MeerKAT image reveals heart of the Milky Way
The South African Radio Astronomy Observatory (SARAO) today released a new MeerKAT telescope image of the centre of our galaxy, showing radio emission from the region with unprecedented clarity and depth.
In a statement, SARAO says the international team behind the work is publishing the initial science highlights from this image in The Astrophysical Journal.
The article is accompanied by a public release of the data to the worldwide astronomical community for their further scientific exploration.
The organisation says the image captures radio emission from numerous phenomena, including outbursting stars, stellar nurseries, and the chaotic region around the four million solar mass supermassive black hole that lurks in the centre of our galaxy – 25 000 light-years from Earth.
Radio waves penetrate the intervening dust that obscures the view of this region at other wavelengths.
According to SARAO, MeerKAT’s innovative design, sensitivity and geographical vantage point have been the keys to producing the remarkable image, which reveals new supernova remnants – the expanding shells of material left behind when massive stars end their lives explosively – including a rare almost-perfect spherical example. It also provides astronomers with the best insight yet into the population of mysterious ‘radio filaments’ found nowhere else.
MeerKAT, originally the Karoo Array Telescope, is a radio telescope inaugurated in 2018 consisting of 64 antennas spread over a diameter of 8km in the Northern Cape.
SARAO notes that MeerKAT is the most sensitive telescope of its kind in the world and is a precursor to the Square Kilometre Array radio telescope, to be built in SA and Australia within the coming decade.
“I’ve spent a lot of time looking at this image in the process of working on it, and I never get tired of it,” says Dr Ian Heywood from the University of Oxford, Rhodes University and SARAO, and lead author of the study.
“When I show this image to people who might be new to radio astronomy, or otherwise unfamiliar with it, I always try to emphasise that radio imaging hasn’t always been this way, and what a leap forward MeerKAT really is in terms of its capabilities. It’s been a true privilege to work over the years with colleagues from SARAO who built this fantastic telescope.”
SARAO notes this work represents the culmination of three years of detailed analysis of a survey conducted during the telescope’s commissioning phase.
It explains those observations had already led to the iconic inaugural MeerKAT image in 2018, as well as the discovery of a pair of giant radio bubbles, evidence of an explosive outburst from the heart of our galaxy several million years ago.
Now, at last, the image is available in its full complexity for detailed study by astronomers worldwide, it notes.
The new image is based on a mosaic of 20 separate observations using 200 hours of telescope time covering an area of six square degrees (30 times the area of the full Moon).
The data were consistently processed to deliver an angular resolution of four seconds of arc – the angle subtended by a tall person at a distance of 100km, or by the width of a fine human hair held at arm’s length – resulting in a 100 megapixel scientific image.
Processing of the 70 terabytes of raw data was shared between two supercomputers in Cape Town: the Centre for High Performance Computing’s Lengau and IDIA’s ilifu.
Data processing and imaging were assisted by Rhodes / SARAO PhD student Isabella Rammala, who is investigating the compact radio sources in the image.
SARAO says the highly-linear features pervading the image are radio-emitting magnetised threads. Up to 100 light-years long, these unique structures have defied a conclusive explanation for their origin since discovery over 35 years ago.
Uncovering more mysteries
MeerKAT has discovered many more such filaments than were previously known, and the new data release will allow astronomers to study these objects as a population for the first time.
The first inroad into such work is presented in a companion paper in The Astrophysical Journal Letters.
Of late, the MeeKAT has made several ground-breaking discoveries. In December last year, an international team of astronomers utilised the radio telescope to discover a mysterious chain of hydrogen gas clouds the size of a massive galaxy.
The previous month, the radio telescope revealed new, previously unseen cosmic puzzles.
In June, the telescope produced a striking image showing a combination of cosmic features never before seen, revealing unexpected details of the inner workings of enormous radio galaxies.
In April 2020, an international team of astronomers uncovered unusual features in the radio galaxy ESO 137-006 using MeerKAT data.