I imagine that virtually any good book on astronomy would include a photo of what can best be described as the sky’s “smoke ring.” 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, the Lyra. Although generally considered a summer constellation Lyra, it is still very well positioned for viewing now that the autumn season is more than two weeks into it.
This week, around 10 p.m. local daylight time, go outside and look due east. About two-thirds of the way up from the horizon, you’ll see a brilliant blue-white star. This is Vega, the brightest star in Lyra. The only other star brighter than Vega at that hour is the yellow-orange Arcturus in the constellation Bootes, the Shepherd. But Arcturus is on the other side of the sky, about halfway due southwest.
The constellation Lyra is said to represent Apollo’s harp. Six fainter stars form a small geometric pattern of a parallelogram attached to an equilateral triangle at the northern corner. Vega shines at the western end of the triangle. The two lowest stars in the parallelogram are Beta and Gamma Lyrae. Beta is sometimes called Sheliac and Gamma is also known as 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 for yourself? Be sure to check out our guides to the best binoculars and the best telescopes.
And if you’re interested in experimenting with your own impressive skywatching photography, don’t miss our guide on how to photograph the night sky . We also have recommendations for the best cameras for astrophotography and the best lenses for astrophotography .
A heavenly curiosity
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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 the size of Jupiter, but dull in light and looked like a fading planet. .
A short time later, Charles Messier also saw it and added it to his catalog of comet masks, listing it as Messier 57 or M57. But like Pellepoix, Messier’s telescope was too crude to give a true picture of what he saw. “It seems to be composed of very small stars,” Messier wrote, adding that “but with the best telescope it is impossible to distinguish them; they are only conjectured.”
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 one of the curiosities of the heavens; a nebula with a regular concentric dark spot in the centre.” However, Herschel incorrectly assumed that he was looking at “a ring of stars.”
Gas bomb or tunnel?
As for the ring’s true nature, it is widely 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 amounts 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 of the original star). The star’s surface temperature is estimated at 216,000 ºF (120,000 ºC). Our own sun is expected to undergo a similar process in a few billion years.
The Ring Nebula is the best-known 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. That’s simply because they generally don’t appear in telescopes as point sources of stars, but as small diffuse disks.
For a long time, the explanation for the appearance of the Ring Nebula was that the blurry disk was so much brighter at the edges that it looked like a ring; that we are looking lengthwise through the edge of the gaseous shell. Therefore, there is much more gas in our line of sight 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.
More recent research, however, has confirmed that it is indeed likely a ring or torus of bright material surrounding the central star. Based on images taken from Kitt Peak National Observatory near Tucson, Arizona, some even think that we may be looking at a gas tunnel shaped like a barrel or cylinder.
See for yourself
As for actually viewing the ring, it has a magnitude of +8.8, making it far too faint to see with the naked eye. Any good binoculars can locate it, although it looks almost star-like because of its small apparent diameter. The shape of the ring should be just clear 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 magnifications, the ring clearly looks like a “little ghostly donut.”
You might wonder 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 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 an aperture of at least 12 inches. Even then, you’d need an absolutely dark and clear, pristine night to catch even a brief glimpse of it.
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Only once, almost half a century ago, in 1975, did I see it. It was during the annual midsummer Stellafane convention, just outside Springfield, Vermont. The Ring Nebula was among the objects seen by the 12-inch Porter Tower Telescope on Breezy Hill. However, I must quickly 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 today.
Bottom line: You should certainly have no trouble spotting the Ring Nebula, but the central star will most likely remain out of your reach.
Joe Rao is a lecturer and visiting lecturer at New York’s Hayden Planetarium. He prescribes on astronomy Natural history magazinethe Farmers’ Almanac and other publications.