Detecting radio signals emitted by nearby galaxies could help astronomers figure out how stars form in distant galaxies. Until now, it was only possible to pick up this specific signal from a nearby galaxy, limiting our knowledge to those galaxies closer to Earth. However, these signals become weaker the further away a galaxy is from Earth, making it difficult for today’s radio telescopes to pick them up.

Thanks to gravitational lensing, astronomers from Montreal and India have picked up a radio signal from the most distant galaxy. Astronomers picked up a faint signal from a record-breaking distance — until now at a specific wavelength known as the 21 cm line.

For this discovery, astronomers used the Giant Metrewave Radio Telescope in India. This is the first time this radio signal has been detected at such a great distance, allowing astronomers to explore the secrets of the early universe.

The signal was found to come from a distant galaxy known as SDSSJ0826+5630, which is 8.8 billion light-years away. This distance indicates that the galaxy is closer to the Big Bang.

Interestingly, scientists were also able to measure gas composition. They noted that the atomic mass of the gas content of this particular galaxy is almost twice the mass of the stars visible to us.

atomic hydrogen signal
Images of the atomic hydrogen signal, the detection spectrum and the lens. Credits: Left and middle panels: Chakraborty & Roy, GMRT/NCRA-TIFR Right panel: ESA/NASA HST and eHST/STScI/CADC

Arnab Chakraborty, a postdoctoral researcher at McGill University under the supervision of Professor Matt Dobbs, said: “The detected signal was emitted from this galaxy when the universe was only 4.9 billion years old, giving the researchers a glimpse into the secrets of the early universe. It is the equivalent of looking back in time 8.8 billion years.”

Co-author Nirupam Roy, an associate professor in the Department of Physics at the Indian Institute of Science, said: “Gravity lensing magnifies the signal coming from a distant object to help us see into the early universe. In this particular case, the signal is deflected by the presence of another massive body, another galaxy, between the target and the observer This effectively results in a magnification of the signal by a factor of 30, allowing the telescope to pick it up.”

According to the researchers, these findings show that gravitational lensing can be used to observe distant galaxies under similar conditions. It also creates fascinating new possibilities for using today’s low-frequency radio telescopes to study the cosmic evolution of stars and galaxies.

Magazine reference:

  1. Arnab Chakraborty, Nirupam Roy. Detection of HI 21 cm emission from a galaxy with strong lenses at z ∼ 1.3. Monthly Notices of the Royal Astronomical Society, 519 3, March 2023. DOI: 10.1093/mnras/stac3696