Cassiopeia A

The mystery of how Cassiopeia A exploded is unraveling thanks to new data from NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. In this image, NuSTAR data, which show high-energy X-rays from radioactive material, are colored blue. Lower-energy X-rays from non-radioactive material, imaged previously with NASA's Chandra X-ray Observatory, are shown in red, yellow and green.

The new view shows a more complete picture of Cassiopeia A, the remains of a star that blew up in a supernova event whose light reached Earth about 350 years ago, when it could have appeared to observers as a star that suddenly brightened. The remnant is located 11,000 light-years away from Earth.

NuSTAR is the first telescope capable of taking detailed pictures of the radioactive material in the Cassiopeia A supernova remnant. While other telescopes have detected radioactivity in these objects before, NuSTAR is the first capable of pinpointing the location of the radioactivity, creating maps. When massive star explode, they create many elements: non-radioactive ones like iron and calcium found in your blood and bones; and radioactive elements like titanium-44, the decay of which sends out high-energy X-ray light that NuSTAR can see.

By mapping titanium-44 in Cassiopeia A, astronomers get a direct look at what happened in the core of the star when it was blasted to smithereens. These NuSTAR data complement previous observations made by Chandra, which show elements, such as iron, that were heated by shock waves farther out from the remnant's center.

In this image, the red, yellow and green data were collected by Chandra at energies ranging from 1 to 7 kiloelectron volts (keV). The red color shows heated iron, and green represents heated silicon and magnesium. The yellow is what astronomers call continuum emission, and represents a range of X-ray energies.

The titanium-44, shown in blue, was detected by NuSTAR at energies ranging between 68 and 78 keV.

The NuSTAR observations point to a possible solution to the puzzle of how stars detonate. The fact that the titanium -- which is a direct tracer of the supernova blast -- is concentrated in clumps at the core supports a theory referred to as "mild asymmetries." In this scenario, material sloshes about at the heart of the supernova, reinvigorating a shock wave and allowing it to blow out the star's outer layers.

Image credit: NASA/JPL-Caltech/CXC/SAO

Note: For more information, see PIA17839: Adding a New "Color" to Palate of Cassiopeia A Images, PIA17840: The Creation of Titanium in Stars, PIA17841: Radioactive Core of a Dead Star, PIA17842: The Case of Missing Iron in Cassiopeia A, PIA17844: Evolution of a Supernova, PIA17846: NuSTAR Data Point to Sloshing Supernovas, PIA17845: Sloshing Star Goes Supernova, NASA's NuSTAR Untangles Mystery of How Stars Explode, and Supernovas Slosh Before Exploding.

Supernova Remnant Cassiopeia A

Cassiopeia A: A supernova remnant located about 10,000 light years from Earth.

This new version of Chandra's image of the Cassiopeia A supernova remnant has been specially processed to show with better clarity the appearance of Cas A in different bands of X-rays. This will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

Scale: Image is 8.91 arcmin across (about 29 light years).

Image credit: NASA/CXC/SAO

Note: For more information, see Cassiopeia A: Exploring the Third Dimension of Cassiopeia A.

Cassiopeia A by NuSTAR

This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR. Blue indicates the highest energy X-ray light, where NuSTAR has made the first resolved image ever of this source. Red and green show the lower end of NuSTAR's energy range, which overlaps with NASA's high-resolution Chandra X-ray Observatory.

Light from the stellar explosion that created Cassiopeia A is thought to have reached Earth about 300 years ago, after traveling 11,000 years to get here. While the star is long dead, its remains are still bursting with action. The outer blue ring is where the shock wave from the supernova blast is slamming into surrounding material, whipping particles up to within a fraction of a percent of the speed of light. NuSTAR observations should help solve the riddle of how these particles are accelerated to such high energies

X-ray light with energies between 10 and 20 kiloelectron volts are blue; X-rays of 8 to 10 kiloelectron volts are green; and X-rays of 4.5 to 5.5 kiloelectron volts are red.

The starry background picture is from the Digitized Sky Survey.

Photo credit: NASA/JPL-Caltech/DSS

Cassiopeia A

Cassiopeia A: The debris from an exploded star located about 11,000 light years from Earth.

This two-panel graphic compares an artist's illustration (left) of a simplified picture of the inner layers of a star just before it exploded to form the Cassiopeia A supernova remnant with a Chandra image (right) of what we see today. The different elements are represented by different colors: iron (blue), sulfur and silicon (green), and magnesium, neon and oxygen (red). The Chandra image uses the same color scheme to show the distribution of iron, sulfur and magnesium in the supernova remnant. A comparison of the illustration and the Chandra element map shows clearly that most of the iron, which according to theoretical models of the pre-supernova was originally on the inside of the star, is now located near the outer edges of the remnant.

Scale: Image is 8.4 arcmin across. (about 27 light years)

Illustration credit: NASA/CXC/M.Weiss; X-ray: NASA/CXC/GSFC/U.Hwang & J.Laming

Note: For more information, see Cassiopeia A: A Star Explodes and Turns Inside Out.

Cassiopeia A by WISE

Over 11,000 years ago, a massive, supergiant star came to the end of its life. The star's core collapsed to form an incredibly dense ball of neutrons, and its exterior was blasted away in an immense release of energy astronomers call a supernova.

The light from this supernova first reached Earth from the direction of the constellation Cassiopeia around 1667 A.D. If anyone alive at the time saw it, they left no records. It is likely that large amounts of dust between the dying star and Earth dimmed the brightness of the explosion to the point that it was barely, if at all, visible to the unaided eye.

The remnant of this supernova was discovered in 1947 from its powerful radio emission. Listed as Cassiopeia A, it is one of the brightest radio sources in the whole sky. More recently, the Wide-field Infrared Survey Explorer (WISE), detected infrared echoes of the flash of light rippling outwards from the supernova.

In the image, the central bright cloud of dust is the blast wave moving through interstellar space heating up dust as it goes. The blast wave travels fast -- at an average speed of about 11,000 miles per second (18,000 kilometers per second). By the time WISE took this image, the blast wave has expanded out to about a distance of 21 light-years from the original explosion. The flash of light from the explosion, traveling at the speed of light, has covered well over 300 light-years. The orange-colored echoes further out from the central remnant are from interstellar dust that was heated by the supernova flash centuries after the original explosion.

The colors used in this image represent specific wavelengths of infrared light. Blue and cyan (blue-green) represent light emitted predominantly from stars at wavelengths of 3.4 and 4.6 microns. Green and red represent light mostly emitted by dust at 12 and 22 microns, respectively.

Photo credit: NASA/JPL-Caltech/UCLA