The Ring Nebula M57: A Cosmic Smoke Ring in Lyra

Tucked between two stars in the small constellation Lyra lies one of the most iconic objects in the night sky: the Ring Nebula, also known as Messier 57 (M57). It looks like a tiny, ghostly smoke ring hanging in space, and in a very real sense, that's exactly what it is. This is what happens when a star like our Sun reaches the end of its life and gently exhales its outer layers into the cosmos.

What Is the Ring Nebula?

M57 is a planetary nebula, a glowing shell of ionized gas expelled by a dying star. Despite the name, planetary nebulae have nothing to do with planets. The term dates back to early telescopic observers who thought these round, fuzzy objects resembled the disks of distant planets.

The Ring Nebula sits about 2,300 light-years from Earth. The shell you see is roughly one light-year across and is expanding outward at about 20 kilometers per second. At the center, a tiny white dwarf, the exposed core of the original star, blasts the surrounding gas with ultraviolet radiation, causing it to glow in vivid colors.

How to Find M57

Finding the Ring Nebula is wonderfully straightforward, which is one reason it's such a popular target for beginners:

1. Locate Vega, the brilliant blue-white star almost directly overhead on summer evenings. Vega is the brightest star in Lyra and one of the brightest in the entire sky, you can't miss it.
2. Identify the small parallelogram of fainter stars that forms the body of Lyra, just south of Vega.
3. M57 sits almost exactly halfway between the two southern stars of the parallelogram: Sheliak (β Lyrae) and Sulafat (γ Lyrae).
4. Point your telescope at the midpoint between those two stars, and M57 should be in or very near your field of view.

At magnitude 8.8, M57 is too faint for the naked eye but easily visible in any telescope. Even a small 60mm refractor will show it as a tiny, slightly fuzzy "star" that doesn't quite focus to a point. Bump up to 4 inches of aperture and you'll clearly see the ring shape.

What to Expect at the Eyepiece

The Science: A Star's Final Chapter

About 4,000 years ago, the star at the center of M57 was a red giant, a star not too different from what our Sun will become in about 5 billion years. As it ran out of fuel, it shed its outer layers in a series of gentle puffs, creating the expanding shell of gas we see today.

What remains is a white dwarf about the size of Earth but with roughly 60% of the Sun's mass. Its surface temperature is a scorching 120,000 degrees Celsius, more than twenty times hotter than the Sun's surface. That extreme heat is what makes the surrounding gas glow.

The different colors in photographs of M57 come from different chemical elements being excited by the white dwarf's radiation. The inner regions glow blue-green from doubly ionized oxygen, while the outer edges glow red from hydrogen and nitrogen. Through a telescope, you'll mostly see a grayish-green hue, since your eyes aren't sensitive enough to pick up the reds at such low light levels.

Photographing M57

The Ring Nebula is a satisfying astrophotography target. Its small size means you'll want a longer focal length (1000mm or more) to get a decent image scale. Try 30-60 second sub-exposures at ISO 1600-3200, stacked and processed. Even a modest setup will reveal the ring's color structure. For image processing tips, see our guide to image stacking.

For a comparison with other planetary nebulae, try observing the Cat's Eye Nebula in Draco. It's a very different shape but the same underlying process, a dying star's last breath made visible.