IRAS 23166+1655 (left) and WR 104 (right). Credit: (left) ESA/NASA & R. Sahai;
(right) U.C. Berkeley Space Sciences Laboratory/W.M. Keck Observatory

 

Unwinding the Spirals
Oct 22, 2010

Helical structures abound in the Universe. Galaxies, planetary nebulae, hurricanes: all exhibit characteristic shapes that have been identified in past Picture of the Day articles as electrically induced formations.

The term "planetary nebula" was first applied in the early days of telescopic observation, since they appeared to be round, with a faint greenish tinge, similar to the planet Uranus, so it was assumed that they might also be gas giant planets.

Planetary nebulae are observed to come in all shapes and sizes: round, elliptical, nested cylinders, and now helical spirals. Such features are said to be the result of shock waves, or stellar winds blowing off the parent star, crashing into the slower material ahead of them.

Consensus astronomy sees planetary nebulae as the final stage of senescent stars when they drive off their outer atmospheric layers because of increased internal radiation pressure. It has been suggested that stars like our Sun, middleweights in the galactic stable, do not undergo supernova eruptions as they end their lives—no explosive demise in a blaze of glory. Instead, their gaseous envelopes drift away into space.

According to a recent press release, IRAS 23166+1655 is an example of that process, except that it comprises a binary system, so the fumes of gas and dust are being gravitationally drawn toward a companion star in an 800 year orbit. As stated, the spinning pair thus create a glowing spiral of stellar material as they dance around one another.

WR 104, on the other hand, is a Wolf-Rayet (WR) star, named for astronomers Charles Wolf and Georges Rayet. WR type stars are thought to be three times the diameter and 25 times more massive than the Sun, with a luminosity over 100,000 times greater. The intense radiative output of WR 104 is theorized to blow off its outer layers through "photon pressure." This so-called "stellar wind" flying off the rapidly rotating star is what the Keck telescope image is thought to represent.

As has been discussed in past articles, almost 70 years ago Dr. Charles Bruce noted that planetary nebulae appeared to be similar to electric discharges. Rather than spheres, he reasoned that their shapes were hourglasses, with a central star obscured by a dusty torus, since nebular shapes are similar to the twisted filaments and spirals of electric discharges in plasma.

Electric discharges in a cloud of plasma form double layers along their current axes. Positive charges build up on one side of the cloud and negative charges on the other. A powerful electric field develops between them. If enough current is applied to the double layer it glows otherwise, it remains in "dark mode" and will be invisible. Electric currents flow along the double layers. In plasma, the currents spiral into filaments, which attract each other. However, instead of merging they wind around, sometimes "pinching down" into arc mode discharges. If enough current passes through the plasma cloud, a z-pinch in the double layer will initiate the formation of a star.

Electric double layers can be "pumped" with energy from galactic Birkeland currents in which they are immersed. The excess input power pushes them into "glow mode," while increased flux density draws matter from the surrounding space into filaments, igniting the nebular "gases" electrically

Could this be what is observed in both examples shown above? That question might never be answered experimentally, because the only way to detect double layers in space is to send spacecraft equipped with Langmuir probes through them. However, more local experiments within the Solar System have found double layers like those created in the laboratory. Such structures are known as magnetospheres, magnetotails, cometary nuclei, and comet tails.

Nobel laureate Hannes Alfvén wrote: "...it is unpleasant to base far-reaching conclusions on the existence of a structure which we cannot detect directly. But the alternative is to draw far-reaching conclusions from the assumption that in distant regions, the plasmas have properties which are drastically different from what they are in our own neighborhood. This is obviously far more unpleasant ..."

Stephen Smith