Scottish astronomers push James Webb further back in time

Scottish astronomers push James Webb further back in time


The Edinburgh galaxy is the latest in a series of “farthest” observations by Webb

Scottish astronomers have used the new James Webb Super Space Telescope to spied what they believe to be the most distant galaxy ever observed.

The red spot is 35 billion light years away. We see it as it was just 235 million years after the Big Bang.

It is a preliminary or “candidate” result that requires follow-up study to confirm.

But for now, the University of Edinburgh team is celebrating and marveling at James Webb’s power.

“We’re using a telescope that’s designed to do exactly this kind of thing, and it’s amazing,” said Callum Donnan, an astrophysics graduate student in the university’s Department of Astronomy.

James Webb is the $10 billion successor to the Hubble Space Telescope and is chasing the first stars and galaxies to form in the 13.8 billion year old universe.

These objects are extremely faint, but the new observatory has been specially tuned to capture their glow in infrared light.

James Webb

James Webb

Edinburgh’s record will almost certainly be short-lived.

Since Webb began scientific operations in late June, astronomers have found increasingly distant candidates in his images.

And if projected performance is achieved, scientists could eventually see objects containing Webb that existed perhaps as little as 100 million years after the Big Bang.

So we should expect a slew of announcements over the coming weeks and months.

The Edinburgh target is called CEERS-93316 and is said to have a redshift of 16.7.

Redshift is the term astronomers use when discussing distances in the cosmos.

It is a measure that describes how light coming from an object has been “stretched” to redder wavelengths by the expansion of the universe.

The higher the redshift number assigned to a galaxy, the further away it is and the earlier it is considered in cosmic history.

In the past few days, a stream of ever-increasing redshift numbers has been reported on the popular preprint server arxiv.

Maisie's galaxy

Maisie’s galaxy was found in a wide-field survey conducted by James Webb

The last 24 hours has been a good example of how fast things can move.

The Edinburgh group drew their target from a large-scale survey of the sky that Webb is currently conducting, called the Cosmic Evolution Early Release Science (CEERS) survey.

The team actually conducting this poll came out with their own far-flung candidate called CEERSJ141946.35+525632.8 on Monday.

Dubbed Maisie’s Galaxy after an astronomer’s daughter, this target has a redshift of 14.3, meaning it can be seen about 280 million years after the Big Bang. Not quite as far as CEERS-93316, but still a notable prospect compared to the pre-James Webb era.

However, all of this has one major caveat. The early candidates heralded from Webb observations have yet to undergo full spectroscopic investigation.

This process breaks down the light coming from a galaxy to reveal its component colors – its spectra. These will show most clearly how light originally emitted at visible wavelengths has been stretched into the infrared throughout cosmic history.

Only when that task is complete — and Webb has the tools to do it — will the distance claims become more secure

Graphic showing how James Webb can look back in time

Graphic showing how James Webb can look back in time

Another benefit of spectroscopy is that it reveals the composition of objects.

The theory states that the very first stars powered only with hydrogen, helium and a small amount of lithium – the elements that were formed in the Big Bang.

Heavier atoms — astronomers call them all “metals” — had to be forged in these pioneer stars and their descendants.

“We can take a broad view of the colors in our galaxy, and it’s quite blue, indicating a young stellar population. But it’s not blue enough for this galaxy to be composed of metal-free stars,” Mr Donnan said.

It is Prof. Steve Finkelstein from the University of Texas at Austin, USA, who is the proud father of Maisie.

He will be a guest on the BBC World Service’s Science In Action program on Thursday.

“I had heard a quote for this telescope that it will be transformative. And I said, ‘You know, it’s going to do a lot of really cool things, but is it really going to completely change the way we see the universe? I couldn’t have been more wrong. Textbooks are being rewritten even if we only use the data we received in the first week.”

Note on distances: The universe is expanding. In the time it takes light from objects to reach us, these objects have declined sharply. Their positions are therefore much, much further away today than they were when the light was first emitted.

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