CAPE CANAVERAL, Fla., April 28 (UPI) -- A small telescope with a big mission stands ready for launch Monday, the first step in a two-and-a-half year mission to shed light on the little-known period in cosmic history between the birth of the universe and the formation of its first stars and galaxies.
The Galaxy Evolution Explorer is designed to survey tens of millions of galaxies in the ultraviolet portion of the spectrum so astronomers can compile key data about when star-formation peaked.
"By comparing many galaxies, we can put together a history of star formation in the universe," said GALEX principal investigator Christopher Martin.
Current theory places the birth of the universe about 14 billion years ago in the so-called Big Bang, when all known space, time and matter expanded from a single point. The seeds of the visible universe then formed as clouds of hydrogen and helium gas expanded and cooled. A baby boom of stars appears to have emerged from that process around 8 billion to 10 billion years ago, although scientists are not sure why. GALEX is intended to help answer that question.
The 50-centimeter (19.7-inch) telescope will gather continuous images of galaxies to study their shape, brightness and size. Ultraviolet radiation from targets will be split into component wavelengths by a sophisticated spectrometer in the spacecraft, giving scientists a glimpse into the chemical makeup of the galaxies. Chemicals leave telltale "fingerprints" in the spectra of light and reveal clues about conditions necessary for star formation.
Combined with measurements of how bright the galaxies shine in ultraviolet light, astronomers will be able to determine the rate at which stars are forming within those galaxies.
GALEX researchers said they plan to compile a census of galaxies, pinning each target into an evolutionary timeframe, with the most distant galaxies forming first. By studying how much star formation is going on in the different types of galaxies, scientists hope to learn if a suspected stellar baby boom -- to which our Milky Way galaxy would belong -- actually occurred.
Rather than probe specific distant targets, GALEX is designed to measure large swaths of the sky.
"We will survey 30 billion cubic light years of space during our 28 months of operation," said Martin, an astrophysicists at the California Institute of Technology in Pasadena.
GALEX has a field of view more than twice the size the angular diameter of the full moon as seen from Earth. In comparison, even the Hubble Space Telescope's wide-field camera is 1/500th the size of GALEX.
In addition to charting the evolution of galaxies, the telescope is expected to make the first full-sky ultraviolet surveys of galaxies beyond the Milky Way.
The $72 million telescope is scheduled to be launched between 8 a.m. and 10 a.m., EST, Monday from aboard an air-launched Pegasus rocket. The booster, built by Orbital Sciences Corp., is carried into the sky over the Atlantic Ocean from beneath the wing of a specially modified jet. The booster then ignites, sending the satellite into space.
After GALEX reaches its intended orbit, some 428 miles above Earth's surface, spacecraft ground control teams will take about a month to calibrate the telescope before science operations begin.
Managers expect GALEX to be used in conjunction with the Hubble Space Telescope, as well as NASA's new Space Infrared Telescope Facility, now targeted for launch in August. The infrared observatory was to have been launched before GALEX, but has been delayed to replace suspect equipment on its Delta rocket launch vehicle.
Many of the telescope's studies will be complementary because the ultraviolet galactic emissions actually re-radiate in the infrared range of light after being absorbed and reflected by dust, another key component of star formation, said Martin.
