NEWS: Biggest Galaxy Gang from Young Universe Seen
The VLA consists of 27 individual radio telescopes, each 82 feet in diameters. Together, the radio telescopes work as one giant instrument called an interferometer, which can produce high resolution maps that pin-point tiny details.
Using the VLA, astronomers focused on a patch of sky in the constellation Draco was for 57 hours. The result is the image above in which each individual dot - of 2,000 discrete sources - is likely a galaxy. Extrapolated over the entire sky, that means there would be 2 billion such objects. Previous, shallower surveys conducted using with the VLA showed the distribution of such radio galaxies to be uniform across the sky. This is largely because the era of bright radio sources is in the universe's distant past.
Counting radio sources is not new, as the paper by Jim Condon and his colleagues states, as the first counts of "radio stars" in the 1950s showed that these objects were not stars, after all, but sources far beyond our own galaxy and further away than any optical telescopes at the time could see. But the early surveys were plagued by "confusion," a term that in this case means the misidentification of "bumps" in sky maps due to background noise as actual sources of radio emission. The confusion limit of an interferometer must be well understood in order to make accurate maps of the sky and counts of radio galaxies. With the new, more powerful VLA and a team of scientists that are some of the black-belts of radio interferometry, they were able to accurately count 96 percent of the radio background.