James Webb’s Big Year for Cosmology

The James Webb Space Telescope was designed and built to study the early universe, and hopefully revolutionary our understanding of cosmology. Two years after its launch, it’s doing just that.

One of the first things that astronomers noticed with the James Webb was galaxies that were brighter and larger than our models of galaxy formation suggested they should be. They were like seeing teenagers in a kindergarten classroom, challenging our assumptions of cosmology. But while there were some breathless claims that the Big Bang was broken, those statements were a little overblown.

But still, big, bright, mature galaxies in the early universe are forcing us to reconsider how galaxy formation is supposed to proceed. Whatever nature is telling us through the James Webb, it seems to be that galaxies form far faster than we thought before.

Related to that, for several years cosmologists have recognized a certain tension in their measurements of the present-day expansion rate of the universe, called the Hubble rate. Appropriately called the Hubble tension, the difference comes when comparing measurements of the distant, early universe with measurements of the later, nearby universe.

There’s definitely something funky going on here, but cosmologists can’t figure out exactly what. It might have something to do with our measurements of the deep universe, or it might be because of our lack of understanding of dark matter and dark energy. Either way, the James Webb didn’t help anything by confirming that the tension is very, very real.

No matter what comes out of the Hubble tension problem, the James Webb is delivering spectacular results in other areas. One of its primary missions was to find evidence for Population III stars, the first generation of stars to appear in the universe. There are no such stars left in the modern-day cosmos, as they all apparently died off billions of years ago. So our only hope to detect them is to use super-telescopes like the James Webb.

This year a team reported the first tentative detections of a galaxy in the young universe that just might contain Population III stars. The detection is not confirmed, but hopefully upcoming observation campaigns will tell us if we’re on the right track.

No matter what, we know we have a lot left to learn about the universe, and that the James Webb will continue delivering results – and hopefully a few surprises – for years to come.