Press Release

NASA Swift Satellite to Catch Mysterious Bursts from Deep in the Cosmos

By SpaceRef Editor
July 30, 2004
Filed under ,

The Swift satellite, which will pinpoint the location of distant yet
fleeting explosions that appear to signal the births of black holes,
arrived at Kennedy Space Center today in preparation for an October launch.

These enigmatic flashes, called gamma-ray bursts, are the most powerful
explosions known in the Universe, emitting more than one hundred billion
times the energy than the Sun does in an entire year. Yet they last only a
few milliseconds to a few minutes, never to appear in the same spot again.

The Swift satellite is named for the nimble bird, because it can swiftly
turn and point its instruments to catch a burst “on the fly” to study both
the burst and its afterglow. The afterglow phenomenon follows the initial
gamma-ray flash in most bursts; and it can linger in X-ray light, optical
light and radio waves for hours to weeks, providing great detail.

“Gamma-ray bursts have ranked among the biggest mysteries in astronomy
since their discovery over 35 years ago,” said Dr. Neil Gehrels, Swift Lead
Scientist from NASA’s Goddard Space Flight Center in Greenbelt, Md. “Swift
is just the right tool needed to solve this mystery. One of Swift’s
instruments will detect the burst, while, within a minute, two
higher-resolution telescopes will be swung around for an in-depth
look. Meanwhile, Swift will ‘e-mail’ scientists and telescopes around the
world to observe the burst in real-time.”

The Burst Alert Telescope (BAT) instrument, built by NASA Goddard, will
detect and locate about two gamma-ray bursts per week, relaying a 1- to
4-arc-minute position to the ground within about 20 seconds. This position
will then be used to “swiftly” re-point the satellite to bring the burst
area into the narrower fields of view to study the afterglow with the X-ray
Telescope (XRT) and the UltraViolet/Optical Telescope (UVOT).

These two longer-wavelength (lower-energy) instruments will determine an
arc-second position of a burst and the spectrum of its afterglow at visible
to x-ray wavelengths. For most of the bursts detected with Swift this
data, together with observations conducted with ground-based telescopes,
will enable measurement of the redshift, or distance, to the burst
source. The afterglow provides crucial information about the dynamics of
the burst, but scientists need precise information about the burst in order
to locate the afterglow.

Swift notifies the community — which includes museums and the general
public, along with scientists at world-class observatories — via the
Goddard-maintained Gamma-ray Burst Coordinates Network (GCN). A network of
dedicated ground-based robotic telescopes distributed around the world
await Swift-GCN alerts.

Continuous burst information flows through the Swift Mission Operations
Center, located at Penn State. Penn State, a key U.S. collaborator, built
the XRT with University of Leicester (UK) and the Astronomical Observatory
of Brera (Italy) and the UVOT with Mullard Space Science Lab (UK).

In addition to providing new clues to the nature of the burst mechanism,
Swift’s detection of gamma-ray bursts could provide a bonanza of
cosmological data.

“Some bursts likely originate from the farthest reaches, and hence earliest
epoch, of the Universe,” said Swift Mission Director John Nousek, professor
of astronomy and astrophysics at Penn State. “They act like beacons
shining through everything along their paths, including the gas between and
within galaxies along the line of sight.”

Theorists have suggested that some bursts may originate from the first
generation of stars, and Swift’s unprecedented sensitivity will provide the
first opportunity to test this hypothesis.

With NASA’s High-Energy Transient Explorer (HETE-2), now in operation,
scientists have determined that at least some bursts involve the explosions
of massive stars. Swift will fine-tune this knowledge — that is, answer
such questions as how massive, how far, what kind of host galaxies, and why
are some bursts so different from others?

While the link between some fraction of bursts with the death of massive
stars appears firm, others may signal the merger of neutron stars or black
holes orbiting each other in exotic binary star systems. Swift will
determine whether there are different classes of gamma-ray bursts
associated with a particular origin scenario. Swift may be fast enough to
identify afterglows from short bursts, if they exist. Afterglows have only
been seen for bursts lasting longer than two seconds. “We may be seeing
only half the story so far,” said Gehrels.

The Swift team expects to detect and analyze over 100 bursts a year. When
not catching gamma-ray bursts, Swift will conduct an all-sky survey at
high-energy “hard” X-ray wavelengths, which will be 20 times more sensitive
than previous measurements. Scientists expect that Swift’s enhanced
sensitivity relative to earlier surveys will uncover over 400 new
supermassive black holes.

Swift, a medium-class explorer mission, is managed by NASA’s Goddard Space
Flight Center in Greenbelt, Md., Swift was built in collaboration with
national laboratories, universities, and international partners, including
the Los Alamos National Laboratory, Penn State University, Sonoma State
University, Italy, and the United Kingdom.

More information on Swift is available at:

http://www.gsfc.nasa.gov
and
http://swift.gsfc.nasa.gov

SpaceRef staff editor.