NASA - National Aeronautics and Space Administration

Move over iPod. Among all the multitude of nifty gadgets and gizmos that appeared in 2005, NASA's Swift satellite has taken a top honor in the annual "Best of What's New" award from Popular Science magazine.

Swift is featured in the December issue as a winner in the aviation and space category for 2005.

Image to right: Artist's concept of the Swift spacecraft. Credit: NASA

Swift is a unique, multifaceted satellite dedicated to understanding gamma-ray bursts, the most powerful explosions known. Unlike most NASA satellites, Swift is not an acronym. Swift is, well, swift, and therein lies its novelty.

Moving fast and autonomously, Swift turns on a dime to capture gamma-ray bursts, flashes of light that appear randomly from any direction in the sky and last only a few milliseconds to about a minute. Because they disappear so quickly, these bursts have been a mystery since their discovery 35 years ago. Swift has three main instruments to study bursts: One detects the burst and starts the process of autonomously slewing towards the burst's direction. The other two instruments start observing the burst afterglow and determine a precise location. All this is done within minutes.

"We are detecting and rapidly imaging two bursts per week with Swift" said Neil Gehrels, Swift Principal Investigator. "We are like detectives on the 'crime scene' immediately after the event to look for clues."

CSI: The Milky Way and Beyond

Swift's speed has enabled scientists to solve several mysteries. Long gamma-ray burst, lasting over two seconds, are nearly irrefutably from massive star explosions---stars over 15 times as massive as the sun. The explosion creates a black hole. Swift has solidly confirmed this theory. Working in conjunction with the High Energy Transient Explorer (HETE) mission, Swift has discovered that short gamma-ray bursts, lasting under two seconds, likely arise from collisions---either between a black hole and a neutron star or between two neutron stars.

The past year was full of discoveries. In May Swift saw that many long bursts have multiple explosions, perhaps from the newly formed black hole sloppily gorging on debris from the explosion. In September Swift detected the most distant explosion ever seen, nearly 13 billion light years away.

NASA Goddard developed and built Swift's Burst Alert Telescope, playfully called the BAT. This is the instrument that detects the bursts. The BAT, about the size of a pool table, has the largest-known coded aperture mask---essentially a thin sheet that creates "shadows" of gamma rays passing through onto the detectors below. The angle of the shadow allows scientists to determine the direction to the bursts.

Penn State built Swift's X-ray Telescope and UV-Optical Telescope with Mullard Space Science Laboratory and the University of Leicester in England and Brera Observatory in Milan, Italy. These two longer-wavelength (lower-energy) instruments can determine an arc-second position of a burst and the redshift, or distance, to the burst source. They can also determine physical features in the burst afterglow, such as the type, temperature and velocity of chemical elements present.

Swift gets help from other telescopes, too. Swift is plugged into the Gamma-ray Burst Coordinates Network, created and operated by Dr. Scott Barthelmy of NASA Goddard. Through this computer network, the details of each burst (detected by any telescope) are relayed to the astronomy community. Big observatories such as Hubble, Chandra or Keck can join the search.

While Swift has had a remarkable first year, the mission is really just ramping up. More information about the Swift mission is available at http://www.nasa.gov/swift. Details of each of the bursts that Swift has detected, including a real-time sky map, are at http://grb.sonoma.edu.

Christopher Wanjek
Goddard Space Flight Center