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(The Conversation) On this day three years ago, we witnessed the nail-biting launch of the James Webb Space Telescope (JWST), 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, JWST has already revolutionised 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 to find the very first stars and galaxies formed in the universe.

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

Eerie blue monsters JWST 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 makes for perfect conditions to peer into the depths of the cosmos with infrared light.

The current record for the most distant galaxy confirmed by JWST dates back to a time when the universe was only about 300 million years old. Surprisingly, within this short time window, this galaxy managed to form 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, 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: JWST 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.

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.

JWST has discovered that early galaxies also have unusual chemical features.

They contain a significant amount of nitrogen, far more than what 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.

JWST 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 arges Using massive clusters of galaxies as gigantic magnifying glasses, JWST’s sensitive cameras can also peer deep into the cosmos to find the faintest galaxies.

We pushed further to find the point at which galaxies become so faint, they stop forming stars altogether. This helps us understand the conditions under which galaxy formation comes to an end.

JWST is yet to find this limit. However, it has uncovered many faint galaxies, far more than anticipated, emitting over four times the energetic photons (light particles) we expected.

The discovery suggests these small galaxies may have played a crucial role in ending the cosmic “dark ages” not long after the Big Bang.

The mysterious case of the little red dots The very first images of JWST 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, they were thought to be massive super-dense galaxies that shouldn’t be possible, but detailed observations in the past year have revealed a combination of deeply puzzling and contradictory properties.

Bright hydrogen gas is emitting light at enormous speeds, thousands of kilometres per second, 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, growing rapidly.

But these are not your garden variety active galactic nuclei. For starters: they don’t emit any detectable X-rays, as is normally expected. Even more intriguingly, they seem to have the features of star populations.

Could these galaxies be both stars 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, JWST has also found extremely dead corpses: galaxies in the early universe that are relics of intense star formation at cosmic dawn.

These corpses had been found by Hubble and ground-based telescopes, but only JWST 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 more) 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.

JWST will turn up many more of these objects in the next year and study the existing ones in greater detail. Either way, we will know soon.

What’s next for JWST? Just within its first steps, the telescope has revealed many shortcomings of our current models of the universe. While we are refining our models to account for the updates JWST 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? JWST will soon tell us. (The Conversation)

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

A false-color image obtained by the James Webb Space Telescope (JWST) shows the galaxy JADES-GS-z7-01-QU, the universeÕs earliest-known “dead” galaxy, a galaxy that has stopped star formation, in this undated handout picture obtained by Reuters.
| Photo Credit: Reuters

The James Webb Space Telescope, or JWST for short, is one of the most advanced telescopes ever built. Planning for JWST began over 25 years ago, and construction efforts spanned over a decade. It was launched into space on Dec. 25, 2021, and within a month arrived at its final destination: 930,000 miles away from Earth. Its location in space allows it a relatively unobstructed view of the universe.

The telescope design was a global effort, led by NASA, and intended to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is massive – about 21 feet (6.5 meters) in diameter. That’s nearly three times the size of the Hubble Space Telescope, which launched in 1990 and is still working today.

It’s a telescope’s mirror that allows it to collect light. JWST’s is so big that it can “see” the faintest and farthest galaxies and stars in the universe. Its state-of-the-art instruments can reveal information about the composition, temperature and motion of these distant cosmic objects.

As an astrophysicist, I’m continually looking back in time to see what stars, galaxies and supermassive black holes looked like when their light began its journey toward Earth, and I’m using that information to better understand their growth and evolution. For me, and for thousands of space scientists, the James Webb Space Telescope is a window to that unknown universe.

Just how far back can JWST peer into the cosmos and into the past? About 13.5 billion years.

Time travel

A telescope does not show stars, galaxies and exoplanets as they are right now. Instead, astronomers are catching a glimpse of how they were in the past. It takes time for light to travel across space and reach our telescopes. In essence, that means a look into space is also a trip back in time.

This is even true for objects that are quite close to us. The light you see from the Sun left it about 8 minutes, 20 seconds earlier. That’s how long it takes for the Sun’s light to travel to Earth.

You can easily do the math on this. All light – whether sunlight, a flashlight or a light bulb in your house – travels at 186,000 miles (almost 300,000 kilometers) per second. That’s just over 11 million miles (about 18 million kilometers) per minute. The Sun is about 93 million miles (150 million kilometers) from Earth. That comes out to about 8 minutes, 20 seconds.

But the farther away something is, the longer its light takes to reach us. That’s why the light we see from Proxima Centauri, the closest star to us aside from our Sun, is 4 years old; that is, it’s about 25 trillion miles (approximately 40 trillion kilometers) away from Earth, so that light takes just over four years to reach us. Or, as scientists like to say, four light years.

Most recently, JWST observed Earendel, one of the farthest stars ever detected. The light that JWST sees from Earendel is about 12.9 billion years old.

The James Webb Space Telescope is looking much farther back in time than previously possible with other telescopes, such as the Hubble Space Telescope. For example, although Hubble can see objects 60,000 times fainter than the human eye is able, the JWST can see objects almost nine times fainter than even Hubble can.

The Big Bang

But is it possible to see back to the beginning of time?

The Big Bang is a term used to define the beginning of our universe as we know it. Scientists believe it occurred about 13.8 billion years ago. It is the most widely accepted theory among physicists to explain the history of our universe.

The name is a bit misleading, however, because it suggests that some sort of explosion, like fireworks, created the universe. The Big Bang more closely represents the appearance of rapidly expanding space everywhere in the universe. The environment immediately after the Big Bang was similar to a cosmic fog that covered the universe, making it hard for light to travel beyond it. Eventually, galaxies, stars and planets started to grow.

That’s why this era in the universe is called the “cosmic dark ages.” As the universe continued to expand, the cosmic fog began to rise, and light was eventually able to travel freely through space. In fact, a few satellites have observed the light left by the Big Bang, about 380,000 years after it occurred. These telescopes were built to detect the splotchy leftover glow from the Big Bang, whose light can be tracked in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars and galaxies. The universe was still a very dark place. The cosmic dark ages wouldn’t end until a few hundred million years later, when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light. Before this time period, there is little light for the James Webb Space Telescope to observe, given the conditions of the early universe and the lack of galaxies and stars.

Peering back to the time period close to the Big Bang is not simply a matter of having a larger mirror – astronomers have already done it using other satellites that observe microwave emission from very soon after the Big Bang. So, the James Webb Space Telescope observing the universe a few hundred million years after the Big Bang isn’t a limitation of the telescope. Rather, that’s actually the telescope’s mission. It’s a reflection of where in the universe we expect the first light from stars and galaxies to emerge.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. That includes the evolution of supermassive black holes, the life cycle of stars, and what exoplanets – worlds beyond our solar system – are made of.

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