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Jaw-dropping Images: Uranus' Hidden Rings and Moons
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By European Space Agency
Week in images: 17-21 February 2025
Discover our week through the lens
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By European Space Agency
Week in images: 10-14 February 2025
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By European Space Agency
Week in images: 03-07 February 2025
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This version of a mosaic captured by the star tracker cameras aboard NASA’s Europa Clipper on Dec. 4, 2024, features the names of stars within view of the cameras. NASA/JPL-Caltech This mosaic of a star field was made from three images captured Dec. 4, 2024, by star tracker cameras aboard NASA’s Europa Clipper spacecraft. Showing part of the constel-lation Corvus, it’s the first imagery of space the orbiter has captured since its launch on Oct. 14, 2024.NASA/JPL-Caltech The spacecraft’s star trackers help engineers orient the orbiter throughout its long journey to Jupiter’s icy moon Europa.
Three months after its launch from NASA’s Kennedy Space Center in Florida, the agency’s Europa Clipper has another 1.6 billion miles (2.6 billion kilometers) to go before it reaches Jupiter’s orbit in 2030 to take close-up images of the icy moon Europa with science cameras.
Meanwhile, a set of cameras serving a different purpose is snapping photos in the space between Earth and Jupiter. Called star trackers, the two imagers look for stars and use them like a compass to help mission controllers know the exact orientation of the spacecraft — information critical for pointing telecommunications antennas toward Earth and sending data back and forth smoothly.
In early December, the pair of star trackers (formally known as the stellar reference units) captured and transmitted Europa Clipper’s first imagery of space. The picture, composed of three shots, shows tiny pinpricks of light from stars 150 to 300 light-years away. The starfield represents only about 0.1% of the full sky around the spacecraft, but by mapping the stars in just that small slice of sky, the orbiter is able to determine where it is pointed and orient itself correctly.
The starfield includes the four brightest stars — Gienah, Algorab, Kraz, and Alchiba — of the constellation Corvus, which is Latin for “crow,” a bird in Greek mythology that was associated with Apollo.
Engineers on NASA’s Europa Clipper mission work with the spacecraft’s star trackers in a clean room at the agency’s Jet Propulsion Laboratory in 2022. Used for orienting the spacecraft, the star trackers are seen here with red covers to protect their lenses.NASA/JPL-Caltech Hardware Checkout
Besides being interesting to stargazers, the photos signal the successful checkout of the star trackers. The spacecraft checkout phase has been going on since Europa Clipper launched on a SpaceX Falcon Heavy rocket on Oct. 14, 2024.
“The star trackers are engineering hardware and are always taking images, which are processed on board,” said Joanie Noonan of NASA’s Jet Propulsion Laboratory in Southern California, who leads the mission’s guidance, navigation and control operations. “We usually don’t downlink photos from the trackers, but we did in this case because it’s a really good way to make sure the hardware — including the cameras and their lenses — made it safely through launch.”
Pointing the spacecraft correctly is not about navigation, which is a separate operation. But orientation using the star trackers is critical for telecommunications as well as for the science operations of the mission. Engineers need to know where the science instruments are pointed. That includes the sophisticated Europa Imaging System (EIS), which will collect images that will help scientists map and examine the moon’s mysterious fractures, ridges, and valleys. For at least the next three years, EIS has its protective covers closed.
Europa Clipper carries nine science instruments, plus the telecommunications equipment that will be used for a gravity science investigation. During the mission’s 49 flybys of Europa, the suite will gather data that will tell scientists if the icy moon and its internal ocean have the conditions to harbor life.
The spacecraft already is 53 million miles (85 million kilometers) from Earth, zipping along at 17 miles per second (27 kilometers per second) relative to the Sun, and soon will fly by Mars. On March 1, engineers will steer the craft in a loop around the Red Planet, using its gravity to gain speed.
More About Europa Clipper
Europa Clipper’s three main science objectives are to determine the thickness of the moon’s icy shell and its interactions with the ocean below, to investigate its composition, and to characterize its geology. The mission’s detailed exploration of Europa will help scientists better understand the astrobiological potential for habitable worlds beyond our planet.
Managed by Caltech in Pasadena, California, JPL leads the development of the Europa Clipper mission in partnership with the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, for NASA’s Science Mission Directorate in Washington. APL designed the main spacecraft body in collaboration with JPL and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, NASA’s Marshall Space Flight Center in Huntsville, Alabama, and Langley Research Center in Hampton, Virginia. The Planetary Missions Program Office at Marshall executes program management of the Europa Clipper mission. NASA’s Launch Services Program, based at Kennedy, managed the launch service for the Europa Clipper spacecraft.
Find more information about Europa Clipper here:
https://science.nasa.gov/mission/europa-clipper/
View an interactive 3D model of NASA’s Europa Clipper News Media Contacts
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-287-4115
gretchen.p.mccartney@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Feb 04, 2025 Related Terms
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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 Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Posters Hubble on the NASA App Glossary More 35th Anniversary Online Activities 5 Min Read Straight Shot: Hubble Investigates Galaxy with Nine Rings
LEDA 1313424, aptly nicknamed the Bullseye, is two and a half times the size of our Milky Way and has nine rings — six more than any other known galaxy. Credits:
NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale) NASA’s Hubble Space Telescope has captured a cosmic bullseye! The gargantuan galaxy LEDA 1313424 is rippling with nine star-filled rings after an “arrow” — a far smaller blue dwarf galaxy — shot through its heart. Astronomers using Hubble identified eight visible rings, more than previously detected by any telescope in any galaxy, and confirmed a ninth using data from the W. M. Keck Observatory in Hawaii. Previous observations of other galaxies show a maximum of two or three rings.
“This was a serendipitous discovery,” said Imad Pasha, the lead researcher and a doctoral student at Yale University in New Haven, Connecticut. “I was looking at a ground-based imaging survey and when I saw a galaxy with several clear rings, I was immediately drawn to it. I had to stop to investigate it.” The team later nicknamed the galaxy the “Bullseye.”
LEDA 1313424, aptly nicknamed the Bullseye, is two and a half times the size of our Milky Way and has nine rings — six more than any other known galaxy. High-resolution imagery from NASA’s Hubble Space Telescope confirmed eight rings, and data from the W. M. Keck Observatory in Hawaii confirmed a ninth. Hubble and Keck also confirmed which galaxy dove through the Bullseye, creating these rings: the blue dwarf galaxy that sits to its immediate center-left. NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale)
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Hubble and Keck’s follow-up observations also helped the researchers prove which galaxy plunged through the center of the Bullseye — a blue dwarf galaxy to its center-left. This relatively tiny interloper traveled like a dart through the core of the Bullseye about 50 million years ago, leaving rings in its wake like ripples in a pond. A thin trail of gas now links the pair, though they are currently separated by 130,000 light-years.
“We’re catching the Bullseye at a very special moment in time,” said Pieter G. van Dokkum, a co-author of the new study and a professor at Yale. “There’s a very narrow window after the impact when a galaxy like this would have so many rings.”
Galaxies collide or barely miss one another quite frequently on cosmic timescales, but it is extremely rare for one galaxy to dive through the center of another. The blue dwarf galaxy’s straight trajectory through the Bullseye later caused material to move both inward and outward in waves, setting off new regions of star formation.
How big is the Bullseye? Our Milky Way galaxy is about 100,000 light-years in diameter, and the Bullseye is almost two-and-a-half times larger, at 250,000 light-years across.
This illustration compares the size of our own Milky Way galaxy to gargantuan galaxy LEDA 1313424, nicknamed the Bullseye. The Milky Way is about 100,000 light-years in diameter, and the Bullseye is almost two-and-a-half times larger, at 250,000 light-years across. NASA, ESA, Ralf Crawford (STScI)
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The researchers used Hubble’s crisp vision to carefully to pinpoint the location of most of its rings, since many are piled up at the center. “This would have been impossible without Hubble,” Pasha said.
They used Keck to confirm one more ring. The team suspects a 10th ring also existed, but has faded and is no longer detectable. They estimate it might lie three times farther out than the widest ring in Hubble’s image.
A One-to-One Match with Predictions
Pasha also found a stunning connection between the Bullseye and a long-established theory: The galaxy’s rings appear to have moved outward almost exactly as predicted by models.
“That theory was developed for the day that someone saw so many rings,” van Dokkum said. “It is immensely gratifying to confirm this long-standing prediction with the Bullseye galaxy.”
If viewed from above, it would be more obvious that the galaxy’s rings aren’t evenly spaced like those on a dart board. Hubble’s image shows the galaxy from a slight angle. “If we were to look down at the galaxy directly, the rings would look circular, with rings bunched up at the center and gradually becoming more spaced out the farther out they are,” Pasha explained.
To visualize how these rings may have formed, think about dropping a pebble into a pond. The first ring ripples out, becoming the widest over time, while others continue to form after it.
The researchers suspect that the first two rings in the Bullseye formed quickly and spread out in wider circles. The formation of additional rings may have been slightly staggered, since the blue dwarf galaxy’s flythrough affected the first rings more significantly.
This illustration shows the massive galaxy nicknamed the Bullseye face-on. Dotted circles indicate where each of its rings are, which formed like ripples in a pond after a blue dwarf galaxy (not shown) shot through its core about 50 million years ago. NASA’s Hubble Space Telescope helped researchers carefully pinpoint the location of most of its rings, many of which are piled up at the center. Data from the W. M. Keck Observatory in Hawaii helped the team confirm another ring. NASA, ESA, Ralf Crawford (STScI)
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Individual stars’ orbits were largely undisturbed, though groups of stars did “pile up” to form distinguishable rings over millions of years. The gas, however, was carried outward, and mixed with dust to form new stars, further brightening the Bullseye’s rings.
There’s a lot more research to be done to figure out which stars existed before and after the blue dwarf’s “fly through.” Astronomers will now also be able to improve models showing how the galaxy may continue to evolve over billions of years, including the disappearance of additional rings.
Although this discovery was a chance finding, astronomers can look forward to finding more galaxies like this one soon. “Once NASA’s Nancy Grace Roman Space Telescope begins science operations, interesting objects will pop out much more easily,” van Dokkum explained. “We will learn how rare these spectacular events really are.”
The team’s paper was published on the February 4, 2025 in The Astrophysical Journal Letters.
The Hubble Space Telescope has been operating for over 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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Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
Claire Blome and Ray Villard
Space Telescope Science Institute, Baltimore, MD
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