Highlights: The new observations are proving Albert Einstein right, as usual. In 1916 he predicted in his general theory of relativity that the gravitational field of any mass bends light. Two decades later, he proposed that a massive object could thus act as a lens, bending and distorting radiations from a more distant object so that it would appear as a ring or arc of light. Now by looking through gravitational lenses, astronomers are exploring a wide range of problems in cosmology. They are making new measurements of the age of the universe, and also weighing the universe. According to the standard theory of big-bang cosmology, luminous matter of stars probably contributes less than 1 percent of the cosmic mass, and all ordinary matter, seen and unseen, accounts for no more than 5 percent.
With lensing, astronomers are beginning to find and map the distribution of some of the missing mass -- the unknown and invisible dark matter that shapes the universe and probably controls its ultimate fate. This is the first view of the universe that's not biased to radiation, a claim made by Dr. Anthony Tyson, an astronomer at Bell Labs of Lucent Technologies in Murray Hill, N.J. Prior to this astronomers looked for evidence of dark matter only through its gravitational influence on bright galaxies. Tyson and colleagues are using techniques for lensing observations to "see" dark matter in clusters of galaxies.
Knowing the mass density of the universe, in both ordinary and dark matter, is a critical issue in cosmology. Some Cosmologists have postulated the existence of a pervasive "dark energy," to make up for any deficiency in cosmic mass and explain why the universe's expansion appears to be speeding up, not slowing down.
Lesser radiations from galaxies and single stars can be seen through gravitational lenses. The light from these fainter objects, small blue galaxies seem to predominate in the great depths of space and time that form the backdrop for Tyson's work. When Tyson saw the first of billions of these previously undetected faint blue galaxies toward the limits of the observable universe, he recognized this as a break-through in his dark-matter search. In 1990, Tyson's group began to collect and analyze lensed images of these galaxies, reasoning that they should shed light on the distribution of dark matter in the present universe. Astronomers saw in the distorted light evidence of clumps of dark matter not only in the lensing galaxy clusters but well beyond their glowing structure.
Astonomers found an effective way of mapping the wider distribution of dark matter, which will aid in understanding the mechanisms governing galaxy-cluster formation and a clue to the very nature of dark matter.
Highlights: A team of physicists based at the University of Rome has presented unconfirmed evidence that they may have detected a heavy particle, variously called a neutralino and a weakly interacting, massive particle, or WIMP to solve a 70-year-old mystery in astronomy and possible breakthrough in physics.
The particles would weigh at least 50 times as much as a proton and would almost always pass through other matter without a trace because of an extremely weak ability to interact with it. If this is true then space is swarming with enough of the particles to account for the long-sought "dark matter" that astronomers believe make up about 80 percent of all the mass in the universe.
This particle may belong to an entire family of undiscovered particles predicted by an advanced theory of physics called supersymmetry, regarded as the first step toward an ultimate theory. This theory would marry quantum theory and gravity, and conclude that "most of the matter in the universe is not what we are made of."
Dr. Pierluigi Belli will present the results to a symposium in California during this week. The information can be found on its public Web site: http://www.lngs.infn.it, whose author is Dr. Rita Bernabei. This information was collected over three years in an underground experiment at the Gran Sasso National Laboratory east of Rome. These WIMPs were detected using sodium iodide, which emits tiny flashes of light when particles collide with the detecter which is underground and shielded from cosmic rays.
About one WIMP would exist in a volume of space the size of a coffee cup. Since the sun is orbiting around the center of the Galaxy at 140 miles per second, this means "a billion of them would be passing through your body every second," said Dr. Leszek Roszkowski, a particle physicist at Lancaster University in England.
Highlights: The invisible and so far unidentified dark matter that accounts for 90 percent of the universe could soon be brought to light as scientists develop sensitive detectors capable of sniffing out tiny particles predicted by theory but not yet proven to exist.
But if the weakly interacting massive particles - WIMPs - are detected, the finding could solve fundamental mysteries of the universe. "It will certainly be one of the great discoveries in the history of science," said physicist Joel Primack of the University of California, Santa Cruz. "It will be a window on a completely different aspect of the universe."
Astronomers have known for 70 years that the visible matter is only a small part of the universe. Something that exerts a strong gravitational tug, for instance, causes the outer stars of a spiral galaxy to revolve faster than they should, given what is visible.
Weighty but ghostly WIMPs are currently the prime suspects. Physicists theorize that the tiny particles originated during the Big Bang, but they only interact weakly with the protons and neutrons of the visible universe. If real, 10 trillion WIMPs may be zipping through every 2 pounds of matter here on Earth every second.
Scientists announced the first results from new ultracold detectors last month, ironically while all but debunking the findings of Italian researchers who claimed they possibly found the elusive particles. The Italian Dark Matter Experiment, or DAMA, used detectors that emit flashes of light whenever a particle collides with sodium iodide atoms. Researchers theorized that the number of hits would increase in June and decrease in December, as the Earth moves faster or slower through a theoretical cloud of the hypothetical particles.
Sure enough, the detectors buried a mile underground registered a small increase in bombardments.
Though DAMA's experiment could differentiate possible WIMPs from charged particles, it could not distinguish the elusive mystery matter from ordinary neutrons.
A cryogenic detector cooled to near absolute zero will soon be moved to an abandoned iron mine in northern Minnesota, where it will be shielded by 4,300 feet of rock and earth. Sensitivity is expected to increase by a factor of 100 when the $12 million, six-year project gets under way. The American team should be able to make two specific measurements - the amount of heat released and the amount of electricity that is discharged. This will give a clearer picture of what is causing the event.
Highlights: The search for much of the matter that makes up the universe has been like looking for a wall in a dark room -- you know it's there holding up the ceiling, you just can't see it.
But now astronomers have flipped a light switch, using the brilliance of a distant stellar object to detect tendrils of hydrogen in the vast dark between galaxies. The discovery of the mysterious matter, long predicted but undetected, could reveal much about the large-scale structure of the universe, astronomers say.
But now, using the Hubble Space Telescope, scientists have uncovered the missing half, the National Aeronautics and Space Administration said. The discovery confirms previous predictions of how much hydrogen was created in the first few minutes after the Big Bang, the universe's birth.
"This is a successful, fundamental test of cosmological models," said Todd Tripp, a Princeton University researcher who worked to find the missing hydrogen. "This provides strong evidence that the models are on the right track."
The results of Tripp and his collaborators are being published in the May 1 issue of The Astrophysical Journal.
The astronomers think that the missing matter exists as highly charged hydrogen between galaxies. Since hydrogen is hard to see, they had to seek indirect evidence by looking at oxygen that had been spewed into space by exploding stars. The hot hydrogen heats the oxygen into an excited state that can be observed.
Astronomers found the oxygen by using the light of a distant quasar to probe the invisible space between galaxies, like shining a flashlight beam through a fog. Quasars are distant, very energetic, stellar objects that can spew X-rays and visible light equal to the brightness of trillions of stars.
With Hubble Telescope, the astronomers saw traces of the oxygen in the quasar's light, which had crossed through vast distances of space.
Found on the net at http://hubble.stsci.edu/go/news