A group of astronomers has created a technique that will enable them to “see” through the early Universe’s haze and find the light coming from the universe’s initial stars and galaxies.
The team of scientists, lead by the University of Cambridge, has created a technique that will enable them to see and study the first stars through the hydrogen clouds that covered the Universe some 378,000 years after the Big Bang.
Astronomers have long sought to watch the formation of the earliest stars and galaxies because doing so will help them understand how the Universe changed from the empty space following the Big Bang to the intricate universe of celestial objects we see today, 13.8 billion years later.
The Square Kilometre Array (SKA), a next-generation telescope that should be
finished by the end of the decade, will probably be able to capture images of the earliest light in the Universe, but the challenge for existing telescopes is to find the cosmological signal of the stars through the dense hydrogen clouds.
The signal that scientists hope to discover is anticipated to be around 100,000 times weaker than other radio signals that are also coming from the sky, such as radio waves emanating from our own galaxy.
The very act of using a radio telescope imparts distortions to the signal that is received, which can entirely mask the desired cosmic signal. In contemporary radio cosmology, this is regarded as an extremely difficult observational task. Such instrument-related distortions are frequently held responsible for being the main obstacle in this kind of observation.
The Cambridge-led team has now created a mechanism to look through the primordial clouds and other sky noise signals, eliminating the negative impact of the radio telescope’s distortions. With the help of their technique, which is a component of the REACH (Radio Experiment for the Analysis of Cosmic Hydrogen) experiment, astronomers will be able to observe the first stars by way of their interactions with the hydrogen clouds, much like how we can infer a landscape from the shadows in the fog.
Their approach will raise the standard and dependability of observations made by radio telescopes during this crucial yet unknown period in the Universe’s evolution. Later this year, the first REACH observations are anticipated.
The journal Nature Astronomy published the findings today.
According to main author of the study Dr. Eloy de Lera Acedo of Cambridge’s Cavendish Laboratory, “the Universe was essentially empty and constituted mostly of hydrogen and helium at the time the first stars emerged.”
Added him: “The earliest stars were created when the components ultimately got together due to gravity and the conditions were favorable for nuclear fusion. However, they were encircled by clouds of ‘neutral hydrogen,’ which absorb light very strongly, making it difficult to immediately detect or monitor the light behind the clouds.”
Astronomers have been unable to replicate a result from an experiment to detect the global epoch of reionization signature, or EDGES, that was published in 2018 and hinted at a potential detection of this earliest light. This has led them to believe that the original result may have been caused by interference from the telescope being used.
“Due to the temperature of the hydrogen gas, which should be considerably lower than what our present knowledge of the Universe would allow, the original discovery would require new physics to explain it. Alternately, the explanation might be an unexplained increase in the background radiation’s temperature, which is commonly thought to represent the well-known Cosmic Microwave Background “De Lera Acedo remarked.
“The ramifications would be enormous,” he continued, “if we can confirm that the signal observed in that previous experiment actually originated from the earliest stars.”
Astronomers investigate the 21-centimetre line, an electromagnetic radiation signature from hydrogen in the early Universe, in order to research this stage of the Universe’s evolution, which is sometimes referred to as the Cosmic Dawn. They search for a radio signal that compares the radiation coming from the hydrogen to the radiation coming from behind the hydrogen fog.
The technique created by de Lera Acedo and his associates makes use of Bayesian statistics to identify a cosmological signal in the midst of telescope interference and general sky noise, allowing the signals to be distinguished.
Modern methods and tools from several domains have been needed to accomplish this.
Earlier observations depended on a single antenna, thus the simulations the researchers performed to recreate an actual observation using many antennas improved the data’s trustworthiness.
“Compared to comparable contemporary devices, our technique analyzes data from more antennas and across a larger frequency spectrum. This strategy will provide us with the data we need for our Bayesian data analysis “De Lera Acedo remarked.
Added him: “We essentially abandoned conventional design approaches in favor of developing a telescope that is appropriate for the way we want to analyze the data — a process known as inverse design. This would make it easier for us to quantify things from the Cosmic Dawn and into the era of reionization, when the universe’s hydrogen underwent reionization.”
At the Karoo radio reserve in South Africa, which was chosen for its exceptional circumstances for radio studies of the sky, the telescope’s construction is now being completed. It is remote from radio frequency interference caused by people, such as television and FM radio waves.
The REACH team of more than 30 researchers is diverse and dispersed around the globe, and it includes specialists in big data, Bayesian statistics, antenna design, radio frequency equipment, numerical modeling, digital processing, and both theoretical and observational cosmology. The University of Stellenbosch in South Africa co-leads REACH.
Although the antenna technology used for this instrument is relatively simple, the harsh and remote deployment environment, as well as the strict tolerances required in the manufacturing, make this a very challenging project to work on, according to Professor de Villiers, co-lead of the project at the University of Stellenbosch in South Africa.
He said, “We have great faith we’ll make that elusive discovery and are quite thrilled to see how well the system performs.”
Thanks to research on the Cosmic Microwave Background (CMB) radiation, the Big Bang and the very early Universe are epochs that are well understood. The late and widespread development of stars and other celestial bodies is even well known. A crucial piece of the history of the universe’s jigsaw, however, is the moment when the universe’s first light was produced.
Materials provided by University of Cambridge.