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Comet West in its most dramatic display in March, 1976
 

May 10, 2007
When Comets Break Apart

The unexpected breakup of comets, some at considerable distances from the Sun, has long baffled comet researchers.  But there is no mystery if comets are solid bodies discharging electrically as they move into regions of different charge in the Sun’s electric field.

In 1976, Comet West never approached closer than 30 million kilometers from the Sun. So when a disruption occurred and the comet split into four fragments (subsequent to the display pictured above), astronomers were shocked.

More recently, the explosive break up of Comet Linear in the summer of 2000 provoked even greater amazement. The event occurred well over a hundred million kilometers from the Sun.

In fact, eighty percent of comets that split do so when they are far from the Sun, according to Carl Sagan and Ann Druyan, authors of the book Comet.  Comet Wirtanen fragmended in 1957 a little inside the orbit of Saturn, and something similar occurred to Comet Biela/Bambert.

Strangely, other comets have approached much closer to the Sun and not broken apart. The perihelion of the Great Comet of December 1680, studied by both Newton and Halley, was less than 100,000 kilometers from the Sun, but did not split.

Noting such considerations, Sagan and Druyan write: “The gravitational tides of the Sun or unequal heating cannot be sole causes of the splitting of comets.  We still do not know why comets split”.

In a paper published in the 1960's Dr. Brian G. Marsden, an astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, drew attention to the anomaly of comet fragmentation. Discussing the “sungrazing” comets, he noted that two instances,—1882 II and 1965 VIII—look as if they had split apart near aphelion (their farthest distance from the Sun), well beyond the orbit of Neptune and far above the ecliptic plane. Moreover, the relative velocity of their separation was far greater than could be due by solar heating.

Marsden wrote: “Although most of the comets observed to split have done so for no obvious reason, one really does require an explanation when the velocity of separation is some 20 % of the velocity of the comet itself!  A collision with some asteroidal object at 200 A.U. from the sun, and 100 A.U. above the ecliptic plane, even though it would only have to happen once, is scarcely worthy of serious consideration”.

Thus, according to Sagan and Druyan, “the problem is left unsolved”. But the authors appear to have found a clue without recognizing its significance. “Splitting and jetting may be connected … At the moment Comet West split, the individual fragments brightened noticeably, and propelled large quantities of dust into space in the first of some dozen bursts”.  The same could be said for the more recent Comet Linear breakup.

Why would intense, high-velocity jets and explosions of dust, traveling at supersonic speeds, precede the fragmentation of a comet nucleus? In the electrical model of comets, the answer is obvious. The behavior of comets will never be understood in simple mechanical terms because they are electrified bodies orbiting within the plasma environment of an electrified Sun. The solar plasma behaves like a very good conductor in the Sun's electrical connection with the galaxy. And just like any good conductor, the electric field within the plasma is very low. But unlike good metal conductors, the solar plasma is of extremely low density and therefore its current-carrying ability is limited.

Comets must adjust to the changing plasma potential as they move radially toward or away from the Sun. This adjustment is not so difficult on the long, slow journey through the outer reaches of the solar system. But it usually involves visible electric discharge effects as the comet dashes through the inner solar system.

The comet nucleus behaves like a capacitor. And as any electrical engineer knows, if a discharge occurs within a capacitor it will explode violently. That is what causes comet nuclei to fragment and it is why the event is commonly preceded by outbursts far more energetic than could be explained by sublimating ices. The energy is provided by the stored electrical energy within the nucleus.

All that is required to trigger the comet fragmentation is an electrical breakdown within the comet. In this sense, it may be analogous to the electrical breakdown evident in an earthquake. And that breakdown in the comet may happen with any sudden change in the solar plasma environment. The more sudden the change in the comet's electrical environment, the more likely that flaring and fragmentation will occur. Electrical theorist Wallace Thornhill has noted that the remarkable 300,000 km wide flare-up of comet Halley between the orbits of Saturn and Uranus followed some of the largest solar flares ever recorded (under the assumptions of the “snowball ”theory of comets, the nucleus should be frozen and inert at that distance).

The electrical model also explains why we should expect long-period comets to put on a brighter display than short-period comets. The long-period comets spend a longer time in a region of lower plasma potential than the short-period comets. Consequently, their voltage difference on their approach to the Sun will be higher, leading to a brighter and more energetic discharge.

The “puzzling” absence of small (house-sized) comets may be explained in equally simple terms electrically. Such small objects would readily lose their charge before reaching the inner solar system. But a comet nucleus kilometers in diameter presents a much different electrical profile and its charge could not be dissipated so quickly.

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