An international team of astronomers has published a new map of the sky with more than 25,000 supermassive black holes. The map is the most detailed map of the sky in the low radio frequency range. It was built by astronomers with 52 stations with LOFAR antennas in nine European countries.
One look at the picture above, which is a small snapshot of the sky survey map, and all the little dots look like stars. Scientists determine that the dots are all supermassive black holes, with each black hole in a different, distant galaxy. Radio emissions picked up by antennas scattered across Europe are emitted by matter emitted as it approaches the black hole. Researchers on the study say the map resulted from years of hard work with « incredibly difficult data. »
The team had to invent methods to convert radio signals into images of the sky. To create the sky map, the scientists had to combine 256 hours of observations of the northern sky. Supercomputers running new algorithms to correct for the effects of the ionosphere had to do their job every four seconds. Despite the large number of supermassive black holes in this image, the map covers only four percent of the northern half of the sky.
The astronomers on the research team say they will continue mapping the sky until the entire northern sky is complete. Researchers say the map provides glimpses of large-scale structures in the universe, along with other information.
The researchers didn’t say how long it might take to complete the entire sky map. One of the biggest challenges in creating the map was that observations at longer radio wavelengths are difficult due to Earth’s ionosphere. The team describes the ionosphere as a cloudy lens that constantly moves across the radio telescope.