This rather unusual planetary nebula is the Fine Ring Nebula. Planetary nebulae form from dying stars when they have expanded into a red giant phase and then eject a shell of gas as they evolve into the next phase of their stellar evolution, white dwarfs. Most planetary nebulae are either spherical or elliptical in shape, or are bipolar (featuring two symmetric lobes of material), but the Fine Ring Nebula looks like an almost perfectly circular ring. Astronomers believe that this unusually shaped planetary nebula was formed from a binary system. The interaction between the primary star and its orbiting companion shapes the ejected material.
The stellar object at the center of the Fine Ring Nebula does appear to be a binary system, orbiting with a period of 2.9 days. Observations suggest that the binary pair is almost perfectly face-on from our vantage point, implying that the planetary nebula’s structure is aligned in the same way. Our point of view looks down on the torus (doughnut shape) of ejected material, leading to the strikingly circular ring shape in the image.
Image Credit: ESO