Paula Cleggett-Haleim Headquarters, Washington, DC January 13, 1992 (Phone: 202/453-1547) 12:30 P.M. EST Fred McGehan National Institute of Standards and Technology, Gaithersburg, Md. (Phone: 303/497-3246) RELEASE: 92-2 NASA'S HST SUPPORTS BIG BANG THEORY AND ENDLESS UNIVERSE A team of scientists using NASA's Hubble Space Telescope (HST) has made the most precise measurement to date of the percent of heavy hydrogen in space, which better determines the physical conditions present in the theorized Big Bang at the origin of the universe. The team's findings were presented today at a press conference at the American Astronomical Society's semiannual meeting in Atlanta. The group is headed by Jeffrey Linsky, a National Institute of Standards and Technology (NIST) astronomer and a fellow of the Joint Institute for Laboratory Astrophysics (JILA), a collaboration of NIST and the University of Colorado in Boulder. The Hubble Space Telescope is a cooperative project of NASA and the European Space Agency. Deuterium, also called heavy hydrogen, differs from ordinary hydrogen by having one neutron in addition to one proton in its nucleus. A measurement of the ratio of deuterium to ordinary hydrogen provides a critical test of conditions in the universe at the time of the Big Bang because it is believed that essentially all of the deuterium now present was created at that time. Linsky and his collaborators used the HST's Goddard High Resolution Spectrograph to observe the nearby star Capella, the brightest star in the constellation Auriga and the universe's sixth brightest star. With the highest spectral resolution possible on the Hubble Space Telescope, the scientists dispersed the far ultraviolet light of the star where the strongest absorption by normal hydrogen and deuterium occurs. - more - - 2 - The so-called "Lyman alpha" lines of hydrogen and deuterium are located next to each other in the spectrum. These dark lines are formed when starlight is absorbed by very low density interstellar gas located in the line of sight toward Capella. A careful analysis of the two absorption lines indicates the ratio of deuterium to hydrogen in space is 15 parts per million with an uncertainty of less than 10 percent. This ratio is lower than the ratio in the early universe because of the destruction of some deuterium in the cores of stars and the subsequent dispersal of this deuterium-poor gas into space by stellar winds and supernova explosions. Deuterium has been observed in space previously by the Copernious and International Ultraviolet Explorer satellites. It also has been observed by radio telescopes. But the new measurement by the Hubble Space Telescope greatly reduces the uncertainty in the deuterium abundance. This permits a clear test of the creation of elements in the early universe. If the assumptions of the Big Bang theory for the early universe are correct, the deuterium-to-hydrogen ratio in space today determines the maximum possible amount of ordinary matter that can be present in the universe. This amount of ordinary matter is at least a factor of 10 too small for the universe to be described by the ordinary laws of geometry and for the observed expansion to be halted eventually by gravity as some cosmologists believe. If enough matter in other forms does exist to eventually halt the universe's expansion, then this missing or "dark matter" must exist in an exotic form. If further research finds no evidence for large amounts of "missing matter," then the new deuterium measurements strengthen the idea that the universe will expand forever. If true, the universe had a brilliant beginning but will have no end. The team of astronomers presenting this work also includes Alexander Brown and Kenneth Gayley at JILA; Wayne Landsman and Sara Heap at NASA's Goddard Space Flight Center, Greenbelt, Md.; Blair Savage and Athanassios Diplas of the University of Wisconsin, Madison, Wis.; and Thomas Ayres of the University of Colorado. Jack Brandt of the University of Colorado is the principal investigator of the Goddard High Resolution Spectrograph Program. - end -