An international team of cosmologists has discovered the presence of acoustic “notes” in the sound waves that rippled through the universe after the Big Bang.
The new result – from a detailed analysis of high-resolution images obtained by the BOOMERANG (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics) experiment – provides the most precise measurement to date of several of the parameters which cosmologists use to describe the universe and supports the theory of inflation which proposes that the universe observable today comes from a tiny subatomic region of space that expanded dramatically an instant after the big bang.
BOOMERANG is an extremely sensitive microwave 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 10.5 days collecting signals from the primordial universe in the form of the faint Cosmic Microwave Background (CMB).
The images made by BOOMERANG and a first analysis of the data were published just one year ago in the journal, Nature. This result attracted a lot of attention because the measurements of the sizes of the largest structures in the maps provided convincing evidence that the overall geometry of the universe is ‘flat’. A more detailed analysis of these maps has now shown the presence of smaller structures or “acoustic peaks” in the maps whose properties imply precise values for the overall density and composition of the universe. These results were presented today at the American Physical Society Spring Meeting in Washington, DC.
“These results are a tremendous confirmation of the inflationary model and also agree extremely well with measurements by other astronomers using completely different methods. It looks like now have a “Standard Model of Cosmology,” said Dr Phil Mauskopf from Cardiff University, the BOOMERANG UK team leader.
Cosmologists believe that the universe was created approximately 12-15 billion years ago in an enormous explosion called the Big Bang. The intense heat that filled the embryonic universe is still detectable today as a faint glow of microwave radiation known as the cosmic microwave background (CMB) which is visible in all directions. Whatever structures were present in the very early universe would leave their fingerprints as a very faint pattern of brightness variations in the CMB. By measuring these fingerprints, cosmologists can solve the mystery of the formation of structures in the universe, exploring the origin of all galaxies and stars and, of course of cosmologists.
The CMB was first discovered by a ground-based radio telescope in 1965. Within a few years, Russian and American theorists had independently predicted that the size and amplitude of structures that formed in the early universe would form what mathematicians call a “harmonic series” of structure imprinted on the CMB. In 1991, NASA’s Cosmic Background Explorer satellite (COBE) discovered the first evidence for structure of any sort in the CMB.
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 – in the temperature of the CMB. The new results show the first evidence for a harmonic series of angular scales on which structure is most pronounced.
“The early Universe is full of sound waves compressing and rarefying matter and light, much like sound waves compress and rarefy air inside a flute or trumpet,” said Italian Team leader Paolo deBernardis. “For the first time the new data show clearly the harmonics of these waves.”
Last April, the BOOMERANG team had analyzed only enough data to see just one harmonic peak, said US team leader, Andrew Lange, of the California Institute of Technology: “Using a music analogy, we could tell what note we were seeing – if it was C sharp or F flat. Now, we see not just one, but three of these peaks and can tell not only which note, but also what instrument.”
The presence of these harmonic peaks bolsters the theory that the universe grew from a tiny subatomic region during a period of violent expansion a split second after the Big Bang. “These results show the universe to be made up of energy that has never been measured on earth and support the cosmological theory of inflation that is unexplainable by standard theories of gravity. This is a roadmap for the particle physicists with no way of knowing where it will lead” said Dr. Alessandro Melchiorri of Oxford, one of the team members working on the interpretation of the results.
The images obtained cover about 3 percent of the sky. The BOOMERANG team plans another campaign to the Antarctic in the near future, this time to map even fainter images encoded in the polarisation of the CMB. The scientific payoff of such measurements “promises to be enormous” said Professor Peter Ade, of Cardiff University. “By imaging the polarisation, we may be able to look right back to the inflationary epoch itself – right back to the very beginning of time.”
The 36 team members come from 16 universities and organizations in Canada, Italy, the United Kingdom and the United States. Primary support for the BOOMERANG project comes from NASA and from the National Science Foundation in the United States, the Italian Space Agency, Italian Antarctic Research Programme, and the University of Rome “La Sapienza in Italy; and from the Particle Physics and Astronomy Research Council in the United Kingdom.
For more information and images on BOOMERANG, see:
http://www.physics.ucsb.edu/’boomerang/ or http://oberon.roma1.infn.it/boomerang
Notes for Editors
Further information
Saturday 28 April
Dr Phil Mauskoph (in Italy) on Tel: 00 39 06 4991 4271, mobile: 00 39 348 700 3700
Sunday PM 29 April and Monday AM 1 May
Dr Phil Mauskoph and Professor Peter Ade on Tel: +44 (0)207 882 5032
Monday PM 1 May
Dr Phil Mauskoph and Professor Peter Ade on Tel: +44 (0)29 2087 6170
Contact: Dr Phil Mauskopf
Cardiff University
+44 (0)29 876170
Philip.Mauskopf@astro.cf.ac.uk
