It’s a record that has been broken several times in the past two years alone, and one that we hope to break again soon.
Astronomers using the newly operational James Webb Space Telescope (JWST) have announced the discovery of what appears to be the most distant galaxy to date.
If this sounds familiar, it’s already happened twice this year. In April, astronomers announced their observation of a galaxy at a point in time just 330 million years after the Big Bang. Last month, in other JWST data, another one was found at a point 300 million years after the Big Bang.
The new record, however, is mind-blowing. Discovered in the darkness of the early Universe, it represents a time just 235 million years after the Big Bang… practically a cosmic blink, in the context of the 13.8 billion year age of the Universe.
The discovery of the galaxy candidate, named CEERS-93316, marks the beginning of something wonderful: Webb is poised to open the early Universe wide open, giving us an unprecedented view of the dark reaches and mysterious at the beginning of, well, everything.
A paper led by astrophysicist Callum Donnan of the University of Edinburgh has been presented in the Monthly Notices of the Royal Astronomical Societypending peer review, and is available on the arXiv preprint server.
The first billion years after the Big Bang are of intense interest to cosmologists. During that time, the hot, quantum soup that filled the Universe after it somehow appeared began to form everything: matter and antimatter and dark matter, stars and galaxies and dust.
Because light takes time to travel, any light reaching us from deep space represents an event buried deep in the past; so, in effect, light is a time machine for the far reaches of the Universe. But the early, very early Universe is more difficult: it’s so far away that any light that reaches us is very, very weak.
In addition, the expansion of the Universe has stretched even the most energetic waves into faint rays closer to the infrared parts of the spectrum, making even the most visible objects difficult to read.
This makes detailed reconstructions of that time very difficult. Which is more of a shame since it’s such a critical time.
The era before the birth of the first stars was known as the Cosmic Dawn. It began nearly 250 million years after the Big Bang, filling the entire Universe with an opaque cloud of hydrogen atoms.
It was not until ultraviolet light from the first stars and galaxies reionized the neutrally charged hydrogen that the entire electromagnetic spectrum could be propagated.
Thanks to this epoch of reionization, about a billion years after the Big Bang light could shine again unhindered.
Naturally, we want to know more about the youth of the Universe during this period of fog; how those first stars formed in the dawn clouds, how galaxies coalesced, how supermassive black holes could form so quickly in the first hundreds of millions of years of existence. Looking back into that distant, hazy time is one of the main tasks for which Webb is designed.
Webb can capture infrared and near-infrared light, with the highest resolution of any telescope ever sent into space. It’s designed to excel at detecting these highly redshifted galaxies, so cosmologists can finally get a detailed look at what’s going on, if not at Cosmic Dawn, then at least during reionization.
CEERS-93316, according to Donnan and his colleagues, must be at least fairly close to one of the first galaxies after the Big Bang. The team ruled out other potential explanations for the dim, red light, and their analysis suggests that star formation in the candidate galaxy must have begun between 120 and 220 million years after the Big Bang.
However, to confirm the object’s identity, follow-up spectroscopic observations will be required. This was expected to confirm the redshift; from there, the object could become the subject of a more detailed study and help build a census of the first objects in the Universe.
If CEERS-93316 is a galaxy, it probably won’t wear the most distant galaxy belt for long. Even if CEERS-93316 turns out not to be such a distant galaxy, it’s highly likely that we won’t have time to wait for Webb to turn up an object that is.
Bring us those dark, red, distant treasures, Webb. We can’t wait.
The research was presented in Monthly Notices of the Royal Astronomical Societyand is available on arXiv.
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