miércoles, 12 de enero de 2011
Fastest Spinning Dust Found; Solves Cosmic "Fog" Puzzle
Published January 11, 2011
Small specks of dust found in our Milky Way galaxy are the fastest twirlers yet—spinning more than ten billion times a second, astronomers announced today.
Scientists found the tiny grains—each just 10 to 50 atoms wide—using the recently launched European Space Agency's Planck spacecraft. The find helps solve the mystery of a diffuse microwave "fog" in our galaxy that's puzzled astronomers for decades.
The odd radiation has long been associated with dense, dusty clouds between stars, but its exact source was unclear.
According to the Planck team, the new data suggest that some dust particles in these interstellar clouds are constantly colliding with fast-moving atoms and ultraviolet light.
The nonstop bombardments set the grains spinning, and their ultrafast rotation causes the grains to glow at much higher microwave frequencies than dust found elsewhere in the universe.
Understanding the different behaviors of space dust could help astronomers figure out exactly how stars and planets begin to take shape, said Planck team member Peter Martin.
"Most of the heavier elements that eventually go into building planets—and even you and me—spent most of their life in this universe as dust particles," said Martin, a professor of astronomy at the University of Toronto.
"Planck is giving us some of the most detailed surveys of our galaxy's gas and dust structure and distribution, which we think can give us hints to the birthing process of stars and even the way galaxies like ours can form."
Scraping Bugs off the Cosmic Windshield
Finding the source of the microwave fog will ultimately help the Planck team refine its studies of the cosmic microwave background, or CMB, radiation that was emitted during the big bang, more than 13 billion years ago.
Launched in early 2009, Planck's main mission is to study the CMB. But even though this radiation permeates the universe, the faint glow can be tricky to detect.
Similar wavelengths from sources closer to Earth need to be weeded out for scientists to be sure they're getting an accurate picture of the CMB.
"If we neglect their different emissions, then we get greater errors in our background measurements," said Charles Lawrence, Planck team member and a cosmologist at the Jet Propulsion Laboratory (JPL) in Pasadena, California.
"It's like having different bugs splattered on the windshield of your car and blocking your view outside of things in the distance," Lawrence said.
"We need a clear window on the universe free of any foreground sources of emission so we can accurately measure the background radiation."
Coldest, Biggest Things in the Universe
In addition to the spinning dust, Planck's initial data on non-CMB sources—released today at a meeting of the American Astronomical Society in Seattle, Washington—revealed a menagerie of unusual structures.
For example, Planck found the largest population yet of cold cores, the coldest known objects in the universe.
These clouds of frigid dust and gas inside galaxies have average temperatures of just 7 Kelvin (-447 degrees F, or -266 degrees C). Such cold clouds are hotbeds of star formation, because dense dust helps keep gases cool, allowing the gases to collapse and begin forming stars.
Inside cold cores, stars are at their very earliest stages of formation and are therefore barely detectable as heat sources.
"Each and every one of the over 900 cold cores in the newly released catalog are potentially the sites for the very youngest star formation," said Douglas Scott, a professor at the University of British Columbia in Canada and an investigator for the Planck mission.
"The very cool thing with this announcement is that we have an all-sky survey of these objects, which can now be followed up with other telescopes, where we can get intimate details of stellar birth."
Planck's supersensitivity to microwaves also allowed scientists to discover new examples of the biggest objects in the universe: The craft's initial data revealed nearly 190 galaxy clusters, including some that were previously unknown.
When the CMB travels through hot gas surrounding a galaxy cluster, the gas shifts the radiation's energy level. This shift leaves a distinctive spectral signature known as the Sunyaev-Zeldovich effect.
With Planck able to track this effect, hopes are high that the telescope will discover thousands more galaxy clusters.
"We are talking about the biggest gravitationally bound objects in the universe," JPL's Lawrence said. "So by studying them we learn about how galaxies and structures on the large scale in the universe get together."