Stellar birth control in the early universeOctober 02, 2006New Haven, Conn. - An international team of astronomers based at Yale and Leiden University in The Netherlands found that "old stars" dominated many large galaxies in the early universe, raising the new question of why these galaxies progressed into "adulthood" so early in the life of the universe. Every year only a handful of new stars are born out of the gas that fills the space between the stars in galaxies like the Milky Way. To account for the large number of stars in the Universe today, about 400 billion in the Milky Way alone, it was thought that the "stellar birth rate" must have been much higher in the past. Surprisingly, in this study appearing in the October 2 issue of Astrophysical Journal, astronomers using the 8.1m Gemini telescope in Chile report that many of the largest galaxies in the Universe had a very low stellar birth rate even when the Universe was only about 20 percent of its present age.
"Our new results imply that the stars in many large galaxies were born when the Universe was in its infancy, in the first few billion years after the Big Bang," said team leader Mariska Kriek, a PhD student from Leiden University and Yale. "The results confirm what some astronomers had suspected - galaxies seem to have some method of 'birth control' that is very effective." These new findings add to growing evidence that in big galaxies the formation of new stars was significantly suppressed after an initial period of vigorous activity. "These galaxies had a very violent early youth, but rose into stable adulthood well before many galaxies like the Milky Way were even in kindergarten," said Kriek." The astronomers used the uniquely powerful Gemini Near Infrared Spectrograph, to analyze the light of distant galaxies simultaneously over many different wavelengths. They studied 20 galaxies so distant that their light had been traveling for nearly 11 billion years, or 80 percent of the age of the Universe. "The unexpected finding is what was not found - we expected to see a prominent signal from ionized Hydrogen, the tell-tale signature of star birth. Remarkably, for nine of the twenty galaxies that we observed, this signature is not seen at all," said Pieter van Dokkum, associate professor of astronomy and physics at Yale University. "It gives a firm limit on the stellar birth rate in these objects." One suggestion is that enormous black holes in the centers of large galaxies may be responsible for suppressing star formation. When material spirals into a black hole, huge amounts of energy are released and are rapidly injected into the galaxy's gas. This energy injection may dilute the gas sufficiently to prevent future star birth. "Evidence for the presence of these black holes is seen in several of the galaxies studied, lending support to the idea that black holes serve as cosmic contraceptives in the young Universe,\\\ Yale University Science News and Science Current Events Tag Cloud This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size. Chocolate Reflux Disease Cancer Cells Spiders ALS Gamma-ray Bursts Algal Blooms Quark Peptides Hormone Therapy Ear Infections Earthquakes Hydrogen Storage Antiretroviral T Cells Warfarin Amazon rainforest Nanotubes Sleeping Sickness Hodgkin Lymphoma Spinal Muscular Atrophy Atherosclerosis Microfluidic device Prions Kidney Cancer
See More: Science News Tags | |||||||||||||||||||||
|
Related Early Universe Current Events and Early Universe News Articles Largest ever survey of very distant galaxy clusters completed An international team of researchers led by a UC Riverside astronomer has completed the largest ever survey designed to find very distant clusters of galaxies. Fog lifted on 'dark' gamma-ray bursts, mysterious counterparts to bursts with an afterglow Gamma-ray bursts, with their ability to pierce through gas and dust to shine brightly across the universe, are revealing areas of intense star formation and stellar death where astronomers have been unable to look - the dusty corners of otherwise dust-free galaxies. Ghost Remains After Black Hole Eruption NASA's Chandra X-ray Observatory has found a cosmic "ghost" lurking around a distant supermassive black hole. This is the first detection of such a high-energy apparition, and scientists think it is evidence of a huge eruption produced by the black hole. Hubble repair mission carrying $70 million CU-Boulder instrument on track for May 11 launch A $70 million instrument designed by the University of Colorado at Boulder to probe the evolution of galaxies, stars and intergalactic matter from its perch on the orbiting Hubble Space Telescope is on schedule for its slated May 11 launch from Kennedy Space Center in Florida aboard NASA's space shuttle Atlantis. Rogue Black Holes May Roam the Milky Way It sounds like the plot of a sci-fi movie: rogue black holes roaming our galaxy, threatening to swallow anything that gets too close. In fact, new calculations by Ryan O'Leary and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) suggest that hundreds of massive black holes, left over from the galaxy-building days of the early universe, may wander the Milky Way. Research team co-led by UC Riverside physicist observes production of single-top-quarks A group of 28 scientists at the U.S. Department of Energy's Fermi National Accelerator Laboratory, co-led by UC Riverside's Ann Heinson, has made the first observation of the production of single top quarks - an observation that resulted from proton-antiproton collisions measured by the DZero detector in Fermilab's Tevatron, the world's highest-energy particle collider. Swift Satellite records early phase of gamma ray burst UK astronomers, using a telescope aboard the NASA Swift Satellite, have captured information from the early stages of a gamma ray burst - the most violent and luminous explosions occurring in the Universe since the Big Bang. New stars from old gas surprise astronomers Evidence of star birth within a cloud of primordial gas has given astronomers a glimpse of a previously unknown mode of galaxy formation. The cloud, known as the Leo Ring, appears to lack the dark matter and heavy elements normally found in galaxies today. New recipe for dwarf galaxies: Start with leftover gas There is more than one way to make a dwarf galaxy, and NASA's Galaxy Evolution Explorer has found a new recipe. Cosmologists 'see' the cosmic dawn The images, produced by scientists at Durham University's Institute for Computational Cosmology, show the "Cosmic Dawn" - the formation of the first big galaxies in the Universe. More Early Universe Current Events and Early Universe News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||