Plasma Planetary Nebula
Plasma is not explicitly associated with a planetary nebula but this association is clear.
excerpt from Wikipedia (and most others below):
A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
The Hubble Space Telescope showed that while many nebulae appear to have simple and regular structures when observed from the ground, the very high optical resolution achievable by telescopes above the Earth's atmosphere reveals extremely complex structures.
'Ionized gas' is plasma and plasma naturally forms filaments so the resulting structures from plasma behaviors are photogenic.
Images taken in ultraviolet or X-ray reveal the electrical activity in these shells of gas because synchrotron radiation spans wavelengths beyond the visible range.
from Chandra page titled "A planetary Nebula Gallery" dated 10.10.12
twenty one planetary nebulas within about 5000 light years of the Earth have been observed. The paper also includes studies of fourteen other planetary nebulas, within the same distance range, that Chandra had already observed.
About half of the planetary nebulas in the study show X-ray point sources in the center, and all but one of these point sources show high energy X-rays that may be caused by a companion star, suggesting that a high frequency of central stars responsible for ejecting planetary nebulae have companions.
Another possible X-ray point source is a plasmoid rather than a binary somehow generating higher frequency radiation extending to X-ray and appearing as a single point source.
Following links are some interesting planetary nebulae. Many have a similar pattern of two halves in the overall structure.
Click on the link for any of interest.
M27 Dumbbell Nebula - has a rough rectangular shape with a filament dividing it in half.
explanation: "Similarly to the Helix Nebula and the Eskimo Nebula, the heads of the knots have bright cusps which are local photoionization fronts."
M57 Ring Nebula - at high resolution the ring has filaments across the middle, dividing the ring in half.
M76 Little Dumbbell Nebula - has a rough 'figure 8' shape
M97 Owl Nebula - the eyes of the owl are split by the central bridge
NGC 6543 Cat's Eye Nebula is a complicated arrangement of filaments as separate arcs
IC 3568 Lemon Slice Nebula is a complete sphere inside another sphere with the inner showing many defined filaments while the outer sphere is diffused.
NGC 2392 Eskimo Nebula has a complex inner structure (not symmetrical) while "[the] outer disk contains unusual, light-year-long filaments."
Necklace nebula - its ring has structure extending away from the central star
NGC 7009 Saturn Nebula has several ellipses with active nodes at their ends.
explanation: "The nebula was originally a low-mass star that ejected its layers into space, forming the nebula."
NGC 7293 Helix Nebula is a ring of 'cometary' filaments extending from the central star
excerpt with description:
Its main ring contains knots of nebulosity, which have now been detected in several nearby planetary nebulae, especially those with a molecular envelope like the Ring nebula and the Dumbbell Nebula. These knots are radially symmetric (from the [central star] and are described as "cometary", each centered on a core of neutral molecular gas and containing bright local photoionization fronts or cusps towards the central star and tails away from it.
NGC 5189 Spiral Nebula - has a 'figure 8' shape but some arcs are broken
Only a mention of the 'point symmetric knots' and ' two dense low-ionization regions' but without explanation
my comment to the above collection:
Some of the explanations for these PNe structures are awkward.
Here is the Chandra image of 4 planetary nebulae in a page cited at the top, showing multiple wavelengths:
There is one star type often associated with planetary nebula.
excerpt from Wikipedia:
Wolf–Rayet stars, often abbreviated as WR stars, are a rare set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. Their surface temperatures range from 30,000 K to around 210,000 K, hotter than almost all other stars. They were previously called W-type stars referring to their spectral classification.
Classic (or Population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven mass loss. A separate group of stars with WR spectra are the central stars of planetary nebulae (CSPNe), post asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core.
Only a minority of planetary nebulae have WR type central stars, but a considerable number of well-known planetary nebulae do have them.
The wikipedia topic has a list of "Planetary Nebulae with WR type central stars" including NGC 5189. Including the others here makes this post too long.
The fusion model for stars (ignoring plasma behaviors) affects how these planetary nebulae are explained, relying on 'strong stellar winds' but these structures are not formed by a meteorological process.
Some WR stars even 'ceased fusion' so only the 'bare core' remains as the source of visible light. This is awkward.
This collection is interesting when knowing uncontrolled ejections and gravity alone cannot create such structures. The popular explanations are inadequate.
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for reference with the others, these interesting PNe were in that Wikipedia list but not shown above:
NGC 2452 is a roughly 5-sided object with filaments and holes
The blue haze across the frame is what remains of a star like our Sun after it has depleted all its fuel. When this happens, the core of the star becomes unstable and releases huge numbers of incredibly energetic particles that blow the star's atmosphere away into space. At the centre of this blue cloud lies what remains of the nebula's progenitor star. This cool, dim, and extremely dense star is actually a pulsating white dwarf, meaning that its brightness varies over time as gravity causes waves that pulse throughout the small star's body.
A pulsating star with gravity causing waves affecting the brightness is an odd explanation.
NGC 2867 is a sphere around a star but no explanation is found.
NGC 1371 - 1372 is a double lobed object given two NGC numbers
NGC 5315 is an irregular cloud having a rough square hole around the central star.
NGC 7026 is a rough rectangular cloud with a rough square hole to the left of the central star.
NGC 1501 Oyster Nebula is a rough sphere having structure
NGC 6751 Glowing Eye Nebula has inner and outer rings each having a complex filamentary structure
NGC 6369 Little Ghost Nebula has a wider inner ring with a diffused outer ring
MCn18 Engraved Hourglass Nebula has multiple non-concentric rings
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