed to detect gamma-ray bursts. The experiment currently consists of four telescopes located in Australia, Namibia, Turkey, and at the McDonald observatory near Fort Davis, Texas.The ROTSE project is a...
telescope in Los Alamos, New Mexico. The ROTSE-I was operated by a team under Dr. Carl Akerlof of the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
and included members from Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
and Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory
The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...
. The robotic telescope was fully automated, responding to signals from NASA's BATSE instrument aboard the Compton Gamma Ray Observatory within seconds, without human intervention. In the dark hours of the morning of January 23, 1999, the Compton satellite recorded a gamma-ray burst that lasted for about a minute and a half. There was a peak of gamma and X-ray emission 25 seconds after the event was first detected, followed by a somewhat smaller peak 40 seconds after the beginning of the event. The emission then fizzled out in a series of small peaks over the next 50 seconds, and eight minutes after the event had faded to a hundredth of its maximum brightness. The burst was so strong that it ranked in the top 2% of all bursts detected.
Compton reported the burst to its ground control facility at NASA Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
in Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
the moment it began, and Goddard immediately sent the data out over the "gamma-ray Burst Coordinates Network (GCN)". While Compton, as mentioned, could not provide precise locations of bursts, the location was good enough for the wide-field ROTSE-I. The camera array automatically focused on the region of the sky and obtained an image of the burst 22 seconds after it was detected by Compton, with subsequent images obtained every 25 seconds after that.
ROTSE-I could image cosmic objects as faint as magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
16, and GRB hunters had expected the visible component of a GRB to be very faint. Instead, the visible component reached magnitude 9. It was so bright that it could have been seen by an amateur astronomer with good binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
. The object that produced it increased in brightness by a factor of 4,000 in less than a minute.
Because ROTSE-I operated automatically (while its creators slept) the news of ROTSE-I's accomplishment didn't make it out on the networks until later in the day, and in the meantime other observatories were focusing on the event, by then designated "GRB 990123".
The BeppoSAX
BeppoSAX
BeppoSAX was an Italian–Dutch satellite for X-ray astronomy which played a crucial role in resolving the origin of gamma-ray bursts , the most energetic events known in the universe...
satellite had also seen the burst, and pinned down its location to within a few arcminutes
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
. This data was sent out, and four hours after the burst the area was imaged with the 1.52 meter (60 inch) Schmidt camera at Palomar Mountain
Palomar Mountain
Palomar Mountain is a mountain in the Peninsular Ranges in northern San Diego County. It is famous as the location of the Palomar Observatory and Hale Telescope, and known for the Palomar Mountain State Park.-History:...
in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. The image revealed a magnitude 18 optical transient that wasn't on archive images of the same area.
The next night, the fading object, by now down to magnitude 20, was imaged by the Keck telescope, and the 2.6 meter Nordic Optical Telescope
Nordic Optical Telescope
The Nordic Optical Telescope is an astronomical telescope located at Roque de los Muchachos Observatory, La Palma in the Canary Islands. First light came in 1988, with regular observing beginning in 1989. It is funded by Denmark, Sweden, Iceland, Norway and Finland...
in the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
. The observations revealed absorption lines with a redshift of 1.6, implying a distance of 9 billion light-years.
The Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
performed observations on the location of GRB 990123, sixteen days after the event. It had faded by more than a factor of three million in that time. The Hubble was able to pick up the traces of a faint galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, whose blue color suggested it was forming new stars at a rapid rate.