February 1, 2023

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A record-breaking signal from the galaxy far, far away is the furthest ever detected: ScienceAlert

Hydrogen is an essential building block of the universe. Whether stripped down to its charged core or packed into a molecule, the nature of its existence can tell you a lot about the features of the universe on the largest scales.

For this reason, astronomers are very interested in detecting signals from this element, wherever they may be found.

Now the effect of light on uncharged atomic hydrogen has been measured farther from Earth than ever before, by some margin. The Giant Metrewave Radio Telescope (GMRT) in India picked up a signal with an extension review time – The time between the emission of light and its detection – is 8.8 billion years.

Image of a radio signal from the galaxy. (Chakraborty & Roy/NCRA-TIFR/GMRT)

This gives us an exciting glimpse into some of the very first moments in the universe, which are currently estimated to be around 13.8 billion years old.

“A galaxy emits different types of radio signals,” says cosmologist Arnab Chakrabortyfrom McGill University in Canada. “Until now, it was only possible to pick up this particular signal from a nearby galaxy, which limits our knowledge of those galaxies closest to Earth.”

In this case, the radio signal emitted by atomic hydrogen is a light wave with a length of 21 cm. The long wave is not very active, nor is the light intense, which makes it difficult to detect at a distance; the The time of the previous record review It was only 4.4 billion years old.

Due to the large distance traveled before being intercepted by GMRT, the 21 cm emission line was extended by space expansion to 48 cm, a phenomenon described as redshift from the light.

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The team used gravitational lensing to detect the signal, which originates from a distant star-forming galaxy called SDSSJ0826+5630. Gravitational lensing is where light gets magnified as it follows the curved space around a massive object that lies between our telescopes and the original source, effectively acting as a huge lens.

Gravitational lens imaging
Illustration showing how gravitational lensing works. (Its blackness is cold)

“In this specific case, the signal is bent by the presence of another massive object, another galaxy, between the target and the observer,” says astrophysicist Nirupam RoyFrom the Indian Institute of Science.

“This effectively magnifies the signal by a factor of 30, allowing the telescope to pick it up.”

The results of this study will give astronomers hope that they will be able to make other similar observations in the near future: distances and return times that were previously off limits are now within reason. If the stars align, that is.

Atomic hydrogen forms when hot ionized gas from the regions around the galaxy begins to fall onto the galaxy, cooling along the way. Eventually, it turns into molecular hydrogen, and then into stars.

Being able to look back so far in time could teach us more about how our galaxy initially formed, as well as lead astronomers toward a better understanding of how the universe behaved when it was very young.

These latest findings “will open new and exciting possibilities for investigating the cosmic evolution of neutral gas using current and upcoming low-frequency radio telescopes in the near future,” the researchers wrote in their paper. published paper.

Research published in Monthly Notices of the Royal Astronomical Society.