New insights into dark energy and neutrinos revealed

Washington, Apr 3 (ANI): Analysis of data from the National Science Foundation- (NSF) funded 10-meter South Pole Telescope (SPT) in Antarctica provides new support for the most commonly accepted explanation of dark energy, the source of the mysterious force that is behind accelerating expansion of the universe.

The results begin to hone in on the tiny mass of the neutrinos, the most abundant particles in the universe, which until recently were thought to be without mass.

The SPT data strongly support Albert Einstein's cosmological constant - the leading model for dark energy- even though researchers base the analysis on only a fraction of the SPT data collected and only 100 of the over 500 galaxy clusters detected so far.

"With the full SPT data set we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos," said Bradford Benson, an NSF-funded postdoctoral scientist at the University of Chicago's Kavli Institute for Cosmological Physics.

These most recent SPT findings are only the latest scientifically significant results produced by NSF-funded researchers using the telescope in the five years since it became active, noted Vladimir Papitashvili, Antarctic Astrophysics and Geospace Sciences program director in NSF's Office of Polar Programs.

"The South Pole Telescope has proven to be a crown jewel of astrophysical research carried out by NSF in the Antarctic," he said.

"It has produced about two dozen peer-reviewed science publications since the telescope received its 'first light' on Feb. 17, 2007. SPT is a very focused, well-managed and amazing project."

The 280-ton SPT stands 75 feet tall and is the largest astronomical telescope ever built in the clear and dry air of Antarctica.

SPT specifically was designed to tackle the dark-energy mystery. The 10-meter telescope operates at millimeter wavelengths to make high-resolution images of Cosmic Microwave Background (CMB) radiation, the light left over from the big bang.

Scientists use the CMB to search for distant, massive galaxy clusters that can be used to pinpoint the properties of dark energy and also help define the mass of the neutrino.

"The CMB is literally an image of the universe when it was only 400,000 years old, from a time before the first planets, stars and galaxies formed in the universe," Benson said.

"The CMB has travelled across the entire observable universe, for almost 14 billion years, and during its journey is imprinted with information regarding both the content and evolution of the universe."

The new SPT results are based on a new method that combines measurements taken by the telescope and by NASA and European Space Agency X-ray satellites, and extends these measurements to larger distances than previously achieved.

The most widely accepted property of dark energy is that it leads to a pervasive force acting everywhere and at all times in the universe. This force could be the manifestation of Einstein's cosmological constant that assigns energy to space, even when it is free of matter and radiation.

Einstein considered the cosmological constant to be one of his greatest blunders after learning that the universe is not static, but expanding.

Einstein introduced the cosmological constant into his theory of general relativity to accommodate a stationary universe, the dominant idea of his day.

But his constant fits nicely into the context of an accelerating universe, now supported by countless astronomical observations.

Others hypothesize that gravity could operate differently on the largest scales of the universe. In either case, the astronomical measurements point to new physics that have yet to be understood.

As the CMB passes through galaxy clusters, the clusters effectively leave "shadows" that allow astronomers to identify the most massive clusters in the universe, nearly independent of their distance.

The number of clusters that formed over the history of the universe is sensitive to the mass of the neutrinos and the influence of dark energy on the growth of cosmic structures.

"Neutrinos are amongst the most abundant particles in the universe," Benson said.

"About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with 'normal' matter."

The existence of neutrinos was proposed in 1930. They were first detected 25 years later, but their exact mass remains unknown. If they are too massive they would significantly affect the formation of galaxies and galaxy clusters, Benson said.

The SPT team has been able to improve estimates of neutrino masses, yielding a value that approaches predictions stemming from particle physics measurements.

"It is astounding how SPT measurements of the largest structures in the universe lead to new insights on the evasive neutrinos," said Lloyd Knox, professor of physics at the University of California at Davis and member of the SPT collaboration. (ANI)