astronomy

Ring Nebula

Ring Nebula is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ring Nebula rather than just read about it. In short: The Ring Nebula is a planetary nebula in the northern constellation of Lyra, about mid-way between the prominent stars Beta and Gamma Lyrae. It is also catalogued as Messier 57, M57 and NGC 6720.

Key takeaways

Ring Nebula belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ring Nebula to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ring Nebula from memory before moving on to harder problems.

Reference excerpt

The Ring Nebula is a planetary nebula in the northern constellation of Lyra, about mid-way between the prominent stars Beta and Gamma Lyrae. It is also catalogued as Messier 57, M57 and NGC 6720. The nebula was discovered by Charles Messier in 1779. It has an apparent visual magnitude of 8.8, which is too faint to be visible with the naked eye, but it can be readily observed with a small telescope.

A planetary nebula is formed when a star, during the last stages of its evolution before becoming a white dwarf, expels a vast luminous envelope of ionized gas into the surrounding interstellar space. The progenitor star for the ring nebula is now a carbon-oxygen white dwarf with an apparent visual magnitude of +15.75. Based on parallax measurements, this star is located at a distance of approximately 2,570 light-years (790 pc) from the Sun. After expanding for 1,610 years, the nebula currently has a diameter of 1 ly.

History This nebula was discovered by the French astronomer Charles Messier while searching for comets in late January 1779. Messier's report of his independent discovery of Comet Bode reached fellow French astronomer Antoine Darquier de Pellepoix two weeks later, who then independently rediscovered the nebula while following the comet. Darquier later reported that it was "...as large as Jupiter and resembles a planet which is fading" (which may have contributed to the use of the persistent "planetary nebula" terminology). It would be entered into Messier's catalogue as the 57th object. Messier and German-born astronomer William Herschel speculated that the nebula was formed by multiple faint stars that were unresolvable with his telescope. In 1800, German Count Friedrich von Hahn announced that he had discovered the faint central star at the heart of the nebula a few years earlier. He also noted that the interior of the ring had undergone changes, and said he could no longer find the central star. In 1864, English amateur astronomer William Huggins examined the spectra of multiple nebulae, discovering that some of these objects, including M57, displayed the spectra of bright emission lines characteristic of fluorescing glowing gases. Huggins concluded that most planetary nebulae were not composed of unresolved stars, as had been previously suspected, but were nebulosities. The nebula was first photographed by the Hungarian astronomer Eugene von Gothard in 1886.

Observation

M57 is found south of the bright star Vega, which forms the northwestern vertex of the Summer Triangle asterism. The nebula lies about 40% of the distance from Beta (β) to Gamma (γ) Lyrae, making it an easy target for amateur astronomers to find. The nebula disk has an angular size of 1.5 × 1 arcminutes, making it too small to be resolved with 10×50 binoculars. It is best observed using a telescope with an aperture of at least 20 cm (8 in), but even a 7.5 cm (3 in) telescope will reveal its elliptical ring shape. Using a UHC or OIII filter greatly enhances visual observation, particularly in light polluted areas. The interior hole can be resolved by a 10 cm (4 in) instrument at a magnification of 100×. Larger instruments will show a few darker zones on the eastern and western edges of the ring and some faint nebulosity inside the disk. The central star, at magnitude 14.8, is difficult to spot.

Properties M57 is 0.787 kpc (2,570 light-years) from Earth. It has a visual magnitude of 8.8. Photographs taken over a period of 50 years show the rate of nebula expansion is roughly 1 arcsecond per century. Spectroscopic observations show that the expansion velocity along the line of sight is 20–30 km/s. M57 is illuminated by a central white dwarf with an apparent magnitude of 15.75. The interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized oxygen emission lines at 495.7 and 500.7 nm. These emission lines are so-called "forbidden lines" which occur only in regions of very low density containing no more than a few thousand atoms per cubic centimeter. In the outer region of the ring, part of the reddish hue is caused by hydrogen emission at 656.3 nm, forming part of the Balmer series of lines. Forbidden lines of ionized nitrogen or N II contribute to the reddishness at 654.8 and 658.3 nm.

Nebula structure M57 is thought to be a prolate spheroid with strong concentrations of material along its equator. From Earth, the symmetrical axis is viewed at about 30°. Overall, the observed nebulosity has been estimated to be expanding for approximately 1,610 ± 240 years.

Central star The central star was discovered by Hungarian astronomer Jenő Gothard on September 1, 1886, from images taken at his observatory in Herény, near Szombathely. Within the last two thousand years, the central star of the Ring Nebula has left the asymptotic giant branch. It no longer produces its energy through nuclear fusion and, in evolutionary terms, it is now becoming a compact white dwarf star. The central star now consists primarily of carbon and oxygen with a thin outer envelope composed of lighter elements. Its mass is about 0.61–0.62 M☉, with a surface temperature of 125,000±5,000 K. Currently it is about 300 times more luminous than the Sun, but its apparent magnitude is only +15.75. In 2025 JWST observed a dust disk around the central star.

See also List of planetary nebulae Messier object New General Catalogue List of Messier objects NGC 6565, which is undergoing a similar process and is of the same type

Notes

References

External links

WorldWide Telescope M57 (The Ring Nebula) M57 Calar Alto Observatory Messier 57 SEDS Astronomy Picture of the Day Infrared Ring Nebula (2005 March 11) Ring Nebula Deep Field (2009 November 6) M57: The Ring Nebula (2009 November 15) The Scale of the Universe – Interactive (2012 March 12) M57 – Planetary Nebula in Lyra NightSkyInfo M57 Archived 2007-03-13 at the Wayback Machine ESA/Hubble Ring Nebula (M57) in Lyra Constellation Guide (May 26, 2013) Szymanek, Nik; Lawrence, Pete. "M57 – Ring Nebula". Deep Sky Videos. Brady Haran. The Ring Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with Ring Nebula

Start with the simplest possible case. Write down what Ring Nebula claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ring Nebula before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ring Nebula ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ring Nebula

In research: Ring Nebula appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ring Nebula in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ring Nebula is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1779, Discoveries by Charles Messier, Lyra, so understanding it makes those chapters shorter.
In everyday life: Look for Ring Nebula outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ring Nebula in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ring Nebula means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ring Nebula out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ring Nebula in simple terms?

The Ring Nebula is a planetary nebula in the northern constellation of Lyra, about mid-way between the prominent stars Beta and Gamma Lyrae. It is also catalogued as Messier 57, M57 and NGC 6720.

Why does Ring Nebula matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ring Nebula?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ring Nebula.