                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                              2019 September 6

                           Recycling Cassiopeia A
         Image Credit: X-ray - NASA, CXC, SAO; Optical - NASA,STScI

   Explanation: Massive stars in our Milky Way Galaxy live spectacular
   lives. Collapsing from vast cosmic clouds, their nuclear furnaces
   ignite and create heavy elements in their cores. After a few million
   years, the enriched material is blasted back into interstellar space
   where star formation can begin anew. The expanding debris cloud known
   as Cassiopeia A is an example of this final phase of the stellar life
   cycle. Light from the explosion which created this supernova remnant
   would have been first seen in planet Earth's sky about 350 years ago,
   although it took that light about 11,000 years to reach us. This
   false-color image, composed of X-ray and optical image data from the
   Chandra X-ray Observatory and Hubble Space Telescope, shows the still
   hot filaments and knots in the remnant. It spans about 30 light-years
   at the estimated distance of Cassiopeia A. High-energy X-ray emission
   from specific elements has been color coded, silicon in red, sulfur in
   yellow, calcium in green and iron in purple, to help astronomers
   explore the recycling of our galaxy's star stuff. Still expanding, the
   outer blast wave is seen in blue hues. The bright speck near the center
   is a neutron star, the incredibly dense, collapsed remains of the
   massive stellar core.

                    Tomorrow's picture: Wolf's dusty cave
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

