An expanding nebula, or cloud, of gas thrown off by a dying star just before the star settles down to its ultimate endpoint as a white dwarf. Planetary nebulae are among the brightest and best-studied nebular objects in the sky, even though they are generally a few thousand light-years from Earth. The many shapes of planetary nebulae reflect poorly understood processes that occur inside most stars late in their lives. The Sun is likely to eject a planetary nebula in about 5 billion years. Many of the most prominent planetary nebulae seen today formed and emerged from their dusty cocoons within just the past 1000–2000 years.