The Sharpest CMB Pictures Yet

The sharpest pictures yet of the cosmic microwave background, with a resolution of as good as 6 minutes of arc, allow one to resolve blobs of matter with masses of about 5-80 x 10¹⁴ solar masses, which corresponds to the mass of galaxy clusters. In other words, the new map of cosmic microwave background (CMB) reveals, for the first time, the primordial knots of matter from which grew the largest luminous celestial objects visible today.

Just as the sun's glowing disk is the "surface of last scattering" for photons emerging from the solar interior, so the CMB is the surface of last scattering for photons emerging from the hot plasma about to condense into the first neutral atoms at a moment some 300,000 years after the big bang.

The instrument used to make the new CMB measurement, the Cosmic Background Imager (CBI), camps at an elevation of 16,700 feet on a high and dry plateau in Chile. CBI is an array of 13 antennas which can be steered together to look at selected regions overhead. A total of 40 square degrees of sky was surveyed.

As with previous CMB studies (Update 537) the CBI results can be cast into the form of a plot of minute temperature differences versus the angular sample size. This "power spectrum" features the peaks previously seen and offers hints of further peaks. Various cosmological parameters, such as matter density (omega, the ratio of the observed density to the critical density for closing the universe, was measured to be 0.99) were found to be consistent with the inflationary standard model. (Press release and preprints available at Cosmic Background Imager website.)