NASA’s Galaxy Evolution Explorer (GALEX) will carry a
telescope into Earth orbit that will observe a million
galaxies, across 10 billion years of cosmic history, to help
astronomers determine when the stars we see today had their
origins.
GALEX is set to launch, no earlier than April 28, 2003, from
Cape Canaveral Air Force Station, Fla. A Pegasus XL rocket,
released by an L-1011 jet aircraft, will launch the
satellite. The aircraft will climb to approximately 39,000
feet and release the launch vehicle and payload. The science
mission will start after an initial month of in-orbit
testing.
From its orbit high above Earth, the spacecraft will sweep
the skies, for up to 28 months, using state-of-the-art
ultraviolet detectors. Looking in the ultraviolet will
single out galaxies dominated by young, hot, short-lived
stars that give off a great deal of energy at that
wavelength. These galaxies are actively creating stars,
therefore providing a window into the history and causes of
galactic star formation.
“The Galaxy Evolution Explorer is crucial to understanding
how galaxies, the basic structures of our universe, form and
function,” said Anne Kinney, director of astronomy and
physics in the Office of Space Science, NASA Headquarters,
Washington. “Its ultraviolet observations will round out the
knowledge we gain from observations in infrared and other
wavelengths,” she said.
Astronomers believe the universe originated approximately
13.7 billion years ago in the cataclysmic “Big Bang.”
Galaxies, the basic building blocks of the universe, began
to appear as the fireball of hydrogen and helium gas
expanded and cooled. Recent observations suggest star
formation peaked eight to 10 billion years ago. This mission
is specifically designed to investigate whether this
occurred and why.
The centerpiece of the satellite is a 50-centimeter-diameter
(19.7-inch) telescope. It is equipped with sensors that will
gather continuous images of galaxies in the ultraviolet to
study their shape, brightness and size. Ultraviolet light,
the type of invisible energy responsible for sunburn, is at
the higher end of the electromagnetic spectrum, just above
visible light in frequency, but below X-rays and gamma rays.
A device called a spectrometer will break down the light
into component colors, just as a prism separates white light
into a rainbow. These measurements will enable scientists to
determine the distances of galaxies, and thus, their places
in cosmic history. Combined with precise measurements of the
ultraviolet brightness of galaxies, astronomers will be able
to determine the rate at which stars are forming within
those galaxies.
“This mission will provide the first comprehensive map of a
universe of galaxies under construction and bring us closer
to understanding how they, and our own Milky Way, were
built,” said Christopher Martin, the mission’s principal
investigator and an astrophysics professor at the California
Institute of Technology in Pasadena.
Scientists will use data from the mission to learn when
carbon, oxygen and other chemical elements were created
inside blazing stars. Most of the elements found in the
human body originated in stars. We are literally made of
stardust. The mission will also conduct the first
ultraviolet surveys of the entire sky beyond our own galaxy,
including the first wide-area spectroscopic surveys. Rich in
objects, from galaxies to quasars to white dwarf stars, this
vast data archive will serve as a resource for the entire
astronomical community.
The GALEX mission is led by the California Institute of
Technology, which is also responsible for science operations
and data analysis. NASA’s Jet Propulsion Laboratory,
Pasadena, Calif., a division of Caltech, manages the mission
and built the science instrument. The mission was developed
under NASA’s Explorers Program, managed by the Goddard Space
Flight Center, Greenbelt, Md. GALEX international partners
include South Korea and France.
For information about the mission and NASA’s Explorers
Program on the Internet, visit:
