NASA, ESA, CSA, Simon Lilly (ETH Zurich), Daichi Kashino (Nagoya University), Jorryt Matthee (ETH Zurich), Christina Eilers (MIT), Rongmon Bordoloi (NCSU), Ruari Mackenzie (ETH Zurich)
The James Webb Space Telescope is the most powerful telescope ever sent into space. As such, this helps usher in a new era of astrophysics. Astronomers can now study galaxies that are more distant and older than ever before.
“If you were a paleontologist, you would dig deeper and deeper to find the oldest bones. In astronomy, we look at our history,” says Jorge Moreno, associate professor of astronomy at Pomona College. “We need to go back in time, but we don’t have a time machine. So we’re looking at very far distances.”
As they peer into the deep and distant history of the universe, scientists are shocked to discover that galaxies have appeared in our cosmic history much earlier than expected.
This is a galactic controversy that arouses the enthusiasm and perplexity of astronomers around the world.
So what worries astronomers about these galaxies? Not only does JWST discover that galaxies formed 200 to 500 million years after the Big Bang, but also that they are bigger And more shiny than predicted by astronomers.
Using light to look into the past
The most distant galaxies observed by the telescope are also among the oldest galaxies in our universe. The James Webb Space Telescope can see them because it captures the faint light they emit.
As light from these far reaches of the universe approaches the telescope, it is in the infrared range of light and is no longer visible to the naked eye. Light visible to humans is only a fraction of the total range of light in the electromagnetic spectrum.
NASA and A. Feild (STScI)
This light traveled a long time before reaching the telescope. For reference, it takes about eight minutes for light to travel from the sun to your eyes. Light from Proxima Centauri, the Sun’s closest neighboring star, takes a little over four years to reach us here on Earth.
Seeing a teenager while waiting for kindergarten
Light is a double-edged sword in the context of these galaxies. This is what allows us to study galaxies. But there’s more than astronomers might have expected.
A galaxy’s brightness can be related to its mass, because a galaxy’s light comes from stars. If you assume a certain average luminosity and mass of a star, you can roughly estimate the mass of a galaxy.
But most of the modeling astronomers have done so far has led them to believe there isn’t enough time for galaxies to reach such mass in such a short time.
“It’s like you go to kindergarten and see a teenager,” Moreno says.
However, Moreno says this assumption that luminosity equals mass is not always accurate. For example, there could be an active supermassive black hole at the center of these early galaxies with bright accretion disks or high-energy jets that would make the galaxies appear artificially massive. Or, if there is hot dust in the galaxies – which appears very bright in infrared wavelengths captured by the James Webb Space Telescope – that would also make the galaxies appear more massive than they are. are.
When young galaxies are advanced for their age
Most galaxies are divided into two types: spirals, which look like disks with arms of dust and gas; and ellipticals, which look more like spheres of soft light.
Until now, scientists thought that all galaxies from this relatively early period in the history of the universe would have been too young to have been forced into this binary. Instead, astronomers thought the galaxies would be… blobs. But Moreno and other astronomers like him are excited to now study what look like fairly highly structured galaxies.
“Some of them look a lot like galaxies in the local universe,” he says. “They appear to have extra structure and maybe even spiral arms. That wasn’t something we really expected.”
The high level of structure and luminosity of these galaxies leads some astrophysicists to question the age of the universe.
The universe appears to be no more than 13.8 billion years old
In an attempt to explain the incredibly bright, highly structured – and perhaps quite massive – galaxies existing so early in the universe’s timeline, some researchers have postulated that the universe is about twice as old as previously thought. thought before. They increase the age of the universe from 13.8 billion years to approximately 26.7 billion years.
An article published earlier this year in the journal Monthly Notices of the Royal Astronomical SocietyI came to this conclusion after combining two models of the universe. One of them is the commonly accepted model for the expansion of the universe. This model explains that as the universe expands, light from galaxies must travel farther and therefore changes from a bluer spectrum of light to a redder spectrum of light. The other model it is combined with has been debunked. This is called the tired light model, and it claims that as light travels through the universe, it becomes redder because it is “tired” or losing energy.
Moreno says that while he thinks the combination of models is clever, it is not supported by scientific evidence.
“I think in science, if you already have a simpler model than that, you should stick with it, unless you have extraordinary evidence to do otherwise.”
Moreno also cautions people against jumping quickly to the hypothesis that the universe is twice as old as previously thought. If this were true, scientists would be able to prove it through direct observation of stars and galaxies older than 13.8 billion years, the currently accepted age of the universe.
No such evidence has been found.
Pause to discover ancient and galactic wisdom
NASA is receiving more data from the James Webb Space Telescope every day, and this additional data is paving the way for new solutions.
But for Moreno, stopping to think about the conclusions we draw based on observations is also important.
The same goes for the lessons learned from these galaxies, which Moreno says alternately go through periods of brightening and dimming. “I think that’s something we need to learn from them: it’s important to have times where we’re really excited to discover things. But there are times when we need to calm down, take a break and really think clearly and slowly.”
This episode was produced by Rachel Carlson. It was edited by Rebecca Ramirez and Berly McCoy. Anil Oza checked the facts. Josh Newell was the sound engineer. Special thanks to James Davenport.
Questions or controversies? Email us at [email protected].