April 27, 2000 -- 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 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 120,000 feet (37 kilometers) for 10 1/2 days. The results will be published in the April 27 issue of Nature.

Above: The Cosmic Microwave Background (CMB) sky over Mt. Erebus in Antarctica. In this fanciful picture, the CMB sky looms behind the prelaunch preparations of BOOMERANG. The BOOMERANG images of the early universe have been overlaid onto the sky to indicate what size that the fluctuations would appear if a standard 35mm camera were sensitive to microwave light. The color map of the CMB images has been changed here to aesthetically match the rest of the
picture. The CMB images and the prelaunch picture are available separately. [more images]

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Today, the universe is filled with galaxies and clusters of galaxies. But 12 to 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 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 tried to obtain high-resolution images of this radiation. NASA's Cosmic Background Explorer satellite discovered the first evidence for structures, or spatial variations, in the microwave background in 1991.

The BOOMERANG images are the first to bring the cosmic microwave background into sharp focus. The images reveal hundreds of complex regions 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.

Above: An image of the primordial universe captured by the BOOMERANG telescope over a 10 day period from December 1998 - January, 1999. Enormous structures in the early universe which are invisible to the unaided eye become apparent when observed using a telescope sensitive to mm-wave light. This is a slice of a larger image, which covers approximately 1800 square degrees of the southern sky. For scale, the apparent size of the moon is indicated on the bottom right of the page. [more images]

"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, Pasadena. "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 3 percent of the sky. The team's analysis of the size of the structures in the cosmic microwave background 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 occurring a split second after the Big Bang. The enormous expansion would have stretched the geometry of space until it was flat.

Above: By observing the characteristic size of hot and cold spots in the BOOMERANG images, the geometry of space can be determined. Cosmological simulations predict that if our universe has a flat geometry, (in which standard high school geometry applies), then the BOOMERANG images will be dominated by hot and cold spots of around 1 degree in size (bottom center). If, on the other hand, the geometry of space is curved, then the bending of light by this curvature of space will distort the images. If the universe is closed, so that parallel lines converge, then the images will be magnified by this curvature, and structures will appear larger than 1 degree on the sky (bottom left). Conversely, if the universe is open, and parallel lines diverge then structures in the images will appear smaller (bottom right). Comparison with the BOOMERANG image (top) indicates that space is very nearly 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 28 million cubic feet (800,000 cubic meters), carried the two-ton telescope 5,000 miles (8,000 km) and landed within 31 miles (50 km) 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.

Right: The BOOMERANG Telescope being readied for launch. With Mt. Erebus as a backdrop, NASA/NSBF personnel inflate the 1 million m³ (28 million cubic foot) balloon which will carry the BOOMERANG telescope on its 10 day trip around the Antarctic continent. In order to make its exquisitely sensitive measurements, BOOMERANG is lifted above 99% of the atmosphere to an altitude of 35km (120,000 ft.). The continuous sunlight and stable air currents over Antarctica enable 10 to 20 day long stratospheric balloon flights. This launch was preceded by two months of assembly at McMurdo research station, and half a decade of development and construction by a international team of researchers. [more images]Web Links

BOOMERANG home page -from the University of California at Santa Barbara

BOOMERANG Press Page - lots of pretty pictures and well-written information about the the CMB images

NASA's Scientific Balloon Program - at the NASA Wallops Flight Facility

COBE Educational Resources - Students, educators and others interested in NASA's Cosmic Background Explorer (COBE) mission or cosmology can find information here.

Topics:

• Origins of Universe
• Universe