The universe at different wavelengths
By comparing the temperature-anisotropy pattern of the cosmic microwave background, measured by the WMAP satellite (top), with the intensity variations in the hard X-ray background, obtained via the HEAO-1 mission (bottom), Stephen Boughn and Robert Crittenden have identified evidence for the integrated Sachs-Wolfe effect (ISW). Three other groups have also found preliminary signals of the ISW effect in comparisons of WMAP data with optical and radio maps that trace the distribution of matter.