Cat’s Eye Nebula

Unlike the Crab Nebula, which is a supernova remnant, the Cat’s Eye Nebula is a planetary nebula. A planetary nebulae is a glowing shell of ionized gas that was ejected from a red giant star in the twilight years of a Sun-like star. While most planetary nebulae are morphologically simple, the Cat’s Eye Nebula is structurally complex, with concentric rings surrounding an inner core. The mechanism that gives rise to its structure is not well-understood, and is an ongoing area of research.

(Right: Image by the Hubble)