Scientists release first taste of data from Planck mission
BY STEPHEN CLARK
Posted: January 11, 2011
Europe's Planck observatory has pulled back the curtain on some of the coldest and most complex corners of the universe, revealing ancient superclusters of galaxies and yielding new data on phenomena closer to home, scientists announced Tuesday.
Scientists already have the Planck's first image of the universe, but the picture is dominated with bright light from our own galaxy blocking out dimmer missions further back in time. It takes years to properly analyze the data, remove local sources and see the subtle background radiation left over from the Big Bang.
"Planck is a machine that is designed to measure the first light that comes at a very early time in the universe," said Jan Tauber, Planck's chief scientist at the European Space Agency. "This light is called the cosmic microwave background. When we observe it, we are basically making a map of the universe as it was at an early time, an early time when the universe had very few features."
The cosmic microwave background is the relic light from the Big Bang. It takes a special instrument in space to see tiny variations in the light's temperature, or brightness, which gives scientists information on structure formation in the infant universe.
As astronomers peel away layers of light in Planck's imagery - a process called component separation - the data give scientists an unprecedented trip back in time. Not only does the telescope see ancient light from 13 billion years ago, it also observes relatively recent activity in the Milky Way and nearby galaxies.
It's a fortunate byproduct, according to Tauber.
"In order to get the final objective of Planck, which is the first light after the Big Bang, we first have to understand everything that is in between," Tauber said from Paris.
In the first phase of their analysis, scientists found compelling new images of galaxy superclusters, one of the largest known structures in the universe. These groups of galaxies measure up to hundreds of millions of light years across.
Planck has already observed 21 confirmed new galaxy clusters, and because the telescope scans the whole sky, it has a good chance of finding many more. Scientists hope Planck will see some of the most massive superclusters and catch one of the galaxy structures in the early stages of forming.
Researchers say Planck is ideally-suited for a census of galaxy superclusters. By the end of 2011, it will have completed five sky surveys at higher sensitivities than any mission before.
"One of the things you should realize about Planck is that it's an all-sky machine," Tauber said. "This gives you the ability to do statistics. Have been able to observe clusters in these frequencies before? Yes, but in very small parts of the sky. Being able to get the big picture is very important. It allows us to find new things, superclusters, big objects, really interesting stuff."
Planck is the first mission in nearly 20 years to survey the sky for superclusters.
The superclusters are contained in walls, or filaments, in a spiderweb-like structure. The superclusters appear as bright knots in telescope images.
"We have seen the two largest formed scales in the universe," said Nabila Aghanim, a researcher from Universite Paris Sud and the French National Center for Scientific Research, or CNRS. "And by tracing the knots, we may have some insight on the walls, the filaments, of the cosmic web."
The largest supercluster found so far covers an area of the sky four times bigger than the full moon, but it is invisible to the human eye, Aghanim said.
At that rate, galaxies may have produced up to three sun-like stars per day. About one sun-like star forms in the Milky Way each year.
Demonstrating its unparalleled sensitivity, Planck has also uncovered unimaginably cold regions, cataloguing approximately 10,000 star-forming "cold cores," according to NASA, a major partner in the project. Thousands of the cold pockets were observed by Planck for the first time.
Temperatures in these cold clumps are as low as 7 Kelvin, or minus 447 degrees Fahrenheit. Planck's most sensitive detectors are chilled to 0.1 Kelvin to detect such frigid parts of the universe.
"This is the first census of the whole sky that is being made of these sites of star formation," Tauber said. "We find clumps that are so cold that they really approach the physical limits of how cold they can get."
Planck has also explained a previously unknown source of microwave emissions coming from within our own galaxy. According to Clive Dickinson of the University of Manchester in the United Kingdom, rapidly spinning grains of interstellar dust give off a glow of light in a process called electric dipole radiation.
"This is a great result made possible by the exceptional quality of the Planck data," Dickinson said.
Data released Tuesday are part of the first batch of results produced by Planck. The mission's cosmic microwave background data will be released by January 2013, according to ESA.
"The mission is now close to completing its third survey of the entire sky, and we are extremely satisfied with its performance so far," Tauber said.
Planck's high-frequency and low-frequency instruments are both working as planned. Both instruments will observe the sky through at least the end of 2011, when the liquid helium coolant runs out for the more sensitive high-frequency instrument, which must be chilled to nearly absolute zero.
The low-frequency instrument could continue working in 2012, according to Tauber.
"There is a fairly high probability that after this year, we will continue operating with just one instrument," Tauber said.