I suppose any good astronomy book would contain a photograph of what might best be described as the “smoke ring” of the sky. Others might call it a cosmic doughnut or bagel, but the popular name for this object is simply the Ring Nebula, located in the constellation Lyra. Although generally considered a summer constellation, Lyra is still very well placed for viewing, now more than two weeks into the fall season.
Go out this week around 10 p.m. local daylight time and face due east. About two-thirds of the way up the horizon, you will see a bright, bluish-white star. This is Vega, the brightest star in Lyra. The only other star at this time that surpasses 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 halfway up in the southwest.
The constellation Lyra was believed to represent the harp of Apollo. Six fainter stars form a small geometric pattern of a parallelogram attached at its north corner to an equal triangle. Vega shines in the western part of the triangle. The two lowest stars in the parallelogram are Beta and Gamma Lyrae. Beta is sometimes also known as Sheliak and Gamma is also called Sulafat. Between these two stars, but a little closer to Sulafat, is the Ring Nebula.
Want to see the Ring Nebula or other nebulae for yourself? Be sure to check out our guides for the best binoculars and telescopes.
And if you want to get started with skywatching photography, don’t miss our guide on how to photograph the night sky. We also have recommendations for the best cameras and lenses for astrophotography.
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 contoured disk, as large as Jupiter, but dulled by light and resembling a disappearing planet.
Shortly after, Charles Messier also saw it and added it to his catalog of masked comets under the name Messier 57 or M57. But like Pellepoix’s, Messier’s telescope was too rudimentary to give a faithful image of what he observed. “It seems composed of very small stars,” Messier wrote, adding that “but with the best telescope it is impossible to distinguish them; we simply suspect them. »
It was not until six years later, in 1785, that Sir William Herschel (the discoverer of Uranus) actually saw M57 as a ring. “It is one of the curiosities of the heavens: a nebula which has a regular concentric dark spot in the middle.” Herschel, however, wrongly assumed that it was a “ring of stars.”
Gas shell or tunnel?
As for the true nature of the ring, it is generally believed that in the distant past, a star nearing the end of its life and having exhausted all of its nuclear fuel spewed large masses of gas into space in a gaseous shell. This surrounding gas is still expanding and is made visible by the illumination of its extremely hot central star (which is just the core left over from the original star). The surface temperature of the star has been estimated at 216,000ºF (120,000ºC). Our own Sun is expected to undergo a similar process in a few billion years.
The Ring Nebula is the most famous and one of the brightest examples of what astronomers call “planetary” nebulae. But despite their name, planetary nebulae have absolutely nothing to do with planets. This is simply because they generally appear in telescopes not 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 hazy disk was so much brighter at its edges that it looked like a ring; that we are looking through the edge of the gaseous shell lengthwise. Therefore, there is much more gas in our field of vision and the refraction of light from the central star makes it brighter, because each particle acts like a prism or mirror and reflects the rays back to us.
More recent research, however, has confirmed that it is indeed a ring or torus of bright material surrounding its central star. In fact, based on photographs taken from the Kitt Peak National Observatory near Tucson, Arizona, some believe we might actually be observing a barrel- or cylinder-shaped gas tunnel.
See it for yourself
To see the ring with your own eyes, it shines at a magnitude of +8.8, and is therefore far too faint to be seen with the naked eye. Any good pair of binoculars will locate it, although it will almost look like a star due to its small apparent diameter. The shape of the ring may begin to become obvious to most eyes in small telescopes using 100x magnification, although a telescope of at least 6 inches is recommended to see the ring clearly. With larger instruments and higher magnifications, the ring appears distinctly as a “tiny ghostly doughnut.”
You might ask if the central star is visible in the “donut hole”. The answer is yes and no.” The magnitude of this star is approximately +15. This means that it is almost 4,000 times fainter than the faintest star 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 an absolutely dark, clear, pristine night to have any luck. to have a brief overview.
I saw him only once, almost half a century ago, in 1975. It was at the annual mid-summer festival. Stellafane convention, just outside of Springfield, Vermont. The Ring Nebula was one of the objects visible through the 12-inch Porter Turret Telescope atop Breezy Hill. I hasten to add, however, that my eyes were much younger at the time, and the overall level of light pollution in much of New England was considerably less then than it is today.
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 is an instructor and guest speaker in New York Hayden PlanetariumHe writes about astronomy for Natural history reviewTHE Farmers’ Almanac and other publications.