James Webb is close to seeing the cosmic dawn – 11/25/2023 – Science

More than two decades after helping to conceive the James Webb Space Telescope, British astronomer Richard Ellis of University College London believes we have never been so close to glimpsing the cosmic dawn – the moment when the first stars and galaxies began to emerge. shine in the Universe.

One of the objectives of the satellite, which at this point already has more than a year of scientific observations completed, was precisely to probe the depths of the cosmos, which is equivalent to observing the past, since the light from these more distant objects takes billions of years to reach. reach us. And that’s what he’s doing.

“The Universe is 13.8 billion years old. And the [Telescópio Espacial] Hubble looked back to when the Universe was 500 million years old. Webb looked back another 200 million years in time, and what we found is that the galaxies we see in these previously unexplored regions are brighter than we expected, which suggests that somehow the stars in them are different,” said Ellis. , in conversation with Sheet.

The interview took place during his visit to Brazil to participate in the III NAT Lectures in Astrophysics, an event organized by the Astrophysics Center of Unicid (Universidade Cidade de São Paulo) this month.

“I think it’s telling us that we’re close to the cosmic dawn, but I don’t understand what else it’s telling us. I feel it in the air that it’s exciting, but I don’t know why yet. We’re getting closer to a discovery.”

Ellis highlights that recent studies have shown that the Universe appears to have matured very quickly – perhaps faster than predicted by the standard cosmological model, our main theory to explain the evolution of the cosmos since the Big Bang. But he thinks it’s too early to rule it out.

“There has been some controversy that perhaps galaxies developed too quickly, that in the first 500 million years galaxies as large as the Milky Way formed, and this would challenge the standard cosmological model,” he says. “The newspapers love the story, but I don’t think we’re at that point yet.”

Read the main excerpts from the interview below.

You were involved with the original design of the James Webb Space Telescope in the 1990s. What is it like to see it now in space?
Yes, I was the only European astronomer on the committee that was set up by the Americans in 1993 to think about the next big thing, so soon after the launch of Hubble in 1990. We wrote our report in 1996 and proposed what we called the Space Telescope of Next Generation, who would ultimately be named James Webb. But it took 25 years from that report to its release on Christmas Day 2021, and there have been many ups and downs. I was there at the beginning, when we proposed the science that Webb could do, and there were two themes, two big questions that motivated him: one was to find planets like Earth around other stars and the other was to look into the past, to when the first galaxies emerged and the first stars shone, and what’s exciting is that in Webb’s first year of science results we’ve made great progress on both questions.

Is Webb then fulfilling the expectations created when it was conceived?
Even more than that. Its performance is better than we expected. It’s more efficient perhaps because we were cautious about how precisely we would be able to produce the instruments and, secondly, the launch. The departure, from French Guiana, was so perfect that the telescope has more fuel, so it can survive in its position for 20 years, instead of what had been planned – 5 to 10 years. It’s great news.

His research focus is on the cosmological side of things, on the first galaxies and stars in the Universe. Has Webb ever brought any surprises?
I actually brought it. With Hubble, we were able to see the Universe when it was 5% of its current age. The Universe is 13.8 billion years old. And Hubble looked back to when the Universe was 500 million years old. Webb looked back another 200 million years in time, and what we found is that the galaxies we see in these previously unexplored regions are brighter than we expected, which suggests that somehow the stars in them are different.

Will it be possible to determine whether they are from the so-called Population 3, the hypothetical first stars to appear in the Universe?
I hope so. The signal we are looking for would be that of a galaxy that does not have the heavy elements, such as carbon, oxygen, nitrogen, iron, because they are all made in stars, so the first generation of them could only contain hydrogen and helium. There are already two candidate Webb galaxies where researchers believe they have found this Population 3, but the burden of proof is very strict. I think these studies are not yet convincing, but within a year we are already finding possible Population 3 candidates. It is very exciting and I am optimistic that we will make this detection at some point.

The results of recent years seem to suggest the image of a Universe that had a very short adolescence. It goes from a baby Universe to a mature one very quickly. Is this an accurate assessment?
Yes, mature galaxies, which are rotating and look familiar, appeared in the first billion years, so if the Universe were a human and its age of 13.8 billion years was a human lifetime, at five years of life it I would already be an adult. He matured very quickly.

Does this align with our most accepted cosmological model?
There has been some controversy that perhaps the galaxies developed too quickly, that in the first 500 million years galaxies as large as the Milky Way formed, and this would challenge the standard cosmological model. But most astronomers think that the masses of these galaxies are very uncertain and that the results are not that convincing. Sure, the newspapers love the story that the standard model of cosmology needs to be thrown out, but I don’t think we’re at that point yet.

On the other hand, there is a real controversy in cosmology at the moment, which is the so-called Hubble tension, the fact that we measure different values ​​for the Hubble constant depending on the method used. How do you see this, and can Webb help?
Webb can help. The two methods that are in tension are those of close and distant scale. The Hubble constant is the rate at which the Universe is expanding today, and we can measure it locally by looking at variable stars in galaxies, whose period of variability tells us how luminous they are. If we know this, and see how bright they are from Earth, we can get the distance. And, of course, we measure the expansion of the Universe with the speed of galaxies. But the result we get from these parameters is significantly different from what we get from the structure in the Big Bang glow. [a radiação cósmica de fundo].

In my opinion, there are enough uncertainties in the local method that this discrepancy is not yet convincing. But Webb has the ability, being more powerful than Hubble, to extend these local measurements even further, and with more precision. It’s still early days, but I hope Webb makes better measurements that will either confirm the discrepancy with greater significance or show that the voltage is false. If the tension survives, then yes, there is something wrong with the standard model of the Universe. It could be that the initial expansion story has some feature we don’t yet understand, which would be exciting, but I personally don’t think we’re there yet. I don’t lose any sleep over this.

Do you have any issues that make you lose sleep?
This thing about why these galaxies are brighter. I wouldn’t say I lose sleep, but I’m excited that these galaxies Webb is finding are brighter than expected. And I think it’s telling us that we’re close to the cosmic dawn, but I don’t understand what else it’s telling us. I feel it in the air that it’s exciting, but I still don’t know why. We are approaching a discovery.

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Richard Ellis, 73

Graduated in astronomy from University College London (UCL) with a doctorate in astrophysics from the University of Oxford, Ellis was the only European astronomer to participate in the committee that designed, in 1996, what would come to be known as the James Webb Space Telescope, launched in 2021. Today he is professor of astrophysics at UCL and works on observational cosmology, more specifically the origin and evolution of galaxies. He is the author of the book “When Galaxies Were Born: The Quest for Cosmic Dawn” (Princeton University Press, 2022).