An international team of scientists has produced the clearest three-dimensional view yet of the Ring Nebula - one of the night sky's most iconic celestial objects.
The Ring Nebula is perhaps one of the most photographed objects in the night sky, dating back to its first image in 1886, but its intrinsic structure has been debated for as long as it has been observed.
Now, using Submillimeter Array (SMA) advanced radio-wavelength mapping techniques, the team has determined that the nebula has an ellipsoidal structure, resolving the longstanding debate.
By mapping the emission from carbon monoxide (CO) gas, the observations provided valuable insights into its structure. The CO emission highlights cold molecular gas surrounding the hot gas and dust seen in images captured by the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST).
The findings are the result of collaborative work by researchers from institutions including Rochester Institute of Technology, the Center for Astrophysics at Harvard & Smithsonian, Macquarie University, the Jet Propulsion Laboratory, and the National Radio Astronomy Observatory, alongside The University of Manchester's Professor Albert Zijlstra.
Professor Joel Kastner from Rochester Institute of Technology, said: "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.
"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 the nebula might be ring-shaped or resemble a soap bubble. However, the new model, based on SMA data, confirms its ellipsoidal structure and provides a more detailed understanding of the velocities and locations of carbon monoxide molecules ejected by the dying star that generated the Ring Nebula - detail that can't be inferred from telescopic images, even using powerful NASA space observatories like HST and JWST.
The team's findings indicate that roughly 6,000 years have elapsed since the dying star, then a red giant, ejected the molecular gas that envelopes the nebula. The SMA data also reveal high-velocity blobs of gas observed at each end of the ellipsoidal shell suggesting the presence of a companion star influencing the nebula's formation.
Professor Zijlstra from The University of Manchester said: "The Ring Nebula is an iconic object in the night sky, a favourite for professional and amateur astronomers alike. But understanding the real structure of this nebula has been very hard. The appearance of a ring is deceptive. The new data reveals a slightly deformed barrel seen from the top, with a large bubble coming out through the top and bottom of the barrel. In JWST images, these are seen superposed, but the new data allows us to separate them from their different velocities. The bubble is inclined with respect to the barrel. Now we will need to find out how a star can eject two such different structures in different directions! That remains a bit of a mystery."
These findings follow similar research done by Kastner and his team on the Southern Ring Nebula, one of the first objects observed by the JWST. This new approach of using the combination of SMA mapping and JWST imaging to tease out the 3D structures of these objects gives scientists a fresh way to understand the final, dying stages of sun-like stars.
Kastner added: "The stars that generate planetary nebulae like the Ring and Southern Ring may have produced much of the carbon in the Universe.
"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."
The research will be presented at the 245th meeting of the American Astronomical Society on 12 - 16 January 2025 and has been sent for publication in a journal .
