Gamma-ray bursts (GRBs) are the most powerful explosions the Universe has seen since the Big Bang. They occur approximately once per day and are brief, but intense, flashes of gamma radiation. They come from all different directions of the sky and last from a few milliseconds to a few hundred seconds. So far scientists do not know what causes them. Do they signal the birth of a black hole in a massive stellar explosion? Are they the product of the collision of two neutron stars? Or is it some other exotic phenomenon that causes these bursts?
With Swift, a NASA mission with international participation, scientists have a tool dedicated to answering these questions and solving the gamma-ray burst mystery. Its three instruments give scientists the ability to scrutinize gamma-ray bursts like never before. Within seconds of detecting a burst, Swift relays its location to ground stations, allowing both ground-based and space-based telescopes around the world the opportunity to observe the burst's afterglow. Swift is part of NASA's medium explorer (MIDEX) program and was launched into a low-Earth orbit on a Delta 7320 rocket on November 20, 2004. The Principal Investigator is Dr. Neil Gehrels (NASA-GSFC).
All Swift systems are operating normally.
In early 2016 NASA's Swift mission started an intensive high-cadence monitoring campaign of NGC 4151, one of the nearest galaxies to contain an actively accreting supermassive black hole at its center. Swift looked at the galaxy's nucleus every 6 hours for 69 consecutive days in order to constrain its temporal variability at X-ray, ultraviolet and optical energies. This technique allows Swift to probe the central regions of AGN in which the bulk of the luminosity is produced and emitted. The results of these observations were published today on the Astrophysical Journal. The study, led by researcher Rick Edelson, found that the Swift data rule out the standard reprocessing model for AGN and instead favor the presence of two separate reprocessings: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.
Thanks to its unique capabilities, NASA's Swift mission is uniquely poised to characterize the activity and evolution of comets, and active asteroids. Swift's sensitivity at ultraviolet wavelenghts allows scientists to detect hydroxyl, an important tracer of cometary activity formed when water molecules are destroyed by solar UV light. Astronomer Dennis Bodewits, a research scientist at the University of Maryland, uses Swift to follow several Oort Cloud comets and over 15 different asteroids as they cruise through our Solar System. Thanks to extensive Swift observing campaigns, Bodewits obtained spectacular images of the comet Siding Spring during its Mars flyby and spotted a rare and violent collision between two asteroids. These results were honored by the asteroid (10033) Bodewits, named after the lead author of the Swift studies. The announcement was made during the third 'Asteroids, Comets, and Meteroids' meeting, held in Montevideo, Uruguay.
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On September 23, 2012 NASA's Swift satellite discovered a bright flash of gamma-rays produced by the explosion of a star. The event, dubbed GRB120923A, was rapidly localized by the X-ray Telescope on-aboard Swift, and later observed with a wide array of optical and infrared telescopes. An international team of astronomers, led by Nial Tanvir at the University of Leicester, found that the explosion happened when the Universe was only 670 million years old, less than five percent of its present age. Only two of the more than 1,000 gamma-ray bursts seen with Swift have earlier measured ages. Gamma-ray bursts represent a powerful tracer of star-formation in the early Universe, and are the only known signature of primordial stars at such distances.
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