Get ready to see our galaxy like never before.
Astronomers from the International Centre of Radio Astronomy Research (ICRAR) have released an incredible image of the Milky Way shining in low-frequency radio light, revealing a spectacular realm invisible to the human eye — and indeed most telescopes.
Made by meticulously stitching together thousands of observations over eighteen months, the epic mosaic shows a galaxy awash with the circular blotches of supernova remnants, the leftovers of a catastrophic explosion that destroys a star.
“This vibrant image delivers an unparalleled perspective of our galaxy at low radio frequencies,” Silvia Mantovanini, an ICRAR researcher at Curtin University who led the effort and is lead author of an accompanying paper in Publications of the Astronomical Society of Australia, said in a statement.
“It provides valuable insights into the evolution of stars, including their formation in various regions of the galaxy, how they interact with other celestial objects, and ultimately their demise,” she added.
The map is made from two surveys taken with the Murchison Widefield Array, a massive radio telescope in Australia comprising over 4,000 antennas spread across nearly three square miles. The first survey completed in 2015 called GLEAM imaged the entire southern night sky, and a follow-up survey, GLEAM-X, performed it again with a higher sensitivity three years later.
To combine the thousands of observations, the team used a technique called image domain gridding to correct for the differences caused by the time between which the two surveys were taken.
“It was important to correct for the ionosphere distortions — shifts in radio waves caused by irregularities in Earth’s upper atmosphere,” Mantovanini and her colleague Natasha Hurley-Walker, a radio astronomer at Curtin, explained in a writeup for The Conversation. “Otherwise, these distortions would shift the position of the sources between observations.”
The final image covers a staggering 95 percent of the Milky Way visible from the southern hemisphere, in radio frequencies between 72 MHz to 231 MHz, they said.
In addition to its epic scope is its well-defined spectrum of colors, which helps astronomers distinguish the cosmic structures behind the radio light. Emissions from a supernova remnant shine in orange, while star forming regions called stellar nurseries glow in blue. In a normal image without the colors, Mantovanini explained in a video release, you wouldn’t be able to tell them apart because they have exactly the same shape.
The map is perhaps the most impressive and comprehensive example of what astronomers are calling a “low-surface brightness universe” of objects that are being revealed by the latest advanced radio telescopes. Some of these objects include impossibly circular supernova remnants, and a class of exotic structures called odd radio circles, or ORCs, that are the size of entire galaxies and whose origins remain a complete mystery.
Newer radio telescopes are expected to uncover even more hidden layers of the cosmos.
“Only the world’s largest radio telescope, the SKA Observatory’s SKA-Low telescope, set to be completed in the next decade on Wajarri Yamaji Country in Western Australia, will have the capacity to surpass this image in terms of sensitivity and resolution,” Hurley-Walker said in the statement.