The ‘beautiful confusion’ of the first billion years is on display

Susan CassinHe, an astronomer at the Space Telescope Science Institute, showed images from previous observatories compared to those of the James Webb Space Telescope. It was like the eye doctor turning the lens so that the last lines on the eye chart were in focus. “Thank you Webb, that’s a $10 billion difference,” she said. People laughed and nodded.

The James Webb Space Telescope is unique in its ability to see a young universe, which has drifted away from us in space and time. Its infrared sensors, its extremely cold location in space, and its heliosphere — which blocks light from the Sun, Moon, and Earth — are uniquely suited to identifying the first galaxies and their stars. These objects are too faint and have the wrong wavelengths to be seen by previous observatories, such as the Hubble Space Telescope.

For astronomers, atmospheres are collective. Many of the presentations at the KITP conference included calls for collaborators and partners to share ideas.

“It was a crazy competition when the first data dropped. Now it’s about coming up with ideas,” he said. Caitlin Casey From the University of Texas, Austin. “There is a huge amount of data, and everyone has enough of it.”

Astrophysicist Rachel SomervilleThe community is striving to understand the James Webb Space Telescope data and its implications, said he, who co-organized the meeting. Observers see things that are not explained in current theories about the evolution of the young universe.

“Many presentations have shown that there is a tension between theory and observation,” he said. Fabio Pacucci from Harvard University, in one example of cosmological minimization. To illustrate the confusion astronomers feel about this once-in-a-lifetime telescope that is upending what we know about the young universe, he showed a satirical slide: a cartoon of a dog sitting at a table drinking coffee while his house is on fire, captioned “This is good.”

The biggest and brightest

Astronomers keep pointing out one of the most significant galaxies seen so far, an unexpectedly bright speck of light called JADES-GS-z14-0. Heinlein, of the University of Arizona, is part of the team that discovered it in collaboration with the James Webb Space Telescope Distance confirmed In May 2024. It is the oldest known galaxy, toppling the previous record holder, which was Found With the same team in 2023.

At the time the galaxy brightened, the sound waves generated by the massive clap that started the universe were still ringing through the void. The first stars were born during a catastrophic baby boom, and some were already dead. Also lurking were the dark cores of black holes, regions of space where gravity is so strong that even light cannot escape. And there was this cluster of stars, resolved as a mysterious scorpion in the filters of the James Webb Space Telescope. Two instruments on the James Webb Space Telescope were able to discern the brightness of JADES-GS-z14-0 and its distance from Earth. Because of the accelerating expansion of the universe, objects found at great distances date back a very long time. Astronomers can figure out their ages based on their light stretching out to longer wavelengths, known as redshift. Based on the latest measurements, the galaxy has been determined to be located at a redshift of 14.18, meaning we see it as it appeared 300 million years after the Big Bang, when the universe was about 2% of its current age.

Initially, astronomers speculated that such massive, bright objects in the very early universe were inconsistent with the prevailing theoretical model of the universe. But people have watered down this claim. Our best model of the universe – a set of equations that describe the evolution of matter and radiation along with dark energy and dark matter – is not dead yet.

“There was a lot of excitement” in the early days of JWST, he said Alice Shapley From the University of California, Los Angeles. “There’s no need for that. The data is so beautiful; let’s just study the universe we have.”

Astrophysicists are united around three star-based theories about how galaxies grow so quickly. One would think that the stars during the cosmic dawn were very different from the stars today. For example, the stars in JADES-GS-z14-0 may be extremely bright but are not actually very massive. Although this seems reasonable, it is also difficult for theoretical modellers to address. The relationship between a star’s brightness and its mass is a fundamental value that is introduced into computer simulations. If this value — known as the initial mass function, or IMF — was different in the early universe, researchers would have to rewrite their simulations to be able to accommodate the IMF that changes over time.

But nature doesn’t care about the computational issues we face, and a variable IMF is in principle one of the most plausible ways to understand what we see. “The IMF is really a house of cards that we build everything on. There are many reasons to believe that it is very different at very high redshift,” Casey said.

Another theory is that early, ultra-luminous galaxies were undergoing furious bursts of star formation. Over the course of 10 million or 100 million years, the brightness of a galaxy can change by a factor of 100 as star formation ramps up and down. This is like a candle that turns into a floodlight within a few seconds. Relatedly, during these busy periods, supernova explosions may have made things appear brighter than they otherwise would.

The third theory indicates that the process of star formation was more efficient at that time than it is now. In a typical galaxy today, a small fraction of the gas is formed into stars; The Milky Way galaxy builds between two and six sun-sized stars per year. But the smallness and compactness of the early universe may have made it a better star factory. Some calculations put the gas-to-star conversion at nearly 100%, meaning fast and furious star birth. Pratika Dayal From the University of Groningen in the Netherlands.

All of these tweaks to current theory come with side effects, like changes in how much dust there should be, and mysteries about how these magnificent baby booms stabilize. And they’re not even the only ideas out there. Andrea FerraraA cosmologist at the Scuola Normale Superiore in Pisa, Italy, showed his colleagues in Santa Barbara a new model that attempts to explain bright early galaxies by changing the amount of dust inside them, which normally blocks starlight. His model assumed that the stellar wind was blowing up more dust. “Reducing dust attenuation is my favorite hypothesis, although I am completely open to the other two,” he told the audience. But he acknowledged that his calculations might not hold up at a redshift of 14, meaning they might not work for galaxies like JADES-GS-z14-0.

“So please don’t discover other galaxies,” he concluded, laughing.

Large black holes

Theories about the stars are not the only ideas. Some astrophysicists point to active supermassive black holes, which they say may heat up the surrounding gas and cause galaxies like JADES-GS-z14-0 to appear extremely bright.

In a series of papers published in May, the JADES team said the galaxy is full of stars, and that their brightness cannot be explained by black holes. But other galaxies have such dark hearts. We know that supermassive black holes weighing hundreds of millions or billions of Suns anchor the centers of young galaxies. The James Webb Space Telescope sees smudged light from many early galaxies, Indicating And their gas is also suspended by a central supermassive black hole. How did large black holes get there?

Since black holes were first predicted as a result of Albert Einstein’s theory of gravity, astrophysicists have envisioned how they might form from the internal gravitational collapse of dying stars. They now know that the universe is full of black holes that formed in this way. But cosmologists have difficulty understanding supermassive black holes. Somehow, these black holes grew large and fast enough to form the galaxies that formed around them. If they had started out as collapsed stars, they would have grown at amazing rates that defy physical explanation.