1. Describe what is meant by a planetary nebula.
(1) Describe what is meant by a planetary nebula.
(2) Suggest why most photographs show planetary nebulae as rings—doesn't the gas surround the core from all directions?
(3) To eject mass from a star in a planetary nebula, the core of the star must exert a force on the outer layers of the star. What force is then exerted on the core and what does this imply?