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Hubble's Close-Up View of a Shock Wave from a Stellar Explosion
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By NASA
This graphic features data from NASA’s Chandra X-ray Observatory of the Cassiopeia A (Cas A) supernova remnant that reveals that the star’s interior violently rearranged itself mere hours before it exploded. The main panel of this graphic is Chandra data that shows the location of different elements in the remains of the explosion: silicon (represented in red), sulfur (yellow), calcium (green) and iron (purple). The blue color reveals the highest-energy X-ray emission detected by Chandra in Cas A and an expanding blast wave. The inset reveals regions with wide ranges of relative abundances of silicon and neon. This data, plus computer modeling, reveal new insight into how massive stars like Cas A end their lives.X-ray: NASA/CXC/Meiji Univ./T. Sato et al.; Image Processing: NASA/CXC/SAO/N. Wolk The inside of a star turned on itself before it spectacularly exploded, according to a new study from NASA’s Chandra X-ray Observatory. Today, this shattered star, known as the Cassiopeia A supernova remnant, is one of the best-known, well-studied objects in the sky.
Over three hundred years ago, however, it was a giant star on the brink of self-destruction. The new Chandra study reveals that just hours before it exploded, the star’s interior violently rearranged itself. This last-minute shuffling of its stellar belly has profound implications for understanding how massive stars explode and how their remains behave afterwards.
Cassiopeia A (Cas A for short) was one of the first objects the telescope looked at after its launch in 1999, and astronomers have repeatedly returned to observe it.
“It seems like each time we closely look at Chandra data of Cas A, we learn something new and exciting,” said Toshiki Sato of Meiji University in Japan who led the study. “Now we’ve taken that invaluable X-ray data, combined it with powerful computer models, and found something extraordinary.”
As massive stars age, increasingly heavy elements form in their interiors by nuclear reactions, creating onion-like layers of different elements. Their outer layer is mostly made of hydrogen, followed by layers of helium, carbon and progressively heavier elements – extending all the way down to the center of the star.
Once iron starts forming in the core of the star, the game changes. As soon as the iron core grows beyond a certain mass (about 1.4 times the mass of the Sun), it can no longer support its own weight and collapses. The outer part of the star falls onto the collapsing core, and rebounds as a core-collapse supernova.
The new research with Chandra data reveals a change that happened deep within the star at the very last moments of its life. After more than a million years, Cas A underwent major changes in its final hours before exploding.
“Our research shows that just before the star in Cas A collapsed, part of an inner layer with large amounts of silicon traveled outwards and broke into a neighboring layer with lots of neon,” said co-author Kai Matsunaga of Kyoto University in Japan. “This is a violent event where the barrier between these two layers disappears.”
This upheaval not only caused material rich in silicon to travel outwards; it also forced material rich in neon to travel inwards. The team found clear traces of these outward silicon flows and inward neon flows in the remains of Cas A’s supernova remnant. Small regions rich in silicon but poor in neon are located near regions rich in neon and poor in silicon.
The survival of these regions not only provides critical evidence for the star’s upheaval, but also shows that complete mixing of the silicon and neon with other elements did not occur immediately before or after the explosion. This lack of mixing is predicted by detailed computer models of massive stars near the ends of their lives.
There are several significant implications for this inner turmoil inside of the doomed star. First, it may directly explain the lopsided rather than symmetrical shape of the Cas A remnant in three dimensions. Second, a lopsided explosion and debris field may have given a powerful kick to the remaining core of the star, now a neutron star, explaining the high observed speed of this object.
Finally, the strong turbulent flows created by the star’s internal changes may have promoted the development of the supernova blast wave, facilitating the star’s explosion.
“Perhaps the most important effect of this change in the star’s structure is that it may have helped trigger the explosion itself,” said co-author Hiroyuki Uchida, also of Kyoto University. “Such final internal activity of a star may change its fate—whether it will shine as a supernova or not.”
These results have been published in the latest issue of The Astrophysical Journal and are available online.
To learn more about Chandra, visit:
https://science.nasa.gov/chandra
Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
Visual Description
This release features a composite image of Cassiopeia A, a donut-shaped supernova remnant located about 11,000 light-years from Earth. Included in the image is an inset closeup, which highlights a region with relative abundances of silicon and neon.
Over three hundred years ago, Cassiopeia A, or Cas A, was a star on the brink of self-destruction. In composition it resembled an onion with layers rich in different elements such as hydrogen, helium, carbon, silicon, sulfur, calcium, and neon, wrapped around an iron core. When that iron core grew beyond a certain mass, the star could no longer support its own weight. The outer layers fell into the collapsing core, then rebounded as a supernova. This explosion created the donut-like shape shown in the composite image. The shape is somewhat irregular, with the thinner quadrant of the donut to the upper left of the off-center hole.
In the body of the donut, the remains of the star’s elements create a mottled cloud of colors, marbled with red and blue veins. Here, sulfur is represented by yellow, calcium by green, and iron by purple. The red veins are silicon, and the blue veins, which also line the outer edge of the donut-shape, are the highest energy X-rays detected by Chandra and show the explosion’s blast wave.
The inset uses a different color code and highlights a colorful, mottled region at the thinner, upper left quadrant of Cas A. Here, rich pockets of silicon and neon are identified in the red and blue veins, respectively. New evidence from Chandra indicates that in the hours before the star’s collapse, part of a silicon-rich layer traveled outwards, and broke into a neighboring neon-rich layer. This violent breakdown of layers created strong turbulent flows and may have promoted the development of the supernova’s blast wave, facilitating the star’s explosion. Additionally, upheaval in the interior of the star may have produced a lopsided explosion, resulting in the irregular shape, with an off-center hole (and a thinner bite of donut!) at our upper left.
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Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Corinne Beckinger
Marshall Space Flight Center, Huntsville, Alabama
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corinne.m.beckinger@nasa.gov
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Last Updated Aug 28, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
5 min read
Astronomers Map Stellar ‘Polka Dots’ Using NASA’s TESS, Kepler
Scientists have devised a new method for mapping the spottiness of distant stars by using observations from NASA missions of orbiting planets crossing their stars’ faces. The model builds on a technique researchers have used for decades to study star spots.
By improving astronomers’ understanding of spotty stars, the new model — called StarryStarryProcess — can help discover more about planetary atmospheres and potential habitability using data from telescopes like NASA’s upcoming Pandora mission.
“Many of the models researchers use to analyze data from exoplanets, or worlds beyond our solar system, assume that stars are uniformly bright disks,” said Sabina Sagynbayeva, a graduate student at Stony Brook University in New York. “But we know just by looking at our own Sun that stars are more complicated than that. Modeling complexity can be difficult, but our approach gives astronomers an idea of how many spots a star might have, where they are located, and how bright or dark they are.”
A paper describing StarryStarryProcess, led by Sagynbayeva, published Monday, August 25, in The Astrophysical Journal.
Watch to learn how a new tool uses data from exoplanets, worlds beyond our solar system, to tell us about their polka-dotted stars.
NASA’s Goddard Space Flight Center
Download images and videos through NASA’s Scientific Visualization Studio.
NASA’s TESS (Transiting Exoplanet Survey Satellite) and now-retired Kepler Space Telescope were designed to identify planets using transits, dips in stellar brightness caused when a planet passes in front of its star.
These measurements reveal how the star’s light varies with time during each transit, and astronomers can arrange them in a plot astronomers call a light curve. Typically, a transit light curve traces a smooth sweep down as the planet starts passing in front of the star’s face. It reaches a minimum brightness when the world is fully in front of the star and then rises smoothly as the planet exits and the transit ends.
By measuring the time between transits, scientists can determine how far the planet lies from its star and estimate its surface temperature. The amount of missing light from the star during a transit can reveal the planet’s size, which can hint at its composition.
Every now and then, though, a planet’s light curve appears more complicated, with smaller dips and peaks added to the main arc. Scientists think these represent dark surface features akin to sunspots seen on our own Sun — star spots.
The Sun’s total number of sunspots varies as it goes through its 11-year solar cycle. Scientists use them to determine and predict the progress of that cycle as well as outbreaks of solar activity that could affect us here on Earth.
Similarly, star spots are cool, dark, temporary patches on a stellar surface whose sizes and numbers change over time. Their variability impacts what astronomers can learn about transiting planets.
Scientists have previously analyzed transit light curves from exoplanets and their host stars to look at the smaller dips and peaks. This helps determine the host star’s properties, such as its overall level of spottiness, inclination angle of the planet’s orbit, the tilt of the star’s spin compared to our line of sight, and other factors. Sagynbayeva’s model uses light curves that include not only transit information, but also the rotation of the star itself to provide even more detailed information about these stellar properties.
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This artist’s concept illustrates the varying brightness of star with a transiting planet and several star spots. NASA’s Goddard Space Flight Center “Knowing more about the star in turn helps us learn even more about the planet, like a feedback loop,” said co-author Brett Morris, a senior software engineer at the Space Telescope Science Institute in Baltimore. “For example, at cool enough temperatures, stars can have water vapor in their atmospheres. If we want to look for water in the atmospheres of planets around those stars — a key indicator of habitability — we better be very sure that we’re not confusing the two.”
To test their model, Sagynbayeva and her team looked at transits from a planet called TOI 3884 b, located around 141 light-years away in the northern constellation Virgo.
Discovered by TESS in 2022, astronomers think the planet is a gas giant about five times bigger than Earth and 32 times its mass.
The StarryStarryProcess analysis suggests that the planet’s cool, dim star — called TOI 3384 — has concentrations of spots at its north pole, which also tips toward Earth so that the planet passes over the pole from our perspective.
Currently, the only available data sets that can be fit by Sagynbayeva’s model are in visible light, which excludes infrared observations taken by NASA’s James Webb Space Telescope. But NASA’s upcoming Pandora mission will benefit from tools like this one. Pandora, a small satellite developed through NASA’s Astrophysics Pioneers Program, will study the atmospheres of exoplanets and the activity of their host stars with long-duration multiwavelength observations. The Pandora mission’s goal is to determine how the properties of a star’s light differs when it passes through a planet’s atmosphere so scientists can better measure those atmospheres using Webb and other missions.
“The TESS satellite has discovered thousands of planets since it launched in 2018,” said Allison Youngblood, TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “While Pandora will study about 20 worlds, it will advance our ability to pick out which signals come from stars and which come from planets. The more we understand the individual parts of a planetary system, the better we understand the whole — and our own.”
Facebook logo @NASAUniverse @NASAUniverse Instagram logo @NASAUniverse By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Alise Fisher
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alise.m.fisher@nasa.gov
NASA Headquarters, Washington
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Last Updated Aug 25, 2025 Related Terms
Astrophysics Exoplanet Atmosphere Exoplanets Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research Goddard Space Flight Center Kepler / K2 Stars TESS (Transiting Exoplanet Survey Satellite) The Universe View the full article
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The Artemis II Orion stage adapter, built at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA Media are invited to NASA’s Marshall Space Flight Center in Huntsville, Alabama, at 2 p.m. CDT Thursday, Aug. 14 to view the final piece of space flight hardware for the agency’s SLS (Space Launch System) rocket for the Artemis II mission before it is delivered to NASA’s Kennedy Space Center in Florida. All other elements of the SLS rocket for Artemis II are stacked on mobile launcher 1 in the Vehicle Assembly Building at Kennedy. Artemis II, NASA’s first mission with crew aboard the SLS rocket and Orion spacecraft, is currently scheduled for a 10-day trip around the Moon no later than April 2026.
The Orion stage adapter, built by NASA Marshall, connects the SLS rocket’s interim cryogenic propulsion stage to NASA’s Orion spacecraft. The small ring structure is the topmost portion of the SLS rocket. The adapter will also carry small payloads, called CubeSats, to deep space.
Media will have the opportunity to capture images and video and speak to subject matter experts. Along with viewing the adapter for Artemis II, media will be able to see the Orion stage adapter for the Artemis III mission, the first lunar landing at the Moon’s South Pole.
This event is open to U.S. media, who must confirm their attendance by 12 p.m. CDT Wednesday, Aug. 13, with Jonathan Deal in Marshall’s Office of Communications at jonathan.e.deal@nasa.gov. Media must also report by 1:30 p.m. Thursday, Aug.14 to the Redstone Arsenal Joint Visitor Control Center Gate 9 parking lot, located at the Interstate 565 interchange at Research Park Boulevard, to be escorted to the event.
Through Artemis, NASA will send astronauts to explore the Moon for scientific discovery, economic benefits, and build the foundation for the first crewed missions to Mars.
For more on SLS, visit:
https://www.nasa.gov/humans-in-space/space-launch-system
Jonathan Deal
Marshall Space Flight Center, Huntsville, Ala.
256.631.9126
jonathan.e.deal@nasa.gov
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Last Updated Aug 11, 2025 EditorBeth RidgewayLocationMarshall Space Flight Center Related Terms
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By NASA
Technicians at the Astrotech Space Operations Facility near NASA’s Kennedy Space Center in Florida conduct illumination testing on Friday, July 18, 2025, by flashing a bright light that simulates the Sun into the two-panel solar array that will help power the agency’s IMAP (Interstellar Mapping and Acceleration Probe) observatory on its upcoming journey to a destination about one million miles away from Earth Lagrange Point 1.Credit: NASA/Kim Shiflett NASA invites media to view the agency’s IMAP (Interstellar Mapping and Acceleration Probe) spacecraft and two other missions — the Carruthers Geocorona Observatory and the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Follow On–Lagrange 1 (SWFO-L1) observatory, which will launch along with IMAP as rideshares.
Media will have the opportunity to photograph the three spacecraft and speak with subject matter experts representing all three missions. The event will take place on Thursday, Aug. 28, at the Astrotech Space Operations payload processing facility in Titusville, Florida. Confirmed media will receive additional details after registering.
To participate in the event, media must RSVP by 11:59 p.m. on Tuesday, Aug. 19, by submitting their request online at: https://media.ksc.nasa.gov.
The IMAP mission will study the heliosphere, a vast magnetic bubble created by the Sun that protects our solar system from radiation incoming from interstellar space. Carruthers will use its ultraviolet cameras to monitor how material from the Sun impacts the outermost part of Earth’s atmosphere. The SWFO-L1 mission will observe solar eruptions, and monitor incoming space weather 24/7, providing early warnings and validating forecasts that protect vital communication and navigation infrastructure, economic interests, and national security, both on Earth and in space.
NASA is targeting no earlier than September for the launch of these three missions on a SpaceX Falcon 9 rocket from Launch Complex 39A at the agency’s Kennedy Space Center in Florida.
NASA’s media accreditation policy is available online. For questions about accreditation, please email: ksc-media-accreditat@mail.nasa.gov.
Facility Access
Due to spacecraft cleanliness requirements, this invitation is open to a limited number of media with no more than two individuals per media organization. This event is open to U.S. citizens who possess a valid government-issued photo identification and proof of U.S. citizenship, such as a passport or birth certificate.
Media attending this event must comply with cleanroom guidelines. This includes wearing specific cleanroom garments; avoiding cologne, cosmetics, and high-heeled shoes; cleaning camera equipment under the supervision or assistance of contamination control specialists; and placing all electronics in airplane mode in the designated areas near the spacecraft. NASA will provide detailed guidance to approved media.
Observatories Information
The three observatories are preparing to launch to Lagrange point 1, which lies about a million miles from Earth toward the Sun. There, they will orbit this gravitational balance point, holding a steady position between Earth and the Sun. NASA’s IMAP will use its 10 instruments to map the heliosphere’s edge and reveal how the Sun accelerates charged particles, filling in essential puzzle pieces to understand the space weather environment across the solar system. The mission’s varied instruments also will provide near real-time space weather data to scientists on Earth.
The Carruthers observatory will image the glow of ultraviolet light emitted by the uppermost parts of Earth’s atmosphere — called the geocorona — to help researchers understand how our planet’s atmosphere is shaped by conditions in space. NOAA’s SWFO-L1 will use its suite of instruments to sample the solar wind and interplanetary magnetic field, while its onboard coronagraph will detect coronal mass ejections and other solar events. Together, these real-time observations of space weather enable precautionary actions to protect satellites, power grids, aviation, and communication and navigation technology.
Learn more about NASA’s IMAP at:
https://science.nasa.gov/mission/imap/
-end-
Abbey Interrante
Headquarters, Washington
301-201-0124
abbey.a.interrante@nasa.gov
Sarah Frazier
Goddard Space Flight Center, Greenbelt, Md.
202-853-7191
sarah.frazier@nasa.gov
Leejay Lockhart
Kennedy Space Center, Florida
321-747-8310
leejay.lockhart@nasa.gov
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Last Updated Aug 08, 2025 LocationNASA Headquarters Related Terms
NASA Headquarters Carruthers Geocorona Observatory (GLIDE) Goddard Space Flight Center Heliophysics Heliophysics Division IMAP (Interstellar Mapping and Acceleration Probe) Kennedy Space Center Space Weather The Sun View the full article
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By European Space Agency
Data from ESA’s Soil Moisture and Ocean Salinity (SMOS) mission can be used to estimate how much carbon is stored in forests – and a study has improved our understanding of how reliable this proxy is and how long-term datasets from SMOS can help us to monitor this valuable resource.
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