Astronomers in Australia have pieced together the largest and most detailed low-frequency radio image of the Milky Way’s galactic plane. The result is a new view of the galaxy, one that shows where stars are born, grow old, and plough through space in between. This colorized view, carefully pieced together from more than 23,000 individual images collected over more than ten years, portrays the galaxy not in starlight but in ambient radio emission. Each hue corresponds to a different frequency of elongated astrophysical phenomena otherwise obscured from human vision due to being both too faint and too large. The International Centre for Radio Astronomy Research at Curtin University, which produced the new galaxy portrait, has published a paper on the findings in Publications of the Astronomical Society of Australia.
A radio portrait of the Galactic Plane
The focal point of the project was the dense, disk-like band known as the Galactic Plane. Nearly 98,000 radio sources were plotted and enhanced within it, including the H II regions surrounding newborn stars, the planetary nebulae shed by stars comparable to our Sun as they die, the remains of exploded stars, and a diffuse haze of cool clouds and distant galaxies.
- Compared to a version released six years ago, the latest map is twice as sharp, a full ten times more discerning, and covers double the sky area. That performance leap propels astronomers deep into the Galaxy’s bustling neighborhoods, rendering objects formerly too faint or spread out too far to be positively pinpointed.
Low-frequency radio waves, typically in the tens to a few hundreds of megahertz, are downright vulnerable to non-thermal emission from high-energy electrons in magnetic fields— a signature of supernova remnants and cosmic-ray operations. By assigning low frequencies to shades of red, frequencies to shades of blue, and representing the whole using a palette of colors, the PAC team efficiently mapped the Galaxy’s spectral index, a life or death attempt that divides hot thermal gas from aged synchrotron emission.
The outcome is a high-quality visual interface of astrophysical wrongdoers: huge, transcendentally red circles usually disclose the wave of remnants driven by long-faded supernovas, while dense blue bundles signal ionized gas around star clusters. In traditional radio portraits, these domains can blend; here, their colors reveal the leading physics at a glance.
- Doctoral student Silvia Mantovanini leads the PAC study, an interdisciplinary effort combining more than 40,000 hours of observations. The PAC student, Silvia Mantovanini, spent around 1.5 years processing the data using high-energy supercomputers to validate the workflow by precisely calibrating and correcting ionospheric deviations, cautiously eliminating faint artificial artifacts, and seamlessly combining thousands of different observations of an individual pointing into a systematically stable, scientifically reliable, unified whole.
That computational lift paid off by boosting the map’s dynamic range—its ability to register both bright, complex regions and the dimmest filaments without washing out either—and by delivering consistent spectral information across the entire field. The observations come from the Murchison Widefield Array, a low-frequency radio telescope array in remote Western Australia. Its location in a federally protected radio-quiet zone keeps human-made interference to a minimum, a crucial advantage when chasing faint signals. Observing from the Southern Hemisphere also gives an unobstructed view of the Galactic Center, the most crowded and dynamic region of the Milky Way. The MWA’s wide field of view and dense sampling of low frequencies make it ideal for mapping the Galaxy’s diffuse emission and for measuring how radio brightness changes with frequency—measurements that underpin the image’s color scheme and the science it unlocks.
This dataset opens doors across stellar astrophysics. Pulsars—fast-spinning neutron stars—emit beams that sweep past Earth like celestial lighthouses. By tracking their brightness across frequencies, astronomers can probe the plasma along the line of sight, refine distance estimates, and test models of how pulsars generate their radio emission.
The map also advances the long-running effort to complete the Milky Way’s supernova remnant census. Low frequencies are particularly sensitive to old, faded remnants whose high-energy glow has ebbed. Identifying these relics helps reconstruct the Galaxy’s recent star-formation and explosion history, calibrate cosmic-ray production, and trace the structure of magnetic fields on large scales.
Crucially, the radio view complements surveying the optical and infrared from missions like Gaia and ground-based observatories. The researchers’ cross-matching of catalogs allows them to connect radio-emitting gas to different stellar populations. Hence, it unveils how feedback from massive stars sculpts the interstellar medium.
These demonstrated techniques are just a glimpse of what is arriving soon with the Square Kilometre Array, now under construction, with a low-frequency component in Western Australia. During the upcoming years, SKA-Low will provide even finer detail and deeper sensitivity. However, it will also depend on the calibration and processing and spectral mapping led by source research. Thus, the new image is currently a benchmark in radio astronomy: a sweeping atlas of our Galaxy full of data. Therefore, it encourages astronomers worldwide to use it for discovery and invites us all to admire the Milky Way as we have never seen before.
