“Amazing” – Cat’s Eye Nebula first seen in 3D

An image of the Cat’s Eye Nebula taken by the Hubble Space Telescope. Credit: NASA / CXC / SAO / K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

Astronomers discover rings with near-perfect symmetry in the Cat’s Eye Nebula

The researchers built the first computer-generated three-dimensional model of the Cat’s Eye nebula, revealing a pair of symmetrical rings around the nebula’s outer shell. The symmetry of the rings suggests that they were formed by a precession jet originating from the nebula’s central star. This provides strong evidence of a binary star in the center of the nebula. The study was recently published in the journal Royal Astronomical Society Monthly Notices and was led by Ryan Clairmont.

A planetary nebula forms when a dying star expels its outer layer of gas, creating a colorful shell-like structure characteristic of planetary nebulae. NGC 6543, or Cat’s Eye Nebula, is one of the most complex planetary nebulae known. It is located about 3,000 light years from Earth and can be seen in the constellation of Draco. The Cat’s Eye Nebula was also seen in great detail from the Cat's Eye Nebula

A side-by-side comparison of the three-dimensional model of the Cat’s Eye Nebula created by Clairmont and the Cat’s Eye Nebula photographed by the Hubble Space Telescope. Ryan Clairmont (left), NASA, ESA, HEIC and The Hubble Heritage Team (STScI / AURA) (right) (CC BY-NC-SA 4.0).

The nebula’s mysterious structure confused astrophysicists because it could not be explained by previously accepted theories for the formation of planetary nebulae. More recent research has shown that precession jets were potential modeling mechanisms in complex planetary nebulae such as NGC 6543, but lacked a detailed model.

Clairmont, an astronomy enthusiast, decided to try to establish Cat’s Eye’s detailed 3D structure to learn more about the potential mechanism that gave it its intricate shape. To do this, he turned to Dr. Wolfgang Steffen of the National Autonomous University of Mexico and Nico Koning of the University of Calgary, who developed SHAPE, a 3D astrophysical modeling software particularly suitable for planetary nebulae.

The researchers used spectral data from the San Pedro Martir National Observatory in Mexico to reconstruct the three-dimensional structure of the nebula’s three-dimensional structure. These provide detailed information on the internal movement of the material in the nebula. Along with this data and images from the Hubble Space Telescope, Clairmont built a new 3D model, establishing that rings of high-density gas were wrapped around the outer shell of the Cat’s Eye. Surprisingly, the rings are almost perfectly symmetrical to each other, suggesting that they were formed by a jet, a stream of high-density gas ejected in opposite directions from the nebula’s central star.

The jet showed a precession, similar to the swinging motion of a top. When the jet swung, or pressed, it drew a circle, creating the rings around the cat’s eye. However, the data indicates that the rings are only partial, which means that the precession jet never completed a full 360-degree rotation and that the emergence of the jets was only a short-lived phenomenon. The duration of the outflows is important information for the theory of planetary nebulae. Since only binary stars can power a precession jet in a planetary nebula, the team’s findings are strong evidence for the existence of such a system at the center of Cat’s Eye.

Since the angle and direction of the jet changed over time, it likely formed all the features seen in the cat’s eye, including the jets and knots. Using the three-dimensional model, the researchers were able to calculate the inclination and opening angle of the previous jet based on the orientation of the rings.

Ryan Clairmont, the lead author of the paper and now a potential undergraduate student at Stanford University, said, “When I first saw the Cat’s Eye Nebula, it was amazing. It had a beautiful and perfectly symmetrical structure. I was even more surprised that its 3D structure was not fully understood. “

He continued: “It was very rewarding to be able to do astrophysical research on my own that actually has an impact in the field. Precession jets in planetary nebulae are relatively rare, so it’s important to understand how they contribute to the formation of more complex systems like the eye. Ultimately, understanding how they are formed provides information on the eventual fate of our Sun, which will one day become a planetary nebula itself. “

Reference: “Morphokinematic Modeling of the Cat’s Eye Symmetrical Point, NGC 6543: Ring-like Remains of a Jet Precessing” by Ryan Clairmont, Wolfgang Steffen and Nico Koning, 15 September 2022, Royal Astronomical Society Monthly Notices.
DOI: 10.1093 / mnras / stac2375

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