Staring at a small patch of sky for more than 50 hours with the ultra-sensitive Karl G. Jansky Very Large Array (VLA), astronomers have for the first time identified discrete sources that account for nearly all the radio waves coming from distant galaxies. They found that about 63 percent of the background radio emission comes from galaxies with gorging black holes at their cores and the remaining 37 percent comes from galaxies that are rapidly forming stars. About 2,000 discrete objects are identified in this VLA image of the distant Universe. This entire image constitutes only about one-millionth of the entire sky.
Credit: B. Saxton from data provided by Condon, et al., NRAO/AUI/NSF