About this object
CRL 2688, also known as the Egg Nebula, is believed to be a proto-planetary nebula, representing the transition to the comparatively well-studied planetary nebula phase. It is well established that the progenitors of planetary nebulae are stars at the tip of the asymptotic giant branch that are losing mass in a `super-wind' phase. However, only a few objects are known which can be reliably identified with this transition from star to planetary, which makes their study very important. This optical image shows the double-lobed nebula, which is illuminated by the central F5 star which is hidden from our direct view by a dust torus. This torus appears as a strong, though small, infrared source with a temperature of 150K. The optical emission is very strongly polarized, at about 40%, which is sufficient to be seen by eye with a Polaroid filter and a moderate-sized telescope. The distance to CRL 2688 is uncertain, but is probably about 3000 light years.
Location: 23 00.3 +36 30 (1950.0), size: about 25 arc seconds (very roughly 0.4 light years) across.