Credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)
This spectacular image records a little area on the edge of the inky Coalsack Nebula, or Caldwell99 Caldwell 99 is a dark nebula– a thick cloud of interstellar dust that entirely shuts out noticeable wavelengths of light from things behind it. The item at the center of the image is a (much smaller sized) protoplanetary nebula. The protoplanetary nebula stage is a late phase in the life of a star in which it has actually ejected a shell of hydrogen gas and is rapidly warming up. This phase just lasts for a couple of thousand years prior to the protoplanetary nebula’s main star reaches approximately 30,000Kelvin At this point, the main star is producing enough energy to make its surrounding shell of gas radiance, becoming what’s referred to as a planetary nebula.
Caldwell 99 is an extremely popular item in the southern night sky. On a clear night, it can be spotted quickly with the naked eye as a dark spot, devoid of stars, beside the Southern Cross in the constellationCrux It is most convenient to identify in the Southern Hemisphere throughout the fall. (Northern Hemisphere observers will wish to be placed near the equator and search for it in the spring.)
Caldwell 99 lies 600 light-years from Earth and has to do with 100 light-years throughout.
