Scientists have made a groundbreaking discovery by successfully capturing radio signals from a galaxy almost 9 billion light-years away from Earth, according to a report by space.com. This marks the first time a signal of this kind has been received from such a distance.
The scientists were able to detect the signals using a unique wavelength known as the “21-centimetre line” or the “hydrogen line,” which is emitted by neutral hydrogen atoms. This wavelength is a direct tracer of the atomic gas content in both nearby and distant galaxies.
“The astronomical distance over which such a signal has been picked up is the largest so far by a large margin. This is also the first confirmed detection of strong lensing of 21 cm emission from a galaxy”, states an IISc statement.
Atomic hydrogen is essential for star formation in a galaxy. When hot ionized gas from the surrounding medium of a galaxy falls onto the galaxy, the gas cools and forms atomic hydrogen, which then becomes molecular hydrogen, and eventually leads to the formation of stars.
“Therefore, understanding the evolution of galaxies over cosmic time requires tracing the evolution of neutral gas at different cosmological epochs”, the statement added.
The radio signal, however, is extremely weak, and it is nearly impossible to detect the emission from a distant galaxy using current telescopes due to their limited sensitivity. The most distant galaxy detected using 21 cm emission was at redshift z=0.376, which corresponds to a look-back time of 4.1 billion years.
Using GMRT data, a team of researchers, including Arnab Chakraborty and Nirupam Roy, have detected a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29. The signal was emitted from this galaxy when the universe was only 4.9 billion years old.