June 7, 2001 PASADENA, Calif. – Astronomers presented a new view of the "nearby" universe, probing the way that galaxies cluster together over distances of hundreds of millions of light years, at today’s meeting of the American Astronomical Society being held in Pasadena, Calif. The new map for the first time covers the whole sky, including the large portion ordinarily hidden by our own galaxy, the Milky Way, and reveals a complicated network of galaxies surrounding us. Galaxies do not uniformly dot the sky, explained University of Massachusetts astronomer Stephen Schneider, who headed up the project. Rather, gravitational forces spur them to form clusters and groups of clusters, called superclusters. The findings offer scientists clues about the conditions that existed during the early days of the universe.
The work is based on the recently completed infrared survey of the entire sky called 2MASS (for 2-Micron All Sky Survey) carried out principally by astronomers at the University of Massachusetts and NASA’s Infrared Processing and Analysis Center. "Infrared light penetrates through the dusty interstellar clouds in galaxies, allowing us to see more clearly out of our own galaxy and to better see other galaxies," said Schneider. "At visual wavelengths very few galaxies are visible in a wide band called the ‘Zone of Avoidance’ girdling the sky because of the dusty disk of the galaxy we live in."
The team of astronomers selected one small region of the survey to carry out more detailed studies of the galaxies’ distribution in space. They targeted a cluster of galaxies called Abell 262, which is part of the Pisces-Perseus supercluster, one of the major concentrations of galaxies in the local universe. Parts of this supercluster were hidden by dust clouds in the Milky Way. "In the new 2MASS map, the supercluster resembles large clumps with long, threadlike filaments strung between them in a spiderweb pattern of galaxies," said Schneider. To determine how far away a galaxy is, scientists rely on a phenonmenon called "redshift." The expansion of the universe implies that the farther away an object is, the faster it is moving away from us, and its emissions are shifted to longer wavelengths of light.
The targeted study presented a small surprise. "We thought we were examining galaxies in Abell 262, about 200 million light-years away, but found instead that most of the galaxies lay in a background supercluster about 1 billion light-years distant," said Schneider. "We’re seeing layer upon layer of structure in the way galaxies cluster. 2MASS is helping us to understand how matter coagulated and collapsed to form structures after the Big Bang, and how those structures are joined together."
The research was conducted using 2Mass, twin infrared telescopes that see wavelengths beyond red light in the rainbow of visible colors. Infrared light enables astronomers to peer past interstellar dust. The 2Mass telescopes are located at Mount Hopkins, Ariz., and Cerro Tololo, Chile. Principal collaborators on the project were Michael Skrutskie of UMass; Thomas Jarrett and Thomas Chester, both of IPAC; and John Huchra, of the Harvard-Smithsonian Center for Astrophysics.
2MASS, the most extensive infrared astronomical survey to date, began operations in 1997, and concluded observations earlier this year. The release of nearly half of the all-sky survey, made available just a few months ago, enabled amateur stargazers and high-level astronomers alike to view a half-million galaxies and 162 million stars on their home computers. The completion of the survey has allowed scientists to explore the entire sky, including the "Zone of Avoidance."
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The above story is based on materials provided by University Of Massachusetts At Amherst.
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