English: When observers look directly at Caldwell 15 through a small telescope, they typically see only the nebula’s sparkling-white central star. However, by averting one’s gaze, glancing away from the central star, the nebula’s bulbous dust clouds come into view. This optical trickery earned this planetary nebula the name “the Blinking Planetary.”

The Blinking Planetary’s bright, white remnant star — known as a white dwarf — is surrounded by a greenish orb of gas and dust, the outer layers of the burned-out star that jettisoned into space. This cloud is flanked on both sides by bursts of red gas called FLIERS, or fast low-ionization emission regions. In these relatively young features, electrically charged atoms shoot off into space at supersonic speeds. This image of Caldwell 15 was captured by Hubble’s Wide Field and Planetary Camera 2 in January 1996 to help astronomers better understand how the nebula’s FLIERS form.

Caldwell 15 was discovered by British astronomer William Herschel in 1793. With a magnitude of 8.8, the nebula is found in the constellation Cygnus, and it is best observed during warm summer nights in the Northern Hemisphere. It will appear low in the northern sky for Southern Hemisphere observers during the winter. Also known as NGC 6826, Caldwell 15 is about 2,200 light-years away from Earth. Young and small, the planetary nebula is only about a thousand years old and less than half a light-year across.

Credit: Credits: Bruce Balick (University of Washington), Jason Alexander (University of Washington), Arsen Hajian (U.S. Naval Observatory), Yervant Terzian (Cornell University), Mario Perinotto (University of Florence, Italy), Patrizio Patriarchi (Arcetri Observatory, Italy) and NASA

For more information about Hubble’s observations of Caldwell 15, see:

hubblesite.org/contents/media/images/1997/38/574-Image.html

For Hubble's Caldwell catalog site and information on how to find these objects in the night sky, visit:

www.nasa.gov/content/goddard/hubble-s-caldwell-catalog