The best target we've ever had for moon hunting
Humanity's most powerful eye on the cosmos has chosen its next questions to ask of the universe. NASA's James Webb Space Telescope, now entering its third operational cycle, will spend 5,500 hours through June 2025 pursuing some of astronomy's most enduring mysteries — from moons orbiting distant worlds to the infant black holes of a universe barely born. In selecting 253 research programs, the scientific community has collectively decided that this is a moment not merely to observe, but to fundamentally reckon with how structure, life, and time itself emerged from the dark.
- The search for exomoons — worlds orbiting worlds around other stars — has long been astronomy's most elusive quarry, and Cycle 3 will mount its most credible attempt yet at a confirmed detection.
- Supermassive black holes billions of times the mass of our sun existed when the universe was less than a billion years old, a fact that defies easy explanation and drives some of Cycle 3's most urgent investigations.
- The epoch of reionization, when the first galaxies tore apart the primordial hydrogen fog, remains poorly understood — and JWST's infrared reach may finally illuminate who lit the universe's first lights.
- With 5,500 observation hours spread across exoplanets, black holes, early galaxies, dark energy, and even Saturn's moon Enceladus, the telescope's agenda reflects a science community racing to answer questions faster than new ones can form.
- Even as Cycle 3 begins, the institute is already opening proposals for Cycle 4, signaling that JWST's revolution is not a moment but an ongoing unraveling of cosmic assumptions.
In late February, the Space Telescope Science Institute announced that 253 research proposals had been selected for the James Webb Space Telescope's third operational cycle — 5,500 hours of observation time stretching from July 2024 through June 2025. The agenda is sweeping, but a few frontiers stand out for their ambition and their stakes.
Among the most anticipated is the hunt for exomoons. Columbia University astronomer David Kipping will lead a team targeting Kepler-167e, a Jupiter-sized planet 1,115 light-years away that he calls the best candidate ever identified for moon detection. The challenge is immense — exomoons block almost no light and must transit their star at precisely the right moment — but a confirmed discovery would mark the first known moon beyond our solar system.
Cycle 3 will also press into the mystery of supermassive black holes, which somehow grew to billions of solar masses before the universe was even a billion years old. One program will investigate whether an ancient molecular cloud from 13.2 billion years ago could have collapsed directly into a massive black hole seed, potentially explaining how these cosmic giants assembled so quickly. Physicist Xavier Calmet of the University of Sussex described these observations as a window into one of the universe's deepest unsolved problems.
The telescope will also continue its signature work: detecting light from the universe's earliest epochs. Cosmologist Luz Angela Garcia highlighted programs focused on the epoch of reionization — roughly 500 million years after the Big Bang — when the first galaxies ionized the neutral hydrogen filling all of space. Understanding which galaxies drove that transformation is, she noted, essential to tracing how the cosmos evolved from a featureless dark expanse into the structured universe we inhabit.
Beyond these headline pursuits, Cycle 3 reaches into stellar physics, interstellar gas clouds, and even our own solar system — studying geysers on Enceladus, the rings of Uranus, and distant Kuiper Belt objects. Having already upended cosmological assumptions in its first two years, JWST now deepens that revolution. Proposals for Cycle 4 open in August 2024, with observations beginning the following July — a reminder that the questions being answered today are already giving rise to the next generation of unknowns.
In July 2024, the James Webb Space Telescope will turn its infrared eye toward one of astronomy's most tantalizing unknowns: moons orbiting planets around distant stars. The Space Telescope Science Institute announced in late February that 253 research proposals have won time on humanity's most powerful space observatory for the next two years, a collective 5,500 hours of observation stretching through June 2025. This third cycle of JWST operations will chase exomoons, probe the hearts of supermassive black holes, and peer back toward the universe's infancy—a scientific agenda that builds on two years of discoveries that have already begun reshaping our understanding of the cosmos.
The hunt for exomoons represents one of the cycle's most ambitious frontiers. David Kipping, an astronomer at Columbia University, will lead a team using the telescope's Near Infrared Imager and Slitless Spectrograph to search for moons around Kepler-167e, a Jupiter-sized gas giant orbiting 1,115 light-years away. Finding exomoons has proven extraordinarily difficult because they block so little light compared to their parent planets, and they must transit their star at precisely the right moment to be detected at all. Kipping called Kepler-167e "the best target we've ever had for moon hunting," and he hopes this observation will yield the first undisputed detection of a world beyond our solar system that orbits another world. Beyond the exomoon search, other Cycle 3 programs will examine whether distant exoplanets possess atmospheres thick enough to support life, particularly those orbiting red dwarf stars—the most common suns in the Milky Way.
The telescope will also train its instruments on supermassive black holes, those cosmic titans that lurk at the centers of most large galaxies. Astronomers believe these objects grew to masses of millions or billions of suns, yet the mechanism of their growth remains mysterious. Some Cycle 3 programs will investigate quasars and the earliest black holes, seeking to understand how such monsters could have assembled before the universe was even a billion years old. One investigation will examine whether a giant molecular cloud from 13.2 billion years ago could have collapsed directly into a "heavy black hole seed," providing a rapid growth pathway that would explain what we observe today. Xavier Calmet, a physicist at the University of Sussex who studies the quantum mechanics of black holes, expressed particular enthusiasm for these observations, noting that they promise to illuminate one of the universe's deepest puzzles.
Perhaps most ambitiously, Cycle 3 will continue the JWST's primary mission: peering back toward the universe's earliest moments. The telescope's infrared sensitivity allows it to detect light that has been stretched into invisibility by the universe's expansion—light that began its journey when the cosmos was only a few hundred million years old. Luz Angela Garcia, a cosmologist at Universidad ECCI in Colombia, highlighted her interest in proposals studying the epoch of reionization, a transformative period roughly 500 million years after the Big Bang when the first galaxies' radiation ionized the neutral hydrogen that filled all of space. Understanding this era requires identifying and characterizing the galaxies that drove it, work that Garcia described as essential to understanding how the universe evolved from a dark, featureless expanse into the structured cosmos we inhabit today.
The breadth of Cycle 3 extends well beyond these headline targets. Astronomers will study stellar physics and stellar populations, examine the gas clouds between stars that seed future planetary systems, and even turn the billion-dollar observatory toward our own cosmic backyard—investigating geysers erupting from Saturn's moon Enceladus, the ring dynamics of Uranus, and icy bodies in the distant Kuiper Belt. The JWST, which cost $10 billion and began transmitting data in 2022, has already upended cosmological assumptions in its first two years of operation. Cycle 3 promises to deepen that revolution, pushing the boundaries of what we can know about the universe's structure, its history, and the strange forces that govern its fate. Already, the Space Telescope Science Institute is preparing for the next round: proposals for Cycle 4 will open in August 2024, with observations beginning in July 2025.
Citas Notables
This is hopefully just the beginning of the exomoon revolution. New worlds that will surely hold some remarkable secrets.— David Kipping, Columbia University astronomer
The JWST Cycle 3 projects are very exciting. Given my own research interests, I am particularly eager to see what we will learn about black holes.— Xavier Calmet, University of Sussex physicist
La Conversación del Hearth Otra perspectiva de la historia
Why is finding an exomoon so much harder than finding an exoplanet?
An exoplanet blocks a measurable amount of starlight as it passes in front of its star. An exomoon orbiting that planet blocks far, far less light—it's like trying to detect a shadow cast by a shadow. You need the moon to transit at exactly the right moment, and you need instruments sensitive enough to catch that tiny dip in brightness.
And the JWST can do this?
It's the best tool we have. The telescope's infrared sensitivity and precision make it possible to detect those subtle signals. Kepler-167e, the target Kipping's team chose, is the most promising candidate yet—if we're going to find an exomoon, this is where it will happen.
What does finding an exomoon actually tell us?
It tells us that moons aren't unique to our solar system. It opens up questions about how common they are, whether they could harbor life, how planetary systems form and evolve. Right now, we're working almost entirely from our own neighborhood. An exomoon would be a whole new category of world to study.
The black hole research seems to focus on a puzzle—how did they grow so fast?
Exactly. We see supermassive black holes in the early universe that shouldn't exist yet, not if they grew the way we thought. They're too massive, too soon. So either our growth models are wrong, or there's a mechanism we haven't understood—like those "heavy black hole seeds" that could collapse directly from gas clouds.
And the early galaxies work—that's about reionization?
Yes. For the first few hundred million years after the Big Bang, the universe was filled with neutral hydrogen—dark, opaque. Then the first galaxies formed and their radiation ionized all that hydrogen, making the universe transparent. We're trying to see those first galaxies and understand how they transformed everything.
Why does that matter now, billions of years later?
Because it shaped everything that came after. Understanding how the universe went from dark to transparent, how the first structures formed, tells us the story of how we got here. It's not just history—it's the foundation of everything.