Thousands of New Radio Signals Have Been Detected From Nearby Cosmic Sources


A powerful radio telescope staring at a satellite galaxy of the Milky Way has detected thousands of hitherto unknown radio sources.

In the direction of the Large Magellanic Cloud, thousands of nearby stars, supernovae, and distant galaxies have been detected in radio wavelengths for the first time, data that could yield new information about the inner workings and evolution of these fascinating objects.

It's all part of the Evolutionary Map of the Universe (EMU) Early Science Project being conducted using the Australian Square Kilometer Array Pathfinder (ASKAP) facility in Australia, one of the most sensitive radio telescopes in operation. It's peering into the radio Universe to obtain more details about how it evolved over time.

"The sharp and sensitive new image reveals thousands of radio sources we've never seen before," explained astronomer Clara Pennock of Keele University in the UK.

"Most of these are actually galaxies millions or even billions of light years beyond the Large Magellanic Cloud. We typically see them because of the supermassive black holes in their centers which can be detected at all wavelengths, especially radio. But we now also start finding many galaxies in which stars are forming at a tremendous rate.

"Combining this data with previous observations from X-ray, optical and infrared telescopes will allow us to explore these galaxies in extraordinary detail."

The Large Magellanic Cloud is a dwarf spiral galaxy that orbits the Milky Way at a distance of around 160,000 light-years. Eventually, in about 2.4 billion years, it will be absorbed by the Milky Way, but for the time being, its proximity makes it an excellent object for learning about the structure of galaxies, and the life cycle of stars.

The research team turned ASKAP's antennas to this galaxy to obtain observations not just of the entire structure, but individual objects within it: stars, supernovae and stellar nurseries, such as the lush Tarantula Nebula, the most active starburst region in the Local Group of galaxies, forming stars at an unusually high rate.

The detections made by the team ranged from baby stars to dead stars - the leftover expanding bubbles of material after a star has gone supernova.

"With so many stars and nebulae packed together, the increased sharpness of the image has been instrumental in discovering radio emitting stars and compact nebulae in the Large Magellanic Cloud," said astrophysicist Jacco van Loon, also from Keele University.

"We see all sorts of radio sources, from individual fledgling stars to planetary nebulae that result from the death of stars like the Sun."

The observations taken represent a significant improvement on previous radio surveys of the Large Magellanic Cloud, the researchers said, allowing for the detection of over 50,000 radio sources. Using combined data, as well as the new ASKAP observations, astronomers will be able to take a closer look at these sources to find out more about them.

For example, the planetary nebulae and supernova remnants will be the subject of future in-depth analyses.

The radio data obtained on the distant galaxies behind the Large Magellanic Cloud can be used to conduct large-scale measurements of their Faraday rotation - the way the radio waves twist when they travel through the intergalactic medium - and neutral atomic hydrogen, which can be mapped to figure out the structure of galaxies.

"It's gratifying to see these exciting results coming from the early EMU observations," said astronomer Andrew Hopkins of Macquarie University in Australia.

"The discoveries from this early work demonstrate the power of the ASKAP telescope to deliver sensitive images over wide areas of sky, offering a tantalizing glimpse of what the full EMU survey may reveal. This investigation has been critical in allowing us to design the main survey, which we expect will start in early 2022."

The research has been published in the Monthly Notices of the Royal Astronomical Society.