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By NASA
Explore This Section Overview Science Science Findings Juno’s Orbits Spacecraft People Stories Multimedia JunoCam Images Jupiter hosts the brightest and most spectacular auroras in the Solar System. Near its poles, these shimmering lights offer a glimpse into how the planet interacts with the solar wind and moons swept by Jupiter’s magnetic field. Unlike Earth’s northern lights, the largest moons of Jupiter create their own auroral signatures in the planet’s atmosphere — a phenomenon that Earth’s Moon does not produce. These moon-induced auroras, known as “satellite footprints,” reveal how each moon interacts with its local space environment.
Juno capturing the marks on Jupiter of all four Galilean moons. The auroras related to each are labeled Io, Eur (for Europa), Gan (for Ganymede), and Cal (for Callisto). NASA/JPL-Caltech/SwRI/UVS team/MSSS/Gill/Jónsson/Perry/Hue/Rabia Before NASA’s Juno mission, three of Jupiter’s four largest moons, known as Galilean moons — Io, Europa, and Ganymede — were shown to produce these distinct auroral signatures. But Callisto, the most distant of the Galilean moons, remained a mystery. Despite multiple attempts using NASA’s Hubble Space Telescope, Callisto’s footprint had proven elusive, both because it is faint and because it most often lies atop the brighter main auroral oval, the region where auroras are displayed.
NASA’s Juno mission, orbiting Jupiter since 2016, offers unprecedented close-up views of these polar light shows. But to image Callisto’s footprint, the main auroral oval needs to move aside while the polar region is being imaged. And to bring to bear Juno’s arsenal of instruments studying fields and particles, the spacecraft’s trajectory must carry it across the magnetic field line linking Callisto and Jupiter.
These two events serendipitously occurred during Juno’s 22nd orbit of the giant planet, in September 2019, revealing Callisto’s auroral footprint and providing a sample of the particle population, electromagnetic waves, and magnetic fields associated with the interaction.
Jupiter’s magnetic field extends far beyond its major moons, carving out a vast region (magnetosphere) enveloped by, and buffeted by, the solar wind streaming from our Sun. Just as solar storms on Earth push the northern lights to more southern latitudes, Jupiter’s auroras are also affected by our Sun’s activity. In September 2019, a massive, high-density solar stream buffeted Jupiter’s magnetosphere, briefly revealing — as the auroral oval moved toward Jupiter’s equator — a faint but distinct signature associated with Callisto. This discovery finally confirms that all four Galilean moons leave their mark on Jupiter’s atmosphere, and that Callisto’s footprints are sustained much like those of its siblings, completing the family portrait of the Galilean moon auroral signatures.
An international team of scientists led by Jonas Rabia of the Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, CNES, in Toulouse, France, published their paper on the discovery, “In situ and remote observations of the ultraviolet footprint of the moon Callisto by the Juno spacecraft,” in the journal Nature Communications on Sept. 1, 2025.
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Last Updated Sep 02, 2025 Related Terms
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By NASA
Explore Hubble Science Hubble Space Telescope As NASA Missions Study… Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered AI and Hubble Science Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 4 min read
As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Image: NASA, ESA, David Jewitt (UCLA); Image Processing: Joseph DePasquale (STScI) A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS using the crisp vision of NASA’s Hubble Space Telescope. Hubble is one of many missions across NASA’s fleet of space telescopes slated to observe this comet, together providing more information about its size and physical properties. While the comet poses no threat to Earth, NASA’s space telescopes help support the agency’s ongoing mission to find, track, and better understand near-Earth objects.
Hubble’s observations allow astronomers to more accurately estimate the size of the comet’s solid, icy nucleus. The upper limit on the diameter of the nucleus is 3.5 miles (5.6 kilometers), though it could be as small as 1,000 feet (320 meters) across, researchers report. Though the Hubble images put tighter constraints on the size of the nucleus compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other NASA missions including the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory, as well as NASA’s partnership with the W.M. Keck Observatory, will help further refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 300 million miles from the Sun. This behavior is much like the signature of previously seen Sun-bound comets originating within our solar system.
The big difference is that this interstellar visitor originated in some other solar system elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our solar system at a staggering 130,000 miles (209,000 kilometers) per hour, the highest velocity ever recorded for a solar system visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
“No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second. You can’t project that back with any accuracy to figure out where it started on its path,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations.
The paper will be published in The Astrophysical Journal Letters. It is already available on Astro-ph.
New Evidence for Population of Wandering Space Relics
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.”
This comet was discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on July 1, 2025, at a distance of 420 million miles from the Sun. ATLAS is an asteroid impact early warning system developed by the University of Hawai’i.
In the meantime, other NASA missions will provide new insight into this third interstellar interloper, helping refine our understanding of these objects for the benefit of all. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
To learn more about Hubble, visit: https://science.nasa.gov/hubble
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Comet 3I/ATLAS
Hubble captured this image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus.
Comet 3I/ATLAS Compass Image
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on July 21, 2025. The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal an angular measurement of 1/3600 of o…
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Last Updated Aug 07, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Contact Media Claire Andreoli
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Space Telescope Science Institute
Baltimore, Maryland
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Science Paper: Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS, PDF (1.57 MB)
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Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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By European Space Agency
Image: A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.
ESA's Planetary Defence Office responded promptly to the discovery of the comet, and has been tracking it since the beginning of July.
Now, Hubble's observations from space are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 km, but it could be as small as 320 m across, researchers report.
Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Further observations, including by the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data show that the comet is losing dust in a similar manner to that from previously seen Sun-bound comets originating within our Solar System.
The big difference is that this interstellar visitor originated in some other stellar systems, elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our Solar System at roughly 210 000 km per hour, the highest speed ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million km from the Sun. 3I/ATLAS should remain visible to ground-based telescopes until September, after which it will pass too close to the Sun to observe. It is expected to reappear on the other side of the Sun by early December.
Icy wanderers such as 3I/ATLAS offer a rare, tangible connection to the broader galaxy. To actually visit one would connect humankind with the Universe on a far greater scale. To this end, ESA is preparing the Comet Interceptor mission. The spacecraft will be launched in 2029 into a parking orbit, lying in wait for a suitable target – a pristine comet from the distant Oort Cloud that surrounds our Solar System, or, unlikely but highly appealing, an interstellar object.
While it is improbable that we will discover an interstellar object that is reachable for Comet Interceptor, as a first demonstration of a rapid response mission that waits in space for its target, it will be a pathfinder for possible future missions to intercept these mysterious visitors.
The research paper based on Hubble observations will be published in The Astrophysical Journal Letters.
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By NASA
Explore This Section Science Courses & Curriculums for… STEM Educators Are Bringing… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 4 min read
STEM Educators Are Bringing Hands-On NASA Science into Virginia Classrooms
Professional learning experiences are integral to the enhancement of classroom instruction. Teachers, at the forefront of Science, Technology, Engineering, & Mathematics (STEM) education, play a key role in the advancement of STEM learning ecosystems and citizen science.
On June 24-25, 2025 – despite a major east coast heat wave – twenty-four educators from eight school districts in the Hampton Roads region of southeastern Virginia (Newport News, Hampton City, Virginia Beach City, Isle of Wight County, Poquoson City, Norfolk, York County, and Suffolk Public Schools) converged at the National Institute of Aerospace (NIA) in Hampton, VA for a professional development workshop led by experts from NASA Langley Research Center and the NASA Science Activation program’s NIA-led NASA eClips team. Developed in collaboration with another NASA Science Activation team, GLOBE (Global Learning and Observations to Benefit the Environment) Mission Earth, and with support from the Coastal Virginia STEM Hub (COVA STEM) – a “STEM learning ecosystem targeting pre-K to adult residents in Coastal Virginia” – this two-day training, also provided comprehensive resources, including lesson plans, pacing guides, classroom activities, and books, all designed for integration into Hampton Roads classrooms.
The NASA Langley team led workshop participants through a training about GLOBE, a program dedicated to advancing Earth System science through data collected by volunteer members of the public, also known as ‘citizen scientists’. GLOBE invites educators, students, and members of the public worldwide (regardless of citizenship) to collect and submit cloud, surface temperature, and land cover observations using the GLOBE Observer app – a real-time data collection tool available right on their smartphones. These observations are then used to help address scientific questions at local, regional, and global scales. Through this training, the educators participated in K-20 classroom-friendly sample lessons, hands-on activities, and exploring the GLOBE Observer app, ultimately qualifying them as GLOBE Certified Educators. Earth System science lessons, activities, and information on how to download the GLOBE Observer citizen science app are available on the GLOBE website. Similarly, NASA eClips, which focuses on increasing STEM literacy in K-12 students, provided educators with free, valuable, standards-based classroom resources such as educator guides, informational videos, engineering design packets, and hands-on activities, which are available to educators and students alike on the NASA eClips’ website. Throughout the training, educators collaborated in grade-level groups, brainstorming new ways to integrate these standards-based NASA science resources.
One educator envisioned incorporating GLOBE’s cloud resources and supportive NASA eClips videos into her energy budget unit. Others explored modifying a heat-lamp experiment to include humidity and heat capacity. One teacher enthusiastically noted in response to a GLOBE urban heat island lesson plan, “The hands-on elements are going to be really great deliverables!” The creative energy and passion for education were palpable.
The dedication of both NIA and NASA Langley to education and local community support was evident. This professional learning experience offered educators immediately-applicable classroom activities and fostered connections among NASA science, NASA eClips, the GLOBE Program, and fellow educators across district lines. One educator highlighted the value of these networking opportunities, stating, “I do love that we’re able to collaborate with our colleagues so we can plan for our future units during the school year”. Another participant commented, “This is a great program…I am going to start embedding [this] in our curriculum.”
GME (supported by NASA under cooperative agreement award number NNX16AC54A) and NASA eClips (supported by NASA under cooperative agreement award number NNX16AB91A) are part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, real content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn
GLOBE educator Marilé Colón Robles demonstrates a kinesthetic activity. Share
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By NASA
Before astronauts venture around the Moon on Artemis II, the agency’s first crewed mission to the Moon since Apollo, Mark Cavanaugh is helping make sure the Orion spacecraft is safe and space-ready for the journey ahead.
As an Orion integration lead at NASA’s Johnson Space Center in Houston, he ensures the spacecraft’s critical systems— in both the U.S.-built crew module and European-built service module—come together safely and seamlessly.
Mark Cavanaugh stands in front of a mockup of the Orion spacecraft inside the Space Vehicle Mockup Facility at NASA’s Johnson Space Center in Houston.NASA/Robert Markowitz With nearly a decade of experience at NASA, Cavanaugh currently works within the Orion Crew and Service Module Office at Johnson. He oversees the technical integration of the European Service Module, which provides power, propulsion, and life support to Orion during Artemis missions to the Moon. His work includes aligning and verifying essential systems to keeping the crew alive, including oxygen, nitrogen, water storage, temperature regulation, and spacecraft structures.
In addition to his integration work, Cavanaugh is an Orion Mission Evaluation Room (MER) manager. The MER is the engineering nerve center during Artemis flights, responsible for real-time monitoring of the Orion spacecraft and real-time decision-making. From prelaunch to splashdown, Cavanaugh will lead a team of engineers who track vehicle health and status, troubleshoot anomalies, and communicate directly with the flight director to ensure the mission remains safe and on track.
Mark Cavanaugh supports an Artemis I launch attempt from the Passive Thermal Control System console on Aug. 29, 2022, in the Orion Mission Evaluation Room at NASA’s Johnson Space Center.NASA/Josh Valcarcel Cavanaugh’s passion for space exploration began early. “I’ve wanted to be an aerospace engineer since I was six years old,” he said. “My uncle, who is also an aerospace engineer, used to take me to wind tunnel tests and flight museums as a kid.”
That passion only deepened after a fifth-grade trip from Philadelphia to Houston with his grandfather. “My dream of working at NASA Johnson started when I visited the center for the first time,” he said. “Going from being a fifth grader riding the tram on the tour to contributing to the great work done at Johnson has been truly incredible.”
Turning that childhood dream into reality did not come with a straight path. Cavanaugh graduated from Pennsylvania State University in 2011, the same year NASA’s Space Shuttle Program ended. With jobs in the space industry in short supply, he took a position with Boeing in Houston, working on the International Space Station’s Passive Thermal Control System. He later supported thermal teams for the Artemis Moon rocket called the Space Launch System, and the Starliner spacecraft that flew astronauts Butch Wilmore and Suni Williams during their Boeing Crew Flight Test mission, before a mentor flagged a NASA job posting that turned out to be the perfect fit.
He joined NASA as the deputy system manager for Orion’s Passive Thermal Control System, eventually stepping into his current leadership role on the broader Orion integration team. “I’ve been very lucky to work with some of the best and most supportive teammates you can imagine,” he said.
Mark Cavanaugh with his mother, Jennifer, in front of the Artemis I Orion spacecraft following the thermal vacuum test at the Space Environments Complex at NASA’s Neil Armstrong Test Facility in Sandusky, Ohio. Cavanaugh says collaboration and empathy were key to solving challenges along the way. “I’ve learned to look at things from the other person’s perspective,” he said. “We’re all working toward the same incredible goal, even if we don’t always agree. That mindset helps keep things constructive and prevents misunderstandings.”
He also emphasizes the importance of creative problem-solving. “For me, overcoming technical challenges comes down to seeking different perspectives, questioning assumptions, and not being afraid to try something new—even if it sounds a little ridiculous at first.”
Mark Cavanaugh riding his motorcycle on the Circuit of the Americas track in Austin, Texas. Outside of work, Cavanaugh fuels his love of speed and precision by riding one of his three motorcycles. He has even taken laps at the Circuit of the Americas track in Austin, Texas.
When he is not on the track or in the control room, Cavanaugh gives back through student outreach. “The thing I always stress when I talk to students is that nothing is impossible,” he said. “I never thought I’d get to work in the space industry, let alone at NASA. But I stayed open to opportunities—even the ones that didn’t match what I originally imagined for myself.”
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