Art. LIII.—Some Recent Evidence in favour of Impact.
[Read before the Philosophical Institute of Canterbury, 1st November, 1893.
In the years 1878-79-80, I read before the Institute a series of papers on cosmic evolution, founded on the theory of impact.
The reasoning on which the theory was based was of so obvious a character as to leave little doubt on the mind of any one acquainted with the modern doctrine of energy as to the substantial accuracy of the induction. At the same time, there seemed but small probability that any phenomena would occur, sufficiently striking to actually demonstrate the theory. It is often said, however, that it is the improbable that occurs, and this seems to apply with special force to what Nova Auriga has done to demonstrate the theory of constructive impact.
The theory suggested the existence of dark suns, and, although in my earliest papers I stated that Algol was probably a dead sun revolving around a brilliant one, there then seemed little likelihood of the surmise being proved. Many
will remember, however, that a few years ago the peculiarities of Algol were so disclosed by its spectrum as to enable us not merely to prove the existence of the dark body, but actually to measure it, to weigh it, and to estimate its velocity. It has proved itself to be almost exactly the size of our own sun, and its motion has demonstrated that there must be a still more stupendous dark globe around which Algol is revolving. It would not surprise me were Professor Boys to prove the existence of this globe by his micro-radiometer.
The peculiarities of the motions of Sirius have also shown it to have a dark companion that has not only been weighed, but in powerful telescopes can be actually seen as a feebly luminous body.
The existence of dead suns having been proved, it remained for Nova Auriga to show us the phenomena of the clashing of a pair of such suns. Between the 8th and 10th December, 1891, a star appeared where no trace of a star existed before. No eye saw it for many weeks, but it continued to record its existence automatically by photography. It showed first a considerable increase of light, then a falling-off, then in February it was seen visually. Soon many of the most powerful telescopes in the world were at work, armed with all the resources of our modern methods, and step by step the amazing character of the phenomenon became apparent. The star was double, it had unprecedented velocities, a third body was detected, it expanded into a nebula, it fluctuated in intensity, &c.
But first let me gather together the salient features of impact as described in my papers, and then compare these with the phenomena disclosed by the new star. Were two dead suns to attract each other they would increase their velocities and move in curved paths. If they grazed, their velocities would be many hundred miles per second—five hundred was mentioned as a reasonable mean in the papers. The effects of the collision would only tell on the parts meeting each other, and the impact, instead of extending to the whole body, would affect only a part. This partial impact would produce an intensely heated body that would remain between the two escaping suns, and that would have so little mass that its temperature would cause each molecule to travel in an outward direction until the mass is converted first into a hollow shell of gas (a planetary nebula), and is then finally dissipated entirely into space.
The enormous velocity of the molecules in all directions would cause the spectral lines to broaden into bands with ill-defined edges.
The two impacting suns would be sheared by the impact, would recover their sphericity, and continue to pulsate for
some time; they would spin, and show occasionally their hot and scarred sides. Were they moving in the line of sight they would have their spectral lines displaced—those of the advancing body towards the violet, and of the retreating body towards the red.
The middle body would be made up from the two original bodies, each of which in retreating would entangle highly-heated matter from the other; hence almost all the spectral lines would be identical for the three bodies, and, as the three spectra would overlap, almost all the lines would be triple.
The total light from the planetary nebula would be very feeble, and, if the two wounded suns presented to us their dark sides, the star would nearly disappear, reappearing as the rotation continued.
To put the matter into a few words: A grazing impact generally produces three bodies, a temporary and two variable stars, the temporary star becoming a planetary nebula, and then, as a rule, disappearing; the two variables showing variability for periods ranging from a few years to possibly many centuries, and in about half the cases becoming double stars.
We will now compare this statement of the results of impact, as read in my first papers before the Institute, with the observations on Nova Auriga.
The new star was triple. As the result of his study of eighty-five observers, Alfred Taylor sums up that there was no doubt of that. Professor Vogel gives the velocity of the three bodies as 420, 300, and 23 miles per second respectively. My paper in 1878 showed that when a pair of stars impact the two stars will leave each other, and a third will be produced between them. In 1879 my papers were illustrated by diagrams, one of which showed the three bodies and the character of their motions as already mentioned, the initial velocity being 500 miles per second.
The new star showed remarkable fluctuations of light, and almost absolutely disappeared, so that for several months it was not looked for. It was accidentally rediscovered, and found to be of the tenth magnitude. In my papers I called attention to the fact that the central star would increase in intensity and then slowly and steadily diminish; that the two sheared stars would recover their sphericity, would pulsate, and would also rotate, giving us extraordinary fluctuations of light. If the dark sides of each body were presented to us at once the star would obviously disappear altogether, supposing the central body to have dissipated.
Astronomers incessantly call attention to the fact of the spectrum of all three bodies being identical. Father Sid-greaves is so amazed at this coincidence, and at there being
three bodies, that he suggested a local disturbance as a solution. Obviously this identity of spectra must follow with a grazing impact. Each of the two bodies must entangle a great deal of heated matter from the other, and the middle body is, of course, actually made up of parts of the two originals.
Every element represented in the spectrum had its line or lines in triplicate—one being very broad and having two others superimposed on it. It is evident that a body expanding with incredible velocity in all directions, as I have demonstrated the central body must do, is bound to give broad bands, because of the molecular motion in all directions.
The new star became a planetary nebula. Gregory states in a long article in “Nature” that this is demonstrated in two totally different ways; and Professor Bernard, the discoverer of Jupiter's 5th satellite, says that it had become a planetary nebula of 3secs. of arc, with a tenth-magnitude star in the centre. This observation shows that at this stage the chief light was not from the nebula but from the star. Of course, this is exactly in accordance with the theory of impact, suggesting, as the latter does, a gradual and steady diminution in the intensity of the third body and the occasional reappearance of the struck stars. Professor Bernard also states that the nebula was not there at first. Hence the prediction that a partial impact must produce a hollow shell of gas or planetary nebula is in exact accord with the observation of Nova Auriga. The new star must have been produced by the impact of two very large orbs. Probably the amount sheared off may have been many times as large as our sun; yet it was not likely to have been at all a large fraction of the whole—possibly not large enough to cause the two suns to become orbitally connected into a double star; nor is it even likely to have been large enough to allow the resultant planetary nebula to become permanent; but the data at our disposal are rather conflicting. Taking the average of the best observations, I have calculated that the two impacting bodies were respectively four thousand and eight thousand times the mass of the sun; that the velocity of the smaller body at impact would have been about 4,000 miles per second, and of the larger one about 3,000 miles per second. This would give for the swiftest a velocity of 600 miles per second sixteen days after contact. There seems every reason to suppose that a very large proportion of the luminosity of the two resultant variables will die down within the first year or two. At the same time, there is a large probability that they will be periodically bright enough to show themselves for scores of years. In about ten years their habits will have become regular enough to enable us to predict their ultimate durability.
It may be very difficult to distinguish the light of the two stars, unless satisfactory photographs can be taken. If this be possible a decade should give us a fair insight into their future. I believe that astronomers will then be able to predict that their variability will last more than a century.
Should it be possible to photograph the disc of the nebula through a spectroscope, the disc presented by the different elements will probably be of different dimensions, that of the lighter atoms being the larger. I do not know if any observations to this effect were made, but in the original photographs the bands of the different elements should have been of different widths, the lighter elements being the widest.
If we could get the increased size of the disc and the width of the same elementary band at intervals of time, it would enable us to calculate the actual distance of the body. Everything points to the star being at an incredible distance—at least a hundred times as distant as Alpha Centauri, and, although its light has only just reached us, the fact that the telescope has not divided the two stars, and the small size of the nebula, suggest that it probably occurred before the hero of Crecy was born. The high velocities so long after its birth suggest that it must have been an event of the most gigantic character.
The following gives the state of the theory up to the present time:—
Summary of the Principles of Constructive Impact.
1. There are over a hundred million bright stars in the Milky Way.
2. The companion of Sirius and the dark component of Algol prove the existence of dead suns. These are possibly very numerous.
3. Stars have an independent velocity, or “proper motion,” of about ten miles a second upon an average.
4. This motion is apparently without much order, and will tend to alter the relative distance of stars, and may bring them near each other, and possibly into impact.
5. If they are brought near each other their mutual attraction will alter their velocity, and curve their courses into hyperbolic orbits. If they do not graze they will ultimately again attain their original proper motion.
6. When very near each other their attraction will cause them to be distorted into an egg-shape.
7. The tendency to collision will therefore be increased in these two ways by their mutual attraction. This increase over chance impacts will probably average about a hundred times. The increase in the case of two such bodies as our sun would be over a thousand times.
8. All impacts brought about in this way by deflection will be of a grazing character; consequently, nearly all stellar collisions will be of a grazing character.
9. The average velocity of stars at impact will be hundreds—in many cases thousands—of miles a second. The average proper motion will not appreciably affect the velocity at impact. Thus a proper motion of ten miles will only add one to a colliding velocity of one hundred.
10. A mere graze of the atmosphere of stars obviously will not cause them to coalesce. As a mean result when more than a third of each of two equal bodies collide, coalescence will ensue, but this will depend on the original proper motion. Were nine-tenths of 1830 Groombridge to collide with a similar star the remaining tenth would not be stopped in its course; it would pass on in space, the bulk of the two stars temporarily coalescing.
11. The effect of the collision will be to intensely heat the colliding part.
12. The heating effect of a graze of two stars, of two star-clusters, or two nebulæ, or even of a star plunging through a star-cluster, &c., will not appreciably extend to the parts not colliding. To emphasize this fact such impacts have been called “partial.”
13. Partial impacts generally result in the formation of three bodies; the parts of each whose momentum is destroyed by impact remain behind, and the two cut stars pass on in space.
14. Partial impacts of a third of two equal stars having considerable original proper motion would make the two into three equal bodies; two of them would travel in space in opposite directions, the third would remain at rest between them. If there had been no proper motion the three bodies would coalesce; but if less than a third be cut off each the two bodies become three bodies orbitally connected.
15. The temperature produced by an impact will depend upon the velocity destroyed and upon the chemical constitution. High velocities and heavy molecules both tend to produce high temperature. Consequently the temperature will not depend upon the amount of the graze. Were one-tenth or one-hundredth grazed off the stars, the temperature of the coalesced part would be the same.
16. Although the temperature will be the same, the gravitating-power of the coalesced part will depend upon its mass.
17. Heat is a molecular motion. In a small graze of any given pair of stars the molecules will have the same velocity as in a large graze; but the gravitating force holding the body together will be different. In a large graze the body may be
stable, the velocity not overcoming the attraction. In a small graze the body will expand indefinitely in consequence of its small attractive power, and every particle will have so high a velocity that it will, in general, become an independent wanderer in space.
18. Space will consequently be dusty with free molecules.
19. The mass of gas will obviously expand temporarily into a hollow shell of gas. Herschel tells us this is the condition of planetary nebulæ.
20. A partial impact of stars will consequently generally produce in less than an hour an intensely heated body that will expand enormously without much diminution of heat. It will consequently become very bright indeed. It will then continue to expand until it becomes a planetary nebula. Then it will disappear by dissipating completely into space.
21. The molecules on the far side of the sphere will be retreating from us; those on the near side advancing towards us. The spectrum of such a body will consequently be crossed by broad bright bands, each with a maximum in the centre, and gradually dying imperceptibly away. If this body has any motion in the line of sight, as it probably will have when the two colliding stars are unequal, the line of maximum intensity, although in the centre of the band, will be displaced from its true position.
22. Immediately after the impact the temperatures of different kinds of molecules will be very different from each other. Were the colliding spheres of oxygen they would be sixteen times as hot as if they were similar spheres of hydrogen. The temperature at impact will be proportionate to the atomic weight.
23. In a mixed sphere these inequalities of temperature would quickly equalise themselves. Then when the temperature was uniform the hydrogen would be moving four times as fast as the oxygen. The velocities would vary inversely as the square root of the atomic weights.
24. This difference of velocity will tend to sort the molecules into layers like a lily-bulb, the hydrogen on the outside followed by lithium, &c., in the order of their atomic weights. If there are elements lighter than hydrogen, as spectroscopic observations of the corona suggest, these will, of course, precede hydrogen. In my lectures and papers on this subject I have called this action “selective escape.”
25. Space will be thickly spread with free molecules of the lightest elements. This fact is important as one of the interesting agencies that prevent the theory of dissipation of energy being of cosmic application.
26. A telescopic view of a new planetary nebula produced by a partial impact, if looked at through a prism, should give
a series of discs of diameters diminishing with increase of atomic weight.
27. This fact taken in conjunction with the broadening of the lines into bands will enable us to calculate the distance of such a body.
28. The hydrogen will rob the heavy molecules of their energy; hence in any considerable graze the heavy metals might not expand indefinitely. They would lose their velocity by radiation and work done; they would be attracted back again and form a star. Some planetary nebulæ have such stars.
29. In a partial impact the coalesced part will not have all its motion converted into heat. On the two sides the momentum will not be exactly balanced; the body will consequently tend to spin. It is generic of partial impact that it tends to cause rotation in all the bodies produced, and the rotation is all in the same direction.
30. It is a peculiarity of oxygen that it tends to render its compound with metals less volatile than the metals themselves. Almost all oxides are less volatile than the metals forming them. Consequently when metal and oxygen come together they produce molecules that tend to coalescence. Thus nuclei form in a nebula and it becomes dusty. If the nebula be rotating this dust tends to move in orbits, constantly picking up other dust and molecules. Thus a rotating metallic nebula tends to aggregate, not necessarily into a single body, but into a mass of bodies orbitally connected. If the mass be large it will become a star-cluster; if small, a meteoric swarm.
31. In star-clusters impacts should be frequent. These groups should be photographically watched to notice sudden increase of intensity, and then the pair of impacting stars should be watched for nebula and for variability.
32. Meteoric swarms when near the sun would be distorted, and the constituents would impact with extraordinary frequency; they would become very brilliant, and show as comets. There would be tremendous development of electricity.
33. It is certain that the matter of the tail of a comet does not belong to the comet. It is like the motes in air illuminated by a search-light. The phenomenon of the tail is almost certainly electrical.
34. Such a swarm when near the sun would have its near part drawn in advance of, and its distant part left behind, the general swarm. Its weak attractive power would cause it to divide into a train.
35. The two stars that grazed would have a part cut out of each. This would expose the hot interior. A portion of
each body would also be entangled by the other, further increasing the temperature of the cut part.
36. The star would recover its sphericity chiefly by the molten interior welling up. This by momentum would overfill the space, and there would be a rhythmic tidal action, the molten lake overfilling and then sinking.
37. The retardation of the cut and entangled material would cause these bodies to spin. This would act chiefly on the outer layers. The inside would tend to retain the original rotation of the star.
38. Thus in the sheared stars there are three tendencies struggling with each other—the original rotation, the new rotation, and the tidal action.
39. But the new rotation would be a large component. We have, therefore, a star which rotates and shows us alternately the hot and cool sides. The old rotation and the tidal motion produce other fluctuations of intensity, and also inequalities of the rate of motion.
40. Evidently such a body would be a variable star, and for a time such stars would be in pairs.
41. Such is the case. This duplex character is so striking a phenomenon that the probability of its being the result of chance is one to one hundred sextillions.
42. Conduction, convection, tidal motion, and the contending rotations will tend to bring about equality of temperature. This condition of variability will consequently be a temporary one. The star will ultimately become of uniform luminosity. These are all known peculiarities of variable stars.
43. Convection is due to difference of density. This may result from differences of temperature and from differences of chemical composition. The lake of fire will consist of heavier molecules than the remaining surface, and it will be at a higher temperature. These two will tend to neutralise each other, so that equality of temperature due to convection will not be brought about quickly. It is surprising what a number of agencies there are tending to retain this inequality of temperature. This condition may as an extreme case last thousands of years.
44. The work of cutting the star will be infinitesimal in relation to its available energy, and will not appreciably lessen the velocity of the escaping stars, but the middle body will exercise a powerful attraction. It will exercise a retarding influence preventing the retreat of the two bodies, equal to three times the mass either body loses. Hence when two equal bodies lose a third each they do not become free from the new central body.
45. If the original proper motion were large and the graze small the two stars would escape each other. If the original
motion were small, and the graze on an average more than a tenth, then the two stars would become orbitally connected.
46. Such a pair form a permanent double star. Proctor and other astronomers are of opinion that impacting stars that become orbitally connected could not make double stars, as they would impact again. They overlook the fact that the nebula that retarded their escape will have dissipated before they return, hence the eccentricity will lessen greatly, and, as a rule, instead of impacting again, they will be scores of millions of miles away at perihelion.
47. Double stars should be more often variable than single stars. Struvé has proved that they are hundreds of thousands of times more so than ordinary stars. They should be more frequently coloured. This is also most strikingly the case.
48. They should be associated with nebulæ. Herschel says the association of nebulæ and double stars is truly remarkable.
49. They should be highly eccentric. This is also well known to be the case.
50. A large number of agencies tend to render the orbit less eccentric. These are fully described in my papers of 1880.
51. If stars come into partial impact the tendency to form definite nebulæ other than planetary or cometic seems to be entirely destroyed by the outrush of the high-velocity gas. This is not the case with the impact of nebulæ.
52. Impact may take place between nebulæ, between star - clusters, between meteoric swarms, and, of course, between any two similar or dissimilar celestial bodies. The graze may be large or small; the original bodies may have had a little or great proper motion. Of course, all these peculiarities will tend to vary the results.
53. If two nebulæ come into a slight grazing impact a double nebula will result. This will show a spindle at the centre. As they are parting company they may have temporarily a dumb-bell appearance, but the two sides of the coalesced nebula are moving in opposite directions. A spiral begins to form at the centre, the ends travel on in space, the spiral increases, and ultimately a double spiral results.
54. One or both of the original nebulæ may be entangled in the spiral.
55. If the impact be considerable the two nebulæ do not escape each other, and an annular nebula results. It has gauzelike masses of nebulæ at the poles of the rings, produced by the outrush during the impact.
56. If two universes such as the Magellanic Clouds impact, an annular universe will result. The poles will be covered with nebulous matter, due to the outrush of gas during the millions of years of the impact.
57. Stars will pass through such caps of nebula and will be entrapped, and will attract nebulous matter, and will become nebulous stars, or they may be volatilised altogether and become globular nebulæ.
58. Where globular nebulæ are thick we should expect double, spindle, and spiral nebulæ. These nebulæ are actually found amongst the nebulæ at the polar caps of the Milky Way.
59. Where stars are thick we should expect the result of the impact of stars—such as planetary nebulæ, temporary and variable stars, double stars, and star-clusters. These are all chiefly in the Milky Way.
60. If the universe were formed by such a graze we should expect a greater density of stars where the motion chiefly directed the two original universes. There are two such clustering masses.
61. If the universe were the result of impact there would be much community of motion in adjacent stars. This is a remarkable peculiarity of the stars in the Galactic Ring. Most of these agencies are debated in my paper “On the Origin of the Visible Universe.”
62. Nebulæ would tend to entrap bodies passing through them. These bodies would become orbitally connected, and when the nebula settled down to a sun the bodies would produce a system with planets in all azimuths, in the same way as the comets that our solar system has entrapped are in all azimuths.
63. Were such a body to impact with a similar one, or with a sun, and were the graze considerable, all the planets would be spun roughly into a plane, and the central mass would become a bun-shaped nebula. The agencies that would convert this into a system similar to ours are discussed in my paper “On the Origin of the Solar System,” and in the paper “On Causes tending to lessen the Eccentricity of Planetary Orbits.”
64. It can be shown that if two gaseous suns without original proper motion impact completely, and were the whole of the motion converted into heat and this into expansion, the new sun would have a diameter the sum of the diameters of the original suns. It can also be shown that this condition is one of stable equilibrium.
65. The complete impact of two suns brought together by gravitation does not make a nebula of them, but as soon as the paroxysm of the encounter is over they are of the same temperature as before, and have only increased to the sum of their original diameters.
66. Were there great original proper motion they might become a nebula by complete impact; but were the impact of great energy, then an infinitely diffused cold nebula would
result. Such a nebula would be unstable. Croll's theory to account for an increase in the age of the sun's heat by the impact of two suns is therefore untenable.
The Cosmos possibly Immortal.
67. If our universe be proved from its form and character to have been formed of two previously-existing universes, as appears probable from 56, et seq., then the entire cosmos may be made up of an infinity of universes.
68. Meteoric swarms prove space to be dusty with wandering dark bodies, and “selective escape” proves it also to be spread with countless myriads of molecules of light gas. It is probably due to the dust of space that we see no distant universes other than the Magellanic Clouds.
69. If this be the case, radiation must all be caught by the dust of space, and, unless some agency be found to take this heat away, the dust must be gradually increasing in temperature.
70. Bodies not in orbits occupy but a short time at high velocity. They occupy longer and longer periods as the velocity is reduced. Hence hydrogen gas, independent of matter, will be generally moving slowly. But slowly-moving gas is cold: hence hydrogen gas may be at a lower temperature than any other matter in space.
71. Whenever, by their mutual motions, hydrogen strikes cosmic dust it will acquire the temperature of the latter—that is, it will increase its molecular velocity. It will thus have a new start of motion.
72. Unless it strikes something, the molecule can only lose this motion by radiation, or by doing work. When it has done work it will be further from matter, or in a position of higher potential; and Crooks's experiments prove that molecules do not radiate in free path excepting after encounters.
73. Moving matter not in orbits will tend to move most slowly where there is least matter—that is, where gravitation potential is highest—because in these places it has done most work against gravitation. Where bodies moving indiscriminately move most slowly they obviously tend to aggregate: in other words, the hydrogen of space tends to accumulate in the sparsest portions of space.
74. Thus radiant energy falls on the dust of space, and heats it. This heat gives motion to hydrogen, and the hydrogen then tends to use its new energy to pass to positions of high potential, thus converting low-temperature heat—that is, dissipated energy—into potential energy of gravitation—that is, into the highest form of available energy.
75. This action will tend to go on until attraction is equal in different parts of space; but then we have in one part of space bodies in mass, in another diffused hydrogen.
76. But long before this equality of distribution could ensue another action is set up. The mass of hydrogen will become a retarding trap to indiscriminately-moving bodies.
77. Free bodies moving indiscriminately will tend to pass through such a group of masses as our universe, as 1830 Groombridge is passing through it now. But they will tend to be trapped in any mass of hydrogen. Thus the place that was most void of matter now commences to have more than the regular distribution of matter. A new universe has begun to form.
78. Mutual gravitation between the entrapped bodies tends to concentrate the diffused mass. The new universe is taking form.
79. Where three bodies pass near each other one at least has its velocity increased. In this way it is possible to account for the enormous velocity of 1830 Groombridge. Whenever the velocity is great enough to escape the attraction of the universe the body is lost to it, and some of the other bodies are moving more slowly. If this should occur once only in a thousand cases, seeing that when it does occur the body escapes, if we give time enough, most of the energy of any individual system must be used up in allowing the escape of bodies.
80. We have in these phenomena a complete series of agencies tending to overcome the dissipation of energy and the aggregation of matter. Impact developes heat, separates bodies, and diffuses gas. Radiation falls on, and is absorbed by, the matter of space. As hydrogen loses its velocity it is carried to positions of higher potential by the heat of the dust of space. This gas tends to linger in the empty parts of space, and then becomes a trap for wandering bodies. These wandering bodies are separated from systems by the mutual action of three bodies.
81. Thus, in opposition to the theory of dissipation of energy, there is seen to be the possibility of an immortal cosmos, in which we have no evidence of a beginning or promise of an end.
Explanation of Plate LII.
Diagrams to illustrate Summary of Impact.
Fig. 1. Pair of stars distorted and coming into impact.
Fig. 2. Pair of stars in impact.
Fig. 3. Stars passing out of impact, and formation of third body.
Fig. 4. Showing entanglement of matter in each body.
Fig. 5. Two variables and a temporary star.
Fig. 6. Central body in process of expansion into nebulæ.
Fig. 7. Planetary nebula expanded beyond variable stars.
Fig. 8. Stars associated into a double star by attraction of central body.
Fig. 9. Lessened attraction on return of stars prevents recurrent impact, and makes orbit more circular.