Galaxy map reveals dark business as usual.The most precise map of galaxies has confirmed that much of the cosmos is in the dark. The map, which covers 6 percent of the sky and includes 200,000 galaxies recorded by the Sloan Digital Sky Survey The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico. The project was named after the Alfred P. , supports previous evidence that most of the universe's matter is invisible. Without the gravity provided by this unseen material, dubbed dark matter, galaxies wouldn't have clustered as tightly as the Sloan map indicates they do.
By combining the galaxy map with the newest images of the cosmic microwave background Noun 1. cosmic microwave background - (cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2. , the relic radiation left over from the Big Bang big bang
Model of the origin of the universe, which holds that it emerged from a state of extremely high temperature and density in an explosive expansion 10 billion–15 billion years ago. , astronomers say they have also confirmed the existence of something even stranger. That stuff, known as dark energy, opposes gravity's usual tug, pushing objects apart and causing the universe to expand at an ever-faster rate (SN: 10/11/03, p. 227).
Temperature variations within the cosmic microwave background, as recorded by the Wilkinson Microwave Anisotropy Probe This article or section documents a current spaceflight. Details may change as the mission progresses.
For the radio station, see . (SN: 2/15/03, p. 99), represent tiny lumps in the otherwise smooth soup of the infant universe. These lumps were the seeds from which galaxies arose. By comparing the size of these lumps with that of the vast clusters of galaxies in the Sloan map, astronomers have pinned down several key measures of the universe to an unprecedented accuracy.
Max Tegmark Max Tegmark (born 5 May 1967) is a Swedish-American cosmologist. Tegmark is an Associate Professor at the Massachusetts Institute of Technology where he belongs to the scientific directorate of the Foundational Questions Institute. of the University of Pennsylvania (body, education) University of Pennsylvania - The home of ENIAC and Machiavelli.
Address: Philadelphia, PA, USA. in Philadelphia and a large team of collaborators find that the universe consists of 5 percent ordinary matter, 25 percent dark matter, and 70 percent dark energy. The new analysis puts the age of the universe at 14.1 billion years, give or take a billion years. The researchers announced the results Oct. 28 in two articles posted on the Internet (http://xxx.lanl.gov/abs/astro-ph/0310725, http://xxx.lanl.gov/abs/astro-ph/0310723).
"I've always felt very uneasy about dark energy and dark matter, despite all the papers I've written about them," says Tegmark. "Now, I feel I have to accept them."
Comments David N. Spergel of Princeton University: "I think that this is an important test of the emerging standard model," in which dark matter and dark energy are both required to explain the evolution of the cosmos.
The map's most eye-catching feature is the Sloan Great Wall Not to be confused with the CfA2 Great Wall.
The Sloan Great Wall, a giant wall of galaxies, is the largest known structure in the Universe. Its discovery was announced on October 20, 2003 by J. Richard Gott III and Mario Juric, of Princeton University, and their colleagues. of galaxies, a clustering of galaxies that stretches 1.37 billion light-years across the sky and is the largest cosmic structure ever found. Astronomers worried that such a humongous structure, 80 percent bigger than the famous Great Wall of galaxies first discerned in a sky survey 2 decades ago, might violate the accepted model of galaxy evolution. But modeling by Tegmark, J. Richard Gott John Richard Gott III is a professor of astrophysical sciences at Princeton University. He is especially well known for developing and advocating two cosmological theories with the flavor of science fiction: Time travel, and the Doomsday argument. of Princeton, and their coworkers reveals that such structures arise in about 15 percent of the computer simulations.
"It's a rare feature, but not embarrassingly so," says Gott, whose team recently posted its study's results on the Internet at http://xxx.lanl.gov/abs/astro-ph/ 0310571.