The Ring Nebula’s true structure revealed at last

Back in 1779, a highly unusual object was spotted.

The Ring Nebula can be found just inside the Summer Triangle in the constellation of Lyra: just south of the brightest star, Vega. Found in between the 2nd and 3rd brightest stars in Lyra’s constellation, the imaginary line connecting the blue giant stars Sheliak and Sulafat contains the Ring Nebula, circled in red, which can be spotted even with a pair of off-the-shelf binoculars.

Its circular appearance led to its name: the Ring Nebula.

The above view has been accessible to humanity for nearly 250 years: an object, about the size of Jupiter, with a bright circular annulus gradually faintening toward the outside and inside, but with a bright central point within it. This is the Ring Nebula, or Messier 57 (M57), discovered in 1779.

Its once-uncertain origin is now known: a planetary nebula.

When our Sun runs out of fuel, it will become a red giant, followed by a planetary nebula with a white dwarf at the center. The Cat’s Eye Nebula is a visually spectacular example of this potential fate, with the intricate, layered, asymmetrical shape of this particular one suggesting a binary companion. At the center, a young white dwarf heats up as it contracts, reaching temperatures tens of thousands of Kelvin hotter than the surface of the red giant that spawned it. The hottest young white dwarf surfaces reach ~150,000 K.

The end-state of many Sun-like stars, its blown-off gas gets heated by the hot, central stellar remnant.

Outside of the main features seen in the Ring Nebula, thin, wispy, outermore populations of gas, mostly hydrogen gas, are revealed by the Large Binocular Telescope at Mount Graham International Observatory. By combining data from multiple observatories, composite images revealing unprecedented features can be constructed.

The Ring Nebula has been imaged many times, including by Hubble and JWST.

This image shows the same astronomical object, the Ring Nebula, in three different views: from Hubble (at left), from JWST’s NIRCam instrument (center), and from JWST’s MIRI instrument (right). At longer wavelengths, features unseen in visible light spectacularly appear, and JWST is sensitive enough to unveil many of them for the first time.

That data pinpointed ionized gas, hydrogen molecules, and complex carbon-rich compounds.

This three-panel animation fades between visible light (Hubble) views, near-infrared (JWST NIRCam) views, and even cooler mid-infrared (JWST MIRI) views. This planetary nebula is one of the most well-studied in all of history, with each new set of observations in each wavelength range revealing specific atomic, molecular, and ionization features.

But unlike its deceptive appearance, it’s much more than just a ring.

This mid-infrared view of the Ring Nebula, constructed from multiple filters using JWST’s MIRI, reveals information about the density and temperature of material present. But this is only a two-dimensional view of a true three-dimensional object.

To reveal its true structure, scientists required different, velocity-sensitive data.

This photograph shows the eight separate dish elements that make up the Submillimeter Array on the summit of Mauna Kea. Unlike optical and infrared telescopes, these radio telescopes can observe much cooler, longer-wavelength signals, mapping out neutral molecules such as carbon monoxide in the process.

Using the Submillimeter Array, astronomers mapped out ionized carbon monoxide.

This map shows the carbon monoxide signature as mapped by the Submillimeter Array. Although it looks blurry and ill-defined, the spectral data of each component of this signature can be extracted, enabling a full 3D reconstruction of the CO gas distribution surrounding this nebula.

The shifted light from these molecules reveals how quickly they’re moving at each location.

Submillimeter Array data of the carbon monoxide molecules around the Ring Nebula can have its 3D positions inferred from the spectral shift of the light coming from each location, revealing an overall barrel-like shape, with a large extended central cavity, for the 3D structure of the Ring Nebula.

Astronomers can then reconstruct the Ring Nebula’s full three-dimensional shape.

This schematic shows the geometry and structure of the Ring Nebula (Messier 57) as it would appear if viewed from the side, rather than along our line-of-sight. This shows the nebula’s wide halo, inner region, lower-density lobes of material stretching toward and away from us, and the prominent, glowing disc. New JWST and Submillimeter Array data has now augmented this earlier Hubble-based picture.

It’s a barrel-shaped shell of material, launched approximately 6000 years ago.

By tracing the features of different species of gaseous and ionized molecules, scientists can reconstruct a variety of features: a barrel-shaped “ring” of heated material that’s about 6000 years old, with a tilted, younger polar outflow blowing out along the “long axis” of the nebula’s configuration.

Inside the “barrel,” a younger, slightly tilted polar outflow clears out the interior.

Although JWST is capable of probing long-wavelength, infrared features, there are even cooler gas features that can only be revealed in radio wavelengths. Carbon monoxide data points to a “skin” of neutral gas surrounding and outside of the more energetic features that JWST and Hubble are sensitive too.

Folding in JWST data reveals a thin “skin” of neutral molecules surrounding the barrel’s ionized gas.

This view showcases a three-dimensional model of the Ring Nebula, as well as its inner and outer structures, as we would experience it if it were rotated a full 360 degrees around the main ring structure. Perpendicular lobes, spike-rich emission emerging from dense knots, and the outer halos are all visible.

This work refines and enhances earlier Hubble-based understandings of the Ring Nebula’s structure.

The dying star’s remnant is located directly at the Ring’s center.

Based solely on JWST data, tracing out the brightest portion of the Ring Nebula points to a central location that’s offset from the white dwarf remnant. This mismatch potentially indicates the presence, and location, of a faint companion star.

Finding a central companion star — hitherto undetected — will complete this picture.

By leveraging the infrared JWST (left) and radio-wave Submillimeter Array (right) data together, one can determine where the central remnant star that created the Ring Nebula must be. The two inferred locations aren’t identical, indicating a potential companion star playing a role in the creation of this nebula.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.