SWIFT Satellite to Catch the Most Powerful Flashes
of Light Known in the Universe
Once or twice a day, without warning, there are brief flashes of
highly energetic light that momentarily outshine the rest of the
universe. NASA has chosen to develop a mission that will be capable of
capturing information about these unpredictable bursts of gamma-rays.
The mission, a satellite called Swift, was selected on Oct. 14 as NASA's
next MIDEX (or medium-class explorer) mission. It will be developed at
NASA's Goddard Space Flight Center in Greenbelt, MD.
Dr. Alan Bunner, director of NASA's Structure and Evolution of the Universe
science theme said, "Gamma-ray bursts are one of the biggest mysteries in
astronomy, and Swift is exactly the right tool to discover their origin.
Swift's detection of gamma-ray bursts could provide a bonanza of
cosmological data, for the bursts are thought to originate from the
farthest reaches of the universe and hence early in the age of the
Gamma-rays, invisible to the human eye, are the most energetic form of
radiation, far more powerful than optical light, ultraviolet radiation and
X-rays. Gamma-ray bursts are by far the most energetic events known in
the universe, second only in power to the Big Bang. The cause of these
outbursts -- which, if originated nearby in our galaxy, could cause mass
extinction on Earth -- is not known.
MIDEX missions are part of NASA's goal to
solve such mysteries by incorporating the latest technology into smaller
satellites that can be built and launched quickly and inexpensively.
Swift will be launched in 2003 and operate for three years after that for
a cost of $163 million.
"We are delighted to have Swift selected as the next MIDEX," said Dr. Neil
Gehrels, principal investigator for Swift and an astrophysicist at
Goddard. "New agile pointing systems and telescope technology enable
Swift to respond rapidly and catch hundreds of bursts on the fly. We will
finally be able to get a snapshot of these flashes."
Swift is named for the small, nimble bird, as well as for its ability to
swiftly turn and point its instruments. The satellite will be
able to catch fluttering flashes of gamma rays that last from only
a few milliseconds to a minute before fading away. An afterglow of the
burst may linger in X-ray and optical light for a few hours to a few days.
HST image of the optical afterglow of a gamma-ray burst (Credit: HST GRB Collaboration/NASA)
The Swift team expects the satellite to detect over 300 bursts a year and
determine their location relative to their host galaxies, a feat which has
not yet been accomplished with current telescopes, even for the most
powerful and long-lasting bursts.
Swift will also be connected to the Gamma-Ray Bursts Coordinate Network, a
relay system operated by Goddard that informs other satellites within
seconds that a burst is occurring. This enables X-ray and optical
telescopes to view the gamma-ray burst afterglow and obtain such valuable
information as spectra and redshift -- all providing insight to a burst's
Gehrels said that among the gamma-ray burst origin theories are such
concepts as the merging of neutron stars or black holes, the formation of
a massive black hole, and a star explosion called a hypernova, which is at
least a thousand times more powerful than the already potent supernova.
Swift will determine whether there are different classes of gamma ray
bursts that could be associated with a particular origin scenario.
The main instrument aboard Swift is the Burst Alert Telescope. The
telescope will detect and locate about one gamma-ray burst per day,
relaying a 1-4 arc minute position to the ground within about 15 seconds.
This position will then be used to "swiftly" re-point the satellite to
bring the burst area into the narrower fields of view of the two other
Swift instruments designed to study the afterglow: the X-ray Telescope and
the UltraViolet/Optical Telescope. These longer-wavelength (lower-energy)
instruments will determine an arc-second position of a burst and determine
the redshift, or distance, to the burst source.
When not catching gamma-ray bursts, Swift will conduct an all-sky survey
in hard X-rays that will be 100 times more sensitive than current hard
X-ray telescopes. This sensitivity should uncover over 400 new
supermassive black holes.
Swift is an international collaboration with partners in Italy and Great
Britain. The lead university partner is Pennsylvania State University,
led by Dr. John Nousek. The spacecraft partner is Spectrum Astro.
Swift is a key component of NASA's Structure and Evolution of the Universe
theme, dedicated to unraveling the mysteries of the cosmos and ensuring
future cosmic journeys. A detailed description of Swift is available at
Credits: NASA/Marshall (left) and NASA/Goddard.