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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
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
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Related Links and Documents
Science Paper: Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS, PDF (1.57 MB)
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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
Captured at a location called “Falbreen,” this enhanced-color mosaic features decep-tively blue skies and the 43rd rock abrasion (the white patch at center-left) of the NASA Perseverance rover’s mission at Mars. The 96 images stitched together to create this 360-degree view were acquired May 26, 2025.NASA/JPL-Caltech/ASU/MSSS In this natural-color version of the “Falbreen” panorama, colors have not been enhanced and the sky appears more reddish. Visible still is Perseverance’s 43rd rock abrasion (the white patch at center-left). The 96 images stitched together to create this 360-degree view were acquired May 26, 2025.NASA/JPL-Caltech/ASU/MSSS ‘Float rocks,’ sand ripples, and vast distances are among the sights to see in the latest high-resolution panorama by the six-wheeled scientist.
The imaging team of NASA’s Perseverance Mars rover took advantage of clear skies on the Red Planet to capture one of the sharpest panoramas of its mission so far. Visible in the mosaic, which was stitched together from 96 images taken at a location the science team calls “Falbreen,” are a rock that appears to lie on top of a sand ripple, a boundary line between two geologic units, and hills as distant as 40 miles (65 kilometers) away. The enhanced-color version shows the Martian sky to be remarkably clear and deceptively blue, while in the natural-color version, it’s reddish.
“Our bold push for human space exploration will send astronauts back to the Moon,” said Sean Duffy, acting NASA administrator. “Stunning vistas like that of Falbreen, captured by our Perseverance rover, are just a glimpse of what we’ll soon witness with our own eyes. NASA’s groundbreaking missions, starting with Artemis, will propel our unstoppable journey to take human space exploration to the Martian surface. NASA is continuing to get bolder and stronger.”
The rover’s Mastcam-Z instrument captured the images on May 26, 2025, the 1,516th Martian day, or sol, of Perseverance’s mission, which began in February 2021 on the floor of Jezero Crater. Perseverance reached the top of the crater rim late last year.
“The relatively dust-free skies provide a clear view of the surrounding terrain,” said Jim Bell, Mastcam-Z’s principal investigator at Arizona State University in Tempe. “And in this particular mosaic, we have enhanced the color contrast, which accentuates the differences in the terrain and sky.”
Buoyant Boulder
One detail that caught the science team’s attention is a large rock that appears to sit atop a dark, crescent-shaped sand ripple to the right of the mosaic’s center, about 14 feet (4.4 meters) from the rover. Geologists call this type of rock a “float rock” because it was more than likely formed someplace else and transported to its current location. Whether this one arrived by a landslide, water, or wind is unknown, but the science team suspects it got here before the sand ripple formed.
The bright white circle just left of center and near the bottom of the image is an abrasion patch. This is the 43rd rock Perseverance has abraded since it landed on Mars. Two inches (5 centimeters) wide, the shallow patch is made with the rover’s drill and enables the science team to see what’s beneath the weathered, dusty surface of a rock before deciding to drill a core sample that would be stored in one of the mission’s titanium sample tubes.
The rover made this abrasion on May 22 and performed proximity science (a detailed analysis of Martian rocks and soil) with its arm-mounted instruments two days later. The science team wanted to learn about Falbreen because it’s situated within what may be some of the oldest terrain Perseverance has ever explored — perhaps even older than Jezero Crater.
Tracks from the rover’s journey to the location can be seen toward the mosaic’s right edge. About 300 feet (90 meters) away, they veer to the left, disappearing from sight at a previous geologic stop the science team calls “Kenmore.”
A little more than halfway up the mosaic, sweeping from one edge to the other, is the transition from lighter-toned to darker-toned rocks. This is the boundary line, or contact, between two geologic units. The flat, lighter-colored rocks nearer to the rover are rich in the mineral olivine, while the darker rocks farther away are believed to be much older clay-bearing rocks.
More About Perseverance
NASA’s Jet Propulsion Laboratory, which is managed for the agency by Caltech, built and manages operations of the Perseverance rover on behalf of NASA’s Science Mission Directorate in Washington, as part of NASA’s Mars Exploration Program portfolio. Arizona State University leads the operations of the Mastcam-Z instrument, working in collaboration with Malin Space Science Systems in San Diego, on the design, fabrication, testing, and operation of the cameras.
For more about Perseverance:
https://science.nasa.gov/mission/mars-2020-perseverance
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By NASA
Explore Hubble 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 Hubble and Artificial Intelligence 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 2 min read
Hubble Surveys Supernova-Rich Spiral
This NASA/ESA Hubble Space Telescope image features the face-on spiral galaxy NGC 1309. ESA/Hubble & NASA, L. Galbany, S. Jha, K. Noll, A. Riess Rich with detail, the spiral galaxy NGC 1309 shines in this NASA/ESA Hubble Space Telescope image. NGC 1309 is about 100 million light-years away in the constellation Eridanus.
This stunning Hubble image encompasses NGC 1309’s bluish stars, dark brown gas clouds, and pearly-white core, as well as hundreds of distant background galaxies. Nearly every smudge, streak, and blob of light in this image is an individual galaxy, some shining through less dense regions of NGC 1309 itself. The only exception to this extragalactic ensemble is a star near the top of the frame identified by its diffraction spikes. The star is positively neighborly at just a few thousand light-years away in the Milky Way galaxy.
Hubble turned its attention toward NGC 1309 several times; previous Hubble images of this galaxy were released in 2006 and 2014. Much of NGC 1309’s scientific interest derives from two supernovae, SN 2002fk in 2002 and SN 2012Z in 2012. SN 2002fk was a perfect example of a Type Ia supernova, which happens when the stripped-down core of a dead star (a white dwarf) explodes.
SN 2012Z, on the other hand, was a bit of a renegade. It was classified as a Type Iax supernova: while its spectrum resembled that of a Type Ia supernova, the explosion wasn’t as bright as expected. Hubble observations showed that in this case, the supernova did not destroy the white dwarf completely, leaving behind a ‘zombie star’ that shone even brighter than it did before the explosion. Hubble observations of NGC 1309 taken across several years also made this the first time astronomers spotted a star system that later produced an unusual supernova explosion of a white dwarf.
Text Credit: ESA/Hubble
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Last Updated Jul 31, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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By NASA
The NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 3285B, a member of the Hydra I cluster of galaxies.ESA/Hubble & NASA, R. J. Foley (UC Santa Cruz) The swirling spiral galaxy in this NASA/ESA Hubble Space Telescope image is NGC 3285B, which resides 137 million light-years away in the constellation Hydra (the Water Snake). Hydra has the largest area of the 88 constellations that cover the entire sky in a celestial patchwork. It’s also the longest constellation, stretching 100 degrees across the sky. It would take nearly 200 full moons, placed side by side, to reach from one side of the constellation to the other.
NGC 3285B is a member of the Hydra I cluster, one of the largest galaxy clusters in the nearby universe. Galaxy clusters are collections of hundreds to thousands of galaxies bound to one another by gravity. The Hydra I cluster is anchored by two giant elliptical galaxies at its center. Each of these galaxies is about 150,000 light-years across, making them about 50% larger than our home galaxy, the Milky Way.
NGC 3285B sits on the outskirts of its home cluster, far from the massive galaxies at the center. This galaxy drew Hubble’s attention because it hosted a Type Ia supernova in 2023. Type Ia supernovae happen when a type of condensed stellar core called a white dwarf detonates, igniting a sudden burst of nuclear fusion that briefly shines about 5 billion times brighter than the Sun. The supernova, named SN 2023xqm, is visible here as a blueish dot on the left edge of the galaxy’s disk.
Hubble observed NGC 3285B as part of an observing program that targeted 100 Type Ia supernovae. By viewing each of these supernovae in ultraviolet, optical, and near-infrared light, researchers aim to disentangle the effects of distance and dust, both of which can make a supernova appear redder than it actually is. This program will help refine cosmic distance measurements that rely on observations of Type Ia supernovae.
Text credit: ESA/Hubble
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