NGC 6818 is a planetary nebula also known as the Little Gem Nebula. It about 6,000 light-years away in the constellation Sagittarius. The cloud is a bit more than half a light-year across, huge compared to its central star but still a little gem as nebulas go.
When stars like the Sun are ready to “retire,” they shed their outer layers into space which creates glowing clouds of gas called a planetary nebulae. The ejection of mass is uneven, and planetary nebulae often have very complex shapes. NGC 6818 has a bright and enclosed central bubble surrounded by a larger, more diffuse cloud. It appears that the stellar wind from the central star propels the outflowing material, shaping NGC 6818. As the fast stellar wind smashes through the slower-moving cloud, it creates particularly bright blowouts in the bubble’s outer layers.
Image Credit: NASA