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25 Images to Celebrate NASA’s Chandra 25th Anniversary
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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.
News Media Contact
Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Corinne Beckinger
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
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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This National Aviation Day graphic shows Orville Wright surrounded by the faces of some of NASA’s aeronautical innovators.NASA / Maria Werries The first “A” in NASA stands for Aeronautics – so naturally that means today, Aug. 19, National Aviation Day, is one of our favorite days all year!
National Aviation Day was first proclaimed in 1939 by President Franklin Roosevelt to celebrate the birthday of aviation pioneer Orville Wright, who, with his brother Wilbur, in 1903, were the first humans to achieve powered flight.
Each year since the President first marked the occasion, sky-faring Americans have come together on this date in an annual celebration of flight – a time to revel in spreading our wings and slipping the surly bonds of Earth.
All of us at NASA share in that celebration. We love everything about flight, whether it’s into space or within Earth’s atmosphere.
Our aeronautical innovators are dedicated to improving the design of airplanes to carry on pioneering new technologies in high-speed flight, airframes and propulsion methods, aerospace engineering modelling, and automating airspace and safety management.
Our heritage in aviation research goes back more than 100 years. We’ve helped air travel become a safe, efficient, reliable form of transportation. If you’re heading to an airport, keep an eye out for these NASA-developed aviation technologies you might see on your flight:
WINGLETSNASA studies led to development of vertical extensions that can be attached to wing tips in order to reduce aerodynamic drag without having to increase wingspan. Winglets help increase an airplane’s range, decrease fuel use, and today can be seen on airplanes everywhere.NASA CHEVRON NOZZLESWorking with its industry partners, NASA researchers determined an effective way to reduce noise levels on the ground and in the passenger cabin was to add saw tooth-shaped cut outs, or chevrons, to structures such as exhaust nozzles and cowlings of jet engines.NASA / The Boeing Company GLASS COCKPITS NASA created and tested the concept of replacing dial and gauge instruments with flat panel digital displays. The displays present information more efficiently and provide the flight crew with a more easily understood picture of the aircraft’s health and position.NASA Langley / Sean Smith How Will You Celebrate?
How else can you celebrate National Aviation Day? Here are seven ideas:
Visit your local science museum or NASA visitor center
Explore your local science center for exhibits about aviation and how an airplane flies. And if you live within a short drive from Norfolk, Virginia; Cleveland, or San Francisco, you might consider checking out the visitor centers associated with NASA’s Langley Research Center, Glenn Research Center, or Ames Research Center, respectively. These major NASA field centers play host to the majority of NASA’s aeronautics research. (NASA’s Armstrong Flight Research Center, the fourth of NASA’s aeronautics centers, is located within the restricted area of Edwards Air Force Base in California so they do not have a public visitor’s center.)
Watch an aviation-themed movie
There’s no shortage of classic aviation-themed movies available to watch in any format (streaming, DVD, cinema, library rentals, etc.), and with any snacks (popcorn, nachos, gummies, etc.). We dare not attempt a comprehensive list, but a good place to start is our documentary “X-59: NASA’s “Quesst” for Quiet Supersonic Flight” available to stream on NASA+.
Build an airplane
Why not? It doesn’t have to be big enough to actually fly in – plastic model kits of the world’s most historic aircraft can be just as rewarding and just as educational, especially for kids who might be thinking about a career as an engineer or technician. In fact, many astronauts will tell you their love of aviation and space began with putting models together as a child. Another idea: Grab some LEGO bricks and build the airplane of your dreams. Or make it easy on yourself, fold a paper airplane and shoot it across the room.
Take an introductory flight lesson
Pilots will tell you there is a wonderful sense of freedom in flying, not to mention the incredible views and the personal sense of accomplishment. At the same time, being a pilot is not for everyone, but you won’t know unless you try! Many general aviation airports in the nation have a flight school that may offer an introductory flight lesson at a discounted price. And if you want a taste of flight without leaving the ground, computer desktop flight simulators such as Microsoft Flight Simulator or X-Plane are popular choices and can get you into the virtual sky in short order.
Visit your local library or download a NASA e-book
Aviation-themed books, whether fact or fiction, are all over the shelves of your local library – literally. That’s because there’s no single Dewey Decimal number for aviation. A book about aviation history will be in a different section of the library than a book about how to design an airplane. And creative nonfiction books such as the Mark Vanhoenacker’s “Skyfaring,” or autobiographies such as Eileen Collins’ “Through the Glass Ceiling to the Stars,” are off on yet another shelf. Don’t hesitate to ask your librarian for help. And when you get back from the library, or while still there, jump online and check out the NASA e-books you can download and own for free.
Have a plane spotting picnic near an airport
At Washington’s National Airport, it’s Gravelly Point. In Tampa, Florida it’s International Mall. If you live near a major international airport, chances are you know the best place where the locals can go to watch aircraft take off and land up close. Be sure to take heed of any security restrictions about where you can and can’t go. But once you have your spot picked out, then load up your picnic basket and camp out for an evening of plane spotting. See how many different types of airplanes you can count or identify.
Follow what we’re doing to transform aviation
NASA’s aeronautical innovators are working to transform air transportation to meet the future needs of the global aviation community. Sounds like a big job, right? It is and there are many ways in which NASA is doing this. Improving an airplane’s aerodynamics, making airplanes more efficient and quieter, working with the Federal Aviation Administration to improve air traffic control – the list could go on for many thousands of more words. Bookmark our NASA Aeronautics topic page and follow us on social media @NASAaero.
So remember this National Aviation Day, NASA is with you when you fly!
About the Author
John Gould
Aeronautics Research Mission DirectorateJohn Gould is a member of NASA Aeronautics' Strategic Communications team at NASA Headquarters in Washington, DC. He is dedicated to public service and NASA’s leading role in scientific exploration. Prior to working for NASA Aeronautics, he was a spaceflight historian and writer, having a lifelong passion for space and aviation.
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