Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2009 December 31
Dust and the Helix Nebula
NASA, JPL-Caltech, Kate Su (Steward Obs, U. Arizona) et al.Explanation: Dust makes this cosmic eye look red. The eerie
Spitzer Space Telescope image shows
infrared radiation from the well-studied
Helix Nebula (NGC 7293) a mere 700 light-years away in the constellation
Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a
planetary nebula, representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula's central star itself is immersed in a surprisingly bright infrared glow.
Models suggest the glow is produced by a dust
debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system's
Kuiper Belt or cometary
Oort cloud. Formed in the distant planetary system, the comet-like bodies would have otherwise survived even the dramatic late stages of the star's
evolution.
