|
|
|
|
|
Surprising observations shake up galactic theories UNIVERSITY OF COLORADO-BOULDER NEWS RELEASE Posted: August 14, 2006 A heavy form of hydrogen created just moments after the Big Bang has been found to exist in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation, says a new international study led by the University of Colorado at Boulder.
The FUSE deuterium study, six years in the making, solves a 35-year- old mystery concerning the distribution of deuterium in the Milky Way while posing new questions about how stars and galaxies are made, according to the research team. A paper on the subject by a team of international researchers led by Linsky is being published in the Aug. 20 issue of The Astrophysical Journal. "Since the 1970s, we have been unable to explain why deuterium levels vary all over the place," said Linsky. "The answer we found is as unsettling as it is exciting." Since deuterium -- a hydrogen isotope containing a proton and a neutron -- is believed burned and lost forever during star formation, scientists think the amount of deuterium present in the universe is "pure" and serves as a tracer for star creation and galaxy building over billions of years, said Linsky. While primordial deuterium in the distant, early universe has been measured at concentrations of about 27 parts per million parts hydrogen atoms, measurements by FUSE and NASA's Copernicus satellite have shown a "patchy" distribution of the element in the Milky Way galaxy, often at far lower levels. In 2003, Princeton University's Bruce Draine, a co-author on the new study, developed a model showing that deuterium, when compared to hydrogen, might preferentially bind to interstellar dust grains. The observations by FUSE -- which can detect the telltale spectral fingerprints of deuterium in the ultraviolet energy range -- strongly support the theory, according to The Astrophysical Journal paper authors. "Where there are high concentrations of interstellar dust in the galaxy, we see lower concentrations of deuterium gas with FUSE," said Linsky. "And where there is less interstellar dust, we are measuring higher levels of deuterium gas." In relatively undisturbed areas of the universe -- like regions around Earth's sun, for example -- deuterium atoms systematically "leave" the gas phase and replace normal hydrogen atoms in dust grains, said Linsky. When a pocket of the universe is disturbed by events like a supernova shock wave or violent activity triggered by nearby hot stars, the dust grains are vaporized, releasing deuterium atoms back into a gas, which has been measured by FUSE, the researchers said. Scientists assumed from astrophysical theories that at least one- third of the primordial deuterium present in the Milky Way was destroyed over time as it cycled through the stars, said Linsky. But according to the new FUSE findings, the present-day deuterium abundance is less than 15 percent below the primordial values. "This implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto the galaxy over its lifetime than had been thought," said Linsky. "In either case, our models of the chemical evolution of the Milky Way will have to be revised significantly to explain this important new result." Launched in 1999, FUSE is a NASA Explorer mission developed in cooperation with the French and Canadian Space Agencies and by Johns Hopkins University, CU-Boulder and the University of California, Berkeley. CU-Boulder's Center for Astrophysics and Space Astronomy designed and built the mission's $9 million spectrograph, which collects and funnels UV light from the satellite's four telescopes. The paper was co-authored by scientists from Princeton, Johns Hopkins and Northwestern universities, the Space Telescope Science Institute, CU-Boulder, the University of Wisconsin-Madison, the University of Texas-Austin, NASA-Goddard, the Laboratoire d'Astrophysique in Marseille, France, and the Observatoire de Paris- Meudon in Meudon, France. Other CU-Boulder co-authors include JILA's Brian Wood, CASA's Michael Shull and CASA doctoral graduate Seth Redfield. |
|
|
|
 |
|||||||||||||||||||||
The Hubble Space Telescope has become astronomy's crown jewel for knowledge and discovery. The great observatory was placed high above Earth following its launch aboard space shuttle Discovery on April 24, 1990. The astronauts of STS-31 recount their mission in this post-flight film presentation.
Space shuttle Atlantis is delivered to Kennedy Space Center's launch pad 39B on August 2 to begin final preparations for blastoff on the STS-115 mission to resume construction of the International Space Station.
Just after 1 a.m. local time August 2, the crawler-transporter began the slow move out of the Vehicle Assembly Building carrying space shuttle Atlantis toward the launch pad.
Astronauts Jeff Williams and Thomas Reiter will conduct a U.S.-based spacewalk outside the International Space Station on August 3. To preview the EVA and the tasks to be accomplished during the excursion, station managers held this press conference from Johnson Space Center in Houston.
The long voyage of exploration to Jupiter and its many moons by the Galileo spacecraft began on October 18, 1989 with launch from Kennedy Space Center aboard the space shuttle Atlantis. The crew of mission STS-34 tell the story of their flight to dispatch the probe -- fitted with an Inertial Upper Stage rocket motor -- during this post-flight presentation film.
Space shuttle Atlantis is transported to the cavernous Vehicle Assembly Building where the ship will be mated to the external fuel tank and twin solid rocket boosters for a late-August liftoff.
A camera was mounted in the front of space shuttle Discovery's flight deck looking back at the astronauts during launch. This video shows the final minutes of the countdown and the ride to space with the live launch audio included. The movie shows what it would be like to launch on the shuttle with the STS-121 crew.
A high-altitude WB-57 aircraft flying north of Discovery's launch trajectory captures this incredible aerial footage of the space shuttle's ascent from liftoff through solid rocket booster separation.
This is the full launch experience! The movie begins with the final readiness polls of the launch team. Countdown clocks then resume ticking from the T-minus 9 minute mark, smoothly proceeding to ignition at 2:38 p.m. Discovery rockets into orbit, as seen by ground tracker and a video camera mounted on the external tank. About 9 minutes after liftoff, the engines shut down and the tank is jettisoned as the shuttle arrives in space.
MiTEx -- an experimental U.S. military project to test whether the advanced technologies embedded in two miniature satellites and a new upper stage kick motor can operate through the rigors of spaceflight -- is launched from Cape Canaveral aboard a Boeing Delta 2 rocket.