CFHT, Current Image of the Week


January 17th, 2000

Cassiopeiae A: A Young Supernova Remnant

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Cassiopeiae A: A Young Supernova Remnant

Credit: Image courtesy of T. Douvion & P.O. Lagage
CEA/DSM/DAPNIA/Service d'Astrophysique, Saclay, France

(for more details see: Douvion et al., 1999, Astronomy & Astrophysics, Vol. 352, p. L111-L115.)

At the end of its life, a massive star explodes in what is known as a Supernova. During that dramatic episode, the star releases incredible amounts of energy and its luminosity increases by large factors, enough sometimes to make it the brightest object in a galaxy, like Supernova 1987A in the Small Magellanic cloud for example. These explosions are however short-lived and the bright object soon vanishes, at least in appearance. This week's image shows a part of what is left of a Supernova that explode about 320 years ago in the constellation Cassiopeia. The object that exploded near the center is not visible, but the material that was ejected during the explosion is seen as bright filaments. This is called a supernova remnant This material is still moving outward at typical speeds of 5000 kilometers per second! Cassiopeiae A, or Cas A as it is nicknamed by astronomers, is located 3400 parsecs away, about 11000 light years, in our Galaxy.

Because the material in the filaments was ejected by a massive star, it contains heavy elements like Oxygen, Sulfur and Argon, but no Hydrogen or Helium! Spectroscopic observations of the filaments done by the astronomers' team allowed to study the internal structure of the Supernova, especially the mixing properties between the different layers. Their results imply that Supernovae like Cas A are probably not the main dust factory in the Galaxy.

Supernova explosions like this one are however thought to be the main source of heavy elements enrichment in the interstellar medium. This material will eventually be used to form new stars. The heavy atoms we find today in meteorites falling on Earth are thought to have been formed in other Supernovea. The heavy elements found on Earth or on the other planets of our Solar System also. Even our own bodies were formed with elements that were once produced by Supernova explosions...

Technical description: This image was obtained in August 1998 with the Subarcsecond Imaging Spectrograph (SIS). A wide filter centered on a wavelength of 675nm was used. The total integration time to obtain the image was 5 minutes.

next week: NGC 2244, A Stellar Cluster in the Rosette Nebula

editors: François Ménard & Jean-Charles Cuillandre
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