After the moon and planets, the Ring Nebula must be one of the top three deep sky objects sought out by astronomers of all stripes. Many a spring and summer night I’ve made my “pilgrimage to the Ring”. And why not? It’s easy to spot not far from the brilliant star Vega in the constellation Lyra and looks like a smoke ring frozen in time.
The Ring Nebula was discovered in a 2.5″ refracting telescope by Antoine Darquier de Pellepoix in 1779. He described it as “a very dull nebula, but perfectly outlined; as large as Jupiter and looks like a fading planet.” Not long after, famed French comet hunter Charles Messier stumbled on while tracking a new comet across the sky. Messier promptly added it to his catalog of fuzzy things that resemble comets, dubbing it M57.
Located about 2,000 light years from Earth and spanning nearly one light year (6 trillion miles) end to end, our entire solar system would fit inside the doughnut hole with room to spare. The Ring is one of many planetary nebulae, so called because their rounded shapes reminded early telescopic observers of planets.
Planetaries are the cast-off mantles and atmospheres of sun-sized stars when they run out of fuel in their cores. What’s left is an exceedingly hot, planet-sized core called a white dwarf star. The gassy remains fluoresce green, red and blue in the flood of energetic ultraviolet light radiating from the dwarf. Each color represents a different element; oxygen glows green, helium blue and nitrogen red.
The nebula’s expanding at the fantastic speed of 43,000 mph (69,000 kph) but because of its great distance won’t show a whit of difference in size during a human lifetime. But 10,000 years from now, the Ring will have grown so large and faint it will merge with the interstellar medium, the thin soup of gas between the stars from which future generations of stars are born.
While the nebula looks like a bagel with a thick doughy exterior and empty center, it’s more like a jelly doughnut. In a small telescope, the center appears empty but larger scopes reveal that its interior is filled with less dense gas. Astronomers have combined ground-based telescopic views with new observations using the Hubble Space Telescope to give us a clear three-dimensional understanding of what we’re seeing.
“We are gazing almost directly down one of the poles of this structure, with a brightly colored barrel of material stretching away from us. Although the center of this doughnut may look empty, it is actually full of lower density material that stretches both towards and away from us, creating a shape similar to a rugby ball slotted into the doughnut’s central gap,” says a recent NASA/ESA release on the topic.
In other words, there’s much more there than meets the eye. With only one perspective – we’re stuck on Earth after all – the nebula’s “inner jelly doughnut” self required careful observation and data-teasing to fathom. The next time we point our scopes in the Ring’s direction we can enjoy and appreciate it from a new perspective.