The first two years of JWST science operations have already yielded astonishing discoveries – and the best is almost certainly yet to come.
On July 11, 2022, after decades of planning and construction, and more than six months after launch, deployment, and careful calibration, the James Webb Space Telescope (JWST) finally unveiled its first science image to the world.
Galaxy cluster SMACS 0723, located “only” four billion light-years from Earth, provided the target, and JWST delivered not only our best, most detailed image ever of that galaxy cluster, but glimpsed hundreds of extremely distant objects behind it: objects whose light was stretched, distorted, and magnified by the foreground galaxy cluster that was nominally its science target. Many of those distant objects turned out to be galaxies from the first few hundred million years of cosmic history, challenging Hubble’s old cosmic distance record immediately.
Fast-forward to late 2024, and not only has that record been smashed by JWST, but the most distant galaxy as of early 2022 – GN-z11 – is presently only the eleventh most distant galaxy known to humanity, with galaxies measured by JWST holding all of the top ten spots.
In addition, JWST has set new cosmic records for: the most distant gravitational lens ever discovered, the earliest protocluster of galaxies ever spotted, the most distant supermassive black hole ever found, and the farthest red supergiant star ever detected, among many others. It’s worth noting that none of the objects found had any properties that made them special or unique; they simply happen to represent the most distant objects of their particular class that JWST has revealed so far.
Rewriting the cosmic record books
In other words, although many new cosmic records have been set during JWST’s first two years of science operations, we should fully expect the telescope to extend all of these records in the future – particularly as longer observing times are leveraged to reveal fainter, more distant objects, while surveying ever-larger regions of the sky.
All of the most distant galaxies, for example, have been found by the JADES, GLASS, UNCOVER, and CEERS collaborations, but humanity is still awaiting the final science results from the largest, deepest set of galaxy observations conducted with JWST: the COSMOS-Web survey. There are already more than a dozen candidate objects that could break the current cosmic distance record, assuming their suspected properties survive spectroscopic follow-up, making it eminently possible that many of these recently set records have already been broken by JWST data awaiting analysis and/or publication.
However, as impressive as these early results are, they represent discoveries that were expected with JWST’s capabilities. What’s far more remarkable are the discoveries that weren’t anticipated, but that only occurred because of two things occurring in combination.
First, we dared to look in great depth and gory detail at objects or regions of space where we didn’t know what to expect. Second, and perhaps most importantly, we looked at these objects and regions with new capabilities, allowing ourselves the possibility of discovering something wholly unanticipated.
This latter aspect is what astronomers call “discovery potential,” and it’s due to the fact that JWST combines superior resolution, tremendous light-gathering power, and optimization over a range of wavelengths that are being probed in unprecedented detail. Together, these factors have enabled JWST’s most surprising, revolutionary, and unexpected discoveries.
Although it’s a matter of personal preference, I would rate the following three discoveries as the most astonishing.
1) Supermassive black holes don't come from stars
At the center of nearly every large galaxy is a supermassive black hole. In modern times, more than 10 billion years after the hot Big Bang, these black holes can be enormous – millions or even billions of times the mass of the Sun – but typically only add up to, at most, about 0.1% of the mass of stars within their host galaxy. However, black holes have been found with very large masses, of hundreds of millions or even a billion or more solar masses, back when the universe was under one billion years old.
In theory, there are two major scenarios for how these black holes could have formed: either they were formed from early generations of stars that lived, died, and gave rise to black hole remnants that merged and grew into a supermassive black hole, or they formed independently of stars, creating massive seed black holes that would gradually grow in mass while accumulating ever-greater numbers of stars around them.
Prior to JWST, we didn’t know which of these scenarios to favor. However, a set of important JWST observations, including combined JWST infrared and Chandra X-ray observations of object UHZ-1, have shown us that early black holes were more massive relative to the stars in their galaxies as compared with today. Instead of a mass ratio of 0.1%, early galaxies show ratios of 1%, 10%, or possibly even 100%, indicating that high-mass black hole seeds formed independently of and before the majority of stars.
These observations suggest that large black holes likely formed within the first 200 million years of cosmic history, pointing to an origin that disfavors the idea that they come from stars – one of JWST’s greatest cosmic surprises.
2) Enormous numbers of parentless giant planets, including in binary pairs, are born wherever star-formation occurs
The Great Orion Nebula, located a mere 1,300 light-years away, is the closest large star-forming region to Earth, with thousands of newborn and still-forming stars inside of it. While infrared observations prior to JWST were capable of mapping out the gas, dust, and a large number of protostars found inside the nebula, JWST could see fainter, smaller, and lower-mass objects than any other infrared observatory.
When observing the interior of this nebula with JWST’s novel instruments and capabilities, scientists discovered a surprise: not only were there large numbers of Jupiter-mass (or even super-Jupiter) planets found in isolation, without a parent star of any type, but a whopping 9% of them were found bound together in binary systems.
This new species of binary “failed star” systems are known as JuMBOs: Jupiter-Mass Binary Objects. If not for JWST’s newly tapped discovery potential, combined with the decision to look deeply into the Orion Nebula, these JuMBOs would still remain unknown to humanity.
3) Our own Solar System, with an asteroid and Kuiper belt, may not have a “typical” number of belts
As recently as 1990, there were no planets known to exist beyond our Solar System. At present, there are over 5,500 confirmed exoplanets, teaching us that planets of all sizes and masses can be found at any distance from their parent star. However, much still remains to be discovered about how planets’ moons and other important features form within young stellar systems.
For a long time, humanity has assumed that the structure of our Solar System – with planets, an asteroid belt, more planets, a Kuiper belt, and finally a diffuse Oort cloud – would be typical, and such features would be ubiquitous elsewhere in the universe. That’s why JWST observations of the bright star Fomalhaut, the nearest young stellar system to Earth that still has a debris disk around it, were so tantalizing to scientists.
When we looked, however, what we found was shocking: in addition to an inner disk, corresponding to our asteroid belt, and an outer ring that corresponds to our Kuiper belt, scientists discovered a third, intermediate belt between them, a feature that was wholly unexpected.
Prior to JWST, we assumed our Solar System was a typical example of a planetary system in the universe. Today, in the aftermath of these Fomalhaut observations, we don’t even know how many “belts” are typical, and whether two, three, or some other number are most common among planetary systems.
Two decades of discovery
Owing to its near-perfect launch on December 25, 2021, JWST was able to conserve an inordinate amount of its on-board fuel for science operations, rather than expending it to reach its destination at the L2 Lagrange point (1.5 million km more distant from the Sun than Earth is). While the initial plan was that JWST would have somewhere between 5.5 and 10 years of science operations, the revised number in the aftermath of that launch is more like 22 to 23 years, implying that we still have a full two decades of JWST science ahead of us.
Sure, a significant number of new records will be set, and many records that JWST currently holds will likely be broken again. But the thing you should most expect – and, I would argue, the discoveries you should be most excited for – are the ones that will arise simply because we looked at some aspect of the universe with new capabilities, which enables serendipitous and unexpected surprises. From planets to stars to galaxies to black holes and more, the greatest revolutions that JWST will bring to humanity are almost certainly still ahead of us.
A theoretical astrophysicist by training, Ethan Siegel took the unconventional path of ditching research to become a full-time science communicator. He is the creator of the science site Starts With a Bang and author of Infinite Cosmos: Visions from the James Webb Space Telescope, published by National Geographic.
