A team of astronomers from the International Centre of Radio Astronomy Research (ICRAR) in Australia has produced a remarkable new radio color image of the Milky Way galaxy. This innovative image, created by assigning different radio frequencies to RGB colors, unveils large-scale astrophysical phenomena and serves as a valuable resource for scientists studying star lifecycles.
Constructed over more than 40,000 hours, this low-frequency radio image of the Milky Way stands as the largest radio color image ever produced, highlighting extensive astrophysical structures. It is especially effective in identifying remnants of supernovae. Image credit goes to Silvia Mantovanini and the GLEAM-X Team.
The universe is akin to a photographer”s backdrop, illuminated by various types of electromagnetic radiation. While gamma radiation is the most intense and can cause significant damage to biological structures, radio waves, which exist at the lower end of the spectrum, are generally harmless and omnipresent. Although much of the radio frequency exposure on Earth stems from human technologies such as AM/FM radios and WiFi, natural sources also contribute significantly. The cosmos emits radio waves from phenomena including quasars, active galactic nuclei, supernova remnants, and even planets like Jupiter, which radiates more radio waves than our Sun.
Observing radio waves presents several advantages to astronomers. Due to their long wavelengths, radio waves can penetrate dust and gas clouds that obscure other forms of radiation. They can be detected in any weather condition and at any time of day or night. Their unique properties allow astronomers to visualize different physical processes and create high-resolution images using interferometers. This capability is particularly beneficial for imaging young stars and the planets forming around them, which are often hidden from view by thick dust.
The Australian research team utilized radio telescopes to execute a comprehensive survey of the Milky Way, which took over 18 months and required extensive supercomputer resources to compile observations into a single massive image of the galaxy. The radio wavelengths were mapped to an RGB scheme to make the data interpretable for human eyes. This project, known as the GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended III: Galactic plane, is detailed in the Publications of the Astronomical Society of Australia. Silvia Mantovanini, a PhD student at Curtin University, serves as the lead author.
“This low-frequency image allows us to unveil large astrophysical structures in our Galaxy that are difficult to image at higher frequencies,” explained Natasha Hurley-Walker, the principal investigator for GLEAM-X.
This new image builds upon a previous one released in 2019. While that earlier image was part of the original GLEAM survey, the new version is derived from the GLEAM-X project. The former focused on extragalactic features, whereas the new image emphasizes the Milky Way, boasting double the resolution, covering twice as much sky, and being ten times more sensitive. This comprehensive view of the Milky Way will significantly contribute to ongoing research in various fields.
“This vibrant image delivers an unparalleled perspective of our Galaxy at low radio frequencies,” said Mantovanini. “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.”
The image allows astronomers to differentiate between supernova remnants (SNR), which appear as large red circles, and stellar nurseries, visible as smaller blue circles. Mantovanini has a particular interest in SNR, and this new image will enhance efforts to identify and study more of these structures. Hundreds have already been detected, but many others likely remain hidden, as they can often resemble other celestial features.
In their research, the authors anticipate discovering an additional 2,000 SNR along the galactic plane. “We are confident this data release will help find more faint and old elements of the SNR population, helping to fill the current gap,” the authors stated.
A notable feature of the new image is its ability to distinguish young stars from SNR, both of which are surrounded by gas. “You can clearly identify remnants of exploded stars, represented by large red circles. The smaller blue regions indicate stellar nurseries where new stars are actively forming,” Mantovanini stated.
The image highlights HII regions, areas of ionized hydrogen generated by the ultraviolet radiation from young stars. These regions become optically thick at low radio frequencies and stand out against the background. The boxes illustrate three known objects, with their appearances at infrared wavelengths displayed in smaller panels.
The distinct colors in the image will be crucial for determining the origins of emissions, particularly in identifying SNR, as these thermal sources can often lead to confusion.
Studying our home galaxy presents unique challenges compared to observing other galaxies. Astronomers often encounter difficulties peering into the galactic center due to extreme concentrations of dust and stars, which can obscure views.
Associate Professor Natasha Hurley-Walker, who leads the GLEAM-X survey, expressed optimism about the new image”s contribution to understanding the Milky Way”s structure. “This low-frequency image allows us to unveil large astrophysical structures in our Galaxy that are difficult to image at higher frequencies. No low-frequency radio image of the entire Southern Galactic Plane has been published before, making this an exciting milestone in astronomy.”
This groundbreaking image is not expected to hold the title of the most sensitive and detailed for long. A global collaboration is underway to develop the SKA Observatory”s SKA-Low telescope, which aims to provide the highest-resolution images in the field of astronomy. “Only the world”s largest radio telescope will have the capacity to surpass this image in terms of sensitivity and resolution,” noted Associate Professor Hurley-Walker.
For those interested in the full details of this groundbreaking research, the complete article can be found in the Publications of the Astronomical Society of Australia.
