Why the earliest galaxies are sparking drama and controversy among astronomers

The James Webb Space Telescope is the most powerful telescope ever put into space. As such, its helping usher in a new era of astrophysics. Astronomers can now study farther, earlier galaxies than ever before.

"If you were a paleontologist, you would dig deeper and deeper to find the oldest bones. In astronomy, what we do is look at our history," says Jorge Moreno, an 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 faraway distances."

As they peer into the deep, distant history of the universe, scientists are shocked to find galaxies showed in our cosmic history much sooner than scientists ever expected.

It's a galactic controversy that has astronomers around the world excited—and puzzled.

So what is it about these galaxies that is getting astronomers worked up? Not only is JWST finding galaxies forming 200-500 million years after the Big Bang, but also that they are bigger and brighter than astronomers expected.

Using light to peer into the past

The farthest galaxies seen by the telescope are also some of the earliest galaxies in our universe. The James Webb Space Telescope can see them because it is picking up the faint light emitted by them.

By the time light from these far reaches of the universe approaches the telescope, it is in the infrared range of light, and no longer viewable to the naked eye. The light visible to humans is just a fraction of the total range of light on the electromagnetic spectrum.

This light has been traveling a long time by the time it reaches the telescope. For reference, it takes around eight minutes for light to travel from the sun to your eye. Light from Proxima Centauri, the nearest stellar neighbor of the sun, takes a little over four years to reach us here on earth.

Seeing a teenager when you expect a kindergartener

Light is a double-edged sword in the context of these galaxies. Its what lets us study the galaxies. But there's so much more of it than astronomers would have expected.

The brightness of a galaxy can be related to its mass, because a galaxy's light comes from stars. If you assume a certain average brightness and mass of a star, you can roughly estimate the mass of a galaxy.

But much of the modeling astronomers have done up to this point has led them to believe that there wasn't enough time for galaxies to get this massive in so little time.

"It's like if you went to a kindergarten and you saw a teenager," says Moreno.

However, Moreno says this assumption that brightness equates to mass may not always be 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 seem artificially massive. Or, if there's hot dust in the galaxies—which looks very bright in the infrared wavelengths picked up by the James Webb Space Telescope—that too would make the galaxies seem more massive than they are.

When young galaxies are advanced for their age

Most galaxies are separated into two types: spirals, which are disk-like with arms of dust and gas; and ellipticals, which are more like spheres of smooth light.

Until now, scientists thought that any galaxies from this relatively early period in the history of the universe would have been too young to have been forced into that binary yet. Instead, astronomers thought the galaxies would be ... blobs. But Moreno and other astronomers like him are excited to now be studying what look like pretty 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 even spiral arms. That wasn't something we really expected."

The high level of structure and brightness in these galaxies is leading some astrophysicists to question the age of the universe.

The universe doesn't look a day over 13.8 billion years old

Roughly.

In an attempt to explain the shockingly bright, highly structured—and possibly quite massive—galaxies existing so early in the timeline of the universe, a researcher has posited that the universe is roughly twice as old as previously believed. They push the age of the universe from a spry 13.8 billion years old to roughly 26.7 billion years old.

An article published earlier this year in the journal Monthly Notices of the Royal Astronomical Society came to this conclusion after combining two models of the universe. One is the commonly accepted model for the expansion of the universe. This model explains that as the universe expands, the light from galaxies must travel further and therefore shifts from a bluer to a redder spectrum of light. The other model it is combined with has been debunked. It's called the tired light model, and it alleges that as light travels across the universe, it gets redder because it gets "tired," or loses energy.

Moreno says that while he thinks that combining the models is clever, it is not supported by scientific evidence.

"I think in science, if you already have a model that's simpler than that, you should stick to it—unless you have extraordinary evidence to do otherwise."

Moreno also cautions people against quickly jumping on this supposition that the universe is twice as old as previously thought. If it were true, scientists would be able to prove it through the direct observation of stars and galaxies that are older than 13.8 billion years old—the current accepted age of the universe.

No such evidence has been found.

Pausing to take in ancient, galactic wisdom

NASA receives more data from the James Webb Space Telescope everyday—and with additional data comes possibilities for new solutions.

But for Moreno, pausing for reflective moments about the conclusions we make based on observations are also important.

So too, are lessons from these galaxies, which Moreno notes alternately go through periods of brightening and dimming. "I think that's something we need to learn from them—that it's important to just have times where we're really excited to discover things. But there are times where we need to quiet down, take a break and really think through things 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 audio engineer. Special thanks to James Davenport.

Questions or controversies? Email us at shortwave@npr.org.