The Webb Telescope repeatedly discovers record-distant galaxies from the very early universe

As written by the scientific server Phys.org, the value of the redshift (z) is 16.7 (so the wavelengths of the radiation coming from this object were relatively stretched 16.7x during the long journey through space).

At the same time, the potential galaxy is located at a record distance from us (approximately 35 billion light years). The experts were literally mesmerized by how big a leap in knowledge the mere start of operation of the new powerful telescope brought.

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Using the previous best instruments of this kind, i.e. the Hubble Space Telescope and the Spitzer Space Telescope (in combination with powerful ground-based telescopes), astronomers have so far only found objects with a cosmological redshift of z=10-11, which represents objects much closer to us and existing at a significantly later stage in the development of the early universe. However, to accurately verify the redshift (z) value, astronomers will need to subject the new galaxy to a set of spectroscopic measurements, so for now they are cautiously talking only about the candidate for the new most distant galaxy.

The James Webb Space Telescope (JWST) has been working diligently since around mid-July 2022. Due to the fact that its sensitive instruments can also capture a significant part of electromagnetic radiation with wavelengths longer than visible light (so-called infrared radiation or light), it is destined to demanding observation of very distant objects in space, located practically on the border of the universe visible to us.
How is it possible? On the one hand, infrared light coming from distant stars, galaxies, etc. objects passes through layers of interstellar and intergalactic dust and gas better than radiation visible to the eye. Secondly, and this is perhaps even more important, due to the large so-called cosmological redshift, the originally visible radiation coming from very distant stars or galaxies is often shifted from the band of visible or ultraviolet light into the infrared radiation region during their observation. This is because during its long journey through space, its wavelength is significantly lengthened (relatively stretched) due to the expansion of space, sometimes by 10 times or more. Therefore, we can observe extremely distant space objects in the infrared rather than in the visible range of the light spectrum.

Thanks to observations made by the NIRCam (Near Infrared Camera), which is JWST’s primary imager, scientists have determined that the object CEERS-93316 cannot be a low-mass star or a bare active galactic nucleus. Since the dating of the observed object CEERS-93316 can lie only 250 million years after the big bang, cosmologists here strive to find out what is happening in such a young galactic candidate, i.e. in a galaxy existing or formed shortly after the big bang (VT). The stars themselves in the universe probably started to form a little earlier, between 100-200 million years after the big bang. By comparison, the current most distant observed star in the universe (Earendel) is about 12.9 billion light-years away.

Photo: Donnan et al. (2022)

Image of CEERS-93316

After the Big Bang, the universe was in a period known as the Dark Ages for a while, until the first stars began to be born. So this galaxy may be one of the first ever to be born in the universe. Cosmologists have already found more similar galaxies in the very early universe that may actually have existed earlier than current theoretical computer simulations predict, so there are a number of interesting and open questions about the formation of the first stars and galaxies.

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Study co-author Dr. Rebecca Bowler explained: “JWST can in principle detect galaxies with redshifts greater than 20, i.e. existing even before 200 million years after the Big Bang.” These galaxies will be very difficult to find, she says, but it is possible in principle.

“The most distant observed phenomenon in the universe is the cosmic microwave background (CMB), which is a kind of ‘afterimage’ or relic of the big bang itself that is still observable today,” said her colleague Callum Donnan, lead author of the study. “This radiation dates from approximately 400,000 years after the Big Bang and has been observed by various instruments and astronomical satellites over the years. The James Webb Space Telescope certainly won’t be able to see that far into the past, but it is capable of examining the earliest stages of galaxy formation.”

The cosmological redshift (or redshift) is a kind of “step brother” of the ordinary radiation redshift. With a normal red shift, the wavelength of the respective radiation/wave is stretched towards the red part of the spectrum, which occurs when the observer and the nearby observed luminous object move away from each other. It is also known as the Doppler phenomenon, after the name of its discoverer, Christian Doppler (a similar phenomenon also exists in the field of radio or sound waves). However, cosmological redshift (otherwise denoted by the letter z) is observed, on the other hand, for objects that are very distant in space and time from the observer, when it is not possible to directly talk about the instantaneous relative speed. While this is certainly not the usual Doppler phenomenon, it manifests itself very similarly:
Since the universe is expanding slightly relative to each location, the further apart two cosmic objects are, the more they appear to be moving away from each other. (However, we observe this phenomenon significantly only on the scale of galaxies or even larger cosmic structures. It was discovered during the 20s of the last century by the astronomer Edwin Hubble). And if its radiation reaches the Earth from a very distant object, the same universal cosmic expansion (i.e. the expansion of all space) during the path of said radiation will also ensure that its original wavelength gradually expands relatively, sometimes many times over.
So it is true that the more distant the observed galaxy is and its position in the universe moves away from us proportionally quickly due to the expansion of the universe, the more its light comes to us with an adequately more relatively “stretched” wavelength. Therefore, if astronomers know this factor of relative expansion of the wavelength of the object’s radiation (cosmological redshift z), they can assign to it an approximate distance in millions or billions of light years and vice versa. At the same time – the more distant space objects are from us, the longer it takes for their light to reach us, so looking into the very distant universe also means looking into the deep past, sometimes even into the very early phase of the universe.

No further observations are planned

Donnan and Bowler said there are no further observations planned for CEERS-93316 yet, but they hope there will be in the future. Shortly before the discovery of this object, another early galaxy candidate, GLASS-z13, was discovered in JWST data in June. As the name suggests, this object has a cosmological redshift of z=13 and was captured as it existed 300 million years after the Big Bang, roughly 13.5 billion years ago. In total, JWST has so far detected 6 galactic candidates with redshifts greater than z=12 in the early stage of the universe’s evolution. These galaxies are likely to be small compared to our Milky Way (they “only” contain about a billion stars, while our Milky Way contains 200-300 billion stars), but given the very early stage of the universe when they were observed, they are still relatively large . The distances in space were also much smaller then than they are today. While our current distance from GLASS-z13 is about 33 billion light-years, it was only 3 billion light-years away when the light we observed today was emitted from this object. Scientists also discovered a galaxy with a redshift of z=14, which was given the maiden name of Maisie.

The Webb Telescope took a selfie

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In its plan to observe the most distant galaxies from the very early universe, JWST has so far planned to examine a respectable number of 88 candidate galaxies, some of which date back less than 200 million years after the Big Bang. It will be interesting to find out when the very first galaxies in the universe began to form.

The article is in Czech

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