Unprecedented images of the Milky Way’s center revealed by astrophysicists


CAPE TOWN, South Africa — It’s the Milky Way like you’ve never seen it before. An international team of researchers has produced a new radio image of the center of our galaxy using the South African MeerKAT telescope, the most powerful of its kind in the world.

The image is of unprecedented depth and clarity. It captures radio emission from numerous phenomena, including outbursting stars and  stellar nurseries. It gives a stunning view of the chaotic region around the 4 million solar mass supermassive black hole that lurks in the center of our galaxy, 25,000 light-years from Earth.

Led by Dr. Ian Heywood from the University of Oxford’s Department of Physics, the findings have been accepted for publication in The Astrophysical Journal.

Supernova remnant SNR G359.1-0.5
In the center of the image is the supernova remnant SNR G359.1-0.5. To the left is the Mouse, a runaway pulsar formed and ejected by the supernova event. In the upper right is one of the longest and most famous radio filaments known as the Snake.( CREDIT: I. Heywood, SARAO, Rhodes/ SWNS)

Radio waves pass unhindered through the large quantities of dust that obscure the view of the Galactic center at other wavelengths. This allows scientists to see the energetic processes associated with star formation, outbursts from the central supermassive black hole, and the interplay of charged particles moving at close to the speed of light with the complex magnetic fields woven through the region.

The quality of the image is such that the team of researchers have discovered new candidate supernova remnants — the expanding shells of material left behind when massive stars end their lives – including a rare, almost-perfect spherical example.

The new image also significantly increases the known examples of the mysterious radio filaments that are only seen at the Galactic center. These are highly-linear, magnetized threads of radio emission, the exact origin of which has remained a mystery since their discovery over 35 years ago.

Supernova remnants
The lower two of these shell-like features are supernova remnants, with SNR G1.0-0.1 on the left and SNR G0.9+0.1 on the right. The uppermost shell is the Sagittarius D HII region, a site of recent star formation. SNR G0.9+0.1 has a pulsar wind nebula at its center, showing a tangled complex of radio emission. Polar outflows from this nebula appear to be distorting the shell of the supernova, particularly towards the north. (CREDIT: I. Heywood, SARAO, Rhodes/SWNS)

These new observations will allow these objects to be studied as a population for the first time. The first inroads into such a study are presented in a companion paper, accepted for publication in The Astrophysical Journal Letters.

The MeerKAT telescope’s design, sensitivity, and geographical vantage point have been the keys to producing these unprecedented images. MeerKAT is a radio interferometer, located in the arid Karoo region of South Africa’s Northern Cape province. It is the precursor instrument for the dish-component of the forthcoming 2-billion Euro Square Kilometer Array project.

The University of Oxford plays a key role with MeerKAT. Two of the telescope’s flagship Large Survey Projects are being co-led by Oxford astrophysics. Their expertise on the technical and data-processing aspects of radio interferometry means Oxford also played a leading part in the commissioning and early scientific verification of the telescope. It was that involvement that led to the production of this work.

Emission from the Galactic centre radio bubble
The complex, cirrus-like emission from the Galactic center radio bubble dominates this image. This is traversed by the Radio Arc, a complex of many parallel radio filaments. The radio bubble nestles against the diffuse Sagittarius A region in the lower center of the image. The bright dot at the center of this region is Sagittarius A*, a 4 million solar mass supermassive black hole. This image captures the chaotic complexity of the very heart of our Galaxy. (CREDIT: I. Heywood, SARAO, Rhodes)

“It has been a true privilege to work for many years with our South African colleagues who built this remarkable telescope,” Heywood tells South West News Service in a statement. “When I show these images to people who might be new to radio astronomy, or otherwise unfamiliar with it, I always try to impress upon them that it really hasn’t always been this way. MeerKAT is really demonstrating the ‘discovery machine’ potential that we astronomers always hope a new telescope will have. Just point it at the sky and you will soon find a new puzzle that has the community scratching their heads. While we will use these new observations to address some long-standing mysteries about the Galactic center, I’m sure the image will also generate some mysteries of its own.”

Professor Rob Fender, head of astrophysics at Oxford, tells SWNS that the telescope could help solve many mysteries that astronomers have long studied. “MeerKAT is a truly remarkable radio telescope which is paving the way towards the first phase of the Square Kilometre Array, in which Oxford proudly plays a major role,” he says. “These observations demonstrate both the power of cutting-edge observational technology and how much still remains to be understood about the Universe.”

Spherical supernova remnant
A rare, almost-perfect spherical supernova remnant that has been discovered at the edge of the MeerKAT mosaic. Numerous compact radio sources are also visible, many of which signpost supermassive black holes at the centers of galaxies far beyond our own. There is also an intriguing tailed radio source visible on the right of the image, which could be an object in our galaxy moving at high speed, leaving a trailing wake. CREDIT: I. Heywood, SARAO.)

So what’s next for Heywood and his team?

“There is much more that can be done through further processing of the data. The next step is to produce images that measure the polarization of the radio light as well as its brightness, which will allow us to map out the complex magnetic field that exists in the Galactic center region, and investigate its relationship with the central supermassive black hole, the population of radio filaments, and the radio bubbles,” he says. “This image is just the beginning!”

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