English: This image, which looks a little like an enormous bubble in space, features a planetary nebula known as EGB 6. It was imaged by the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab. Planetary nebulae, notoriously, have nothing to do with planets. They form during the dying millennia of intermediate-mass stars, stars with masses between one and eight times the mass of the Sun. “Dying millennia” might sound like a very long time, but compared to the overall lifespan of a star, planetary nebulae are extremely short-lived. Towards the end of their life cycle, intermediate-mass stars enter the red giant phase, during which fusion reactions temporarily reignite in a dying star’s core. Layers of gas, shed or ejected during the red giant phase, absorb vast amounts of energy and create the gorgeous phenomena known as planetary nebulae. The dying millenia only last about 20,000 years, a mere blink of an eye when you consider that intermediate-mass stars shine steadily for between 30 million to 10 billion years (depending on their mass) before they die.