This image of MyCn18, a young planetary nebula located about 8,000 light-years away, is of great interest to researchers because it sheds new light on the poorly understood ejection of stellar matter that accompanies the slow death of Sun-like stars. In previous ground-based images, MyCn18 appears to be a pair of large outer rings with a smaller central ring, but the fine details cannot be seen. This Hubble image reveals the true shape of MyCn18 to be an hourglass (here turned sideways) with an intricate pattern of "etchings" in its walls.
According to one theory for the formation of planetary nebulae, the hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud that is more dense near its equator than near its poles. What appears as a bright elliptical ring in the center is seen on closer inspection to be a potato shaped structure with a symmetry axis dramatically different from that of the larger hourglass. The hot star, which has been thought to eject and illuminate the nebula and was therefore expected to lie at its center of symmetry, is clearly off center. Another unexpected feature in MyCn18 that is revealed by this Hubble image is the pair of intersecting elliptical rings in the central region that appear to be the rims of a smaller hourglass.
Camera: WFPC2
Technical Information: Picture composed from three separate images taken in the light of ionized nitrogen (represented by red), hydrogen (green), and doubly-ionized oxygen (blue).
Credits: R. Sahai and J. Trauger (JPL), the WFPC2 science team, and NASA
