Using warped space-time as a magnifying glass, astronomers have found the most distant signal of its kind from a remote galaxy, and it could blow a window into how our universe formed.
The highest ever radio frequency signal, picked up by India’s Ground Meter Radio Telescope (GMRT), came from the galaxy SDSSJ0826+5630, located 8.8 billion light years from Earth, which meaning that the signal was emitted when the universe was about a third of its current age.
The signal is an emission line from the most primordial element in the universe: neutral hydrogen. After the Big bang, this element existed throughout the cosmos as a turbulent mist from which the first stars and galaxies eventually coalesced. Astronomers have long searched for distant signals from neutral hydrogen for a glimpse of the moment when stars began to shine, but those signals are difficult to see, given the extraordinary distances in question.
Now, a new study, published December 23 in the journal Monthly Notices of the Royal Astronomical Society, (opens in a new tab) shows that an effect called gravitational lensing could help astronomers find evidence of neutral hydrogen.
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“A galaxy emits different types of radio signals,” study lead author Arnab Chakraborty (opens in a new tab)cosmologist at McGill University in Canada, said in a statement (opens in a new tab). “Until now, it was only possible to catch this particular signal from a nearby galaxy, limiting our knowledge to those galaxies closer to Earth.”
The ‘dark age’ of the universe
Forged around 400,000 years after the beginning of the universe, when protons and electrons first combined with neutrons, neutral hydrogen occupied the early cosmos throughout the so-called dark ages, before the first stars and galaxies appeared. life.
When stars are forming, they blast out fierce ultraviolet light that knocks the electrons out of much of the hydrogen atoms in the space around them, ionizing the atoms so that they are no longer neutral. Eventually, young stars lose their ultraviolet intensity, and some of the ionized atoms combine into neutral hydrogen. The detection and study of neutral hydrogen can provide insight into the life of the earliest stars, as well as the prehistory of stars.
Neutral hydrogen emits light at a characteristic wavelength of 21 centimeters. But using neutral-hydrogen signals to study the early universe is hard work, because the long-lived, low-intensity signals are often drowned out over vast cosmic distances. So far, the most distant 21 cm hydrogen signal detected was 4.4 billion light years away.
Peers gravitational lenses into the past
To find a signal at twice the previous distance, the researchers turned to an effect known as gravitational lensing.
In his general theory relativityAlbert Einstein explained that gravity it is not produced by an invisible force but rather by 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 telescope and its source. In this case, the space-warping object was the massive star-forming galaxy SDSSJ0826+5630, which used its powerful masking effect to act as a lens that directed a faint and distant neutral hydrogen signal into focus. for the GMRT.
“In this specific case, the signal is bent by the presence of another massive body, another galaxy, between the target and the observer,” study co-author Nirupam Roy, associate professor of physics at the Indian Institute of Science, said in the statement. “This effectively increases the signal by a factor of 30, allowing the telescope to pick it up.”
Now that the researchers have found a way to probe previously unreachable clouds of hydrogen, they want to use it to better chart the universe through its various cosmological ages and, hopefully, the moment when the find first shining stars.