2025 in Review: Highlights from the Space Telescope Science Institute

In 2025, staff at the Space Telescope Science Institute (STScI) supported a broad range of exciting and innovative initiatives on behalf of the international astronomical community and the public. Throughout the year, we continued serving as the science operations center for the Hubble Space Telescope, leading the science and mission operations for the James Webb Space Telescope, and sharing the support of the science operations for the upcoming Nancy Grace Roman Space Telescope. Our ongoing commitment to the curation and dissemination of data from 25 active and past space missions and multiple ground-based surveys from the Barbara A. Mikulski Archive for Space Telescopes (MAST), as well as our efforts in advancing the Habitable Worlds Observatory mission concept were also notable endeavors in 2025. Additionally, we remained steadfast in bringing science to the world through internationally recognized news and public outreach programs. 

Letter from the Director

The Space Telescope Science Institute’s mission is clear — to help humanity explore the universe. Thanks to our 850 colleagues and our trusted partners at NASA, the European Space Agency, the Canadian Space Agency, and the Association of Universities for Research in Astronomy, our work operating advanced space telescopes enables scientific discovery all year. STScI is proud to serve as a powerful force multiplier for science in the U.S. and around the world.

Our current missions continue to push the boundaries of human knowledge and innovation. In April, we celebrated the 35th anniversary of the Hubble Space Telescope with new observations of the ice clouds on Mars. In October, STScI received a record-breaking number of proposals for the James Webb Space Telescope’s fifth annual cycle of observations, for which we offered brand new ways of observing with Webb. Throughout 2025, Hubble and Webb chased the interstellar comet 3I/ATLAS across the sky, providing unique measurements of its size and chemical composition. After careful consultation with the astronomical community, the Director’s Rocky Worlds program commenced — a joint Hubble and Webb endeavor to search for signs of atmospheres on nearby terrestrial planets, a stepping stone on the path to search for life in the universe.

The past year highlighted the promise of future astrophysics space missions, building on Hubble and Webb’s legacies. In July, we co-sponsored the symposium  "Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology," with Johns Hopkins University and NASA’s Exoplanet Science Institute, with organizing help from NASA’s Goddard Space Flight Center, Jet Propulsion Laboratory, and an international team of astronomers and technologists. The symposium brought together more than 500 scientists, technologists, and policymakers to explore NASA’s forthcoming mission to search for signs of life beyond our solar system. 

In November, after months of remarkable progress toward launch on the Nancy Grace Roman Space Telescope, our colleagues at NASA reached a climactic milestone — the integration of the telescope’s inner and outer segments — and in December, STScI launched the Roman Research Nexus, a cloud-based science platform to provide open access to Roman’s vast survey data. 

This was also a year of inspiring the workforce for the future of space and technology. In June, we welcomed the 33rd cohort of Space Astronomy Summer Program interns. Each intern was matched with a science or engineering mentor, completed tailored projects, and presented their findings at the program’s culminating symposium. In August, we held the inaugural James Webb Space Telescope Summer School, welcoming early-career researchers who are new to the field. Participants learned about early-universe transient science, and observational and analytical techniques with Webb while getting to know Baltimore City. Throughout the year, our scientists also held conversations with the public through our Deep Space Dialogues series.

In 2026, I look forward to expanding the frontiers of space astronomy with our brilliant teams, our trusted partners, and you — our supporters, collaborators, learners, and community members.

Clear Skies,

Jen Lotz
Director, Space Telescope Science Institute

 

Exploration: Excellence in Science

The Hubble and Webb space telescopes continue to push the frontiers of space science and helped researchers produce high-impact discoveries that continue to uncover the mysteries of the universe and expand our understanding of the unknown. Throughout the year, you may have read or heard about many of these discoveries made by scientists awarded NASA research grants and observing time on the world’s most powerful observatories. A particular highlight is a category of objects referred to as “Little Red Dots,” which was discovered with Webb. By analyzing Webb’s deep imaging and spectroscopic observations, astronomers have identified numerous compact, red sources that belong to this intriguing class. As a collective finding, these dots may hint that supermassive black holes played a larger role than expected in sculpting the conditions of the early universe.

Webb has also observed objects that existed even earlier in the universe. In 2025, the telescope characterized supernova GRB 2501314A, which existed when the universe was only 730 million years old. What’s remarkable is that it showed a striking similarity to phenomena observed much closer to home. This result also adds confidence to researchers’ use of supernovae as tracers of cosmic expansion.

Closer to our Milky Way galaxy, Hubble has mapped the swarm of two-dozen satellite galaxy companions to our neighbor, the Andromeda galaxy. The telescope helped researchers trace these galaxies’ evolution and individual star formation history. Astronomers also dove into a decade of Hubble data to measure the precise positions of stars — and now suggest that Andromeda may not be destined for a collision with the Milky Way galaxy after all.

Hubble’s sensitivity to blue and ultraviolet light is crucial to characterizing energetic phenomena, particularly explosive objects like supernovae and merging black holes that brighten rapidly and then disappear in hours, days, or months. Hubble’s collaborative observations with the Chandra X-ray Observatory identified an intermediate black hole candidate candidate caught in the act of swallowing a star in the outskirts of the relatively nearby elliptical galaxy NGC 6099.

Moving into our solar neighborhood, both missions have added to what we know about systems around other stars. Webb observations of TOI-561 b, a rocky world orbiting much closer to its star than Mercury does the Sun, suggest that this lava world has an atmosphere. Hubble data known as spectra have revealed evidence that white dwarf stars consume their planetary systems.

Together, Webb and Hubble have embarked on the Rocky Worlds Director’s Discretionary Time program, a large-scale initiative devoted to searching for evidence of atmospheres on terrestrial (rocky) planets that orbit nearby red dwarf stars. (Our Sun is a yellow dwarf star.) The targets all lie along the “cosmic shoreline,” which means that they potentially have retained their atmospheres. Webb is being used to search for the planets’ atmospheric signatures, while Hubble probes the activity of the host stars. (Learn more about the program.)

Looking to the future of astronomy, STScI played a leading role in organizing the conference, “Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology,” held at the Johns Hopkins University Bloomberg Center in Washington, D.C., in late July. More than 400 scientists and engineers attended in person, and over 100 people joined online. The schedule included more than 120 talks, which covered topics spanning the full range of astrophysics and technology development. This meeting was sponsored by the Space Telescope Science Institute, Johns Hopkins University, and NASA’s Exoplanet Science Institute, with organizing help from NASA’s Goddard Space Flight Center, Jet Propulsion Laboratory, and a team of astronomers and technologists from around the world, reinforcing that the U.S. continues to be global convener for space science and exploration. The first part of the proceedings were published in early 2026, and the second part will be published later in 2026.

Overall, both Hubble and Webb remain in high demand by the astronomical community. Hubble’s Cycle 33 call for proposals resulted in 833 applications, with 151 approved, a six-to-one oversubscription. Webb saw an unparalleled submission of about 2,900 proposals that requested 101,751 observing hours (8,000 hours were offered in Cycle 5), resulting in a 13-to-one oversubscription.

Technological Innovations

The Barbara A. Mikulski Archive for Space Telescopes (MAST) hit a major milestone in 2025. MAST now hosts more than 1 billion data files generated by more than 23 past and present space missions, and multiple ground-based surveys, including PanSTARRS and the Sloan Digital Sky Surveys. MAST continues to update and improve the interfaces that allow users from 169 countries to find and download data for their research. Over a third of those users now access MAST in the cloud, using mobile phones in addition to standard computers and tablets.

We’re also thinking broadly about the tools STScI staff use and offer to the community. Generative Artificial Intelligence (AI) tools are playing an increasing role in many aspects of modern science and technology, including our own. AI offers the potential to simplify and streamline routine activities, but also presents ethical challenges, particularly with regard to bias and maintaining confidentiality for proprietary information. To support its adoption, STScI has defined a framework that enables our staff to use in-house AI tools to explore potential advances without jeopardizing our standards or integrity.

Monitoring Our Backyard

Events within the solar system can have a direct effect on Earth. All three of our missions have key capabilities to track and characterize our immediate neighbors, helping keep Americans safe from physical and economic threats. 2025 saw the third visit from an interstellar interloper, the comet 3I/ATLAS. Hubble and Webb were crucial in providing the sensitivity necessary to track its precise position at large distances, and helped astronomers determine its orbit. Hubble showed that the diameter of the comet’s solid, icy nucleus is between 1,000 feet (320 meters) and 3.5 miles (5.6 kilometers) across. Roman will play a key role in tracking future fast-moving visitors to our solar system, as well as maintaining surveillance of local objects that may be on Earth-approaching orbits, like asteroid 2024 YR4.

Hubble is particularly effective in tracing the impacts of the Sun on other planets within the solar system, as proven by its ultraviolet observations of aurorae, like those on Jupiter, Uranus, and Neptune. Together, Hubble and Webb provide holistic, multiwavelength views of our planetary neighbors, tracing methane on Saturn’s largest moon, Titan, and surveying large-scale dust storms on Mars. Hubble’s longevity has also enabled scientists to monitor atmospheric changes on Uranus as it moves through its 84-year climate cycle. Combined with Roman, these observatories furnish a highly effective complement to missions that directly travel to each planet.

Making Roman Real

STScI is the Science Operating Center (SOC) for NASA’s next great observatory, the Nancy Grace Roman Space Telescope, partnering with the Science Support Center (SSC) at Caltech/IPAC, and the Roman Project Office at NASA’s Goddard Space Flight Center. Roman is scheduled to launch no later than May 2027 and is on track as early as fall 2026. STScI participated in thermal vacuum testing of Roman’s integrated instruments, telescope, and spacecraft assembly, which concluded in October 2025. The full observatory was successfully integrated into a single unit in November 2025 and is expected to ship to Kennedy Space Center in Florida in June 2026.

Roman is a survey telescope. Each observation with Roman’s Wide Field Imager (WFI), its camera, produces images or spectra covering an area about 100 times greater than Hubble’s infrared camera. The bulk of Roman’s observing time over its primary five-year mission will be devoted to four community-defined surveys, the three Core Community Surveys (its High-Latitude Wide-Area Survey, High-Latitude Time-Domain Survey, and Galactic Bulge Time-Domain Survey) along with the Galactic Plane General Astrophysics Survey. The remaining time will be allocated to other general astrophysics surveys. Roman’s first Call for Proposals was issued by the Science Support Center in December with a deadline in mid-March 2026. The scale and scope of public and private collaboration required to prepare this highly specialized mission for launch is only possible because of American ingenuity and NASA’s convening power, further cementing our country’s legacy of leadership in space science and exploration.

STScI and Caltech/IPAC collaborated to develop the Ready, Set, Roman! training suite of webinars designed to enable the community to take full advantage of Roman’s capabilities. STScI also supported multiple activities at the winter 2026 American Astronomical Society (AAS) meeting, including hosting a proposal preparation workshop, and participating in the STScI and Roman town halls.

All of Roman’s data will be available freely and rapidly — there is no proprietary period. As the WFI Science Operating Center, STScI is responsible for providing community access to Roman’s observations. With data at the petabyte level, which exceeds what individual computers can hold and process, users will need to work where the data are — in the cloud. To support researchers, STScI created the Roman Research Nexus, a science platform where everyone around the world can access the mission’s data on the cloud. Released in mid-December 2025, the Nexus provides easy access to data as they become available, along with collaborative tools and computing resources for data exploration and analysis.

Roman’s high-precision wide-area surveys will transform astrophysics. With launch slated as soon as September 2026 and a three-month commissioning period, science observations may start as early as January 2027. STScI is ready to support the community’s research programs.

 

By the Numbers

In 2025, researchers from around the world applied for observing time and funding to use NASA’s Hubble Space Telescope and NASA’s James Webb Space Telescope. Astronomers’ requests far exceeded the time and funds available. In 2025, researchers published almost 1,100 peer-reviewed papers using Hubble data, and 1,025 peer-reviewed papers using Webb data.

Oversubscription Ratios

 

 

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