Images of four planetary nebulas have been released from the first survey of such objects made with NASA's orbiting Chandra X-ray Observatory.
They are part of a survey of 21 planetary nebulas within about 5,000 light years of the Earth, the Smithsonian Astrophysical Observatory in Cambridge, Mass., reported Thursday.
The observatory controls Chandra's science and flight operations for NASA.
Planetary nebulas form when a star like the Sun uses up all of the hydrogen in its core and expands into a red giant, with a radius that increases by tens to hundreds of times.
The star sheds most of its outer layers, eventually leaving behind a hot core that ejects a fast solar wind of particles into the ejected atmosphere, creating the graceful, shell-like filamentary structures seen in the images.