Astronomy

Ring Nebula structure revealed

Thursday, January 23, 2025

RIT Professor Joel Kastner leads a team that has revealed the true three-dimensional structure of the Ring Nebula, showing it as an ellipsoid. Using radio-wavelength mapping of carbon monoxide emissions, the team provides new insights into the nebula's formation and structure.

The Ring Nebula, one of the most photographed objects in the night sky since its first image was captured in 1886, has had its intrinsic structure debated for over a century. Now, a research team led by Professor Joel Kastner from Rochester Institute of Technology’s Chester F. Carlson Center for Imaging Science and School of Physics and Astronomy has obtained the clearest three-dimensional view of the nebula.

RIT professor leads research showing Ring Nebula structure

Image credit: NASA/ESA/O'Dell/Ferland/Henney/Peimbert/Thompson; SMA image and SMA/JWST image overlay: Joel Kastner/RIT

The team used radio-wavelength mapping of carbon monoxide (CO) gas emissions through the Submillimeter Array (SMA) to determine that the Ring Nebula has an ellipsoidal shape. The CO emission reveals cold, molecular gas that surrounds the hot gas and dust observed in images from the Hubble Space Telescope (HST) and, more recently, the James Webb Space Telescope (JWST).

“We looked at the data and the ellipsoidal structure was obvious, so we could put together a simple geometrical model. Now, we understand the structure of this nebula,” said Kastner. “The James Webb Space Telescope gives us a collapsed image of what the object looks like in the sky. The SMA allows us to accurately measure the velocities of the molecular gas in the nebula, so we can see what's moving toward or away from us.”

Previous theories suggested that the nebula might be ring-shaped or have a soap bubble structure, but the model derived from SMA data revealed it is an ellipsoid. The data pinpoint the velocities and locations of carbon dioxide molecules ejected by the dying star that created the Ring Nebula, providing insight into its three-dimensional structure, which can't be inferred from telescopic images alone.

The team’s modeling suggests that roughly 6,000 years have passed since the former red giant star expelled the molecular gas that now surrounds the nebula. SMA data also reveal evidence of the influence of a companion star, located at the center of the nebula, through high-velocity gas blobs ejected from each end of the ellipsoidal shell.

This work follows similar research on the Southern Ring Nebula, one of the first objects observed by the JWST. Kastner and his team are also behind a paper that offers a deeper understanding of the Southern Ring's structure, set for publication in the spring of 2024. The new approach, combining SMA mapping and JWST imaging, offers scientists a fresh perspective on the final, dying stages of sun-like stars.

One of the most photographed images in the night sky comes into focus for the first time

“The stars that generate planetary nebulae like the Ring and Southern Ring may have produced much of the carbon in the universe,” said Kastner. “We can watch that carbon on its way to being recycled into the next generation of stars and planets when we observe these amazing objects.”

Kastner is the lead author of a paper on this new three-dimensional view of the Ring Nebula, which is about to be submitted to The Astrophysical Journal. The research team includes RIT astrophysical sciences and technology graduate students Diana Ryder and Paula Moraga Baez (who received her Ph.D. in Fall 2024). Other co-authors are David Wilner (Center for Astrophysics, Harvard & Smithsonian), Orsola De Marco (Macquarie University, Australia), Raghvendra Sahai (Jet Propulsion Laboratory), Al Wootten (National Radio Astronomy Observatory), and Albert Zijlstra (University of Manchester, UK). Kastner’s research on molecular gas in planetary nebulae is supported by a grant from the National Science Foundation.

Ring Nebula captured by Webb

Image credit: NASA, ESA, Hubble Heritage Project (STScI, AURA)

The Ring Nebula, located about 2,500 light-years from Earth, is a stunning example of a planetary nebula, formed when a star sheds its outer layers as it nears the end of its life. The NASA/ESA/CSA James Webb Space Telescope has captured this nebula in unprecedented detail, offering extraordinary spatial resolution and spectral sensitivity. These observations reveal intricate features across both infrared wavelengths, with the NIRCam (Near-InfraRed Camera) showing the filament structure of the inner ring, while MIRI (Mid-InfraRed Instrument) highlights the concentric features in the outer ring.

The nebula contains approximately 20,000 dense globules rich in molecular hydrogen, while its inner region consists of very hot gas. The main shell has a thin ring of polycyclic aromatic hydrocarbons (PAHs) emitting enhanced light, and just beyond the outer ring, roughly ten concentric arcs are observed. These arcs are believed to be the result of interactions between the central star and a low-mass companion orbiting at a distance similar to that of Earth to Pluto.

The Ring Nebula’s shape resembles a distorted doughnut, with a brightly colored material stretching outward from one of its poles. While the center appears empty, it actually contains low-density material that extends in and out, creating a rugby ball-like shape.

First discovered in 1779 by astronomers Antoine Darquier de Pellepoix and Charles Messier, the Ring Nebula has long been a subject of study, offering valuable insights into the life cycle of stars. These observations from the James Webb Space Telescope continue the work of earlier research, including that by the Hubble Space Telescope.