Each of these same-scale images shows the Cassiopeia A supernova remnant in a different wavelength. Each image will print on one overhead transparency. The purpose is to show the differences in the information conveyed by the image in each wavelength. The transparencies are designed to be superimposed as overlays. Each image is surrounded by small symbols (squares, triangles and circles) that when matched, will orient and align the images to superimpose accurately. These overlays allow superimposition of all four wave lengths simultaneously. Note that the on-line composite provides superimposition of images in selected pairs only. The overlays can be used as a classroom orientation with any of the activites listed below. Students can pursue individual investigations by using the on-line composite option.
These overlays can be used in conjunction with any of the investigations, tasks, or activities on this page which ask students to compare and contrast objects in different wavelengths. These include the Electromagnetic spectrum and CAS Timeline investigations, and the perfomance tasks "Signals from the Cosmos", "Point of View", "The universe Rated R!", and "Portrait Gallery of the X-Ray Universe".
The X-ray image of Cas A shows an expanding shell of hot gas produced by the explosion. This gaseous shell is about 10 light years in diameter, and has a temperature of about 50 million degrees.
The optical image of Cas A shows matter with a temperature of about ten thousand degrees. Some of these wisps contain high concentrations of heavy elements and are thought to be dense clumps of ejected stellar material.
(Credit: MDM Obs.)
The infrared image of Cas A shows dust grains that have been swept up and heated to several hundred degrees by the expanding hot gas. It is not known whether the dust grains were ejected by the star millions of years before it exploded or during the explosion.
Cas A gets its name from radio astronomers, who 'rediscovered' it in 1948 as the strongest radio source in the constellation of Cassiopeia. About 5 years later optical astronomers found the faint wisps, and it was determined that Cas A is the remnant of an explosion that occurred about 300 years ago. The radio emission comes from high-energy electrons moving in large spirals around magnetic field.
Cas A Composite Gallery | Cas A Timeline Activity | Cas A Photo Album