by Ann » Thu May 25, 2023 2:07 pm
The structure of the Cat's Eye Nebula is very intricate: The twirls, curls, shocks, nested spheres, inner spirals and jets are all consequences of mass loss. The question is how these structures have come about.
To me there appear to be similarities between central stars of planetary nebulas and Wolf-Rayet stars:
The edge of nebula M1-67 surrounding Wolf-Rayet star WR 124 is also tattered and broken, although less so than the outer edge of the halo surrounding the Cat's Eye Nebula. To me, the outer boundary of the halo of the Cat's Eye Nebula suggests a violent mass loss event. But the nested shells inside the halo suggest something else to me - maybe something similar to Wolf-Rayet star WR 140?
Science Alert wrote about WR 140:
The star is what is known as a colliding wind binary, consisting of an extremely rare Wolf-Rayet star, called WR 140, and a hot, massive O-type star companion – another rare object.
...
Both stars in the WR 140 system have fast stellar winds, blowing out into space at around 3,000 kilometers (1,864 miles) per second. Both are therefore losing mass at a pretty furious rate.
...
When the two stars enter periastron – a distance about a third greater than the distance between Earth and the Sun – they become close enough that their powerful winds collide.
This produces shocks in the material around the stars, accelerating particles and generating energetic radiation, such as X-rays. These colliding winds also induce episodes of dust formation as the material in the colliding stellar wind cools.
...
Because the binary star's orbit has a 7.94-year period, the wind collision and dust production occur like clockwork every 7.94 years. This means you can count the rings of the nebula around the binary, like tree rings, to determine the age of the outermost visible dust shell.
Click to play embedded YouTube video.
Could the central star of the Cat's Eye nebula be a binary star? I guess that's possible:
Wikipedia wrote:
It is also suspected that the central WR:+O7 spectral class PNN star, HD 164963 / BD +66 1066 / PPM 20679 of the nebula may be generated by a binary star. The existence of an accretion disk caused by mass transfer between the two components of the system may give rise to polar jets, which would interact with previously ejected material. Over time, the direction of the polar jets would vary due to precession.
Outside the bright inner portion of the nebula, there are a series of concentric rings, thought to have been ejected before the formation of the planetary nebula, while the star was on the asymptotic giant branch of the Hertzsprung–Russell diagram. These rings are very evenly spaced, suggesting that the mechanism responsible for their formation ejected them at very regular intervals and at very similar speeds. The total mass of the rings is about 0.1 solar masses. The pulsations that formed the rings probably started 15,000 years ago and ceased about 1000 years ago, when the formation of the bright central part began (see above).
Further, a large faint halo extends to large distances from the star. The halo again predates the formation of the main nebula. The mass of the halo is estimated as 0.26–0.92 solar masses.
Oh, and - as for my comparison with the central star of the Cat's Eye Nebula and a WR star, Wikipedia said that the central star of the Cat's Eye Nebula has a WR-like spectrum:
Surface temperature for the central PNN is about 80,000 K, being 10,000 times as luminous as the sun. Stellar classification is O7 + [WR]-type star.
Ann
[float=left][img3="Cat's Eye Wide and Deep.
Image Credit & Copyright: Jean-François Bax, Guillaume Gruntz"]https://apod.nasa.gov/apod/image/2305/NGC6543_wide1024.jpg[/img3][/float][float=right][img3="The Cat's Eye Nebula. Nordic Optical Telescope and Romano Corradi (Isaac Newton Group of Telescopes, Spain) "]https://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Heic0414b.jpg/1024px-Heic0414b.jpg[/img3][/float]
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The structure of the Cat's Eye Nebula is very intricate: The twirls, curls, shocks, nested spheres, inner spirals and jets are all consequences of mass loss. The question is how these structures have come about.
To me there appear to be similarities between central stars of planetary nebulas and Wolf-Rayet stars:
[img3="Wolf Rayet star WR 124 and the nebula M1–67 surrounding it by James Webb. Credits: NASA, ESA, CSA, STScI, Webb ERO Production Team"]https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Wolf-Rayet_124_%28NIRCam_and_MIRI_composite_image%29.tif/lossy-page1-1024px-Wolf-Rayet_124_%28NIRCam_and_MIRI_composite_image%29.tif.jpg[/img3]
The edge of nebula M1-67 surrounding Wolf-Rayet star WR 124 is also tattered and broken, although less so than the outer edge of the halo surrounding the Cat's Eye Nebula. To me, the outer boundary of the halo of the Cat's Eye Nebula suggests a violent mass loss event. But the nested shells inside the halo suggest something else to me - maybe something similar to Wolf-Rayet star WR 140?
[float=left][img3="Nested shells around binary star WR 140. Credits: JWST/MIRI/Judy Schmidt"]https://www.sciencealert.com/images/2022/08/webb-image-of-wr-140-full-642x839.jpg[/img3][/float][float=right][img3="Nested shells around the main structure of the Cat's Eye Nebula. Credits: NASA, ESA, HEIC, and The Hubble Heritage Team."]https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Catseye-big.jpg/1024px-Catseye-big.jpg[/img3][/float]
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[quote][url=https://www.sciencealert.com/extraordinary-phenomenon-in-space-captured-by-spellbinding-new-image]Science Alert[/url] wrote about WR 140:
The star is what is known as a colliding wind binary, consisting of an extremely rare Wolf-Rayet star, called WR 140, and a hot, massive O-type star companion – another rare object.
...
Both stars in the WR 140 system have fast stellar winds, blowing out into space at around 3,000 kilometers (1,864 miles) per second. Both are therefore losing mass at a pretty furious rate.
...
When the two stars enter periastron – a distance about a third greater than the distance between Earth and the Sun – they become close enough that their powerful winds collide.
This produces shocks in the material around the stars, accelerating particles and generating energetic radiation, such as X-rays. These colliding winds also induce episodes of dust formation as the material in the colliding stellar wind cools.
...
Because the binary star's orbit has a 7.94-year period, the wind collision and dust production occur like clockwork every 7.94 years. This means you can count the rings of the nebula around the binary, like tree rings, to determine the age of the outermost visible dust shell.[/quote]
[youtube]https://www.youtube.com/watch?v=AdtJA-seD8Q[/youtube]
Could the central star of the Cat's Eye nebula be a binary star? I guess that's possible:
[quote][url=https://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Kinematics_and_morphology]Wikipedia[/url] wrote:
It is also suspected that the central WR:+O7 spectral class PNN star, HD 164963 / BD +66 1066 / PPM 20679 of the nebula may be generated by a binary star. The existence of an accretion disk caused by mass transfer between the two components of the system may give rise to polar jets, which would interact with previously ejected material. Over time, the direction of the polar jets would vary due to precession.
Outside the bright inner portion of the nebula, there are a series of concentric rings, thought to have been ejected before the formation of the planetary nebula, while the star was on the asymptotic giant branch of the Hertzsprung–Russell diagram. These rings are very evenly spaced, suggesting that the mechanism responsible for their formation ejected them at very regular intervals and at very similar speeds. The total mass of the rings is about 0.1 solar masses. The pulsations that formed the rings probably started 15,000 years ago and ceased about 1000 years ago, when the formation of the bright central part began (see above).
Further, a large faint halo extends to large distances from the star. The halo again predates the formation of the main nebula. The mass of the halo is estimated as 0.26–0.92 solar masses.[/quote]
Oh, and - as for my comparison with the central star of the Cat's Eye Nebula and a WR star, Wikipedia said that the central star of the Cat's Eye Nebula has a WR-like spectrum:
[quote]Surface temperature for the central PNN is about 80,000 K, being 10,000 times as luminous as the sun. Stellar classification is O7 + [WR]-type star.[/quote]
Ann