I would guess that almost any good astronomy book will contain a picture of what can best be described as a “smoke ring” in the sky. Others may 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 positioned for viewing, now more than two weeks into the fall season.
Go outside this week around 10:00 PM local summer time and look east. About two-thirds of the way up from the horizon, you’ll spot a brilliant bluish-white star. This is Vega, the brightest star in Lyra. The only other star at this hour that surpasses Vega in brightness is yellow-orange Arcturus in the constellation Volovar, the Shepherd. But Arcturus will be in the opposite part of the sky, about mid-southwest.
The constellation Lyra was supposed to represent Apollo’s harp. Six fainter stars form a small geometrical pattern of a parallelogram attached at its northern corner to an equilateral triangle. Vega shines in the western part of the triangle. The two lowest stars in the parallelogram are Beta and Gamma Lyra. Beta is sometimes also known as Celiac and Gamma is also called Sulafat. Between these two stars, but a bit closer to Sulafat is where you’ll find the Ring Nebula.
Want to see the Ring Nebula or other nebulae for yourself? Be sure to check out our guides to the best binoculars and the best telescopes.
And if you’re interested in taking on some impressive sky-watching photography of your own, don’t miss our guide on how to photograph the night sky. We also have recommendations for the best astrophotography cameras and the best astrophotography lenses.
Heavenly 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 defined disk as large as Jupiter, but dull in light and looking like a fading planet.
A little later, Charles Messier also saw it and added it to his catalog of comet masks, naming it Messier 57 or M57. But like de Pelepois, Messier’s telescope was too crude to give a true picture of what he was looking at. “It appears to be composed of very small stars,” wrote Messier, adding that “but with the best telescope it is impossible to distinguish them; they just suspect each other’.
It was only six years later, in 1785, that Sir William Herschel (the discoverer of Uranus) actually saw M57 as a ring. “It is among the curious things of the heavens; a nebula that has a properly concentric dark spot in the middle.” However, Herschel incorrectly assumed that he was looking at a ‘ring of stars.’
Gas shell or tunnel?
As for the true nature of the ring, it is generally believed that sometime in the distant past, a star that was nearing the end of its life and had used up all its nuclear fuel ejected large masses of gas into space in a gaseous envelope. This surrounding gas is still expanding and becomes visible by the light from its extremely hot central star (which is just the core left of the original star). The star’s surface temperature is estimated at 216,000º F (120,000º C). Our sun is expected to undergo a similar process in a few billion years.
The Ring Nebula is the best known and among the brightest examples of what astronomers call “planetary” nebulae. But despite their name, planetary nebulae have absolutely nothing to do with planets. Simply because they usually 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 nebulous disk was so much brighter around its edges that it looked like a ring; that we are looking through the edge of the gas shell lengthwise. Therefore, there is much more gas in our line of sight and the refraction of light from the central star makes it brighter because each particle acts as a prism or mirror and reflects the rays back to us.
However, more recent research has confirmed that it is indeed a ring or halo of bright material surrounding the central star. In fact, based on photos taken by the Kitt Peak National Observatory near Tucson, Arizona, some believe we may actually be looking down at a barrel- or cylinder-shaped tunnel of gas.
See it for yourself
As for actually seeing the ring yourself, it shines at magnitude +8.8 and is therefore too faint to see with the naked eye. Any good pair of binoculars will detect it, although it will look almost like a star due to its small apparent diameter. The shape of the ring may just begin to become apparent to most eyes in small telescopes using 100 degree magnification, although at least a 6-inch telescope is recommended to see the ring clearly. With larger instruments and higher magnifications, the ring looks distinctly like a “little ghost doughnut.”
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 approximately +15. That means it’s 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’d need an absolutely dark and clear, pristine night to get even a brief glimpse of it.
Only once, nearly half a century ago, in 1975, did I see it. It was on the annual New Year’s Day Stellaphan convention, just outside of Springfield, Vermont. The Ring Nebula was one of the objects visible through the 12-inch Porter Dome Telescope atop Breezy Hill. However, I hasten to add that my eyes were much younger then, and the general level of light pollution in much of New England was considerably less then than it is now.
Bottom line: You should certainly have no problem observing the Ring Nebula, but it’s highly likely that its central star will remain out of your reach.
Joe Rao serves as an instructor and guest speaker in New York Hayden Planetarium. He wrote about astronomy for Journal of Natural History.on Farmer’s Almanac and other publications.
