NASA's Swift Produces Best Ultraviolet Maps of the Nearest Galaxies

June 3, 2013

J. D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov

Lynn Chandler
Goddard Space Flight Center, Greenbelt, Md.
301-286-2806
lynn.chandler-1@nasa.gov

RELEASE: 13-169

NASA'S SWIFT PRODUCES BEST ULTRAVIOLET MAPS OF THE NEAREST GALAXIES

WASHINGTON -- Astronomers at NASA and Pennsylvania State University
have used NASA's Swift satellite to create the most detailed
ultraviolet light surveys ever of the Large and Small Magellanic
Clouds, the two closest major galaxies.

"We took thousands of images and assembled them into seamless
portraits of the main body of each galaxy, resulting in the
highest-resolution surveys of the Magellanic Clouds at ultraviolet
wavelengths," said Stefan Immler, who proposed the program and led
NASA's contribution from the agency's Goddard Space Flight Center in
Greenbelt, Md.

Immler presented a 160-megapixel mosaic image of the Large Magellanic
Cloud (LMC) and a 57-megapixel mosaic image of the Small Magellanic
Cloud (SMC) at the 222nd American Astronomical Society meeting in
Indianapolis on Monday.

The new images reveal about 1 million ultraviolet sources in the LMC
and about 250,000 in the SMC. The images include light ranging from
1,600 to 3,300 angstroms, which is a range of UV wavelengths largely
blocked by Earth's atmosphere.

"Prior to these images, there were relatively few UV observations of
these galaxies, and none at high resolution across such wide areas,
so this project fills in a major missing piece of the scientific
puzzle," said Michael Siegel, lead scientist for Swift's
Ultraviolet/Optical Telescope (UVOT) at the Swift Mission Operations
Center at the university in State College, Pa.

The LMC and SMC lie about 163,000 light-years and 200,000 light-years
away, respectively, and orbit each other as well as our own Milky Way
galaxy. The LMC is about one-tenth the size of the Milky Way and
contains only 1 percent of the Milky Way's mass. The SMC is half the
size of the LMC and contains about two-thirds of its mass.

Despite their modest sizes, the galaxies loom large in the sky because
they are so close to us. Both extend far beyond the UVOT's field of
view, which meant thousands of images were needed in order to cover
both galaxies in three ultraviolet colors centered at wavelengths of
1,928 angstroms, 2,246 angstroms, and 2,600 angstroms.

Viewing in the ultraviolet allows astronomers to suppress the light of
normal stars like the sun, which are not very bright at such higher
energies, and provides a clearer picture of the hottest stars and
star-formation regions. No telescope other than UVOT can produce such
high-resolution wide-field multicolor surveys in the ultraviolet.
Swift's wide-field imaging capabilities provide a powerful complement
to the deeper, but much narrower-field imaging power of NASA's Hubble
Space Telescope.

To produce the 160-megapixel LMC mosaic, Swift's UVOT acquired 2,200
snapshots for a cumulative exposure of 5.4 days. The 57-megapixel SMC
image comprises 656 individual images with a total exposure of 1.8
days.

Both images have an angular resolution of 2.5 arcseconds, which is a
measure of their sharpness. Sources separated by this angle, which is
equivalent to the size of a dime seen from 1 mile away, are visible
as distinct objects.

"With these mosaics, we can study how stars are born and evolve across
each galaxy in a single view, something that's very difficult to
accomplish for our own galaxy because of our location inside it,"
Immler said.

The Large and Small Magellanic Clouds are readily visible from the
Southern Hemisphere as faint, glowing patches in the night sky. The
galaxies are named after Ferdinand Magellan, the Portuguese explorer
who in 1519 led an expedition to sail around the world. He and his
crew were among the first Europeans to sight the objects.

Pennsylvania State University manages the Swift Mission Operations
Center, which controls Swift's science and flight operations. Goddard
manages Swift, which was launched in November 2004. The satellite is
operated in collaboration with Penn State, the Los Alamos National
Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va.
International collaborators are in the United Kingdom and Italy, and
the mission includes contributions from Germany and Japan.

For images related to this release, please visit:

http://go.nasa.gov/16wz7da

For more information about Swift, visit:

http://www.nasa.gov/swift


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