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Fossil galaxy reveals clues to early universe JOHNS HOPKINS UNIVERSITY NEWS RELEASE Posted: January 18, 2006 A tiny galaxy has given astronomers a glimpse of a time when the first bright objects in the universe formed, ending the dark ages that followed the birth of the universe. Astronomers from Sweden, Spain and the Johns Hopkins University used NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite to make the first direct measurement of ionizing radiation leaking from a dwarf galaxy undergoing a burst of star formation. The result, which has ramifications for understanding how the early universe evolved, will help astronomers determine whether the first stars -- or some other type of object -- ended the cosmic dark age. Considered by many astronomers to be relics from an early stage of the universe, dwarf galaxies are small, very faint galaxies containing a large fraction of gas and relatively few stars. According to one model of galaxy formation, many of these smaller galaxies merged to build up today's larger ones. If that is true, any dwarf galaxies observed now can be thought of as "fossils" that managed to survive -- without significant changes -- from an earlier period. Led by Nils Bergvall of the Astronomical Observatory in Uppsala, Sweden, the team observed a small galaxy, known as Haro 11, which is located about 281 million light years away from Earth in the southern constellation of Sculptor. The team's analysis of FUSE data produced an important result: between 4 percent and 10 percent of the ionizing radiation produced by the hot stars in Haro 11 is able to escape into intergalactic space. Ionization is the process by which atoms and molecules are stripped of electrons and converted to positively charged ions. The history of the ionization level is important to understanding the evolution of structures in the early universe, because it determines how easily stars and galaxies can form, according to B-G Andersson, a research scientist in the Henry A. Rowland Department of Physics and Astronomy at Johns Hopkins and a member of the FUSE team. "The more ionized a gas becomes, the less efficiently it can cool. The cooling rate in turn controls the ability of the gas to form denser structures, such as stars and galaxies," Andersson said. The hotter the gas, the less likely it is for structures to form, he said. The ionization history of the universe therefore reveals when the first luminous objects formed, and when the first stars began to shine. The Big Bang occurred about 13.7 billion years ago. At that time, the infant universe was too hot for light to shine. Matter was completely ionized: atoms were broken up into electrons and atomic nuclei, which scatter light like fog. As it expanded and then cooled, matter combined into neutral atoms of some of the lightest elements. The imprint of this transition today is seen as cosmic microwave background radiation. The present universe is, however, predominantly ionized; astronomers generally agree that this reionization occurred between 12.5 and 13 billion years ago, when the first large-scale galaxies and galaxy clusters were forming. The details of this ionization are still unclear, but are of intense interest to astronomers studying these so-called "dark ages" of the universe. Astronomers are unsure if the first stars or some other type of object ended those dark ages, but FUSE observations of "Haro 11" provide a clue. The observations also help increase understanding of how the universe became reionized. According to the team, likely contributors include the intense radiation generated as matter fell into black holes that formed what we now see as quasars and the leakage of radiation from regions of early star formation. But until now, direct evidence for the viability of the latter mechanism has not been available. "This is the latest example where the FUSE observation of a relatively nearby object holds important ramifications for cosmological questions," said Dr. George Sonneborn, NASA/FUSE Project Scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. This result has been accepted for publication by the European journal Astronomy and Astrophysics. The FUSE project is a NASA Explorer mission developed in cooperation with the French and Canadian space agencies by the Johns Hopkins University, Baltimore, Md., the University of Colorado, Boulder, and the University of California, Berkeley. The mission is operated out of Johns Hopkins University's Homewood campus in Baltimore. NASA Goddard manages the program for NASA's Science Mission Directorate. |
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After reaching Lockheed Martin's Vertical Integration Facility following the early morning drive across the Cape, a crane lifts the New Horizons spacecraft into the 30-story building for mounting atop the awaiting Atlas 5 vehicle.
The New Horizons spacecraft, mounted atop a special transporter, departs Kennedy Space Center's Payload Hazardous Servicing Facility after spending three months in the building undergoing testing, final closeouts, filling of its hydrazine fuel, mating with the third stage kick motor and spin-balance checks. The probe was driven to the Atlas 5 rocket's assembly building at Complex 41 for mating with the launcher.
With New Horizons enclosed within the Lockheed Martin Atlas 5 rocket's nose cone, a large decal reading: "New Horizons: Pluto-Kuiper Belt Mission" is applied to the payload fairing.
The New Horizons is packed away for its launch to Pluto as workers slide the two-piece Atlas 5 rocket nose cone around the spacecraft at the Kennedy Space Center Payload Hazardous Servicing Facility. The Swiss-made shroud protects the spacecraft during ascent through Earth's atmosphere.
Space shuttle Columbia's mission in January 1990 sought to retrieve the Long Duration Exposure Facility -- a bus-size platform loaded with 57 experiments -- that had been put into orbit six years earlier. LDEF was supposed to be picked up within a year of its launch. But plans changed and then the Challenger accident occurred. Columbia's STS-32 crew got into space, deployed a Navy communications satellite, then fulfilled their LDEF recovery mission, carried out a host of medical tests and returned to Earth with a nighttime touchdown in the California desert. The crew presents this post-flight film of mission highlights.
This film looks at the highlights in NASA's history from its creation in the 1950s, through the glory days of the Mercury, Gemini and Apollo programs, birth of the space shuttle and the loss of Challenger, launch of Hubble and much more.
If at first you don't succeed, keep on trying. That is what the astronauts of space shuttle Endeavour's maiden voyage did in their difficult job of rescuing a wayward communications satellite. Spacewalkers were unable to retrieve the Intelsat 603 spacecraft, which had been stranded in a useless orbit, during multiple attempts using a special capture bar. So the crew changed course and staged the first-ever three-man spacewalk to grab the satellite by hand. The STS-49 astronauts describe the mission and narrate highlights in this post-flight presentation.