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.