Using warped space-time as a magnifying glass, astronomers have captured the most distant signal from a distant galaxy, and it could open a window into how our universe formed.
The record-breaking radio frequency signal, picked up by the Giant Metrewave Radio Telescope (GMRT) in India, came from the galaxy SDSSJ0826+5630, located 8.8 billion light-years from Earth, which means the signal went off when the universe was roughly a third of its current age. .
The signal is an emission line from the universe’s most primordial element: neutral hydrogen. In the wake of the great explosionThis element was present throughout the universe as a turbulent haze from which the first stars and galaxies eventually formed. Astronomers have long searched for distant signals of neutral hydrogen in hopes of finding the moment when the first stars began to shine, but these signals have proven difficult to pinpoint, given the extraordinary distances involved.
Now, a new study, published December 23 in the journal Monthly Notices of the Royal Astronomical Society, (Opens in a new tab) He shows that an effect called gravitational lensing can help astronomers detect evidence of neutral hydrogen.
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“A galaxy emits different types of radio signals,” said the study’s lead author Arnav Chakraborty (Opens in a new tab)cosmologist at McGill University in Canada, he said in a statement (Opens in a new tab). “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.”
The “dark age” of the universe
Formed about 400,000 years after the beginning of the universe, when protons and electrons first associated with neutrons, neutral hydrogen filled the bleak early universe throughout its so-called dark age, before the first stars and galaxies appeared.
When stars form, they blast powerful ultraviolet rays that strip electrons from much of their hydrogen. atoms in the space around it, thus ionizing the atoms so that they are no longer neutral. Eventually, the young stars lose their ultraviolet intensity, and some of the ionized atoms recombine into neutral hydrogen. The discovery and study of neutral hydrogen can provide insight into the life of the first stars, as well as the era before stars existed.
Neutral hydrogen emits light with a characteristic wavelength of 21 cm. But using neutral hydrogen signals to study the early universe is a challenging task, as signals of long wavelength and low intensity often drown out across vast cosmic distances. To date, the farthest 21 cm hydrogen signal detected was 4.4 billion light-years away.
Peer lens gravity at last
To find a signal at twice the previous distance, the researchers turned to an effect called gravitational lensing.
in his general theory RelativityAlbert Einstein explained it gravity It is not produced by an invisible force, but rather is our experience of space-time curvature and distortion in the presence of matter and energy. Gravitational lensing occurs when a massive object sits between our telescopes and its source. In this case, the twisting object of space was the giant star-forming galaxy SDSSJ0826+5630, which used a strong warping effect to act as a lens that directs a faint, distant neutral hydrogen signal into the focus of the GMRT.
“In this specific case, the signal is bent by the presence of another massive object, another galaxy, between the target and the observer,” said a co-author of the study. Nirupam RoyAssociate Professor of Physics at the Indian Institute of Science. “This effectively magnifies the signal by a factor of 30, allowing the telescope to pick it up.”
Now that researchers have found a way to probe previously inaccessible clouds of hydrogen, they want to use it to better map the universe through various cosmic ages and, hopefully, pinpoint the moment when the first stars began to shine.