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By NASA
5 Min Read NASA’s Webb Reveals Distorted Galaxy Forming Cosmic Question Mark
The galaxy cluster MACS-J0417.5-1154. Full image below. Credits:
NASA, ESA, CSA, STScI, V. Estrada-Carpenter (Saint Mary’s University). It’s 7 billion years ago, and the universe’s heyday of star formation is beginning to slow. What might our Milky Way galaxy have looked like at that time? Astronomers using NASA’s James Webb Space Telescope have found clues in the form of a cosmic question mark, the result of a rare alignment across light-years of space.
“We know of only three or four occurrences of similar gravitational lens configurations in the observable universe, which makes this find exciting, as it demonstrates the power of Webb and suggests maybe now we will find more of these,” said astronomer Guillaume Desprez of Saint Mary’s University in Halifax, Nova Scotia, a member of the team presenting the Webb results.
Image A: Lensed Question Mark (NIRCam)
The galaxy cluster MACS-J0417.5-1154 is so massive it is warping the fabric of space-time and distorting the appearance of galaxies behind it, an effect known as gravitational lensing. This natural phenomenon magnifies distant galaxies and can also make them appear in an image multiple times, as NASA’s James Webb Space Telescope saw here. Two distant, interacting galaxies — a face-on spiral and a dusty red galaxy seen from the side — appear multiple times, tracing a familiar shape across the sky. Active star formation, and the face-on galaxy’s remarkably intact spiral shape, indicate that these galaxies’ interaction is just beginning. NASA, ESA, CSA, STScI, V. Estrada-Carpenter (Saint Mary’s University). While this region has been observed previously with NASA’s Hubble Space Telescope, the dusty red galaxy that forms the intriguing question-mark shape only came into view with Webb. This is a result of the wavelengths of light that Hubble detects getting trapped in cosmic dust, while longer wavelengths of infrared light are able to pass through and be detected by Webb’s instruments.
Astronomers used both telescopes to observe the galaxy cluster MACS-J0417.5-1154, which acts like a magnifying glass because the cluster is so massive it warps the fabric of space-time. This allows astronomers to see enhanced detail in much more distant galaxies behind the cluster. However, the same gravitational effects that magnify the galaxies also cause distortion, resulting in galaxies that appear smeared across the sky in arcs and even appear multiple times. These optical illusions in space are called gravitational lensing.
The red galaxy revealed by Webb, along with a spiral galaxy it is interacting with that was previously detected by Hubble, are being magnified and distorted in an unusual way, which requires a particular, rare alignment between the distant galaxies, the lens, and the observer — something astronomers call a hyperbolic umbilic gravitational lens. This accounts for the five images of the galaxy pair seen in Webb’s image, four of which trace the top of the question mark. The dot of the question mark is an unrelated galaxy that happens to be in the right place and space-time, from our perspective.
Image B: Hubble and Webb Side by Side
Image Before/After In addition to producing a case study of the Webb NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument’s ability to detect star formation locations within a galaxy billions of light-years away, the research team also couldn’t resist highlighting the question mark shape. “This is just cool looking. Amazing images like this are why I got into astronomy when I was young,” said astronomer Marcin Sawicki of Saint Mary’s University, one of the lead researchers on the team.
“Knowing when, where, and how star formation occurs within galaxies is crucial to understanding how galaxies have evolved over the history of the universe,” said astronomer Vicente Estrada-Carpenter of Saint Mary’s University, who used both Hubble’s ultraviolet and Webb’s infrared data to show where new stars are forming in the galaxies. The results show that star formation is widespread in both. The spectral data also confirmed that the newfound dusty galaxy is located at the same distance as the face-on spiral galaxy, and they are likely beginning to interact.
“Both galaxies in the Question Mark Pair show active star formation in several compact regions, likely a result of gas from the two galaxies colliding,” said Estrada-Carpenter. “However, neither galaxy’s shape appears too disrupted, so we are probably seeing the beginning of their interaction with each other.”
“These galaxies, seen billions of years ago when star formation was at its peak, are similar to the mass that the Milky Way galaxy would have been at that time. Webb is allowing us to study what the teenage years of our own galaxy would have been like,” said Sawicki.
The Webb images and spectra in this research came from the Canadian NIRISS Unbiased Cluster Survey (CANUCS). The research paper is published in the Monthly Notices of the Royal Astronomical Society.
Image C: Wide Field – Lensed Question Mark (NIRCam)
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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Space Telescope Science Institute, Baltimore, Md.
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Last Updated Sep 04, 2024 Editor Stephen Sabia Contact Laura Betz laura.e.betz@nasa.gov Related Terms
Astrophysics Galaxies Galaxies, Stars, & Black Holes Galaxy clusters Goddard Space Flight Center Gravitational Lensing James Webb Space Telescope (JWST) Science & Research The Universe View the full article
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By NASA
On Aug. 30, 1984, space shuttle Discovery lifted off on the STS-41D mission, joining NASA’s fleet as the third space qualified orbiter. The newest shuttle incorporated newer technologies making it significantly lighter than its two predecessors. Discovery lofted the heaviest payload up to that time in shuttle history. The six-person crew included five NASA astronauts and the first commercial payload specialist. During the six-day mission, the crew deployed a then-record three commercial satellites, tested an experimental solar array, and ran a commercial biotechnology experiment. The astronauts recorded many of the activities using a large format film camera, the scenes later incorporated into a motion picture for public engagement. The mission marked the first of Discovery’s 39 trips to space, the most of any orbiter.
Left: Space shuttle Discovery rolls out of Rockwell’s Palmdale, California, facility. Middle: Discovery atop the Shuttle Carrier Aircraft during the cross-country ferry flight. Right: Discovery arrives at NASA’s Kennedy Space Center in Florida.
Space shuttle Discovery, the third space-qualified orbiter in NASA’s fleet and named after several historical ships of exploration, incorporated manufacturing lessons learned from the first orbiters. In addition, through the use of more advanced materials, the new vehicle weighed nearly 8,000 pounds less than its sister ship Columbia and 700 pounds less than Challenger. Discovery rolled out of Rockwell International’s plant in Palmdale, California, on Oct. 16, 1983. Five of the six crew members assigned to its first flight attended the ceremony. Workers trucked Discovery overland from Palmdale to NASA’s Dryden, now Armstrong, Flight Research Center at Edwards Air Force Base (AFB), where they mounted it atop a Shuttle Carrier Aircraft (SCA), a modified Boeing 747, for the transcontinental ferry flight to NASA’s Kennedy Space Center (KSC) in Florida. Discovery arrived at KSC on Nov. 9 following a two-day stopover at Vandenberg Air Force, now Space Force Base, in California.
Left: STS-41D crew patch. Middle: Official photograph of the STS-41D crew of R. Michael “Mike” Mullane, front row left, Steven A. Hawley, Henry “Hank” W. Hartsfield, and Michael L. Coats; Charles D. Walker, back row left, and Judith A. Resnik. Right: Payloads installed in Discovery’s payload bay for the STS-41D mission include OAST-1, top, SBS-4, Telstar 3C, and Leasat-2.
To fly Discovery’s first flight, originally designated STS-12 and later renamed STS-41D, in February 1983 NASA assigned Commander Henry W. Hartsfield, a veteran of STS-4, and first-time flyers Pilot Michael L. Coats, and Mission Specialists R. Michael Mullane, Steven A. Hawley, and Judith A. Resnik, all from the 1978 class of astronauts and making their first spaceflights. In May 1983, NASA announced the addition of Charles D. Walker, an employee of the McDonnell Douglas Corporation, to the crew, flying as the first commercial payload specialist. He would operate the company’s Continuous Flow Electrophoresis System (CFES) experiment. The mission’s primary payloads included the Leasat-1 (formerly known as Syncom IV-1) commercial communications satellite and OAST-1, three experiments from NASA’s Office of Aeronautics and Space Technology, including the Solar Array Experiment, a 105-foot long lightweight deployable and retractable solar array. Following the June 1984 launch abort, NASA canceled the STS-41F mission, combining its payloads with STS-41D’s, resulting in three communications satellites – SBS-4 for Small Business Systems, Telstar 3C for AT&T, and Leasat 2 (Syncom IV-2) for the U.S. Navy – launching on the flight. The combined cargo weighed 41,184 pounds, the heaviest of the shuttle program up to that time. A large format IMAX® camera, making its second trip into space aboard the shuttle, flew in the middeck to film scenes inside the orbiter and out the windows.
Left: First rollout of Discovery from the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida. Right: The June 26 launch abort.
The day after its arrival at KSC, workers towed Discovery to the Orbiter Processing Facility (OPF) to begin preparing it for its first space flight. They towed it to the Vehicle Assembly Building (VAB) on May 12, 1984, for mating with its External Tank (ET) and Solid Rocket Boosters (SRBs). The completed stack rolled out to Launch Pad 39A a week later. On June 2, engineers successfully completed an 18-second Flight Readiness Firing of Discovery’s main engines. Post test inspections revealed a debonding of a thermal shield in main engine number 1’s combustion chamber, requiring its replacement at the pad. The work pushed the planned launch date back three days to June 25. The failure of the shuttle’s backup General Purpose Computer (GPC) delayed the launch by one day. The June 26 launch attempt ended just four seconds before liftoff, after two of the main engines had already ignited. The GPC detected that the third engine had not started and shut all three down. It marked the first time a human spaceflight launch experienced an abort after the start of its engines since Gemini VI in October 1965. The abort necessitated a rollback to the VAB on July 14 where workers demated Discovery from the ET and SRBs. Engineers replaced the faulty engine, and Discovery rolled back out to the launch pad on Aug. 9 for another launch attempt. The six-person crew participated in the Terminal Countdown Demonstration Test, essentially a dress rehearsal for the actual countdown to launch, on Aug. 15. A software issue delayed the first launch attempt on Aug. 29 by one day.
Left: The STS-41D crew pose at Launch Pad 39A at NASA’s Kennedy Space Center in Florida following the Terminal Countdown Demonstration Test. Right: Liftoff of Discovery on the STS-41D mission.
Finally, on Aug. 30, 1984, Discovery roared off its launch pad on a pillar of flame and within 8 and a half minutes entered orbit around the Earth. The crew got down to work and on the first day Mullane and Hawley deployed the SBS-4 satellite. On the second day in space, they deployed Leasat, the first satellite designed specifically to be launched from the shuttle. On the third day, they deployed the Telstar satellite, completing the satellite delivery objectives of the mission. Resnik deployed the OAST-1 solar array to 70% of its length to conduct dynamic tests on the structure. On the fourth day, she deployed the solar array to its full length and successfully retracted it, completing all objectives for that experiment.
The deployment of the SBS-4, left, Leasat-2, and Telstar 3C satellites during STS-41D.
Walker remained busy with the CFES, operating the unit for about 100 hours, and although the experiment experienced two unexpected shutdowns, he processed about 85% of the planned samples. Hartsfield and Coats exposed two magazines and six rolls of IMAX® film, recording OAST-1 and satellite deployments as well as in-cabin crew activities. Clips from the mission appear in the 1985 IMAX® film “The Dream is Alive.” On the mission’s fifth day, concern arose over the formation of ice on the orbiter’s waste dump nozzle. The next day, Hartsfield used the shuttle’s robotic arm to dislodge the large chunk of ice.
Left: Payload Specialist Charles D. Walker in front of the Continuous Flow Experiment System. Middle: Henry “Hank” W. Hartsfield loading film into the IMAX® camera. Right: The OAST-1 Solar Array Experiment extended from Discovery’s payload bay.
On Sep. 5, the astronauts closed Discovery’s payload bay doors in preparation for reentry. They fired the shuttle’s Orbital Maneuvering System engines to slow their velocity and begin their descent back to Earth. Hartsfield guided Discovery to a smooth landing at Edwards AFB in California, completing a flight of 6 days and 56 minutes. The crew had traveled 2.5 million miles and orbited the Earth 97 times.
Left: The STS-41D crew pose in Discovery’s middeck. Right: Space shuttle Discovery makes a perfect landing at Edwards Air Force Base in California to end the STS-41D mission.
By Sept. 10, workers had returned Discovery to KSC to prepare it for its next mission, STS-51A, in November 1984. During its lifetime, Discovery flew a fleet leading 39 missions, making its final trip to space in February 2011. It flew both return to flight missions, STS-26 in 1988 and STS-114 in 2005. It launched the Hubble Space Telescope in 1990 and flew two of the missions to service the facility. Discovery flew two mission to Mir, docking once. It completed the first docking to the International Space Station in 1999 and flew a total of 13 assembly and resupply missions to the orbiting lab. By its last mission, Discovery had traveled 149 million miles, completed 5,830 orbits of the Earth, and spent a cumulative 365 days in space in the span of 27 years. The public can view Discovery on display at the National Air and Space Museum’s Stephen F. Udvar-Hazy Center in Chantilly, Virginia.
Read recollections of the STS-41D mission by Hartsfield, Coats, Mullane, Hawley, and Walker in their oral histories with the JSC History Office. Enjoy the crew’s narration of a video about the STS-41D mission.
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Sonifications of three images have been released to mark the 25th anniversary of Chandra’s “First Light” image. For Cassiopeia A, which was one of the first objects observed by Chandra, X-ray data from Chandra and infrared data from Webb have been translated into sounds, along with some Hubble data. The second image in the sonification trio, 30 Doradus, also contains Chandra and Webb data. NGC 6872 contains data from Chandra as well as an optical image from Hubble. Each of these datasets have been mapped to notes and sounds based on properties observed by these telescopes.NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida) A quarter of a century ago, NASA released the “first light” images from the agency’s Chandra X-ray Observatory. This introduction to the world of Chandra’s high-resolution X-ray imaging capabilities included an unprecedented view of Cassiopeia A, the remains of an exploded star located about 11,000 light-years from Earth. Over the years, Chandra’s views of Cassiopeia A have become some of the telescope’s best-known images.
To mark the anniversary of this milestone, new sonifications of three images – including Cassiopeia A (Cas A) – are being released. Sonification is a process that translates astronomical data into sound, similar to how digital data are more routinely turned into images. This translation process preserves the science of the data from its original digital state but provides an alternative pathway to experiencing the data.
This sonification of Cas A features data from Chandra as well as NASA’s James Webb, Hubble, and retired Spitzer space telescopes. The scan starts at the neutron star at the center of the remnant, marked by a triangle sound, and moves outward. Astronomers first saw this neutron star when Chandra’s inaugural observations were released 25 years ago this week. Chandra’s X-rays also reveal debris from the exploded star that is expanding outward into space. The brighter parts of the image are conveyed through louder volume and higher pitched sounds. X-ray data from Chandra are mapped to modified piano sounds, while infrared data from Webb and Spitzer, which detect warmed dust embedded in the hot gas, have been assigned to various string and brass instruments. Stars that Hubble detects are played with crotales, or small cymbals.
Another new sonification features the spectacular cosmic vista of 30 Doradus, one of the largest and brightest regions of star formation close to the Milky Way. This sonification again combines X-rays from Chandra with infrared data from Webb. As the scan moves from left to right across the image, the volume heard again corresponds to the brightness seen. Light toward the top of the image is mapped to higher pitched notes. X-rays from Chandra, which reveal gas that has been superheated by shock waves generated by the winds from massive stars, are heard as airy synthesizer sounds. Meanwhile, Webb’s infrared data show cooler gas that provides the raw ingredients for future stars. These data are mapped to a range of sounds including soft, low musical pitches (red regions), a wind-like sound (white regions), piano-like synthesizer notes indicating very bright stars, and a rain-stick sound for stars in a central cluster.
The final member of this new sonification triumvirate is NGC 6872, a large spiral galaxy that has two elongated arms stretching to the upper right and lower left, which is seen in an optical light view from Hubble. Just to the upper left of NGC 6872 appears another smaller spiral galaxy. These two galaxies, each of which likely has a supermassive black hole at the center, are being drawn toward one another. As the scan sweeps clockwise from 12 o’clock, the brightness controls the volume and light farther from the center of the image is mapped to higher-pitched notes. Chandra’s X-rays, represented in sound by a wind-like sound, show multimillion-degree gas that permeates the galaxies. Compact X-ray sources from background galaxies create bird-like chirps. In the Hubble data, the core of NGC 6872 is heard as a dark low drone, and the blue spiral arms (indicating active star formation) are audible as brighter, more highly pitched tones. The background galaxies are played as a soft pluck sound while the bright foreground star is accompanied by a crash cymbal.
More information about the NASA sonification project through Chandra, which is made in partnership with NASA’s Universe of Learning, can be found at https://chandra.si.edu/sound/. The collaboration was driven by visualization scientist Kimberly Arcand (CXC), astrophysicist Matt Russo, and musician Andrew Santaguida, (both of the SYSTEM Sounds project), along with consultant Christine Malec.
NASA’s Universe of Learning materials are based upon work supported by NASA under cooperative agreement award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.
More about Chandra
Chandra, managed for NASA by Marshall in partnership with the CXC, is one of NASA’s Great Observatories, along with the Hubble Space Telescope and the now-retired Spitzer Space Telescope and Compton Gamma Ray Observatory. It was first proposed to NASA in 1976 by Riccardo Giacconi, recipient of the 2002 Nobel Prize for Physics based on his contributions to X-ray astronomy, and Harvey Tananbaum, who would later become the first director of the Chandra X-ray Center. Chandra was named in honor of the late Nobel laureate Subrahmanyan Chandrasekhar, who earned the Nobel Prize in Physics in 1983 for his work explaining the structure and evolution of stars.
Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/mission/chandra-x-ray-observatory/
https://cxc.harvard.edu
News Media Contact
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov
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Last Updated Sep 03, 2024 LocationMarshall Space Flight Center Related Terms
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4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s Student Launch, a STEM competition, officially kicks off its 25th anniversary with the 2025 handbook. By Wayne Smith
NASA’s Student Launch competition kicks off its 25th year with the release of the 2025 handbook, detailing how teams can submit proposals by Wednesday, Sept. 11, for the event scheduled next spring near NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Student Launch is an annual competition challenging middle school, high school, and college students to design, build, test, and launch a high-powered amateur rocket with a scientific or engineering payload. After a team is selected, they must meet documentation milestones and undergo detailed reviews throughout the school year.
Each year, NASA updates the university payload challenge to reflect current scientific and exploration missions. For the 2025 season, the payload challenge will again take inspiration from the Artemis missions, which seek to land the first woman and first person of color on the Moon.
As Student Launch celebrates its 25th anniversary, the payload challenge will include “reports” from STEMnauts, non-living objects representing astronauts. The 2024 challenge tasked teams with safely deploying a lander mid-air for a group of four STEMnauts using metrics to support a survivable landing. The lander had to be deployed without a parachute and had a minimum weight limit of five pounds.
“This year, we’re shifting the focus to communications for the payload challenge,” said John Eckhart, technical coordinator for Student Launch at Marshall. “The STEMnaut ‘crew’ must relay real-time data to the student team’s mission control. This helps connect Student Launch with the Artemis missions when NASA lands astronauts on the Moon.”
Thousands of students participated in the 2024 Student Launch competition – making up 70 teams representing 24 states and Puerto Rico. Teams launched their rockets to an altitude between 4,000 and 6,000 feet, while attempting to make a successful landing and executing the payload mission. The University of Notre Dame was the overall winner of the 2024 event, which culminated with a launch day open to the public.
Student Launch began in 2000 when former Marshall Director Art Stephenson started a student rocket competition at the center. It started with just two universities in Huntsville competing – Alabama A&M University and the University of Alabama in Huntsville – but has continued to soar. Since its inception, thousands of students have participated in the agency’s STEM competition, with many going on to a career with NASA.
“This remarkable journey, spanning a quarter of a century, has been a testament to the dedication, ingenuity, and passion of countless students, educators, and mentors who have contributed to the program’s success,” Eckhart said. “NASA Student Launch has been at the forefront of experiential education, providing students from middle school through university with unparalleled opportunities to engage in real-world engineering and scientific research. The program’s core mission – to inspire and cultivate the next generation of aerospace professionals and space explorers – has not only been met but exceeded in ways we could have only dreamed of.”
To encourage students to pursue degrees and careers in STEM (science, technology, engineering, and math), Marshall’s Office of STEM Engagement hosts Student Launch, providing them with real-world experiences. Student Launch is one of NASA’s nine Artemis Student Challenges – a variety of activities that expose students to the knowledge and technology required to achieve the goals of Artemis.
In addition to the NASA Office of STEM Engagement’s Next Generation STEM project, NASA Space Operations Mission Directorate, Northrup Grumman, National Space Club Huntsville, American Institute of Aeronautics and Astronautics, National Association of Rocketry, Relativity Space and Bastion Technologies provide funding and leadership for the competition.
“These bright students rise to a nine-month challenge for Student Launch that tests their skills in engineering, design, and teamwork,” said Kevin McGhaw, director of NASA’s Office of STEM Engagement Southeast Region. “They are the Artemis Generation, the future scientists, engineers, and innovators who will lead us into the future of space exploration.”
For more information about Student Launch, please visit:
https://www.nasa.gov/studentlaunch
Taylor Goodwin
Marshall Space Flight Center, Huntsville, Ala.
256.544.0034
taylor.goodwin@nasa.gov
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By NASA
On Aug. 29, 1789, German-born British astronomer William Herschel observed a tiny bright dot orbiting around Saturn. His son later named the object Enceladus. Because of its distance from Earth and proximity to bright Saturn, for the next two centuries little remained known about Enceladus other than its size, orbital parameters, and that it held the honor as the most reflective body in the solar system. It took the Voyager flybys through the Saturn system in the early 1980s and especially the detailed observations between 2005 and 2015 by the Saturn orbiter Cassini to reveal Enceladus as a truly remarkable world, interacting with Saturn and its rings. Harboring a subsurface ocean of salty water, Enceladus may possibly be hospitable to some forms of life.
Left: Portrait (1785) of William Herschel by Lemuel Francis Abbott. Image credit: courtesy National Portrait Gallery, London. Middle: Drawing of Herschel’s 40-foot telescope. Right: Portrait (1867) of John Herschel by Julia Margaret Cameron. Image credit: Metropolitan Museum of Art.
Herschel’s previous astronomical accomplishments include the discovery of Uranus in 1781 and two of its moons, Oberon and Titania, in 1787. He also catalogued numerous objects he termed nebulae, but remained frustrated by the limitations of telescopes of his age. He began to build ever larger instruments, finally building the world’s largest reflecting telescope of its time. At 40 feet long, and with a 49-inch diameter primary mirror weighing a ton, it looked impressive although its optical characteristics did not advance the field as much as he had hoped. Nevertheless, Herschel used this telescope to observe Saturn and its five known moons, looking for others. On Aug. 28, 1789, he observed a bright point orbiting the planet and believed he had discovered a sixth moon. On Sept. 17, he discovered a seventh moon orbiting the ringed planet. He did not name these moons, that task fell to his son John who believed Saturn’s moons should be named after the Titans of Greek mythology. He named the first moon Enceladus and the second Mimas.
Left: Relative sizes of Earth, Earth’s Moon, and Enceladus. Right: Best Voyager 2 image of Enceladus.
For nearly two centuries, Enceladus remained not much more than a point of light orbiting Saturn, just another icy moon in the outer solar system. Astronomers estimated its diameter at around 310 miles and its orbital period around Saturn at 1.4 days, with a mean distance from the planet’s center of 148,000 miles. Enceladus has the distinction as one of the brightest objects in the solar system, reflecting almost 100 percent of the Sun’s light. Unusual telescope observations during the 20th century showed an increase in brightness on its trailing side, with no known explanation at the time. In 1966, astronomers discovered a diffuse ring around Saturn, the E-ring, and found in 1980 that its density peaked near Enceladus. The Voyager 1 spacecraft flew within 125,570 miles of Enceladus during its passage through the Saturn system on Nov. 12, 1980. Its twin Voyager 2 came within 54,000 miles on Aug. 26, 1981, during its flyby. These close encounters enabled the spacecraft to return the first detailed images of the moon, showing various terrains, including heavily cratered areas as well as smooth crater-free areas, indicating a very young surface.
Left: False color image of Enceladus from Cassini showing the tiger stripes at bottom. Middle: Limb view of Enceladus showing plumes of material emanating from its surface. Right: Cassini image of Enceladus backlit by the Sun showing the fountain-like plumes of material.
After the Cassini spacecraft entered orbit around Saturn in July 2004, our understanding of Enceladus increased tremendously, and of course raised new questions. Between 2005 and 2015, Cassini encountered Enceladus 22 times, turning its various instruments on the moon to unravel its secrets. It noted early on that the moon emitted gas and dust or ice particles and that they interacted with the E-ring. Images of the moon’s south polar region revealed cracks on the surface and other instruments detected a huge cloud of water vapor over the area. The moon likely had a liquid subsurface and some of this material reached the outside through these cracks. Scientists named the most prominent of these areas “tiger stripes” and later observations confirmed them as the source of the most prominent jets. During the most daring encounter in October 2015, Cassini came within 30 miles of the Enceladus’ surface, flying through the plume of material emanating from the moon. Analysis of the plumes revealed an organic brew of volatile gases, water vapor, ammonia, sodium salts, carbon dioxide, and carbon monoxide. These plumes replenish Saturn’s E-ring, and some of this material enters Saturn’s upper atmosphere, an interaction unique in the solar system. More recently, the James Webb Space Telescope imaged the water vapor plume emanating from Enceladus’ south pole, extending out 40 times the size of the moon itself. The confirmation of a subsurface ocean of salty water has led some scientists to postulate that Enceladus may be hospitable to some forms of life, making it a potential target for future exploration. Enceladus may yet have more surprises, even as scientists continue to pore over the data returned by Cassini.
Left: James Webb Space Telescope image of a water vapor plume emanating from Enceladus. Right: Illustration of the interaction of Enceladus and Saturn’s E-ring.
Map of Enceladus based on imagery from Cassini, turning our view of Enceladus from a small point of light into a unique world with its own topography.
Events in world history in 1789:
January 29 – Vietnamese emperor Quang Trung defeats Chinese Qing forces at Ngọc Hồi-Đống Đa in one of the greatest military victories in Vietnamese history.
March 10 – In Japan, the Menashi-Kunashir rebellion begins between the Ainu people and the Japanese.
April 7 – Selim III succeeds Abdul Hamid I as Sultan of the Ottoman Empire.
April 28 – Aboard the HMS Bounty in the Pacific Ocean, Fletcher Christian leads the mutiny against Captain William Bligh.
April 30 – Inauguration of George Washington as the first President of the United States of America.
July 14 – Citizens storm The Bastille fortress in Paris during the French Revolution.
September 15 – Birth of American writer James Fenimore Cooper in Burlington, New Jersey.
December 11 – Founding of the University of North Carolina, the oldest public university in the United States.
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