Astronomers have devised a new way to “see” through the haze of the early universe so that they can detect light from the first stars and galaxies.
Observing the birth of these bodies has long been a goal of scientists because it will help explain how the universe evolved from the void after the Big Bang to the complex universe we observe today, 13.8 billion years later.
It’s something commissioned by the new James Webb Space Telescope, as well as the Square Kilometer Array (SKA).
But while Webb looks at wavelengths in the infrared, the next generation of the Earth-based SKA telescope — due to be completed by the end of the decade — will study the early universe through radio waves.
For current radio telescopes, the challenge is to detect the stars’ cosmic signal through thick clouds of hydrogen, which obscure vision because they absorb light well.
Distortion from other radio signals can also get in the way, which is one of the severe challenges facing modern radio cosmology.
For example, the signals of distant galaxies that astronomers are trying to detect are about 100,000 times weaker than those that originated in our galaxy.
But researchers led by the University of Cambridge have now developed a new methodology, using mathematics, that will allow them to see primordial clouds and other sky-noise signals.
The birth of the universe: Astronomers developed a new way to “see” through the haze of the early universe so that they could detect light from the first stars and galaxies. This artist’s impression depicts the emergence of stars in the early universe
Their idea, which was part of the REACH experiment in South Africa (pictured), will allow scientists to observe early stars as they interact with clouds of hydrogen that block light.
What is the electromagnetic spectrum?
The electromagnetic spectrum is the range of frequencies that cover the spectrum of radiation.
They cover wavelengths from thousands of miles down to a fraction of the size of an atom’s nucleus.
The ranges of electromagnetic waves are:
- gamma rays
- X ray
- visible light
- microwave radiation
- radio waves
Of the most famous current and upcoming telescopes, James Webb looks at the universe in infrared, Hubble in ultraviolet or visible light, and the next generation Square Kilometer Array will study radio waves.
So it will allow them to avoid the harmful effect of distortions caused by the radio telescope.
Their idea, which was part of the REACH (Radio Experiment for the Analysis of Cosmic Hydrogen), would allow astronomers to observe the oldest stars by their interaction with hydrogen clouds, in the same way we would infer a landscape by looking at shadows. in the fog.
The hope is that it will improve the quality and reliability of observations from radio telescopes looking at this key, undiscovered time in the evolution of the universe.
The first observations are expected from REACH later this year.
“By the time the first stars formed, the universe was mostly empty and made up mostly of hydrogen and helium,” said lead study author Dr. Eloy de Lira Acedo of the Cavendish Laboratory in Cambridge.
He added, “Because of gravity, the elements eventually came together and the conditions were right for nuclear fusion, which is what formed the first stars.
But they were surrounded by clouds of neutral hydrogen, which absorb light well, so it is difficult to detect or notice the light directly behind the clouds.
In 2018, another research group published a result that hinted at a possible detection of this early light, but astronomers were unable to replicate that – leading them to believe that the original result may have been due to interference from the telescope in use.
“The original result requires new physics to explain, due to the temperature of hydrogen gas, which should be much cooler than our current understanding of the universe allows,” said Dr. de Lira Acedo.
The image is an aerial view of the observation site at the REACH Karoo Radio Reserve, South Africa
The Square Kilometer Array Telescope (pictured) is set to explore the evolution of the early universe when it becomes operational later this decade. He will study this through radio waves
“Alternatively, the cause could be an unexplained overheating of the background radiation – usually assumed to be the known cosmic microwave background -“.
“If we can confirm that the signal in that previous experiment was indeed from the first stars, the effects would be massive,” he added.
In order to study this period of the universe’s development, often referred to as the cosmic dawn, astronomers use a 21-centimeter line – a signature of electromagnetic radiation from hydrogen in the early universe.
They are looking for a radio signal that measures the contrast between the radiation from hydrogen and the radiation behind hydrogen fog.
The methodology developed by Dr. de Lira Acedo and colleagues uses Bayes statistics to detect a cosmic signal in the presence of interference from a telescope and general noise from the sky, so that the signals can be separated.
The new James Webb Space Telescope is also tasked with doing this but it looks at wavelengths in the infrared
To do this, the latest technologies and techniques from various fields were needed.
Construction of the SKA telescope is currently being completed at the Karoo Radio Reserve in South Africa, a site selected for its excellent conditions for radio observations of the sky.
It is far from man-made radio frequency interference, for example FM radio and television signals.
The Big Bang and the early times of the universe are epochs well understood, thanks to studies of the cosmic microwave background (CMB).
But the time when the first light was formed in the universe is a key missing piece in the puzzle of the universe’s history.
The new study is published in the journal Nature Astronomy.
SKA will be the largest radio telescope in the world
The Square Kilometer Array (SKA), a joint venture between Australia and South Africa, will be the world’s largest radio telescope.
More sensitive than any current radio telescope, it will enable scientists to study the universe in more detail than ever before.
The telescope is located in South Africa and Australia, and the international headquarters are at Jodrell Bank in the United Kingdom.
Approximately 200 medium frequency dishes (including the current MeerKAT facility which was officially launched in July 2018) will be located in the Karoo region of South Africa.
Artist’s impression of the 3-mile (5 km) central core of the Square Kilometer Array (SKA) antennas
About 130,000 low-frequency antennas will be located in Western Australia.
Both locations are far from sources of radio frequency interference allowing for highly sensitive measurements to be made.
SKA will consist of two devices, SKA-mid (plates) and SKA-low (antennas).
The signals from the dishes will be transmitted via optical fibers to a central computer where they will be combined using a technique called interferometry.
Likewise, the signal from all the antennas will also be combined and converted into scientific data that astronomers will use to study the universe.
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