The Square Kilometre Array (SKA) remains under construction with completion still a few years away. However, engineers recently provided an exciting preview having installed 1,024 of the planned 131,072 antennas and capturing a test image of the sky. The image covers about 25 square degrees and reveals 85 of the brightest known galaxies in the region. Once fully operational, the complete array is expected to detect more than 600,000 galaxies within this same area!
SKA is one of the most ambitious radio astronomy projects. It’s a radio interferometer that crosses two continents with sites in South Africa and Australia and a headquarters at Jodrell Bank in the UK. Once completed, it will consist of thousands of dishes and up to a million antennas working as a single instrument. It will provide unprecedented sensitivity and address fundamental questions about dark energy, early galaxy formation, and cosmic magnetic fields.
Artist's impression of the 5km diameter central core of Square Kilometre Array (SKA) antennas (Credit : SPDO/TDP/DRAO/Swinburne Astronomy Productions)
The technique involves combining signals from multiple receivers to achieve higher resolution than a single instrument could provide. By analyzing interference patterns from the different receivers the result is a virtual telescope with an apertures as large as the distance between the receivers. Due to the greater wavelength of radio waves, antenna are spread across continents yet function as a single instrument, resolving details billions of times smaller than individual telescopes could detect.
The image that has been revealed from the unfinished SKA-Low telescope offers a tantalising glimpse of the scientific discoveries to come from what will be the world's most powerful radio observatory. Using just 1,024 of the planned 131,072 antennas (less than one percent of the final telescope), this preliminary image was collected from the first four connected stations installed over the past year at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory on Wajarri Yamaji Country in Australia. The SKA-Low is one of two telescopes being built by the SKA Observatory, which is co-hosted in Australia and South Africa.
“The quality of this image was even beyond what we hoped for using such an early version of the telescope” Dr George Heald (SKA-Low Lead Commissioning Scientist.
The image from the partially built SKA-Low telescope shows bright dots that are distant galaxies, not stars! Each of the radio-bright galaxies are billions of light years away and contains a supermassive black hole. The hot, fast-moving gas around these black holes emits radio waves that SKA-Low can detect having travelled across the Universe. The central galaxy in the image is especially rare, featuring jets of matter visible in both radio and optical light.
Alcyoneus, a giant radio galaxy with lobed structures spanning 5 mega parsecs (Credit : Martijn Oei)
The antennas used for this image are less than 1% of the fully completed telescope and covers an area just under 6 km, yet they found 85 galaxies in an area equal to 100 full moons during a 7-hour observation. By 2026/2027 a further 16,000 more antennas will be added making SKA-Low the most sensitive radio telescope of its kind, capable of detecting over 4,500 galaxies in the same area. By 2028/2029, with 78,000 antennas, it will detect more than 23,000 galaxies there. The completed telescope will have over 130,000 antennas spread across 74 km, and from 2030, deep surveys of this area could reveal up to 600,000 galaxies.
Source : ‘Beyond what we'd hoped': SKA-Low's first glimpse of the Universe