This is NGC 6818. It’s 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 read to “retire,” they shed their outer layers into space which creates glowing clouds of gas called 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