Finding the Early Universe's Secrets: Astronomers Catch a Radio Signal from a Faraway Galaxy

 By Mcgill University 

January 18, 2023

It may now be possible to investigate galaxies that are far further away from Earth.

How do stars develop in galaxies far away? By observing radio emissions from neighbouring galaxies, astronomers have long sought an answer to this issue. However, these signals are difficult for the present generation of radio telescopes to detect since they get weaker the further a galaxy is from Earth.

Now, astronomers may peek into the mysteries of the early cosmos thanks to work by researchers from India and Montreal who were able to pick up a radio signal at the 21 cm line from the galaxy that is now the farthest away. This is the first instance of this kind of radio signal being found at such a great distance, thanks to the Giant Metrewave Radio Telescope in India.

"A galaxy produces a variety of radio frequencies. According to Arnab Chakraborty, a post-doctoral researcher at McGill University working under Professor Matt Dobbs' direction, "Up until now, it has only been feasible to catch this specific signal from a neighbouring galaxy, restricting our knowledge to those galaxies closer to Earth."

But with the aid of a common occurrence called gravitational lensing, we are able to pick up a weak signal at a record-breaking distance. This will enable us to comprehend the makeup of galaxies located at far larger separations from Earth, he continues.

A peek into the early universe in the past

For the first time, the scientists were able to pick up a signal from the far-off star-forming galaxy SDSSJ0826+5630 and determine the gas composition of the galaxy. The scientists found that the atomic mass of the gas in this specific galaxy is almost double that of the stars that are visible to us.

The team's signal, which was produced by this galaxy when the universe was just 4.9 billion years old, provided a window into the early cosmos's mysteries. According to Chakraborty, a cosmology student at McGill's Department of Physics, "it's the equivalent of a look-back in time of 8.8 billion years."

detecting the signal coming from a far-off galaxy

To enable us to look into the early cosmos, gravitational lensing enlarges the signal from a far-off object. The signal is distorted in this particular instance because there is another large object—another galaxy—between the target and the observer. As a result, the signal is essentially magnified by a factor of 30, making it possible for the telescope to detect it, according to co-author Nirupam Roy, an Associate Professor in the Department of Physics at the Indian Institute of Science.

These findings, according to the researchers, show that gravitational lensing may be used to see distant galaxies under comparable circumstances. It also creates fascinating new possibilities for using current low-frequency radio telescopes to study the cosmic development of stars and galaxies.

NCRA-TIFR designed and runs the Giant Metrewave Radio Telescope. McGill University and the Indian Institute of Science provided funding for the study.

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