NGC281 - The Pacman Nebula

This incredible nebula is designated SH-2 308, The Dolphin (or Dolphin Head) Nebula. The data I used to process this image was captured via remote-telescope using the Telescope.live network, which has several sites around the world where astrophotographers can collect data without having to physically go to these remote, dark sky locations. This particular site has a Takahashi FSQ-106ED (106 mm) F3.6 telescope paired with a 61MP QHY 600M Pro camera, in Heaven's Mirror Observatory, Australia. The data was 300-second exposures, with 84 of Hydrogen-Alpha, 82 Sulfur-II, and 84 Oxygen-III. Of those, 37 H-A were bad, as were 24 S-II and 38 O-III. Bad data ranges from blurred, to obscured (clouds) to obstructed (objects, airplanes, etc).

You can clearly see the star in the center of the "dolphin head" - it's categorized as a Wolf-Rayet star, born from huge clouds of hydrogen with 10 to 100 times the mass of our sun, and one of the brightest and hottest types of stars known. This particular one has burned through the hydrogen at its core and ejected much of the outer layer of hydrogen, which is what we see now making the shape of the dolphin. Stars spend most of their lives in a balance between gravity pulling its mass inward, and highly energized particles creating radiation "pressure" pushing outward, and this balance can last billions of years. But when a star exhausts the hydrogen in its core, what's left is helium, the byproduct of hydrogen fusion. Fusion of helium requires a much higher temperature and pressure than that of hydrogen, so when the core runs out of hydrogen for fusion, the outward radiation pressure decreases, and the core begins to collapse due to gravity. When the collapsing helium core has compressed enough to reach the critical pressure and temperature for helium fusion, it's like putting a match to a grill that's had the gas on for a while, like an explosive detonation. That is what ejects the hydrogen that was outside the core, which was not undergoing fusion. This star is now almost exclusively burning Helium and some carbon, and the much higher temperature of the helium fusion, and higher radiation, is what we see illuminating and exciting the expanding cloud of ionized hydrogen. There doesn't seem to be a precise consensus for the distance of SH2-308, as estimates vary from 1875 light years to 5870 light years, but most place it at about 4750 light years away.