Star Death: Cassiopeia A

Tracing tattered remains of an exploded star.
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Cassiopeia A Interactive

The Cassiopeia A supernova remnant appears as a luminous, roughly circular cloud with a mix of purple and white colors against the dark backdrop of space. The interior appears mottled with dark and bright filaments. Faint glimmers of white around the edges highlight its spherical shape.
A roughly square image is rotated clockwise about 45 degrees, with solid black in the corners on the top left, top right, bottom left, and bottom right. Within the image is a circular-shaped nebula with complex structure. On the circle’s exterior, particularly at the top and left of the image, lie curtains of material glowing orange. Interior to this outer shell lies a ring of mottled filaments of bright pink studded with clumps and knots. At center right, a greenish loop extends from the right side of the ring into the central cavity. Translucent wisps of blue, green, and red appear throughout the image. A roughly square image is rotated clockwise about 45 degrees, with solid black in the corners on the top left, top right, bottom left, and bottom right. Within the image is a circular-shaped nebula with complex structure. On the circle’s exterior, particularly at the top and left of the image, lie curtains of material glowing orange. Interior to this outer shell lies a ring of mottled filaments of bright pink studded with clumps and knots. At center right, a greenish loop extends from the right side of the ring into the central cavity. Translucent wisps of blue, green, and red appear throughout the image.
Cassiopeia A, a circular-shaped cloud of gas and dust with complex structure. The inner shell is made of bright pink and orange filaments studded with clumps and knots that look like tiny pieces of shattered glass. Around the exterior of the inner shell, particularly at the upper right, there are curtains of wispy gas that look like campfire smoke. The white smoke-like material also appears to fill the cavity of the inner shell, featuring structures shaped like large bubbles. Around and within the nebula, there are various stars seen as points of blue and white light. Cassiopeia A, a circular-shaped cloud of gas and dust with complex structure. The inner shell is made of bright pink and orange filaments studded with clumps and knots that look like tiny pieces of shattered glass. Around the exterior of the inner shell, particularly at the upper right, there are curtains of wispy gas that look like campfire smoke. The white smoke-like material also appears to fill the cavity of the inner shell, featuring structures shaped like large bubbles. Around and within the nebula, there are various stars seen as points of blue and white light.
The Cassiopeia A supernova remnant with bright and dim stars scattered across the black background. The nebula is roughly circular, made of sparse green and purple thread-like filaments with pink edges. There are no filaments in the center of the remnant, allowing the starry background to shine through.
Cassiopeia A supernova remnant, showing a roughly circular cloud of multicolored gas against a black background. The colors range from blue and purple to pink and yellow, resembling a cosmic smoke ring. The outside of the remnant appears as a mottled blue ring. Inside of the blue ring is another wide ring, made of a series of dense filaments in shades of pink, white, and orange. The center of the remnant is dominated by a network of blue filaments. There is a bright white point near the center.
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Electrons from the stellar explosion traveling around magnetic lines at almost the speed of light shine in longer wavelengths.

The supernova blast wave slams into warm surrounding gas and dust, which glows in the mid-infrared, including the "green monster."

Tiny knots of gas from the star itself are visible in the near-infrared and show how the star shattered like glass.

Elements like those seen in near-infrared and visible light are responsible for life on Earth.

Elements in the debris from the exploding star and shocked gas are extremely hot and shine in X-ray light.

Radio
Mid-Infrared
Near-Infrared
Visible and Near-Infrared
X-ray

A Story Of Star Death: Cassiopeia A

Tracing the tattered remains of an exploded star.

Supernova explosions are some of the most destructive events to take place in the cosmos. In one type of supernova, a massive star blows itself apart, sending shockwaves out in all directions, along with an expanding shell of hot gas. Supernovas are one of the ways galaxies become seeded with many elements, such as carbon, nitrogen, oxygen, silicon and iron, that are necessary for planets and life.

Supernovas like the one that created Cassiopeia A (Cas A) are also factories of cosmic dust. Cosmic dust is made up of tiny grains that, with the help of gas, provide the building blocks of planets: dust clumps become pebbles, pebbles become larger rocks, and larger rocks can become planets.

Observations made across different wavelengths of light have allowed researchers to explore what kind of dust is produced in a supernova explosion, how it is formed, and how much dust survives the hostile trip into interstellar space. Cas A is one of the most well-studied objects in modern astronomy, and offers researchers a unique opportunity to explore how these particular objects evolve over time.

Quick Facts: Cassiopeia A

Also known as: Cas A

Type of object: Supernova remnant

Distance from Earth: approximately 11,000 light-years

Size: about 10 light-years across

Location in the sky: Cassiopeia Constellation

Location in the universe: Milky Way Galaxy, outside the Solar System

Did you know: The supernova was not observed on Earth. This fact gives us clues about the condition of the progenitor star right before it exploded — it may have produced lots of dust.

Explore More About Star Death

Find out more with these additional resources from NASA’s Universe of Learning

Credits: Cassiopeia A

Radio image from the Very Large Array: L. Rudnick, T. Delaney, J. Keohane & B. Koralesky, image composite by T. Rector

Mid-infrared light image from the James Space Telescope: NASA, ESA, CSA, STScI, D. Milisavljevic (Purdue University), T. Temim (Princeton University), I. De Looze (University of Gent)

Near-infrared light image from the James Webb Space Telescope: NASA, ESA, CSA, STScI, D. Milisavljevic (Purdue University), T. Temim (Princeton University), I. De Looze (Univeristy of Gent)

Visible and near-infrared light image from the Hubble Space Telescope: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

X-ray image from Chandra X-Ray Observatory: NASA, CXC, SAO

Subject-matter expertise provided by Dr. Rutuparna Das of Harvard University’s Center for Astrophysics

Produced by the Space Telescope Science Institute’s Office of Public Outreach