3 years of the Webb telescope: Here’s what it’s discovered

By Themiya Nanayakkara, Ivo Labbe and Karl Glazebrook, all from the Swinburne University of Technology. Edits by EarthSky.

• The James Webb Space Telescope has been studying space for three years, helping us learn about distant stars, galaxies, and planets.
• It has observed things we could not detect before, like the oldest galaxies and atmospheres of distant planets.
• The Webb also reveals surprising things, such as unexpectedly bright young galaxies, missing dust, and mysterious red dots.

3 years of Webb

Three years ago, on December 25, 2021, we witnessed the nail-biting launch of the James Webb Space Telescope, the largest and most powerful telescope humans have ever sent into space.

It took 30 years to build. But in three short years of operation, Webb has already revolutionized our view of the cosmos.

It’s explored our own solar system, studied the atmospheres of distant planets in search of signs of life, and probed the farthest depths of our universe to find the very first stars and galaxies.

Here’s what Webb has taught us about the early universe since its launch, and the new mysteries it has uncovered.

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Eerie blue monsters

Webb has pushed the boundary of how far we can look into the universe to find the first stars and galaxies. With Earth’s atmosphere out of the way, its location in space provides perfect conditions for its infrared detectors to peer into the depths of the cosmos.

The current record for the most distant galaxy confirmed by Webb dates back to when the universe was only about 300 million years old. Within this short time window, this galaxy surprisingly managed to grow to about 400 million times the mass of our Sun.

This indicates star formation in the early universe was extremely efficient. And this galaxy is not the only one.

When galaxies grow, their stars explode as supernovas, creating dust. The bigger the galaxy, the more dust it has. This dust makes galaxies appear red, because it absorbs the blue light. But here’s the catch: Webb has shown these first galaxies to be shockingly bright, massive and very blue, with no sign of any dust. That’s a real puzzle.

There are many theories to explain the weird nature of these first galaxies. Do they have huge stars that just collapse due to gravity without undergoing massive supernova explosions? Or do they have such large explosions that all dust is pushed away far from the galaxy, exposing a blue, dust-free core? Perhaps the dust is destroyed due to the intense radiation from these early exotic stars? We just don’t know yet.

Artist’s impression of what a blue galaxy in the early universe would look like. Via ESO/M. Kornmesser.

Unusual chemistry in early galaxies

The early stars were the key building blocks of what eventually became life. The universe began with only hydrogen, helium and a small amount of lithium. All other elements, from the calcium in our bones to the oxygen in the air we breathe, were forged in the cores of these stars.

And Webb has discovered that early galaxies have unusual chemical features.

They contain a significant amount of nitrogen – far more than we observe in our sun – while most other metals are present in lower quantities. This suggests there were processes at play in the early universe we don’t yet fully understand.

Webb has shown our models of how stars drive the chemical evolution of galaxies are still incomplete, meaning we still don’t fully understand the conditions that led to our existence.

Small things that ended the cosmic dark ages

Using massive clusters of galaxies as gigantic magnifying glasses – a process called gravitational lensing – Webb has also peered deep into the cosmos to find the faintest galaxies yet.

Webb has uncovered far more faint galaxies than anticipated. And these galaxies are emitting over four times the energetic photons (light particles) scientists expected.

The discovery suggests the light from these small galaxies might have played a crucial role in ending the cosmic ‘dark ages’ not long after the Big Bang. That is, it’s thought that these photons ionized and cleared the opaque fog of hydrogen that permeated the early universe.

Webb discovered the mysterious little red dots

The very first images from Webb resulted in another dramatic, unexpected discovery. The early universe is inhabited by an abundance of ‘little red dots‘: extremely compact red colour sources of unknown origin.

Initially, scientists thought they were massive, impossibly dense galaxies. But detailed observations in the past year have revealed a combination of puzzling and contradictory properties.

Some of the light coming from these dots appears to be not from stars, but from bright hydrogen gas moving at some thousands of kilometres per second. And that’s characteristic of gas swirling around a supermassive black hole.

This phenomenon, called an active galactic nucleus, usually indicates a feeding frenzy, where a supermassive black hole is gobbling up all the gas around it and growing rapidly.

But these are not your garden variety active galactic nuclei. For starters, they don’t emit any detectable X-rays. Even more intriguingly, they seem to have features we’d associate with groups of stars.

Could these galaxies be star populations and active galactic nuclei at the same time? Or some evolutionary stage in between? Whatever they are, the little red dots are probably going to teach us something about the birth of both supermassive black holes and stars in galaxies.

The impossibly early galaxies

As well as extremely lively early galaxies, Webb has also found extremely dead ones. These early galaxies are relics of intense star formation at the cosmic dawn.

These corpses had been found before by Hubble and ground-based telescopes, but only Webb had the power to dissect their light to reveal how long they’ve been dead.

It has uncovered some extremely massive galaxies (as massive as our Milky Way today, and beyond) that formed in the first 700 million years of cosmic history. Our current galaxy formation models can’t explain these objects; they are too big and formed too early.

Cosmologists are still debating whether the models can be bent to fit (for example, maybe early star formation was extremely efficient) or whether we have to reconsider the nature of dark matter and how it gives rise to early collapsing objects. Watch an explainer on this intriguing debate here.

What’s next for Webb?

Within just its first steps, Webb has revealed many shortcomings of our current models of the universe. While we are refining our models to account for the updates Webb has brought us, we are most excited about the unknown unknowns.

The mysterious red dots were hiding from our view. What else is lingering in the depths of cosmos? Webb, hopefully, will soon tell us.

Themiya Nanayakkara, scientist at the James Webb Australian Data Centre; Ivo Labbe, ARC Future Fellow / Associate Professor; and Karl Glazebrook, ARC Laureate Fellow & Distinguished Professor, Centre for Astrophysics & Supercomputing, all from Swinburne University of Technology.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: In the 3 years since it was launched, Webb has made a host of intriguing discoveries. Here’s a rundown of its most important findings so far.

Read more: Weird galaxy: Did Webb find the missing link to first stars?

Read more: MOND and more. Does the universe need a rethink?

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