Supernova Cassiopeia A

The Life and Death of a Star: Revealing the Secrets of a Supernova Remnant in our Galaxy

This image of Cassiopeia A resembles a disk of electric light with red clouds, glowing white streaks, red and orange flames, and an area near the center of the remnant resembling a somewhat circular region of green lightning. X-rays from Chandra are blue and reveal hot gas, mostly from supernova debris from the destroyed star, and include elements like silicon and iron. X-rays are also present as thin arcs in the outer regions of the remnant. Infrared data from Webb is red, green, and blue. Webb highlights infrared emission from dust that is warmed up because it is embedded in the hot gas seen by Chandra, and from much cooler supernova debris. Hubble data shows a multitude of stars that permeate the field of view.

Supernova Remnant Cassiopeia A

A 3D model of Supernova Remnant Cassiopeia A is displayed on screen. This 3D model represents the remaining energy and material from the 340-year-old supernova explosion which created this object. The model consists of a roughly spherical collection of matter, shown here in light green, mottled with bumps and with a hole in the center, like an overly-glazed donut. There are other mottled, bumpy colored regions along the outer edges, in pink, red, blue and dark green, all representative of concentrations of different elements. At two o’clock and between 6-9 o’clock, six spikes of purple protrude to roughly expand the entire circumference of the explosion by another third.

Cassiopeia A is a supernova remnant (the aftermath of an exploded star), located about 11,000 light-years or about 60 quadrillion miles away from Earth.

The model turns roughly 15 degrees to show Cassiopeia A from a slightly different perspective, highlighting the jets at the 2 o’clock position. Cas A is located about 11,000 light-years or about 60 quadrillion miles away from Earth. The light green area, formerly described as resembling an overly-glazed donut, represents silicon debris left behind after the star exploded.

What is a supernova?

When giant stars run out of fuel, they collapse onto themselves and then explode outward, dispersing the shattered remains of the stars into space.

Supernovas are some of the most dramatic events in the cosmos. These titanic events send shock waves rumbling through space and create giant bubbles of gas that have been super-heated to millions of degrees.

The model turns slightly back to highlight the other jets between 6 and 9 o’clock. The mottled areas of color are bumpy and form an uneven ring around the shock wave.

How do we know?

Supernova remnants often glow strongly in high-energy X-rays. The Earth’s atmosphere absorbs X-rays from space, so telescopes have to be launched into orbit, above our atmosphere, to see cosmic X-rays.

This X-ray image of Cassiopeia A resembles a disk of electric blue light, purple clouds, glowing white fog, and red and yellow flames, dotted with glowing orange specks. This is Cassiopeia A, a supernova remnant. Here, elements of the exploded star are being cast into space. The red and yellow flames are silicon and sulfur. The light purple within the cloud is iron, and the blast wave is blue. All were observed by Chandra's X-ray Observatory.

Cassiopeia A in X-ray light.

The Chandra X-ray Observatory - operated for NASA by the Smithsonian - is the most powerful X-ray telescope ever built, and it has been studying Cassiopeia A and many other fascinating objects in space for a quarter century. Chandra has captured supernovas and the remnants they've left behind in spectacular X-ray images, helping to determine the energy, composition, and dynamics of these celestial explosions.

Animation of the Chandra X-ray Observatory, tracing an elliptical orbit around Earth, taking it to one-third the distance to the moon at its farthest point.

 

Chandra mirrors are unique

The photons from high-energy phenomena glance off the nested mirrors like stones skipping across a pond, and are focused on the detectors at the back of the spacecraft.

 

Chandra's mirror technology is revolutionary

The engineering that it took to build Chandra’s mirrors was mind-blowing. Chandra’s mirrors, for example, were polished to the smoothness of a few atoms.

 

How it works:

Photons pass down via  the mirrors and are detected by the instruments at the tail of the telescope. The data Chandra captures is sent to Earth and analyzed by image processors and scientists.

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Anatomy of an exploded star

The model zooms in to the center, revealing a hollowed-out area or cavity and a small sphere embedded in some central matter. Before the massive star exploded, the core imploded, crushing its matter inward and building intense energy. This created a massive explosion, but left behind a dense central stellar remnant called a neutron star.

Neutron Star

At the very center of Cas A is the neutron star, the dense stellar remnant produced by the collapse of the core of the massive star.

A black and white schematic view of Cassiopeia A, with a purple dot in the center, representing the neutron star.

Artist's rendition of a neutron star, a tight sphere of matter with glowing loops indicating energetic fields, growing between north and south poles, and surrounding the neutron star like a cage of energy.

The model spins, stopping to show one side of the bipolar jets. The spikes appear attached to the main structure, but are separate. The discovery of jets shows that there were two primary explosions.

Jets

The Cas A explosion was once believed to be fairly uniform, due to our perspective from Earth and our familiarity with the 2-dimensional images.  With more recent 3-dimensional data, we show evidence for 2 explosions, and an interesting phenomenon where knots of material are moving at varying speeds away from the center. Here we highlight the highest-speed motion of material in opposing jets, jutting out substantially further than the rest of the remnant.

A black and white schematic view of Cassiopeia A, with areas at 10 o'clock and four o'clock highlighted in neon purple, to show the location of the jets.

The model spins dramatically once again and stops in its original orientation, jets at 2 and 8 o’clock.

Shockwaves

Two shock waves have been detected in Cas A: a fast outer shock and a slower inner shock. The inner shock wave is believed to be due to the collision of the ejecta from the supernova explosion with a circumstellar shell of material, heating it to a temperature of ten million degrees. The outer shock wave is analogous to a sonic boom resulting from this collision.

A black and white schematic view of Cassiopeia A, with an overlay of neon turquoise encapsulating the entire remnant and then extending beyond its borders, to show the breadth of the outer shockwave.

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Elemental Composition

We have used spectral data to learn about the elemental composition of the remnant from Cas A’s explosion, mapping certain regions with their dominant elements.  Similar materials are often clumped together in knots throughout the remnant.  We will explore some of the major elements below.

A black and white schematic view of Cassiopeia A, with different areas highlighted in green for iron, red for argon and neon, and light turquoise for silicon.

The model spins to highlight some of the bumpy mottled colored regions. The colors represent dominant regions of elements.

What does this tell us?

By observing Cassiopeia A and other supernova remnants, we learn about our ancient cosmic past.  The early Universe was composed of Hydrogen and Helium, but heavier elements were forged within collapsing stellar interiors.  A stellar explosion’s power disperses these elements. The iron in our blood, the calcium in our bones, and the oxygen we breathe come from stars that exploded long ago. 

 

The model zooms in to show a dark green mottled region, the largest clump of colored data and juts out more than the other regions, making this part asymetrical. This area is dominated by iron.

IRON (Fe)

The same element dominating this area of Cas A is also crucial for building the protein hemoglobin in our red blood cells, which carry oxygen throughout our bodies to all our cells.

A black and white schematic view of Cassiopeia A, with substantial areas highlighted in green for iron.

The model spins for a better view of the other bumpy mottled colored regions, shown in red, orange and blue. The blue color represents silicon.

SILICON (Si)

Silicon is the second most abundant element in the Earth’s crust (after Oxygen), but exists only rarely in pure form on Earth.  Nevertheless, humans use silicon for many things, including cement and other mortar materials, ceramics and glass products, and semiconductor electronics, found in computer chips and circuits.  Plants use silicon for metabolic processes, and some animals secrete silicon skeletal structures.

A black and white schematic view of Cassiopeia A, with a large area highlighted in light turquoise for silicon.This movie shows various silicon skeletal structures, hard, coraline lattices secreted by tiny animals to form skeletons.

The model spins again for another view of the bumpy mottled colored regions, shown in red, orange and blue. The red and orange colors represent argon and neon.

ARGON (Ar)

Argon is the third most abundant gas in our atmosphere and the most abundant noble gas in Earth’s crust. Humans have found several uses for Argon, for example, filling the spaces between glass panes with Argon gas to help keep our homes warm or cool. We also use Argon in some light bulbs.

A black and white schematic view of Cassiopeia A, with different areas highlighted in red for argon and neon.

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NEON (Ne)

Neon is widely recognized as the gas used in tube lighting for signs.  We also use neon on Earth in TV tubes and in certain diagnostic tests involving the lungs. Neon is the fifth most abundant element in the universe, found in small amounts in Earth’s crust, air, and oceans.  Jupiter also has some neon in its atmosphere.  Neon is created under extreme heat and pressure conditions, where oxygen fuses with helium.

A black and white schematic view of Cassiopeia A, with different areas highlighted in green for iron, red for argon and neon.In this composite image of Jupiter, the fifth planet from the sun is set against the blackness of space, flanked by neon purple blobs. Here, Jupiter is presented in exceptionally clear focus. More than a dozen bands of swirling gas streak the surface, each a different texture and shade of grey. The gas giant is encircled by a fine, sky-blue ring, the same color as the large storm which swirls on its surface at our lower right. At the top edge of Jupiter, tilted just to our right of center, is a neon purple strip. A similar, smaller line of neon purple can be found at the bottom edge of the planet. Capping the planet’s magnetic poles, these purple strips represent X-ray auroras, created when high-energy particles collide with gas in the planet’s atmosphere. At our right and left, large hazy blobs of neon purple flank Jupiter, some larger than the gas giant itself. Like the auroras, these purple clouds represent X-rays observed by Chandra.

The model makes one final spin to land back at its original position.

Where is Cassiopeia A?

From a beach in New England in early December, as night falls, three constellations come into view to the North. Many people can easily recognize the Big Dipper and Little Dipper. Constellation Cassiopeia A is close by, and points us to Supernova remnant Cassiopeia A. 

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The Earth sits in the Local Arm of the Milky Way.

Illustration of the Milky Way galaxy as it would be seen from a bird's eye view. The central region looks like a glowing football, with spidery arms spiraling outward. The Local Arm is shown as the second arm out from the center, stemming from the upper right side of the football in this view. The Sun, our star, is located on the Local Arm.

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Illustration of the Milky Way galaxy as it would be seen from a bird's eye view. The central region looks like a glowing football, with spidery arms spiraling outward. The Perseus Arm is shown as the third arm out from the center, stemming from the upper right side of the football in this view. Cassiopeia A is located on the Perseus Arm.

Supernova remnant Cassiopeia A sits in an adjacent arm of the Milky Way, called the Perseus Arm.

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Astronomers calculate that a supernova explodes in our Milky Way galaxy every 50 years on average. However, we do not think a supernova has exploded in our Galaxy for several hundred years, meaning we’re overdue. Betelgeuse, a star in the Orion Arm of the Milky Way, is believed to be heading toward supernova some time in the next 100,000 years.

Illustration of the Milky Way galaxy as it would be seen from a bird's eye view. The central region looks like a glowing football, with spidery arms spiraling outward. The Orion Spur is an offshoot from the second arm out from the center, stemming from the upper right side of the football in this view. Orion is located on the Orion Spur.

When a star blows apart in a supernova, the explosion creates multi-million-degree gas that glows in X-rays for thousands of years. Thankfully, the Earth is far away from any local star that may go supernova.

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We’ve been looking at Cas A for a long time

Our Universe is dynamic:  Cassiopeia A changing over time

Because NASA’s Chandra X-ray Observatory has been studying Cassiopeia A for nearly 25 years, we can watch this exploded star change over time. Even hundreds of years after the star exploded, the debris field is still expanding out into space. The outer rim shows the blast wave from the explosion.

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25 years of imaging and science

Cassiopeia A First Light: August 26. 1999 - There was substantial excitement in the Chandra Operations Control Center  the first time we saw Cassiopeia A in X-rays from Chandra.

These images portray so much more than what you see on the surface. There is information about energy levels, structure, or chemical composition in each of Chandra’s images which are so beautiful.

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NASA’s Chandra X-ray Observatory Celebrates 25 years of studying Cassiopeia A.

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Want to learn more?

We can process and share cosmic data in many ways.

Listen to the Cassiopeia A Sonification here:

A 3D model of Cassiopeia A, printed on a powder printer in multi-colors.

Explore (or 3D print!) the 3D model of the Cassiopeia A supernova remnant.

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Listen to Chandra’s many Sonifications.

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Read more about the Chandra X-ray Observatory here.

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Credit: Images: X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI; IR: NASA/ESA/CSA/STScI/Milisavljevic et al., NASA/JPL/CalTech; Image Processing: NASA/CXC/SAO/J. Schmidt & K. Arcand; 3D model: NASA/CXC/MIT/T.Delaney et al.;  Sonification: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida; Design: NASA/CXC/SAO/Kristin Divona; Animations/Video/3D Design/Production: NASA/CXC/SAO/April Jubett