Comets and Their Mysteries

Sun (Auckland), Volume 1, Issue 27, 23 April 1927, Page 20 (Supplement)

Comets and Their Mysteries

Professor A. W. Bickerton, A.RS.M., well known in Canterbury as a scientist formerly on the staff of Canterbury College, has written the following article on comets for the “Daily Chronicle .** A COMET discovered on November 5 of this year by the Spanish astronomer, Comas Sola, is approaching the earth, and 'n its passage round the sun it may throw some light on the many unsolved problems relating to comets in general. During the long ages of ignorance these visitants were looked upon with awe. To some they seemed fiery chariots to carry the soul of a dead hero to eternal glory; to others they were portents of disaster, warning men to repent and change their evil ways. To this day they bristle with a score of unsolved problems. A normal comet consists of a nebulous. star-like head with an immense luminous tall. The tail is frequently curved, sometimes it is multiple, and where its several parts are unequal in volume, the thinner portions tend to be straightest. As the comet travels in its orbit the tail is almost always directed away from the sun. The tail is generally curved in such a way as to suggest that it has been produced by an impulse and that the luminous effect has taken time to travel. The nearer it is to the sun the greater the tail grows, and many comets show a series of partly ensphering shells being projected from their heads towards the sun.

A Swarm of Meteor*. Even the head* of a comet is so thin that stars have been seen through some of them in their densest parts. Comets, too, have passed in front of the sun with no signs of any eclipsing effect. Comets have been known to split in two and travel as two distinct parts, finally to dissipate altogether. Moreover, when the earth passes through the trail of a comet, the sky is lit up with a brilliant display of shooting stars. All of these facts suggest that a comet is simply a swarm of meteors. Let us see how the other recorded facts fit in with this theory. Comets have passed very close to planets and their moons without producing any noticeable effect upon them. Therefore they cannot, in a cosmic sense, be of great mass. Yet some of them pass so close to the sun that unless they were held together by a strong force of gravitation they would be disintegrated. Suppose a comet had' a mass onemillionth that of the earth, it would not be big en > ugh to disturb any of the planets or their satellites in a measurable degree Yet such a met-

eoric swarm w-ould have a mass of six thousand million million tons, and this, I think, is what we must take the mass of a normal comet to be. If the earth were struck by the head of a comet we should probably have a very warm time of it indeed, with no one left to tell the tale of its temperature. Strange Characteristics. And now, assuming that comets are meteoric swarms, let me offer a few suggestions to account for their many extraordinary characteristics. When a comet approaches the sun the particles composing the swarm are almost certainly held in leash by mutual gravitation. Each meteor has an independent orbit. As the comet gets close to the sun the near particles would 1 move enormously faster than the distant ones, and every orbit would be so disturbed that many of the latter would stray away from the general mass never to return. They would continue to move roughly in the comet's orbit. The crowd of particles would extend both lengthways and laterally, gradually spreading space with cosmic dust. It is this spread of material that the earth encounters, giving us the swarms of shooting stars we see when we are passing through a comet’s trail. Again, when a comet approaches the sun the disturbing action of solai attraction would cause many collisions among the meteors which form it temporarily spreading the swarm w-itl gas and other resisting material. This and the heat produced by the collision! would produce a great deal of frictioi and electricity. Both effects wouh cause luminosity, intensified by tin radiation of the sun itself. The Comet’s Tail. All of this relates to the head ot the comet. We now come to the tail, and here we come up against even knottier problems still. For more than 40 years I have examined in vain suggestion after suggestion to account for these extraordinary appendages, and I can only suppose that a comet’s tail is an electrical phenomenon. The sun is known to be an electrified body, and the friction it causes among the comet’s particles produces what is called “electrical separation.” I believe that a comet’s tail shines because of the electrical stress set up by the nucleus, helped by the sun, in the matter lying about in space. What is the origin of comets? The theory of star collisions answers the question. A couple of minor planets grazing would inevitably produce a meteoric swarm. The great majority of star collisions must be grazing impacts, producing a third body and appendages which, in cooling, must pass through the meteoric swarm stage. There is no need to wonder at the number of comets nor that space should be rich enough in particles to be lit up, in the form of a comet’s tail, when electrical disturbances make the cosmic dust luminous, *