(The Conversation) Three years ago today, we witnessed the amazing launch of the James Webb Space Telescope (JWST), the largest and most powerful telescope ever sent into space by humans.
It took 30 years to build, but in three short years of operation, JWST has already revolutionized our view of the universe.
It has explored our own solar system, studied the atmospheres of distant planets in search of signs of life and probed the farthest depths to find the very first stars and galaxies that formed in the universe.
Here’s what the JWST has taught us about the early universe since its launch – and revealed new mysteries.
The terrifying blue monsters JWST have pushed have pushed the limits of how far into the universe we can see to find the first stars and galaxies. Being out of the way of Earth’s atmosphere, its location in space creates ideal conditions for peering into the depths of the universe with infrared light.
The current record for the most distant galaxy confirmed by the JWST dates back to when the universe was only about 300 million years old. Amazingly, within this short time period, this galaxy managed to create a mass approximately 400 million times that of our Sun.
This indicates that star formation was extremely efficient in the early universe. And this galaxy is not alone.
When galaxies grow, their stars explode, creating dust. The larger the galaxy, the more dust it contains. This dust makes galaxies appear red because it absorbs blue light. But there’s a problem: JWST has shown these first galaxies to be surprisingly bright, massive, and very blue, with no trace of dust. This is a real puzzle.
There are many theories to explain the strange nature of these first galaxies. Do they have massive stars that collapse due to gravity without massive supernova explosions? Or do they have such massive explosions that all the dust is blown far away from the galaxy, exposing a blue, dust-free core? Perhaps the dust has been destroyed by the intense radiation of these early alien stars – we don’t know yet.
Unusual Chemistry in Early Galaxies Early stars were key building blocks in the eventual formation of life. The universe began with only hydrogen, helium, and a small amount of lithium. All the other elements, from the calcium in our bones to the oxygen in the air we breathe, were formed in the cores of these stars.
JWST has discovered that even early galaxies have unusual chemical characteristics.
They contain a significant amount of nitrogen, much more than what we see in our Sun, while most other metals are present in smaller quantities. This shows that there were processes going on in the early universe that we do not yet fully understand.
JWST shows 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.
Tiny Things That Ended the Dark Edges of the Universe Using vast clusters of galaxies as giant magnifying glasses, JWST’s sensitive cameras can also peer into the depths of the universe to find faint galaxies.
We went on to find the point where galaxies become so faint that they stop making stars altogether. This helps us understand the conditions under which galaxy formation ends.
JWST has not yet met this limit. However, it has uncovered many fainter galaxies than expected, emitting four times more energetic photons (light particles) than we expected.
The discovery suggests that these small galaxies may have played a key role in ending the cosmic “dark ages” shortly after the Big Bang.
The Mysterious Case of the Little Red Dots The first images from JWST resulted in another dramatic, unexpected discovery. The early universe is populated by an abundance of “little red dots”: extremely compact reddish sources of unknown origin.
Initially, they were thought to be giant ultra-dense galaxies that should not be possible, but detailed observations over the past year have revealed a combination of deeply puzzling and contradictory properties.
The glowing hydrogen gas is emitting light at a rapid speed of thousands of kilometers per second, which is characteristic of gas swirling around a supermassive black hole.
This event, called an active galactic nucleus, usually signals a feeding frenzy where a supermassive black hole is swallowing all the gas around it, and expanding rapidly.
But these aren’t your garden variety active galactic nuclei. For starters: they don’t emit any detectable X-rays, as would normally be expected. What’s even more interesting is that they have characteristics of star populations.
Could these galaxies be both stars and active galaxy nuclei at the same time? Or some evolutionary stage in between? Whatever they are, the little red dots will probably teach us something about the birth of both supermassive black holes and stars in galaxies.
As well as extremely vibrant early galaxies, JWST has also found extremely dead bodies: galaxies in the early universe that are the remains of intense star formation at the cosmic dawn.
These corpses were found by Hubble and ground-based telescopes, but only JWST had the power to dissect their light to reveal how long they had been dead.
It has discovered some extremely massive galaxies (as massive as our Milky Way today and even larger), which formed in the first 700 million years of cosmic history. Our current galaxy formation models cannot explain these objects – they are too large and formed too quickly.
Cosmologists are still debating whether models can be bent to fit (for example, perhaps early star formation was extremely efficient) or whether we need to reconsider the nature of dark matter and how quickly it formed. Gives rise to collapsible objects.
JWST will uncover many more of these objects next year and study existing objects in more detail. Either way, we’ll find out soon.
What’s next for JWST? Even in its first stages, the telescope has exposed many of the shortcomings of our current models of the universe. While we are refining our models to take into account the updates JWST brings us, we are most excited about the unknown unknowns.
Mysterious red dots were hiding from our sight. What else is hidden in the depths of the universe? JWST will tell us soon. (Conversation)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
