This image of the Egg Nebula, also known as CRL2688, shows a pair of mysterious "searchlight" beams emerging from a hidden star, criss-crossed by numerous bright arcs. The image sheds new light on the poorly understood ejection of stellar matter that accompanies the slow death of Sun-like stars.
The Egg Nebula, located roughly 3,000 light-years away, is a large cloud of dust and gas ejected by a central star, which was a red giant a few hundred years ago. A dense cocoon of dust (the dark band in the image center) enshrouds the star and hides it from our view. The image reveals very sharply defined edges of the beams and fine spoke-like features which suggest that, contrary to previous models, the searchlight beams are formed as a result of starlight escaping from ring-shaped holes in the cocoon surrounding the star. The spoke-like features result from shadows cast by blobs of material distributed within the region of the ring-like holes. Such holes may be carved out by a wobbling, high-speed stream of matter -- and could play a crucial role in the shaping of the planetary nebula that will result from CRL2688. Alternatively, the searchlight beams may result from starlight reflected off fine jet-like streams of matter being ejected from the center, and confined to the walls of a conical region around the symmetry axis.
Objects like CRL2688 are rare because they are in an evolutionary phase that lasts for a very short time (~1,000 to 2,000 years). They may, however, hold the key to our understanding of how red giant stars transform themselves into planetary nebulae.
Camera: WFPC2
Technical Information: Image shown in false color.
Credit: R. Sahai and J. Trauger (JPL), the WFPC2 science team, and NASA
