来源： Space.com This Hubble Space Telescope image is not just a beautiful scene, but also a tool scientists can use to study stellar evolution. The Egg Nebula is a pre-planetary nebula — an early form of a planetary nebula, which is a glowing shell of gas and dust shed from a dying sun-like star. And it’s “the first, youngest, and closest pre-planetary nebula ever discovered,” according to NASA. While planetary nebulae don’t have anything to do with planets directly, they do provide the seed material for future star systems that do have planets, much like our own. ...