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As NASA Missions Study Interstellar Comet, Hubble Makes Size Estimate
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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.
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Related Images & Videos 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…
Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
- NASA’s 3I/ATLAS page
- This release on ESA’s website
- Science Paper: Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS, PDF (1.57 MB)
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Wade Sisler: Aficionado of Wonder Serving the Cosmos
Across 42 years at NASA, Wade Sisler — executive producer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland—watched the edge of human knowledge progress. During that time, the tools for visualizing and communicating those discoveries evolved just as rapidly.
Executive Producer Wade Sisler has worked at NASA for 42 years, starting at the agency’s Ames Research Center in California’s Silicon Valley, and now at Goddard Space Flight Center in Greenbelt, Md.Credit: Courtesy of Wade Sisler“I’ve spent my career surrounded by people with amazing curiosity and intellect, pursuing questions that could change the way we see the universe, both literally and metaphorically,” Sisler said.
From his start as a student photographer at NASA’s Ames Research Center in California’s Silicon Valley, Sisler ultimately became a creative force behind some of NASA’s most iconic science storytelling. He transitioned to videography when he realized the wonder and understanding the medium could convey.
Photos taken by Sisler between 1985 and 1992 that showcase emerging NASA technologies.Credit: NASA/Wade Sisler“The fidelity of the story you could tell with pictures through video was so impactful,” he said. “It was just pure awe. So I gave up my Hasselblads, trading the sheer beauty of imagery for the much more powerful storytelling tools that came with the emerging field of video — specifically the ability to take the audience with you to experience the mission.”
From Space Frogs to the Eagle NebulaIn the 1980s and ’90s, Sisler worked as a producer on a wide range of projects, translating complex research into short documentaries and educational broadcasts.
“We were helping people see things that had never been seen before, and showing them relationships that they never knew existed,” he said.
In one of his favorite early assignments, Sisler worked with astronaut Mae Jemison for a video project on space frogs. Jemison was studying how frog embryos develop in microgravity on the space shuttle. Sisler also had a hand in early virtual reality systems, producing one of the first videos depicting how VR could work.
Sisler (left) stands alongside coworkers Marty Curry, Eric James, and branch chief Roland Michealis — fellow members of the photography team at NASA Ames.Credit: Courtesy of Wade SislerSisler eventually moved from NASA Ames to NASA Headquarters in Washington. There, he helped modernize NASA TV.
“They were shifting it from just mission-oriented content to a television news feed, exploring ideas to align with national news interests,” he said.
In one of his pilot stories, he produced a video and story news package about the Hubble Space Telescope’s observations of the Eagle Nebula.
“They handed me a 16-by-20-inch print of the Eagle Nebula right after Hubble imaged it,” he said. His team used a robotic camera to pan around the image while narration explained what viewers were seeing. “We wondered if we put that little microcosm of a story into a news feed, would anybody use it? And it ended up being used thousands and thousands of times, validating the NASA TV model with a bona fide science story and giving me a glimpse of the exciting stuff I could do.”
While at NASA Headquarters, Sisler also negotiated an IMAX agreement that led to new 3D films (including ones Sisler worked on, like the 1997 “Mission to Mir” and 2002 “Space Station 3D”). After a few years, he moved on to NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in 1997 as an executive producer. Goddard’s communications team was small and had little experience in visual storytelling, so he joined the team to nurture its growth.
Sisler stands alongside Office of Communications collaborators Laura Betz and Thaddeus Cesari at the immersive “Beyond the Light” exhibit of James Webb Space Telescope imagery at ARTECHOUSE in Washington, D.C.Credit: Courtesy of Wade Sisler Science for the SensesIn the late ’90s, Wade teamed up with NASA’s Scientific Visualization Studio (based at NASA Goddard) and lead visualizer Horace Mitchell to explore a new frontier in science storytelling. While NASA was already known for its iconic space imagery, much of its data deals with invisible phenomena or abstract processes that aren’t inherently visual. By bringing together scientists, artists, and producers, Sisler helped transform data into visualizations and animations for broader audiences.
“We had to invent ways of visualizing the invisible so meaning was more easily conveyed,” he said. “The result was stories that were not just newsworthy—they were often stunningly beautiful and showed the connections and workings of the Earth and universe in ways we had never seen before.”
The team had a breakout hit in 1998 with an El Niño visualization, which helped drive public understanding of the phenomenon. Sisler also helped launch a NASA Goddard program to link scientific experts with news stations around the world.
“We wanted to put the authentic voices of scientists in the chair to convey their sense of awe while telling people scientifically why it matters,” he said. “Pairing their voices with great visualizations was an unbeatable combination and that became the fundamental way we tell science stories.”
Sisler’s storytelling journey evolved into increasingly ambitious creative partnerships that brought NASA science to new cultural spaces. With “Cosmic Cycles,” a collaboration with the National Philharmonic, Wade helped create a program that paired music from a live symphony with high-resolution NASA imagery, inviting viewers to experience the celestial scenery emotionally, not just intellectually.
Instead of the NASA Goddard team creating a video to go along with music, “The composer drew inspiration from video produced by Goddard,” Sisler said. “It’s one of the best examples of science and art in mutual orbit.”
From left: Multimedia Producer Scott Wiessinger of NASA Goddard, Sisler, maestro Piotr Gajewski of the National Philharmonic, and composer Henry Dehlinger participate in a panel discussion about “Cosmic Cycles: A Space Symphony,” a collaboration between NASA Goddard and the National Philharmonic.Credit: NASA/Joel KowskyThat blending of science and artistic expression reached a new scale in “Beyond the Light,” an art show developed with ARTECHOUSE and James Webb Space Telescope communications lead Laura Betz. Sisler linked artists with NASA scientists to turn cutting-edge astrophysics into a gallery-scale sensory experience. Most recently, Sisler championed a major documentary on Webb called “Cosmic Dawn.” The 1.5-hour film brings viewers on an unprecedented journey through Webb’s delicate assembly, rigorous testing, and triumphant launch.
Many of NASA’s flagship communication programs trace their roots to small teams that Sisler helped assemble and guide. He took a builder’s approach, rolling up his sleeves, testing ideas, and empowering others to scale them. From science storytelling and satellite media tours to the rise of NASA’s audio storytelling, Spanish-language content, Conceptual Image Laboratory animations, social media presence, and live broadcast programming, Sisler played a key role in turning bright ideas into enduring agency assets.
For each of these projects, Sisler worked behind the scenes as a creative force and a connector, bringing together filmmakers, animators, composers, scientists, engineers, astronauts, museum curators, data visualizers, and educators.
Lighting the WayDespite many accolades, Sisler said his proudest accomplishment is the success of the internship program he has led for NASA Goddard’s Office of Communications.
Sisler has served as a mentor for many interns over the years, including students like Talya Lerner, center, standing next to Ed Campion, then-Goddard news chief. Sisler has referred to his own career as “the internship that never ended” because he had so many opportunities to explore different areas of communications. Credit: NASA/Bill Hrybyk“The thing that stays with me most is seeing where our former interns have landed,” he said. Many now lead their own programs within NASA, shaping the next generation of science storytelling from inside the agency. Others have taken their skills beyond NASA, contributing to science and technology literacy through media, education, and public engagement. “It’s been a privilege to help launch so many of these careers. I’ve always believed that when you combine mentorship, meaningful work, and a little creative freedom, you create a ripple effect that lasts for decades.”
Sisler’s own NASA journey began with a Pathways internship at NASA Ames while he was studying journalism at Baylor University in Texas. His work there drew him into visual storytelling, which led him to pursue photography, video, and science photography at the Rochester Institute of Technology in New York. As he alternated semesters between school and NASA Ames, he refined both his interests and his skills.
Sisler’s goal as an internship program coordinator was to help give the next generation of science communicators the same opportunity. He developed a communication “boot camp” to help interns develop their storytelling chops in many areas and figure out which were their favorites.
“All the interesting stuff happens at the intersections of people’s passions,” he said. “The best, most powerful thing I think I’ve done in my time at NASA is to help guide the next wave of science communicators. Seeing their success is the gift that keeps on giving.”
By Ashley Balzer
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Curiosity Blog, Sols 4622-4623: Kicking Off (Earth) Year 14 With an Investigation of Veins
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Curiosity Blog, Sols 4622-4623: Kicking Off (Earth) Year 14 With an Investigation of Veins NASA’s Mars rover Curiosity, using its Left Navigation Camera, caught the shadow of the rover’s mast looking ahead to new terrain as the mission started its 14th Earth year on Mars. Curiosity acquired this image on Aug. 6, 2025 — Sol 4621, or Martian day 4,621 of the Mars Science Laboratory mission — at 06:24:09 UTC. NASA/JPL-CaltechWritten by Abigail Fraeman, Deputy Project Scientist at NASA’s Jet Propulsion Laboratory
Earth planning date: Wednesday, Aug. 6, 2025.
Today was a very special day for Curiosity as the rover celebrated the start of a 14th year on Mars. Curiosity is currently exploring the mysterious boxwork formations. On Monday, the rover positioned itself at the side of one of the ridges, where the team had spotted tantalizing hints of a complex network of razor-thin veins that may give insight into what is holding the ridges up, compared to the surrounding hollows.
In this plan, the team will use the instruments on Curiosity’s arm and mast to investigate the geometry and composition of these veins to learn more about them. APXS and MAHLI will both observe “Repechón,” a loose block with dark-toned, mottled material exposed on top, as well as “Lago Poopó,” a bright, relatively clean vein network. MAHLI will also collect a side view of “Repechón.” ChemCam will use its laser to analyze two targets, “Vicguna,” a protruding vein edge with nodular texture, and “Ibare,” which has some exposed light-toned veins. Outside of the vein investigation, ChemCam’s telescopic RMI camera will observe layering in a nearby butte and the Mishe Mokwa feature, while Mastcam will take mosaics on “Cachiniba,” a broken block, “Yapacani,” the side of another large boxwork ridge, and “Llullaillaco,” a faraway feature that we imaged from a slightly different location in a previous plan. Additional environmental monitoring observations will round out the plan, followed by a straight-line drive to the east, to an area where several large boxwork ridges intersect that the team has been informally calling “the peace sign” because of its shape.
I usually get nostalgic around landing anniversaries, or “landiversaries,” and this year, I found myself looking back through pictures of landing night. One of my favorites shows me standing next to science team member Kirsten Siebach right after we received the first images from Curiosity. The two of us have the biggest, most excited grins on our faces. We were both graduate students at the time, and both of us were writing thesis chapters analyzing orbital data over regions we hoped to explore with Curiosity one day. I was studying a layer in Mount Sharp that contained hematite, and the team named this feature “Vera Rubin ridge” when Curiosity reached it in 2017. Kirsten, who is now a professor at Rice University, was focused on the boxwork structures, pondering how they formed and hypothesizing what they might tell us about the history of Martian habitability when we reached them.
Thirteen years later, I had another big grin on my face today, as I listened to Kirsten and our incredible science team members excitedly discussing Curiosity’s new images of these same boxwork structures. I was also filled with gratitude for the thousands of people it took to get us to this moment. It was the absolute best way to spend a landiversary.
Learn more about Curiosity’s science instruments
For more Curiosity blog posts, visit MSL Mission Updates
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NASA to Provide Live Coverage of Crew-10 Return, Splashdown
Editor’s Note: This advisory was updated Aug. 7, 2025, to reflect changes in the targeted undocking and splashdown dates.
NASA and SpaceX are targeting no earlier than 6:05 p.m. EDT, Friday, Aug. 8, for the undocking of the agency’s SpaceX Crew-10 mission from the International Space Station. Pending weather conditions, splashdown is targeted at 11:33 a.m., Saturday, Aug. 9. Crew-10 will be the first mission to splash down off the California coast for NASA’s Commercial Crew Program.
NASA astronauts Anne McClain and Nichole Ayers, JAXA (Japan Aerospace Exploration Agency) astronaut Takuya Onishi, and Roscosmos cosmonaut Kirill Peskov are completing a five-month science expedition aboard the orbiting laboratory and will return time-sensitive research to Earth.
Mission managers continue monitoring weather conditions in the area, as undocking of the SpaceX Dragon depends on spacecraft readiness, recovery team readiness, weather, sea states, and other factors. NASA and SpaceX will select a specific splashdown time and location closer to the Crew-10 spacecraft undocking.
NASA’s live coverage of return and related activities will stream on NASA+, Amazon Prime, and more. Learn how to stream NASA content through a variety of platforms.
NASA’s coverage is as follows (all times Eastern and subject to changed based on real-time operations):
Friday, Aug. 8
3:45 p.m. – Hatch closure coverage begins on NASA+ and Amazon Prime.
4:20 p.m. – Hatch closing
5:45 p.m. – Undocking coverage begins on NASA+ and Amazon Prime.
6:05 p.m. – Undocking
Following the conclusion of undocking coverage, NASA will distribute audio-only discussions between Crew-10, the space station, and flight controllers during Dragon’s transit away from the orbital complex.
Saturday, Aug. 9
10:15 a.m. – Return coverage begins on NASA+ and Amazon Prime.
10:39 a.m. – Deorbit burn
11:33 a.m. – Splashdown
1 p.m. – Return to Earth media teleconference will stream live on the agency’s YouTube channel, with the following participants:
- Steve Stich, manager, NASA’s Commercial Crew Program
- Dina Contella, deputy manager, NASA’s International Space Station Program
- Sarah Walker, director, Dragon Mission Management, SpaceX
- Kazuyoshi Kawasaki, associate director general, Space Exploration Center/Space Exploration Innovation Hub Center, JAXA
To participate in the teleconference, media must contact the NASA Johnson newsroom by 5 p.m., Aug. 7, at: jsccommu@mail.nasa.gov or 281-483-5111. To ask questions, media must dial in no later than 10 minutes before the start of the call. The agency’s media credentialing policy is available online.
Find full mission coverage, NASA’s commercial crew blog, and more information about the Crew-10 mission at:
https://www.nasa.gov/commercialcrew
-end-
Joshua Finch
Headquarters, Washington
202-358-1100
joshua.a.finch@nasa.gov
Sandra Jones / Joseph Zakrzewski
Johnson Space Center, Houston
281-483-5111
sandra.p.jones@nasa.gov / joseph.a.zakrzewski@nasa.gov
Steve Siceloff / Stephanie Plucinsky
Kennedy Space Center, Florida
321-867-2468
steven.p.siceloff@nasa.gov / stephanie.n.plucinsky@nasa.gov
