Surprising Astronomy: "Planetary Nebulae"

"Calabash" (Hubble 0828)

    Astronomers of old called them "planets" because  they looked like planets when viewed with earth bound telescopes. Recently, higher resolution telescopes showed them to be distant nebulae; results of stars in their later life stages, cooling, and loosing much of their gassy exterior. A magnetic field of the core caused by orbiting ions restrains the jet to move only out of the poles. These jets send particles into that gas causing the gas to glow and to also move out with increased velocity. There can also be an unseen companion that drags material away from the dying star, causing spiral/ring effects. Black holes are not necessarily involved. Theories as to the true nature of these strangely shaped nebulae are still being developed.
    Ultraviolet images in 1978 showed that dying stars continue to blow winds long after they eject their outer gaseous layers. Then, from 1994 onward, startling detailed images by the orbiting Hubble telescope emerged. Private discussions about them circulated in the astronomy world, but not much was said publicly as these images completely upset previous theories on the disposition of stars.  See

            Hubble Image nebula 0828 ("Calabash")  
            Hubble Image MyCn18 (MyCn18)
            Hubble Image MZ3 ("Ant Nebula"; Menzel 3)
            Hubble Image (Jodrell) ("Bug")  
            Hubble Image ("Boomerang")
            Hubble Image ("Butterfly")
            Hubble Image ("Eta Cartinae")
                      
    Good reproductions of the Calabash, the Ant nebula and other nebula images were published in the July, 2004 Scientific American (some of these facts and images are copied from that article). I came across the 0828 image by accident a few years ago "somewhere on the internet".
    Our present ignorance about how these nebula work is often obscured by journalistic babble. E.g.: "New information ultimately upends the best of theories. Progress is often disruptive. It clears out old niches and prepares the way for big (and often disorientating ) leaps forward" (babble  continues).
    One characteristic evident of these hour-glass shaped nebulae is that the are magnetically controlled. The nature and origin of such magnetic fields have not been discussed in public as far as I can tell. So I will venture an explanation:

    Up to the present such a star has  been fusing hydrogen into nuclei of larger atomic number (Z) along with the accompanying neutrons to make nuclei of atomic weights (W) ever greater. The main star body has been so hot that electrons no longer  associate with the proton/neutron nuclei, so the nuclei bundle together as gravity may attract them to one another while their positive charge has also established a stable standoff distance. Thermal agitation adds some standoff distance, on the average.
    Fusion has advanced far past the atomic number of iron Z=26, W=55, which we know on earth to divide exothermic fusions from the exothermic FISSION of heavy atoms. There is so much extra energy, pressure and density in the star interior, that it has become the natatorium for heavy elements in my opinion. It is even likely that nuclei have been fused that are beyond the highest Z (Neptunium, 93/237) that  we know to exist on our cool earth. Such higher Z nuclei are formed and decay with some equilibrium and concentration, and likely have congregated near the center of a large core.
.     Mid-life: First, it is presumed that this sun-like star is now in a later stage of its life. Previously, it enjoyed the above mentioned sun like life, being relatively large in diameter and engaged in hydrogen gathering and hydrogen fusion for some time. But of late it is becoming starved of hydrogen on its journey through space. It has not encountered a fresh bounty of drifting hydrogen fuel. So it decays, using up whatever hydrogen it previously stored. Or it might be in a late cookie monster stage where it ate too much, got too big, and can no longer satisfy its appetite for hydrogen cookies.
    This aging star will have some rotational angular momentum, as nothing is ever so still as to not possess any. The heavier nuclei gravitate to the aging star's center in proportion to their atomic weight W; the heaviest toward the core's center. At that moment, this  is not important. Some shells or strata of various radii may develop according to some preferred groupings of similar nuclei.
    Mid-life Crisis: Having the misfortune in its journey through space to not recently encounter some drifting clouds of fresh hydrogen, this star begins to cool. In so cooling, it shrinks in diameter as lower temperatures all around justify a smaller radius.  Soon, the rotational  rate (spin) increases. The outer spinning lamina shells will most certainly contain an excess of electrons. Such a rotating shell of charges will evolve a magnetic field aligned along the average axis of spin. Sub shells or spheres might develop where the angular momentum was too small to homogenize or consolidate, so that a multipole star mass will develop. But we will just concentrate on a one-body dipole-like spin model,
    Death Throes: As cooling progresses, the star's overall radius shrinks,  the spin rate of those lamina, especially the core, that have shrunken increases dramatically just as exhibition ice skaters demonstrate by drawing in their arms. The charged lamina, likely gasses heavily charge with electrons that long ago were stripped from their nucleus, comprise a strong circulating current that creates a strong magnetic field with poles on the spin axis.
    At the same time many high Z nuclei, really unstable isotopes, will come to prominence as core density increases. Now it does matter that the Highest Z nuclei are concentrated near the core center++; as they are the least stable of the lot and most prone to fission.  As the core also cools, it's greater pressure and density cause the high Z nuclei to be compressed ever closer together, tending toward a critical mass  Eventually, this core goes into a soft critical condition where profuse and perhaps prolonged fission occurs. The product nucleons are charged; each fission propels charged particles having various velocities. The spun magnetic field is strong enough to constrain their average journey to be only along the magnetic field lines; along either direction of the the spin axis. Though launched in random directions, the final velocity of these launched and positively charged nucleons is only along the spin axis, in either direction.
    Calabash Lives: Thus, the planetary nebulae Calabash evolves; Calabash lives! The expelled particle jet encounters the low pressure of free space, expansion as a gas cloud occurs as in the jet of a rocket, into a parabola of rotation. Similar jets occur as we see in either end of this dying star, Calabash. A precursor, faint, far ahead of the main plume and nearly on the projected spin axis, is seen a signature of the "trigger" fission explosion responsible for generating this impressive display. And we now know the evolution of the hour glass pattern of planetary nebulae.