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 launched into space. As such, it is helping usher in a new era of astrophysics. Astronomers can now study more distant and earlier galaxies 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,” he says Jorge Moreno, associate professor of astronomy at Pomona College. “We have to look back in time, but we don’t have a time machine. So what we do is we look at really long distances.”
As scientists peer into the deep, distant history of the universe, they are shocked to discover that galaxies appeared much earlier in our cosmic history than scientists ever expected.
It’s a galactic controversy that has astronomers all over the world excited—and confused.
So what is it about these galaxies that puzzles astronomers? Not only are JWST galaxies forming 200-500 million years after the big bang, but also that they are larger and more clear than astronomers expected.
Using light to see into the past
The most distant galaxies seen by the telescope are also some of the oldest galaxies in our universe. The James Webb Space Telescope can see them because it picks up the faint light they emit.
By the time light from these far reaches of space approaches a telescope, it is in the infrared region of light and no longer visible to the naked eye. Light visible to humans is only a fraction of the total range of light on Earth electromagnetic spectrum.
NASA and A. Feild (STScI)
This light traveled for a long time before reaching the telescope. By comparison, it takes about eight minutes for light to travel from the Sun to your eye. Light from Proxima Centauri, the Sun’s nearest stellar neighbor, takes just over four years to reach us here on Earth.
Seeing a teenager while you’re waiting for the kindergartner
Light is a double-edged sword in the context of these galaxies. This allows us to study galaxies. But there is much more to it than astronomers would expect.
The brightness of a galaxy can be related to its mass, since the light of the galaxy comes from the stars. If you assume a certain average brightness and mass of the star, you can roughly estimate the mass of the galaxy.
But much of the modeling that astronomers have done up to this point has led them to believe that there hasn’t been enough time for galaxies to reach this mass in such a short time.
“It’s like walking into a kindergarten and seeing a teenager,” Moreno says.
However, Moreno says this assumption that brightness equals mass may not always be accurate. For example, a supermassive black hole could be active at the center of these early galaxies bright accretion disks or high-energy jets that would make galaxies appear artificially massive. Or, if there is hot dust in the galaxies—which shows up very clearly in the infrared wavelengths captured by the James Webb Space Telescope—that would also make the galaxies appear more massive than they are.
When young galaxies are advanced for their age
Most galaxies are divided into two types: spiral, which are disc-shaped with arms of dust and gas; and elliptical, which are more orbs of smooth light.
Until now, scientists thought that any galaxies from this relatively early period in the universe’s history would be too young to have been squeezed into this binary yet. Instead, astronomers thought galaxies would be…balls. But Moreno and other astronomers like him are excited to now be studying what appear to be fairly highly structured galaxies.
“Some of them look a lot like galaxies in the local universe,” he says. “They seem to have added structure and maybe spiral arms. That wasn’t something we really expected.”
The high level of structure and brightness in these galaxies leads some astrophysicists to question the age of the universe.
The universe doesn’t look a day more than 13.8 billion years old
In an attempt to explain the shockingly bright, highly structured—and possibly quite massive—galaxies existing so early in the universe’s timeline, some researchers have hypothesized that the universe is roughly twice as old as previously believed. They push the age of the universe from 13.8 billion years to 26.7 billion years.
An article published earlier this year in the journal Monthly Reports of the Royal Astronomical Society came to this conclusion after combining two models of the universe. One of them is the commonly accepted model of the expansion of the universe. This model explains that as the universe expands, the light from the galaxies has to travel further and therefore shifts from a bluer to a redder spectrum of light. Another model with which it is combined has been revealed. It’s called the tired-light model, and it posits that as light travels through space, it becomes redder because it “gets tired,” or loses energy.
Moreno says that while he thinks combining models is smart, it’s not supported by scientific evidence.
“I think in science, if you already have a model that’s simpler than that, you should stick with it — unless you have extraordinary evidence to do otherwise.”
Moreno also cautions people against jumping to this assumption that the universe is twice as old as previously thought. If this were true, scientists could prove it by directly observing stars and galaxies that are older than 13.8 billion years, the current accepted age of the universe.
No such evidence was found.
We pause to absorb ancient, galactic wisdom
NASA receives more data from the James Webb Space Telescope every day – and with more data comes opportunities for new solutions.
But for Moreno, it’s also important to stop to think about the conclusions we draw from our observations.
Such are the lessons from these galaxies, which, according to Moreno, go through alternating periods of brightening and dimming. “I think that’s something we need to learn from them — that it’s important to have moments when we’re really excited about discovering things. But there are times when we need to quiet down, take a break and really think things through 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 controversy? Email us at [email protected].