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Swift mission graphic

Swift Gamma Ray Burst Explorer

Phase: Operating

Launch Date: November 20, 2004

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Program(s):Astrophysics Explorers, Explorers

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Swift is a first-of-its-kind multi-wavelength observatory dedicated to the study of gamma-ray bursts (GRB) and other transients. GRBs are the most luminous explosions in the universe since the Big Bang. They come randomly from all directions in the sky and last from a few milliseconds to a few hundred seconds. GRBs are believed to occur in the collapse of some massive stars into supernovae or when two neutron stars merge.

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. Swift is three times more sensitive than the BATSE detector aboard the Compton Gamma-Ray Observatory, which was the second Great Observatory acquiring data between 1991-2000. It also has a rapid response spacecraft and multiwavelength payload to perform follow-up observations of GRBs and transients. The hardware was developed by an international team from the United States, the United Kingdom, and Italy, with additional scientific involvement in many countries including Japan, Germany, France, and Denmark.

There are three telescopes onboard Swift: the Burst Alert Telescope (BAT) is a coded-aperture gamma-ray detector that operates between 13 and 300 keV. It detects GRBs and rapidly localizes them to approximately two arcminutes. After the initial burst detection, the spacecraft "swiftly" (approximately 20 to 75 seconds) and autonomously re-points itself to bring the burst location within the field of view of the sensitive narrow-field telescopes to observe the afterglow. The X-Ray Telescope (XRT) measures the 0.2–10 keV X-ray flux from the GRB’s afterglow and localizes the source to within two arcseconds. The Ultraviolet/Optical telescope (UVOT) collects data between 1,600 and 6,000 Angstroms and provides a sub-arcsecond position for the burst. Swift distributes these positions for each GRB to other observatories within seconds of obtaining them. Swift measurements are of great interest to the astronomical community and all data products are available to the public via the internet as soon as they are processed. The Swift mission represents the most comprehensive study of GRB afterglows to date.

Main Mission Objectives:

  • Determine the origin of gamma-ray bursts
  • Use gamma-ray bursts to study the early universe
  • Monitor the sky and respond to all types of transient
  • Perform follow-up observations of sources detected by other observatories
  • Perform the first sensitive hard X-ray survey of the sky.
The brightest gamma-ray burst ever seen in X-rays temporarily blinded Swift’s X-Ray Telescope on 21 June 2010. The image merges the X-rays (red to yellow) with the same view from Swift’s Ultraviolet/Optical Telescope and shows a field of 5 arcmin × 5 arcmin.

In its ten years since launch, Swift has detected and localized around 1,000 GRBs. Among these are more than 80 short (≤ 2 sec) and hard GRBs, about half with likely host identifications and/or redshift estimates. These observations provided support for the theory that these bursts are due to the merging of binary neutron stars.

Science Highlights:

Swift is a powerful and versatile observatory to study transient sources and is increasingly being used for non-GRB science. By early 2015, more than 5000 targets-of opportunity (TOOs) were performed as a result of requests from the community. Many of the TOOs are often made within a few hours of being requested. Some of the science highlights are:

  • Detecting the most distant known object in the universe, GRB 090429B, with a redshift of 9.4. This burst occurred more than 13 billion years ago when the universe was only about 520 million years old.
  • Observing GRB 080319B, a GRB with an afterglow that was bright enough to see with the naked eye from a dark site.
  • Obtaining the first arc second localization and afterglow detection for a short GRB. The >80 short bursts studied so far provide support for the theory that these bursts are due to the merging of binary neutron stars.
  • Witnessing the tidal disruption of a star by a nearby Galactic black hole.
  • Making metallicity measurements of star-forming regions at high redshift (z > 5) using GRBs.
  • Discovering the X-ray flash of the shock breakout from a star’s surface during a supernova explosion.
  • Detecting the first detection of a relativistic tidal disruption of a star by a nearby Galactic black hole.
  • Making metallicity measurements of star-forming regions at high redshift (z > 5) using GRBs.
  • Discovering the X-ray flash of the shock breakout from a star’s surface during a supernova explosion.
  • On September 16 and 17, 2012, BAT triggered multiple times on a previously unknown hard X-ray source a few degrees from the Galactic. The trigger marked the onset of a dramatic transition from the low/hard to the high/soft state of the X-ray Nova “Sw J1745-26”, revealing a previously unknown black hole in our galaxy.
  • Making multi-wavelength observations of the exoplanet HD 189733b with Swift and HST revealed an X-ray flare from the star that was so powerful that it led to the evaporation of the planet’s upper atmosphere. During this process, the Jupiter-sized planet lost around 1,000 tons of gas in the planet’s atmosphere each second.
  • Two independent Swift studies of thermonuclear Type Ia supernovae (SNe Ia) ruled out the presence of massive companion stars in these systems. The lack of any recorded UV or X-ray emission showed that the outgoing shock of the SN explosions does not plow through the winds of massive companion stars or even sun-like stars.
  • The 140-month survey of BAT data catalog contains over 2000 hard X-ray sources, 8-band BAT spectra, and 8-band snapshot lightcurves for all sources.
  • Ultraviolet and X-rays monitoring of comet Garradd (C/2009 P1) showed that the comet produced large amounts of dust and gas well before it reached the snow line. The activity was powered by something other than water ice, which is expected to remain frozen until the comet approaches the snow line.
  • Detecting afterglow emission from a short GRB that is likely due to a kilonova radioactive radiation.
  • Discovering a very young (2500 year old) SNR.
  • Identifying the ultra-long class of GRB.
  • Detecting the nearest luminous Swift + Fermi GRB 130427.
  • Discovering a rare anti-glitch in magnetar 1E 2259+586.
  • By early 2014, more than 2,000 refereed papers have been published that are based on Swift results with more than 40,000 citations. More than half of all Swift papers are from non-GRB fields with an increasing fraction.


  • 2005 Popular Science Magazine “Best of What’s New Award” to the Swift mission.
  • 2007 Rossi Prize to the Swift PI Neil Gehrels and the Swift Team.
  • GRB 080319B (the “naked-eye” gamma-ray burst) was named one of the top ten science news stories of 2008 by the American Institute of Physics.
  • 2009 Astronomical Society of the Pacific Muhlmann Award to the Swift Team.
  • 2009 George W. Goddard Award, SPIE society to Neil Gehrels
  • 2009 Henry Draper Medal, National Academy of Sciences to Neil Gehrels
  • 2012 COSPAR Massey Award to Neil Gehrels.

Swift has been widely recognized as a groundbreaking mission and was highly ranked in all Senior Reviews of the NASA Astrophysics Division operating missions.

Last updated: February 20, 2015

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