I would assume that almost any good astronomy book would include a photograph of what can best be described as a “smoke ring” of the sky. Others might call it a donut or a cosmic bagel, but the popular name for this object is simply the Ring Nebula, located in the constellation Lyra, Lyra. Although generally considered a summer constellation, Lyra is still very well placed for viewing now more than two weeks into the fall season.
Head east this week around 10:00 PM EST. About two-thirds of the way up from the horizon, you’ll see a bright blue-white star. This is Vega, the brightest star in Lyra. The only other star at that hour that outshines Vega in brightness is yellow-orange Arcturus in the constellation Boötes, the Shepherd. But Arcturus will be in the opposite part of the sky, about half way up in the southwest.
The constellation Lyra was supposed to represent Apollo’s harp. The six fainter stars form a small geometric pattern of a parallelogram connected at its northern corner to an equilateral triangle. Vega shines on the western part of the triangle. The two lowest stars in the parallel are Beta and Gamma Lyrae. Beta is sometimes also known as Sheliak and Gamma is also called Sulafat. Between these two stars, but slightly closer to Sulafat, you will find the Ring Nebula.
Want to see the Ring Nebula or other nebulae with your own eyes? Be sure to check out our best binoculars and best binoculars guides.
And if you’re interested in dabbling in your own impressive sky-watching photography, be sure to check out our guide to photographing the night sky. We also have recommendations for the best astrophotography cameras and the best astrophotography lenses.
A celestial curiosity
Antoine Darquier de Pellepoix of Toulouse, France, first saw the Ring Nebula in January 1779. Using a telescope with an aperture of about 3 inches, he described it as a perfectly circumscribed disk as large as Jupiter, but dull in light and looking like a waning planet. .
Shortly thereafter, Charles Messier also saw it and added it to his catalog of maskers of comets, listing it as Messier 57 or M57. But like de Pellepoix, Messier’s telescope was too crude to provide a true image of what he was looking at. “It appears to be composed of very small stars,” Messier wrote, adding that “but with the best telescope they cannot be distinguished; they are only suspected.”
It wasn’t until six years later, in 1785, that Sir William Herschel (the discoverer of Uranus) actually saw M57 as a ring. “It is among the curiosities of the heavens; a nebula that has a regular concentric dark spot in its center.” However, Herschel incorrectly assumed that he was looking at a “ring of stars”.
Gas mantle or tunnel?
As for the true nature of the ring, it is generally believed that sometime in the distant past, a star nearing the end of its life and having used up all its nuclear fuel ejected large masses of gas in its gaseous envelope into space. This surrounding gas is still expanding and is visible due to illumination from the extremely hot central star (which is just the core left over from the original star). The surface temperature of the star was estimated to be 216,000 °F (120,000 °C). Our own sun is expected to undergo a similar process in a few billion years.
The Ring Nebula is the most famous and among the brightest examples of what astronomers refer to as “planetary” nebulae. But despite their name, planetary nebulae have absolutely nothing to do with planets. This is simply because they generally do not appear in telescopes as stellar point sources, but as small diffuse disks.
For a long time, the explanation for the appearance of the Ring Nebula was that the nebulous disk was so much brighter around its edges that it looked like a ring; that we are looking longitudinally over the edge of the gaseous envelope. Therefore, there is much more gas in our field of view, and the refraction of light from the central star makes it brighter, as each particle acts as a prism or mirror, reflecting the rays back to us.
However, more recent research has confirmed that it is indeed likely to be a ring or torus of bright material surrounding the central star. In fact, based on photos taken from the Kitt Peak National Observatory near Tucson, Arizona, some think we might actually be looking down on a barrel- or cylinder-shaped tunnel of gas.
Check it out for yourself
As for actually seeing the ring for yourself, it shines at magnitude +8.8 and is therefore too faint to be seen with the naked eye. Any good telescope will find it, although due to its small apparent diameter it will look almost like a star. The shape of the ring can begin to show to most eyes in small telescopes at 100 magnification, although at least a 6-inch telescope is recommended to see the ring clearly. With larger instruments and higher magnification, the ring appears distinctly like a “little ghost donut”.
You may ask if the central star is visible in the “doughnut hole”. The answer is “yes and no.” The magnitude of this star is roughly +15. This means that it is almost 4000 times fainter than the faintest star that you could see with your eyes without any optical aid. And don’t bother looking for the central star unless you have a telescope with at least a 12-inch aperture. Even then, you’ll need a perfectly dark and clear, pristine night to even have a chance to catch a glimpse of it.
Only once, almost half a century ago, in 1975, did I see it. It was about the annual solstice Stellafan convention, just outside of Springfield, Vermont. The Ring Nebula was one of the objects that could be seen through the 12-inch telescope of the Porter Tower atop Breezy Hill. However, I hasten to add that my eyes were much younger then, and the overall level of light pollution in much of New England was considerably lower then than it is now.
Bottom line: You certainly shouldn’t have a problem seeing the Ring Nebula, but its central star is likely to remain out of your reach.
Joe Rao serves as an instructor and guest lecturer in New York Hayden Planetarium. He writes about astronomy for Science magazine, Farmer’s Almanac and other publications.