Headlines > News > NASA Telescope Helps Confirm Nature of Dark Energy

NASA Telescope Helps Confirm Nature of Dark Energy

Published by Klaus Schmidt on Fri May 20, 2011 5:56 am via: NASA
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PASADENA, Calif. — A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds. The survey used data from NASA’s space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The findings offer new support for the favored theory of how dark energy works — as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein’s concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.

“The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster,” said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. “The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.”

Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.

The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called “standard candles,” which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.

Dark energy is in a tug-of-war contest with gravity. In the early universe, gravity took the lead, dominating dark energy. At about 8 billion years after the Big Bang, as space expanded and matter became diluted, gravitational attractions weakened and dark energy gained the upper hand. Billions of years from now, dark energy will be even more dominant. Astronomers predict our universe will be a cosmic wasteland, with galaxies spread apart so far that any intelligent beings living inside them wouldn’t be able to see other galaxies.

The new survey provides two separate methods for independently checking the supernovae results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. The team began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer. The ultraviolet-sensing telescope has scanned about three-quarters of the sky, observing hundreds of millions of galaxies.

“The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study,” said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. “It provided the scaffolding for this enormous 3-D map.”

The astronomers acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.

This “standard ruler” was used to determine the distance from the galaxy pairs to Earth — the closer a galaxy pair is to us, the farther apart the galaxies will appear from each other on the sky. As with the supernovae studies, this distance data were combined with information about the speeds at which the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.

The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy’s repulsive force.

“Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the Big Bang, is speeding up,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington. “Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy.”

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA’s Jet Propulsion Laboratory in Pasadena, manages the mission and built the science instrument. The mission was developed under NASA’s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d’Etudes Spatiales (CNES) in France collaborated on this mission. Caltech manages JPL for NASA.
PASADENA, Calif. — NASA’s Cassini spacecraft and a European Southern Observatory ground-based telescope tracked the growth of a giant early-spring storm in Saturn’s northern hemisphere that is so powerful it stretches around the entire planet. The rare storm has been wreaking havoc for months and shooting plumes of gas high into the planet’s atmosphere.

Cassini’s radio and plasma wave science instrument first detected the large disturbance, and amateur astronomers tracked its emergence in December 2010. As it rapidly expanded, its core developed into a giant, powerful thunderstorm. The storm produced a 3,000-mile-wide (5,000-kilometer-wide) dark vortex, possibly similar to Jupiter’s Great Red Spot, within the turbulent atmosphere.

The dramatic effects of the deep plumes disturbed areas high up in Saturn’s usually stable stratosphere, generating regions of warm air that shone like bright “beacons” in the infrared. Details are published in this week’s edition of Science Magazine.

“Nothing on Earth comes close to this powerful storm,” says Leigh Fletcher, the study’s lead author and a Cassini team scientist at the University of Oxford in the United Kingdom. “A storm like this is rare. This is only the sixth one to be recorded since 1876, and the last was way back in 1990.”

This is the first major storm on Saturn observed by an orbiting spacecraft and studied at thermal infrared wavelengths, where Saturn’s heat energy reveals atmospheric temperatures, winds and composition within the disturbance.

Temperature data were provided by the Very Large Telescope (VLT) on Cerro Paranal in Chile and Cassini’s composite infrared spectrometer (CIRS), operated by NASA’s Goddard Space Flight Center in Greenbelt, Md.

“Our new observations show that the storm had a major effect on the atmosphere, transporting energy and material over great distances, modifying the atmospheric winds — creating meandering jet streams and forming giant vortices — and disrupting Saturn’s slow seasonal evolution,” said Glenn Orton, a paper co-author, based at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

The violence of the storm — the strongest disturbances ever detected in Saturn’s stratosphere — took researchers by surprise. What started as an ordinary disturbance deep in Saturn’s atmosphere punched through the planet’s serene cloud cover to roil the high layer known as the stratosphere.

“On Earth, the lower stratosphere is where commercial airplanes generally fly to avoid storms which can cause turbulence,” says Brigette Hesman, a scientist at the University of Maryland in College Park who works on the CIRS team at Goddard and is the second author on the paper. “If you were flying in an airplane on Saturn, this storm would reach so high up, it would probably be impossible to avoid it.”

Other indications of the storm’s strength are the changes in the composition of the atmosphere brought on by the mixing of air from different layers. CIRS found evidence of such changes by looking at the amounts of acetylene and phosphine, both considered to be tracers of atmospheric motion. A separate analysis using Cassini’s visual and infrared mapping spectrometer, led by Kevin Baines of JPL, confirmed the storm is very violent, dredging up larger atmospheric particles and churning up ammonia from deep in the atmosphere in volumes several times larger than previous storms. Other Cassini scientists are studying the evolving storm, and a more extensive picture will emerge soon.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The mission is managed by JPL for NASA’s Science Mission Directorate in Washington. The European Southern Observatory in Garching, Germany operates the VLT in Chile. JPL is a division of the California Institute of Technology in Pasadena.

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Two stories in one! Looks like there was a copy/paste error for this news item...
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