Mallika Dureja
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A galaxy buried deep in space sent out a radio signal about 8.8 billion years ago, when the universe was only 4.9 billion years old and still pretty young. The signal came from atomic hydrogen and gave hints about how stars were made. It waited for an eternity for someone to feel its presence. Researchers were able to find it with the help of the Giant Metrewave Radio Telescope (GMRT) in Pune.
Astronomers at the Indian Institute of Science (IISc) in Bengaluru and Canada’s McGill University recently used data from the GMRT to find this signal coming from a faraway galaxy.
IISc says that this is especially interesting because it is the first time that a signal like this has been picked up from such a long way away in space. This is also the first time that strong lensing of 21 cm emission from a galaxy has been found and confirmed.
So you don’t get too confused by all the astronomy terms, we’ll explain things in more detail below.
Atomic hydrogen is used as fuel when stars are being made. When hot, ionised gas from the space around the galaxy falls onto it, it cools and turns into atomic hydrogen, which then turns into molecular hydrogen, which leads to the formation of stars.
This atomic hydrogen sends out radio waves with a wavelength of 21 cm. Low-frequency radio telescopes like the GMRT can easily pick up these waves. So, 21 cm emission is a direct way to find out how much atomic gas is in both close and far galaxies.
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But the radio signals coming from galaxies so far away are so weak that it is almost impossible to find them or study star formation in those galaxies with the telescopes we have now.This is where gravitational lensing, a natural process, helps the scientists out.
“Gravitational lensing makes the signal from a faraway object bigger, which lets us look back into the early universe. In this case, the signal is bent because there is another galaxy between the target and the observer, which is a big body. This effectively makes the signal 30 times stronger, so the telescope can pick it up,” said Nirupama Roy, an Associate Professor in the Department of Physics at IISc.
Great graph on the Ionosphere #HamRadio #RadioWaves #Ionosphere pic.twitter.com/2WnzzP7SvP
— Ham Radio Basics (@HamRadioBasics) January 17, 2023
Thanks to gravitational lensing, the data from the GMRT shows that it is possible to see galaxies far away. Even with the low-frequency radio telescopes we have now, it opens the door to many new and exciting ways to look at how galaxies and stars change over time.
The results have been written up in the Royal Astronomical Society’s Monthly Notices.
