Launched in December 2021 after three decades of development and at a cost of some $10 billion, NASA’s James Webb Space Telescope (JWST) is one of the biggest investments ever made in astronomy. That investment has already paid off enormously: the telescope is revealing incredible new details of the early universe, distant galaxies, potentially habitable exoplanets and even familiar objects in our solar system. JWST is now on the cusp of its fourth year of operations, and researchers seeking to maximize the telescope’s transformational science have unveiled its next planned swathe of groundbreaking observations. But this comes amid increasing budgetary uncertainty in the U.S. and concerns that NASA might be forced to slash its science funding—which could include significant cuts to JWST.
“It’s up and running, it’s been fully commissioned, and it’s returning incredible science,” says Paul Byrne, a planetary scientist at Washington University in St. Louis. “Webb is a marquee flagship program. If we have to cut at all, it seems like an absolute ‘own goal.’”
JWST is located 1.5 million kilometers from Earth, well beyond the orbit of the moon. Here its giant gold-plated mirror can look unhindered into the cosmos, protected by a tennis court–sized sunshield that blocks our star’s light and heat. All this gives JWST unprecedented sensitivity to some of the faint wisps of light reaching us from the first few hundred million years in which the first stars were kindled and galaxies coalesced. But not all the telescope’s achievements have come from so far afield—closer to home, it has captured the first views of the auroras of Neptune, taken images of planets around other stars and helped scientists study neighboring galaxies to probe the limits of dark energy.
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Every year the Space Telescope Science Institute (STScI)—which runs the telescope—enlists hundreds of astronomers to help choose where JWST’s wandering eye should be pointed next. On March 11 the STScI announced the latest batch of programs it had chosen for JWST’s next year of observations, Cycle 4, which runs from July 2025 to June 2026. In total, the allocation committee selected 274 programs from 2,377 submitted proposals from 39 countries—an oversubscription ratio of about nine to one. About 8,500 hours of observing time were awarded—the most ever for JWST.
That record-setting amount was possible this year because, unlike in the previous three cycles, Cycle 4 doesn’t have a block of time reserved on the telescope for scientists that helped build JWST. “In Cycle 3 we allocated around 5,500 hours of time [to the rest of the astronomical community],” says Laura Watkins, head of STScI’s science policy division. “This time we were able to give away more.”
The telescope’s time is split evenly across eight subcategories of astronomy, including exoplanet science, galaxies, the solar system and black holes. Most programs are awarded up to tens of hours of observing time on the telescope, but larger programs can be awarded more than 100 hours. “Three solar system proposals were successful in the largest category this time,” Watkins says. “This was a good year for solar system [science].”
One of those programs will use JWST to hunt for small objects down to a kilometer in size that orbit beyond Neptune, giving us crucial information on the amount of material in the outer solar system. Another large program will take another look at Uranus and Neptune and try to give us a better understanding of their mysterious magnetic fields. It is “going to actually map out the magnetic field,” says Heidi Hammel, an astronomer and planetary scientist at the Association of Universities for Research in Astronomy and a member of the program team. These will be the first magnetic maps made for these two planets in nearly four decades, after the flybys of each world by NASA’s Voyager 2 spacecraft in the late 1980s.
Also in our solar system, JWST will cast its gaze on Jupiter to perform a rather stunning piece of historical investigation. It will study the gas giant planet for signs of an impact that captivated the world in 1994, when Comet Shoemaker-Levy 9 crashed into the planet after breaking apart. That event briefly marred Jupiter’s face with more than 20 giant dark spots, some of which were as large as Earth. Astronomers monitored them using telescopes including Hubble. JWST should be able to detect water, carbon dioxide and other comet-sourced compounds still swirling around the planet from the bygone impact, allowing researchers to better understand how the cometary debris was incorporated into Jupiter and how the giant world’s atmosphere has subsequently recovered.
“Shoemaker-Levy 9 is the gift that keeps on giving,” says Hammel, who led Hubble’s 1994 observations of the comet’s impact. “We’re still using it to understand the dynamics of Jupiter.”
Another big winner in Cycle 4 is white dwarf science, the study of stars like our sun that have exhausted all their fuel and left just a dense, dead stellar core behind. Eight programs on these interesting objects were chosen, and Mary Anne Limbach of the University of Michigan is involved with five of them. “We had a great cycle,” she says. “I’m really excited.” One of her programs will investigate whether white dwarfs could support habitable planets. Experts think planets can endure the end-of-life phase when a sunlike star becomes a white dwarf, but it’s unclear if clement conditions could still persist upon rocky worlds like Earth in the star’s shrunken habitable zone, where liquid water could exist. Limbach will use JWST to seek out rocky Earth-sized planets in the habitable zones of two white dwarfs by looking for telltale infrared glows around these stellar corpses that might indicate the presence of such worlds. “If there is an Earth analog in either of those systems, we should be able to see it,” she says. “And if it’s on the larger side, we should be able to detect carbon dioxide and maybe even a hint of ozone.”
One of the most enduring mysteries discovered by JWST so far has been a strange class of unexplained galaxies in the early universe. Called little red dots (LRDs), they appear very red and compact, suggesting they might be extremely dense clusters of stars or perhaps burgeoning supermassive black holes that are growing into the behemoths found today at the centers of large galaxies. Such is the allure of LRDs that in Cycle 4 a half-dozen separate programs have been chosen to study them, one of which is led by Anthony Taylor of the University of Texas at Austin. He will use JWST to probe the light coming from LRDs to discern if it comes from stars or the white-hot accretion disks that surround feeding black holes. “They’ve really grabbed everyone’s attention,” he says. “With JWST, we have the tools to attack these things.”
But perhaps the hottest research area for JWST concerns planets around cool, dim red dwarf (or M dwarf) stars, which are slightly smaller than our sun. In some respects red dwarfs are ideal planet-hunting targets because they make up the majority of stars in our galaxy, and the worlds they harbor tend to be easier to see through their relatively dim stellar glare. One such red dwarf planetary system, TRAPPIST-1, has seven Earth-sized worlds, several of which are in the star’s habitable zone. There’s a catch, however: red dwarfs are also more prone than our sun to dramatic outbursts of stellar activity that might easily strip away planetary atmospheres to render otherwise Earth-like worlds essentially uninhabitable.
Early observations from JWST have found fewer atmospheres on red dwarf planets than expected, perhaps a result of the volatile relationship between these planets and their star. In several Cycle 4 programs, JWST will study more of these worlds in search of their atmosphere. One of those programs, led by Jacob Lustig-Yaeger of the Johns Hopkins University Applied Physics Laboratory, will look at six planets around three red dwarfs in an attempt to define a “cosmic shoreline” of how big and far from its star such worlds must be to support an atmosphere. “The first-order goal is to figure out which planets have atmospheres and which don’t,” Lustig-Yaeger says—but the stretch goal, he adds, is to help identify targets to search for signs of life in future JWST observing cycles. Most if not all good candidates will be transiting, meaning that they cross the face of their star as seen from Earth—a favorable “backlit” orientation that can allow more details about their atmosphere to be seen.
Katherine Bennett of Johns Hopkins University, meanwhile, will use JWST to look for an atmosphere on a world called LTT 1445Ab, which at 23 light-years away is the closest known rocky planet transiting a red dwarf. The planet is likely too hot to support life but could still be an important test case for improving our understanding of which worlds can have an atmosphere. “We’ll be able to tell both the composition and thickness if there is an atmosphere,” she says, and perhaps even the planet’s surface pressure as well.
In March JWST revealed snapshots of four gas giant planets around a larger star more similar to our sun. Such “direct images” are hard to come by because of how faint planets are against their star, but JWST can spot big, warm worlds that are sufficiently far from their stellar host. William Balmer of STScI, who led those observations, will lead another program in Cycle 4 to image another gas giant around a nearby star that orbits at a similar distance of Saturn around our sun. Balmer hopes to observe ammonia there, which could offer insights about how the planet’s atmosphere operates. “We’re really curious about how the chemistry works on these other planets in other solar systems,” he says; JWST may also be able to possibly see water clouds on the planet.
All these programs represent just a small fraction of JWST’s immense and diverse science. Although in human terms the observatory is only now a toddler in age, JWST is entering its prime. Engineers and scientists are finally feeling familiar with its unique abilities and limitations—which is why rumors of looming budget cuts for the observatory have shocked the astronomical community. “It’s in its prime mission,” says Casey Dreier, senior space policy adviser at the nonprofit science advocacy organization The Planetary Society. Cuts to JWST’s bottom line “might reduce its operational capacity,” Dreier says, something that seems unfathomable given the amount of time and effort that has gone into building and launching this incredible machine.
Already the impacts of budgetary pressures are being felt as part of the Trump administration’s sweeping shake-up of U.S. federal spending. Limbach says that scientists awarded observing time on JWST are given funding by STScI to run their programs that is equivalent to about $5,000 per hour. In Cycle 4, however, the amount of funding on offer is likely to be more constrained. “Usually if you have a program where the science is particularly difficult, you can ask for more funding,” she says. “This year there is a hard limit.” Without adequate funding, “it would be hard to do the science to the quality we have been doing it because we won’t have the manpower,” she adds. “There’s a lot of science that will get left out.”
In previous cycles, astronomers have found out by July or August how much funding they will receive for their programs. This year, more than ever, there will be an anxious wait for that to happen. “This year no one knows,” Limbach says. “There is a lot of uncertainty.”