Dolores Beasley<br />Headquarters, Washington July 23, 2002<br />(Phone: 202/358-1753) <br /><br />Steve Roy<br />Marshall Space Flight Center, Huntsville, Ala.<br />(Phone: 256/544-6535) <br /><br />Megan Watzke<br />Chandra X-ray Observatory Center, CFA, Cambridge, Mass.<br />(Phone: 617/496-7998)<br /><br />RELEASE: 02-134<br /><br />DWARF GALAXIES GIVE UNIVERSE A BREATH OF FRESH OXYGEN<br /><br /> Astronomers have discovered that a nearby dwarf galaxy <br />is spewing oxygen and other "heavy" elements into <br />intergalactic space. This observation from NASA's Chandra X-<br />ray Observatory supports the idea that dwarf galaxies might <br />be responsible for most of the heavy elements between the <br />galaxies. <br /><br />Despite comprising only a very small fraction of the mass of <br />the universe, so-called heavy elements -- everything other <br />than hydrogen and helium -- are essential for the formation <br />of planets and can greatly influence astronomical phenomena, <br />including the rate at which galaxies form. <br /><br />A team led by Crystal Martin of the University of California, <br />Santa Barbara, observed the dwarf galaxy NGC 1569 using <br />Chandra. As reported in an article to be published in The <br />Astrophysical Journal, the group found that huge quantities <br />of oxygen and other heavy elements are escaping from the <br />galaxy in bubbles of multimillion-degree gases thousands of <br />light-years in diameter.<br /><br />"Dwarf galaxies are much smaller than ordinary galaxies like <br />our Milky Way and much more common," said Martin. "Because of <br />their small mass, they have relatively low gravity and matter <br />can escape more easily from dwarfs than from normal galaxies. <br />This makes them very important in understanding how the <br />universe was seeded with various elements."<br /><br />Scientists have speculated that heavy elements escaping from <br />dwarf galaxies in the early universe could play a dominant <br />role in enriching the intergalactic gas from which other <br />galaxies form. Enriched gas cools more quickly, so the rate <br />and manner of formation of new galaxies in the early universe <br />would have been strongly affected by this process. <br /><br />"With Chandra it was possible to test these ideas," said <br />Henry Kobulnicky of the University of Wisconsin, Madison, a <br />member of the research team. "We could trace the distribution <br />of oxygen and other elements in the galaxy and determine how <br />much of this matter is escaping from the galaxy." <br /><br />NGC 1569 is a good case study because it is only about seven <br />million light-years from Earth, and for the last 10 million <br />to 20 million years has been undergoing a burst of star <br />formation and supernova explosions, perhaps triggered by a <br />collision with a massive gas cloud. The supernovae eject <br />oxygen and other heavy elements at high velocity into the gas <br />in the galaxy, heating it to millions of degrees. Hot gas <br />boils off the gaseous disk of the galaxy and expands outward <br />at speeds of hundreds of thousands of miles per hour. <br /><br />The team found large hot bubbles extending above and below a <br />disk of gas along the equator of the galaxy. The measured <br />concentration of oxygen, neon, magnesium and silicon showed <br />that the elements from thousands of supernovas are <br />evaporating out of the galaxy, carrying much of the <br />surrounding gas with them. The astronomers estimate the <br />bubbles are carrying away an amount of oxygen equivalent to <br />that found in about three million Suns. <br /><br />In addition to Martin and Kobulnicky, Timothy Heckman of The <br />John Hopkins University in Baltimore, was part of the team <br />that observed NGC 1569 for 27.4 hours using the Advanced CCD <br />Imaging Spectrometer (ACIS) on April 11, 2001. ACIS was built <br />for NASA by Penn State, University Park, and the <br />Massachusetts Institute of Technology, Cambridge. NASA's <br />Marshall Space Flight Center, Huntsville, Ala., manages the <br />Chandra program for the Office of Space Science, Washington. <br />TRW, Inc., Redondo Beach, Calif., is the prime contractor for <br />the spacecraft. The Smithsonian's Chandra X-ray Center <br />controls science and flight operations from Cambridge, Mass.<br /><br />Images and additional information about this result are <br />available at:<br /><br />http://chandra.harvard.edu<br />and<br />http://chandra.nasa.gov<br /><br /> -end-