Although radio astronomy has been around since the 1930s, it has only been in recent years that astronomers have been able to create high-resolution maps of the radio sky. Sky maps are difficult for radio telescopes because radio antennas have to be focused on an extremely small patch of sky in order to capture high-resolution images. With modern antennas and computer processing, we can now scan the sky fast enough to image the sky in a reasonable time.
In the northern hemisphere, the most detailed radio sky maps were created by the Very Large Array (VLA). In the 1990s, the VLA carried out the first full sky surveys of the northern sky. After its upgrade in the 2000s, the observatory launched the VLA Sky Survey (VLASS), which has mapped nearly 10 million radio sources.
A radio view of the elliptical galaxy Centaurus A. Photo credit: CSIRO
Due to the location of the VLA, it can see about 80% of the sky, but it cannot see the southern sky very well. For this you need a radio observatory in the southern hemisphere. Fortunately, Australia now has a powerful radio telescope array that recently created a detailed radio map.
It is known as the Rapid ASKAP Continuum Survey (RACS) and was carried out by the Australian SKA Pathfinder radio telescope. In just two weeks of data collection, RACS captured images that are five times more sensitive than previous surveys and have twice the resolution. The first data release mapped a million previously undiscovered galaxies in the southern sky.
Some of the objects captured by RACS. Photo credit: CSRIO
This survey marks the first step towards a new way of looking at radio heaven. The fact that the survey was recorded in weeks rather than years means we can see changes in almost real time. Combined with optical surveys and others, we will finally have a detailed view of the astronomical events as they occur. It will help us understand transients such as rapid radio bursts and will surely reveal new phenomena that we never expected.
Reference: D. McConnell et al. "The Rapid ASKAP Continuum Survey I: Design and Initial Results." Astronomical Society of Australia publications 37 (2020): 048.