The winding flare of a dying star has finally been revealed in all its 3D glory.
A team of scientists led by a high school graduate has pieced together the intricate and mysterious nebulae that make up one of the sky’s most famous stellar ghosts – the Cat’s Eye Nebula.
Their model revealed the mechanisms that shaped some of the previously unexplained aspects of the nebula’s structure.
The results may help us understand other such nebulae, and it gives us insight into what might be happening to our own Sun.
The Cat’s Eye Nebula, also known as NGC 6543, is what is known as a planetary nebula. However, they are not related to planets at all; the term originated because their round shape resembles planets. These nebulae are what’s left after a star – like the Sun – has run out of fuel to burn and reaches the end of its life.
Although planetary nebulae share common characteristics, the Cat’s Eye Nebula is one of the most complex examples discovered to date. Although it has an overall round shape, its interior is dominated by a diamond shape, like the pupil of a cat’s eye, filled with knots, shells and filaments.
It’s also one of the most studied nebulae in the sky, but some aspects of its structure are still a little confusing.
They cannot be easily explained within the current model of planetary nebula formation, called the interacting stellar wind model.
According to this model, the star swells up to a red giant (like Betelgeuse) and generates a slow stellar wind that pushes stellar matter out into space.
Then, at the end of this stage of life, the star ejects its outer matter into space, and the core, no longer supported by the outer pressure of nuclear fusion, collapses under the effect of gravity to form a white dwarf.
The very hot white dwarf generates a fast stellar wind that slams into the material in the slower wind, shocking the gas and creating shells.
The point-symmetrical bipolar shape of the Cat’s Eye Nebula does not fit this model.
“When I first saw the Cat’s Eye Nebula, I was amazed by its beautiful, perfectly symmetrical structure,” says Ryan Clairmont, who plans to study at Stanford University. “I was even more surprised that its 3D structure was not fully understood.”
So he did something about it. He enlisted the help of astronomers Wolfgang Steffen from the National Autonomous University of Mexico and Nico Koning from the University of Calgary in Canada and used SHAPE astrophysical modeling software to deconstruct what is happening inside the central region of the Cat’s Eye Nebula.
The Hubble Space Telescope, which made incredibly detailed observations of the nebula in 2008, provided some of the data used.
They also used spectral data from the San Pedro Martir National Observatory in Mexico, which reveals the movements of gas inside the nebula.
The three-dimensional model they built revealed something interesting: spiral rings of high-density gas, partially wrapped around the outer shell of the nebula, arranged symmetrically around its two lobes.
This symmetry suggests that the rings are the result of high-velocity jets ejected from the star’s poles at the center of the cat’s eye. Because the star that produced them was wobbling like a spinning top – a motion called rotational precession – it caused the jets to shoot out in a spiral shape.
Their incompleteness meant that the jets only erupted for a short time before being interrupted.
The only thing we know of that can produce a precession jet in a planetary nebula is a binary star. The star in the center of the cat’s eye is thought to be a Wolf-Rayet type, not quite a white dwarf yet, but not far off, still losing mass as it burns to the top. last of its fuel reserves. Such stars, when paired with another star, can create truly spectacular nebulae.
Previous research has suggested there may be a hidden binary companion at the heart of the Cat’s Eye Nebula. This new finding supports this interpretation.
Future observations and analyzes may take this model into account, to better interpret the strange dynamics of this fascinating nebula.
“It was very rewarding to be able to do astrophysical research myself that really has an impact in the field,” Clairmont said.
“Precessing 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 cat’s eye. Ultimately, understanding how they form provides insight into the eventual fate of our Sun, which will itself one day become a planetary nebula.”
The research was published in the Royal Astronomical Society Monthly Notices.
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