About Cassiopeia A
Cassiopeia A is the remnant of a
supernova explosion that occured over 300 years ago in our Galaxy, at a distance of about 11,000 light years from us. Its name is derived from the constellation in
which it is seen:
Cassiopeia, the Queen. A supernova is the explosion that occurs at the end of a
massive star's life; and Cassiopeia A is the expanding shell of material that remains from such an explosion.
Cassiopeia A in Radio Waves
The radio image (above, to the left) of Cassiopeia A was created with the National Science Foundation's
Very Large Array telescope (above, to the right) in New Mexico.
Cassiopeia A is one of the brightest radio sources in the sky, and has been a popular target of study for radio astronomers for decades.
The material that was ejected from the supernova explosion can be seen in this image as bright filaments.
To see the image better, you may download small (60k), medium (144k) and
large (316k) versions of the image. You can also buy a new poster of this image
here!
Watch the Explosion!
Even though it occurred over 300 years ago, the supernova remnant is still expanding. In fact, the material from the
explosion is moving outward at speeds of over ten million miles an hour! The first movie (below, to the left) shows the expansion of
Cassiopeia A over 16 years. The second movie (below, to the right) zooms in on the western edge of the nebula to show the expansion in detail. Click on an image to
start the movie. Watch closely as the movie loops from the first observations in 1978, to 1994, and then back to 1978. As you watch,
notice that many features moving at different speeds and in different directions. Note: to view these movies
you will need the free QuickTime player (available for Macintosh and Windows).
Cassiopeia A at Many Wavelengths
| |
 |
Cassiopeia A is bright at all energies of the electromagnetic spectrum. This composite image shows Cassiopeia A at many different wavelengths: radio polarization in red (VLA), X-rays in green (CHANDRA) and optical
in blue (HST). Notice the outer shock, visible only in X-rays, as the thin green rim most visible at the top of the image. Also notice the bright ring which is visible at all three wavelengths, and the many different filamentary structures seen at each wavelength.
The compact remains of
the exploded star are visible only in X-rays, as the bright green
spot slightly below and to the left of the geometric center of the bright ring.
You may also be interested in images of Cassiopeia A with the Hubble Space Telescope and the Chandra X-ray Observatory.
|
|
Further Information and Credits
The images and movies were processed at the University of Minnesota by
Lawrence Rudnick, Martha Anderson, Chris Butenhoff, Jonathan
Keohane and Barron Koralesky in collaboration with Rick Perley at the National Radio Astronomy Observatory.
Further information can be obtained from Lawrence Rudnick.
The original maps for epochs 1978 and 1981 of the movies were kindly provided
by Richard Tuffs (MRAO) from data taken with the Cambridge 5km telescope. The 1983 and 1985 Very Large Array maps come from the work of Braun, Gull
and Perley (1987). The National Radio Astronomy Observatory is a facility
of the National Science Foundation operated by Associated Universities,Inc.
under a cooperative agreement.
The Chandra X-ray data for the composite image are from the Chandra Archives of the Jan, 2000
observations of S. Holt. The Chandra X-ray Center is operated for NASA by the Smithsonian
Astrophysical Observatory. The HST WFPC2 optical data are taken from the published work of
R. Fesen et al. (2001). The NASA/ESA Hubble Space Telescope data are obtained at the Space
Telescope Science Institute, which is operatued by the Association of Universities for Research
in Astronomy.
Research on Cassiopeia A leading to the movie has been supported
by the following grants from the National Science Foundation to
the University of Minnesota AST 87-15949, AST 91-00486, AST 93-18959,
and AST 96-19438.
|
