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Einstein Probe detects puzzling cosmic 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.
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
Chandra X-Ray Observatory General Marshall Astrophysics Marshall Space Flight Center Supernova Remnants Supernovae The Universe Explore More
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By NASA
Explore This Section Science For Educators Portable Planetarium takes… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 3 min read
Portable Planetarium takes Thousands of Alaskan Students on a Cosmic Adventure
Exploring the Cosmos and Inspiring Young Minds
From January through June 2025, the Education Outreach Office at the University of Alaska Fairbanks Geophysical Institute (GI) continued its mission of bringing science to life by delivering the magic of its portable planetarium to communities across Alaska. This year, they reached over 1,807 students, educators, and participants through engaging, interactive astronomy experiences.
The portable planetarium is more than just a dome. It’s a getaway to curiosity, discovery and connection. Especially in Alaska’s long, cold winters, the dome offers a warm and welcoming space where learners of all ages can look up, wonder, and learn together. After experiencing the planetarium, feedback from students across the state reflects increased excitement about space, science, and their own place in the universe.
Inside the Dome: The Presentation
Each session begins with a warm introduction, a safety briefing, and a land acknowledgement. Participants experience constellations, planets, and space science concepts through dynamic storytelling and exciting visuals. The presentations connects ancient skywatching traditions with modern science, reminding students that long before the internet, the stars were a source of direction and knowledge. The presentation begins on Earth, exploring the State of Alaska, discussing the moon’s phases, and then, journeys outward to Mars, the last rocky planet, before reaching the gas giants. A standout moment of experience is the “Planet Walk” — an interactive journey from the Sun through the solar system. Learners leave with a new favorite word: ‘heliophysics,’ the science of the Sun and its influence on the solar system.
People Behind the Program
Knowledgeable presenters bring science to life with energy, empathy, and enthusiasm, engaging diverse audiences and making the event a memorable and impactful experience. Soumitra Sakhalkar, for example, is a GI graduate student researcher studying remote sensing of permafrost regions. Another presenter, Austin Smith, is a GI graduate student researcher in space physics. Several GI Communications staff members also contribute to the program’s success with logistics and technology support, crowd control and more.
Giving Thanks
This program is funded in part by the NASA Heliophysics Education Activation Team, which is part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn/about-science-activation/. The remainder of the funding was generously supported by schools and organizations requesting the planetarium program.
One participant shares their planetary knowledge and enthusiasm after attending a planetarium program on January 28, 2025 in collaboration with Fairbanks BEST Homeschool Network. Kalee Meurlott Share
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By NASA
NASA’s Nancy Grace Roman Space Telescope will be a discovery machine, thanks to its wide field of view and resulting torrent of data. Scheduled to launch no later than May 2027, with the team working toward launch as early as fall 2026, its near-infrared Wide Field Instrument will capture an area 200 times larger than the Hubble Space Telescope’s infrared camera, and with the same image sharpness and sensitivity. Roman will devote about 75% of its science observing time over its five-year primary mission to conducting three core community surveys that were defined collaboratively by the scientific community. One of those surveys will scour the skies for things that pop, flash, and otherwise change, like exploding stars and colliding neutron stars.
These two images, taken one year apart by NASA’s Hubble Space Telescope, show how the supernova designated SN 2018gv faded over time. The High-Latitude Time-Domain Survey by NASA’s Nancy Grace Roman Space Telescope will spot thousands of supernovae, including a specific type that can be used to measure the expansion history of the universe.Credit: NASA, ESA, Martin Kornmesser (ESA), Mahdi Zamani (ESA/Hubble), Adam G. Riess (STScI, JHU), SH0ES Team Called the High-Latitude Time-Domain Survey, this program will peer outside of the plane of our Milky Way galaxy (i.e., high galactic latitudes) to study objects that change over time. The survey’s main goal is to detect tens of thousands of a particular type of exploding star known as type Ia supernovae. These supernovae can be used to study how the universe has expanded over time.
“Roman is designed to find tens of thousands of type Ia supernovae out to greater distances than ever before,” said Masao Sako of the University of Pennsylvania, who served as co-chair of the committee that defined the High-Latitude Time-Domain Survey. “Using them, we can measure the expansion history of the universe, which depends on the amount of dark matter and dark energy. Ultimately, we hope to understand more about the nature of dark energy.”
Probing Dark Energy
Type Ia supernovae are useful as cosmological probes because astronomers know their intrinsic luminosity, or how bright they inherently are, at their peak. By comparing this with their observed brightness, scientists can determine how far away they are. Roman will also be able to measure how quickly they appear to be moving away from us. By tracking how fast they’re receding at different distances, scientists will trace cosmic expansion over time.
Only Roman will be able to find the faintest and most distant supernovae that illuminate early cosmic epochs. It will complement ground-based telescopes like the Vera C. Rubin Observatory in Chile, which are limited by absorption from Earth’s atmosphere, among other effects. Rubin’s greatest strength will be in finding supernovae that happened within the past 5 billion years. Roman will expand that collection to much earlier times in the universe’s history, about 3 billion years after the big bang, or as much as 11 billion years in the past. This would more than double the measured timeline of the universe’s expansion history.
Recently, the Dark Energy Survey found hints that dark energy may be weakening over time, rather than being a constant force of expansion. Roman’s investigations will be critical for testing this possibility.
Seeking Exotic Phenomena
To detect transient objects, whose brightness changes over time, Roman must revisit the same fields at regular intervals. The High-Latitude Time-Domain Survey will devote a total of 180 days of observing time to these observations spread over a five-year period. Most will occur over a span of two years in the middle of the mission, revisiting the same fields once every five days, with an additional 15 days of observations early in the mission to establish a baseline.
This infographic describes the High-Latitude Time-Domain Survey that will be conducted by NASA’s Nancy Grace Roman Space Telescope. The survey’s main component will cover over 18 square degrees — a region of sky as large as 90 full moons — and see supernovae that occurred up to about 8 billion years ago.Credit: NASA’s Goddard Space Flight Center “To find things that change, we use a technique called image subtraction,” Sako said. “You take an image, and you subtract out an image of the same piece of sky that was taken much earlier — as early as possible in the mission. So you remove everything that’s static, and you’re left with things that are new.”
The survey will also include an extended component that will revisit some of the observing fields approximately every 120 days to look for objects that change over long timescales. This will help to detect the most distant transients that existed as long ago as one billion years after the big bang. Those objects vary more slowly due to time dilation caused by the universe’s expansion.
“You really benefit from taking observations over the entire five-year duration of the mission,” said Brad Cenko of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the other co-chair of the survey committee. “It allows you to capture these very rare, very distant events that are really hard to get at any other way but that tell us a lot about the conditions in the early universe.”
This extended component will collect data on some of the most energetic and longest-lasting transients, such as tidal disruption events — when a supermassive black hole shreds a star — or predicted but as-yet unseen events known as pair-instability supernovae, where a massive star explodes without leaving behind a neutron star or black hole.
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This sonification that uses simulated data from NASA’s OpenUniverse project shows the variety of explosive events that will be detected by NASA’s Nancy Grace Roman Space Telescope and its High-Latitude Time-Domain Survey. Different sounds represent different types of events, as shown in the key at right. A single kilonova seen about 12 seconds into the video is represented with a cannon shot. The sonification sweeps backward in time to greater distances from Earth, and the pitch of the instrument gets lower as you move outward. (Cosmological redshift has been converted to a light travel time expressed in billions of years.) Credit: Sonification: Martha Irene Saladino (STScI), Christopher Britt (STScI); Visualization: Frank Summers (STScI); Designer: NASA, STScI, Leah Hustak (STScI) Survey Details
The High-Latitude Time-Domain Survey will be split into two imaging “tiers” — a wide tier that covers more area and a deep tier that will focus on a smaller area for a longer time to detect fainter objects. The wide tier, totaling a bit more than 18 square degrees, will target objects within the past 7 billion years, or half the universe’s history. The deep tier, covering an area of 6.5 square degrees, will reach fainter objects that existed as much as 10 billion years ago. The observations will take place in two areas, one in the northern sky and one in the southern sky. There will also be a spectroscopic component to this survey, which will be limited to the southern sky.
“We have a partnership with the ground-based Subaru Observatory, which will do spectroscopic follow-up of the northern sky, while Roman will do spectroscopy in the southern sky. With spectroscopy, we can confidently tell what type of supernovae we’re seeing,” said Cenko.
Together with Roman’s other two core community surveys, the High-Latitude Wide-Area Survey and the Galactic Bulge Time-Domain Survey, the High-Latitude Time-Domain Survey will help map the universe with a clarity and to a depth never achieved before.
Download the sonification here.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Aug 12, 2025 EditorAshley BalzerLocationGoddard Space Flight Center Related Terms
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