An international team of cosmologists has released the first detailed images of the universe in its infancy. The images reveal the structure that existed in the universe when it was a tiny fraction of its current age and 1,000 times smaller and hotter than it is today. Detailed analysis of the images is already shedding light on some of cosmology's outstanding mysteries -- the nature of the matter and energy that dominate intergalactic space and whether space is "curved" or "flat."
The project, dubbed BOOMERANG (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), obtained the images using an extremely sensitive telescope suspended from a balloon that circumnavigated the Antarctic in late 1998. The balloon carried the telescope at an altitude of almost 37 kilometers (120,000 feet) for 10-1/2 days. The results will be published in the April 27 issue of Nature.
Today, the universe is filled with galaxies and clusters of galaxies. But 12-15 billion years ago, following the Big Bang, the universe was very smooth, incredibly hot and dense. The intense heat that filled the embryonic universe is still detectable today as a faint glow of microwave radiation that is visible in all directions. This radiation is known as the cosmic microwave background (CMB).
Since the CMB was first discovered by a ground-based radio telescope in 1965, scientists have eagerly sought to obtain high-resolution images of this radiation. NASA's Cosmic Background Explorer (COBE) satellite discovered the first evidence for structures, or spatial variations, in the CMB in 1991.
The BOOMERANG images are the first to bring the CMB into sharp focus. The images reveal hundreds of complex regions that are visible as tiny variations -- typically only 100-millionths of a degree Celsius (0.0001 C) -- in the temperature of the CMB. The complex patterns visible in the images confirm predictions of the patterns that would result from sound waves racing through the early universe, creating the structures that by now have evolved into giant clusters and super-clusters of galaxies.
"The structures in these images predate the first star or galaxy in the universe," said U.S. team leader Andrew Lange of the California Institute of Technology. "It is an incredible triumph of modern cosmology to have predicted their basic form so accurately."
Italian team leader Paolo deBernardis of the University of Rome La Sapienza added: "It is really exciting to be able to see some of the fundamental structures of the universe in their embryonic state. The light we have detected from them has traveled across the entire universe before reaching us, and we are perfectly able to distinguish it from the light generated in our own galaxy."
The BOOMERANG images cover about three percent of the sky. The team's analysis of the size of the structures in the CMB has produced the most precise measurements to date of the geometry of space-time, which strongly indicate that the geometry of the universe is flat, not curved. This result is in agreement with a fundamental prediction of the "inflationary" theory of the universe. This theory hypothesizes that the entire universe grew from a tiny subatomic region during a period of violent expansion that occurred a split second after the Big Bang. The enormous expansion would have stretched the geometry of space until it was flat.
NASA's National Scientific Balloon Facility was instrumental in flying the giant helium balloon that carried the instruments above the earth's atmosphere. The National Science Foundation (NSF), which provides logistic support for all U.S. scientific operations in Antarctica, facilitated the launch near McMurdo Station and recovery of the payload after the flight. The constant sunshine and prevailing winds at high altitudes in Antarctica were essential to maintaining a stable long-duration balloon flight for the BOOMERANG project. The balloon, with a volume of 800,000 cubic meters (28 million cubic feet), carried the two-ton telescope 8,000 km (5,000 miles) in 10 1/2 days and landed within 50 km (31 miles) of its launch site.
The 36 team members are from 16 universities and organizations in Canada, Italy, the United Kingdom and the United States. Primary support for the BOOMERANG project comes from NSF and NASA in the United States; the Italian Space Agency, Italian Antarctic Research Programme and the University of Rome La Sapienza in Italy; and the Particle Physics and Astronomy Research Council in the United Kingdom. The Department of Energy's National Energy Research Scientific Computing Center provided supercomputing support in the United States.
Astrophysics in Antarctica
The National Science Foundation (NSF), through the U.S. Antarctic Program (USAP), coordinates almost all U.S. scientific research in the Antarctic. NSF is an independent federal agency responsible for providing support for research in almost all fields of science and engineering.
The USAP's goals are: to understand the Antarctic and its associated ecosystems; to understand the region's effects on (and responses to) global processes such as climate; and to use Antarctica's unique features for scientific research that cannot be conducted as well elsewhere.
Among the scientific disciplines encompassed by this broad mandate are astronomy, atmospheric sciences, biology, earth science, environmental science, geology, glaciology, marine biology, oceanography and geophysics.
A variety of conditions both in Antarctica generally and more specifically at the South Pole make the continent a world-class observatory.
Long-Duration Ballooning (LDB): Since 1988 NSF and NASA have developed techniques for flying and recovering large balloon payloads -- in the range of two tons -- at altitudes of roughly 37 kilometers (120,000 feet) for extended periods of approximately two weeks. These techniques position the experiment above 99.7 percent of the atmosphere. For some experiments, this provides scientists with conditions as good as a ride on the space shuttle or even a satellite.
For two reasons, the unique geophysical conditions above Antarctica make LDB flights possible during the austral summer.
Since the balloon is illuminated continuously by sunlight, both directly and by reflection from the underlying clouds or snow, it does not undergo the large changes in temperature, and therefore altitude, that are experienced during the normal diurnal cycle in more temperate regions. There, the daily heating and cooling cycle results in the loss of helium and also ballast, severely limiting flight times, a situation that is avoided above Antarctica. Additionally, each summer for a period of a few weeks, a nearly circular pattern of gentle east-to-west winds is established in the Antarctic stratosphere. The circulation is generated by a long-lived high-pressure area caused by the constant solar heating of the stratosphere. This allows the launching and recovery of a balloon where it can be recovered relatively easily on land.
Over the past decade there have been LBD flights in most Antarctic research seasons -- roughly mid-December through mid-January, with two balloons frequently being flown during the season.
South Pole Astrophysics: Several geophysical attributes make Amundsen-Scott South Pole Station, operated by the USAP, an important and unique observatory:
- Its location at the earth's axis means that any celestial object can be observed for long periods from the same elevation in the sky. Most famously, for many years South Pole was used to make long continuous solar observations, with some runs lasting for over 100 hours.
- The station is located at an altitude of approximately 3,000 meters (10,000 feet), atop the Antarctic ice sheet. The atmosphere at the station also is extremely cold, with the result that there is very little water vapor overhead. Water vapor is the principal cause of atmospheric absorption and variability in broad portions of the electromagnetic spectrum from the near infrared to millimeter radio waves. Many telescopes have exploited this over the past decade, most notably to map submillimeter neutral carbon emission in the galaxy and to measure the anisotropy of the cosmic microwave radiation.
- The Antarctic Muon and Neutrino Array (AMANDA) takes advantage of the extremely clear ice deep below the surface at South Pole to create the world's largest particle detector. AMANDA can detect and track the path of neutrinos that interact in the ice after having passed completely through the earth. AMANDA is presently the only viable high-energy neutrino telescope with over 500 photodetectors buried between 1,400 and 2,400 meters below the surface.
Dolores Beasley, NASA
Andrew Lange, Caltech
For more information and images on BOOMERANG, see:
For background information on scientific research in Antarctica, see: