A comet hunter stumbled on the Ring Nebula and filed it away
Charles Messier was searching for comets in January 1779 when he came across a faint smudge in Lyra. It became the 57th entry in his list of objects not to confuse with comets. What he had found was the glowing shell cast off by a dying star.
Two weeks after Messier's find, Antoine Darquier de Pellepoix spotted the same object while tracking a comet and described it as roughly Jupiter's size, like a fading planet. That comparison may help explain why such objects are still called planetary nebulae, though they have nothing to do with planets. Messier and William Herschel guessed it was a cluster of stars too faint to separate. In 1864 William Huggins settled the matter with a spectroscope: its bright emission lines showed glowing gas, not stars.
The nebula formed when a star near the end of its life puffed off its outer envelope. What remains at the centre, identified from photographs by Jenő Gothard in 1886, is a carbon-oxygen core of about 0.61 solar masses on its way to becoming a white dwarf. It no longer runs on fusion, yet its surface is roughly 125,000 kelvin and it shines about 300 times as brightly as the Sun. The ring lies about 2,570 light-years away, spans about a light-year, and has been expanding for some 1,610 years. In 2025 the James Webb Space Telescope detected a dust disk around the central star.
Its colours map its chemistry. The blue-green interior comes from doubly ionised oxygen emitting so-called forbidden lines, which appear only in gas so thin it holds a few thousand atoms per cubic centimetre at most. The redder outer ring glows with hydrogen and ionised nitrogen. Its true shape is thought to be an elongated spheroid with material bunched around its equator, seen tilted about 30 degrees from its axis.
Amateur astronomers find it south of Vega, about 40 percent of the way from Beta to Gamma Lyrae. At magnitude 8.8 it is invisible to the naked eye and too small for ordinary binoculars, but a 7.5-centimetre telescope shows its oval ring and a 10-centimetre scope at 100 times magnification reveals the central hole.
Source: Ring Nebula
