| At this time the star ejects dust and gas, thereby forming a planetary nebula. |
| Lyra also contains the Ring Nebula, a planetary nebula that appears as a sphere of glowing gas. |
| A star has actually, under our eyes, become a planetary nebula, and the cycle of which he gave the first terms is complete. |
| Astronomers call such an object a planetary nebula, because its round shape resembles that of a planet when viewed with a small telescope. |
| A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers to form bright nebulae with amazing twisted shapes. |
| But, as night follows day, or as a planetary nebula becomes a white dwarf, it has its detractors. |
