Each dot is this image is a distant galaxy. The brightest are galaxies powered by supermassive black holes and shine bright in radio light, but it’s the numerous faint dots that make it special, according to an international team of astronomers.
These are distant galaxies like our own that have never been observed in radio light before.
The image was created thanks to the South African Radio Astronomy Observatory (SARAO) MeerKAT telescope, which recently made the first radio observation sensitive enough to reveal these galaxies.
“To make this image, we selected an area in the Southern Sky that contains no strong radio sources whose glare could blind a sensitive observation,” says SARAO’s Tom Mauch, lead author of a paper in The Astrophysical Journal.
He and colleagues used the 64 MeerKAT dishes to observe this area for 130 hours. The resulting image shows a region of the sky that is comparable in area to five full Moons, containing tens of thousands of galaxies.
“Because radio waves travel at the speed of light, this image is a time machine that samples star formation in these distant galaxies over billions of years,” says co-author James Condon, from the National Radio Astronomy Observatory in the US.
Because only short-lived stars that are less than 30 million years old send out radio waves, we know that the image is not contaminated by old stars.
“The radio light we see from each galaxy is therefore proportional to its star-forming rate at that moment in time.”
The paper is available on the pre-print server arXiv.