ARRHENIUS, WORLDS IN THE MAKING

thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

By the continued ejection of dust-charged masses of gas, probably with gradually decreasing violence, the light intensity of the star must slowly diminish (as seen from the earth) and the distribution of the layers of dust around the luminous core will more and more become uniform.

How violent the explosion must have been, we recognize from the observation that the first ejected masses of hydrogen rushed out with an apparent velocity of at least 700 km. per second.

This velocity is of the same order as that of the most remarkable prominences of the sun.

It will be admitted that these arguments present us with a faithful simile even of the details of the observed course of events, and it is therefore highly probable that our view is in the main correct.

But what has meanwhile become of the new star?

Spectrum analysis tells us that it has been converted into a stellar nebula like other new stars.

The continuous light of the central body has more and more been weakened by the surrounding masses of dust.

By the radiation pressure these masses are driven towards the outer particles of the surrounding gaseous envelope consisting principally of hydrogen, helium, and "nebular matter."

There the dust discharges its negative electricity, and thus calls forth a luminescence which equals that of the nebulae.

We have to consider next that owing to the incredibly rapid rotation, the central main mass of the two stars will, in its outer portions, be exposed to centrifugal forces of extraordinary intensity, and will therefore become flattened out to a large revolving disk.

As the pressure in the outer portions will be relatively small, the density of the gases will likewise be diminished there.

The energetic expansion and, more still, the great heat radiation will lower the temperature at a rapid rate.

We have thus to deal with a central body whose inner portion will possess a high density, and which will resemble the mass of the sun, while the outer portion will be attenuated and nebular.

Distributed about the central body we shall find the rest of the two streams of gases which were ejected immediately after the violent collision between the two celestial bodies.

A not inconsiderable portion of the matter of these spirally arranged outer parts will probably travel farther away into infinite space, finally to join some other celestial body or to form parts of the great irregular spots of nebular matter which are collected around the star clusters.

Another portion, not able to leave the central body, will remain in circular movement about it.

In consequence of this circular movement, which will be extremely slow, the outlines of the two spirals will gradually become obliterated, and the spirals will themselves more and more assume the shape of nebular rings about the central mass.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

This spiral form (Figs. 47 and 48) of the outer portions of the nebulse has for a long time excited the greatest attention.

In almost all the investigated instances it has been observed that two spiral branches are coiling about the central body.

This would indicate that the matter is in a revolving movement about the central axis of the spiral, and that it has streamed away from the axis in two opposite directions.

Sometimes the matter appears arranged as in a coil; of this type the great nebula of Andromeda is the best-known example (Fig. 49).

A closer inspection of this nebula with more powerful instruments indicates, however, that it is also spiral and that it appears coiled, because we are looking at it from the side.

The late famous American astronomer Keeler, who has studied these nebulae with greater success than any one else, has catalogued a great many of them in all the divisions of the heavens which were accessible to his instruments, and he has found that these formations are predominatingly of a spiral nature.

Some nebulae, like the so-called planetary nebulae, offer rather the appearance of luminous spheres.

We may assume in these cases that the explosions were less violent, and that the spirals, therefore, are situated so closely together that they seem to merge into one another.

Possibly the inequalities in their development have become equalized in the course of time.

A few nebuke are ring-shaped, as the well-known nebula of Lyra (see Fig. 50).

These rings may, again, have been formed out of spiral nebulse, and the spirals may have gradually been obliterated by rotation, while the central nebulous matter may have been concentrated on the planets travelling round the central star.

Schaeberle, an eminent American astronomer, has discovered traces of spiral shape also in the Lyra nebula.

TO BE CONTINUED ..
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

Another kind of nebula is the ordinary nebula of vast extension and irregular shape, evidently formed out of most extremely attenuated matter; well-known characteristic examples are found in Orion, about the Pleiades, and in the Swan (Figs. 51, 52, and 53).

In these nebula, portions of a spiral structure have likewise often been discerned.

We have said that the collision between two celestial bodies would result in the formation of a spiral with two wings.

If the impact is such that the two centres of the celestial bodies move straight towards each other, a disk will arise, and not a spiral; or if one star is much smaller than the other, possibly a cone, because the gases will uniformly be spread in all directions about the line of impact.

A perfectly central impact is obviously very rare; but there may be cases which approach this limiting condition more or less, especially when the relative velocity of the two bodies is small.

By slow diffusion a feebly developed spiral may also be converted into a rotating disk-like structure.

The extension of these nebular structures will depend upon the ratio between the mass of the system and the velocity of ejection of the gases.

If, for example, two extinct suns of nearly equal dimensions and mass, like our sun, should collide, some gas masses would travel into infinite space, being hurled out with a velocity of more than 900 km. (550 miles) per second; while other particles, moving at a slower rate, would remain in the neighborhood of the central body.

The nearer to that body, the smaller was their velocity.

From their position they might fall back into the central body, to be reincorporated in it, if two circumstances did not prevent this.

The one circumstance is the enormous radiation pressure of the glowing central mass.

That pressure keeps masses of dust particles floating, which by friction will carry the surrounding masses of gas with them.

Owing to the absorption of the radiation by the dust particles, only the finer particles will be supported farther outside, and at the extreme margin of the nebula even the very finest dust will no longer be maintained in suspension by the greatly weakened radiation pressure.

Thus we arrive at an outer limit for the nebula.

The other circumstance is the violent rotation which is set up by the impact of the central bodies.

The rotation and the centrifugal forces will produce a disk-shaped expansion of the whole central mass.

Owing to molecular collisions and to tidal effects, the angular velocity will in the denser portions tend to become uniform, so that the whole will rotate like a flattened-out ball filled with gas, and the spiral structure will gradually disappear in those parts.

In the more remote particles the velocity will only increase to such an extent as to equal that of a planet moving at the same distance that is to say, the gravitation towards the central body will be balanced by the centrifugal force, and at the very greatest distances the molecular bombardments, as well as gravitation towards the centre, will become so insignificant that any masses collected there will retain their shape for an almost unlimited space of time.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

In the centre of this system the main bulk of the matter would be concentrated in a sun of extreme brightness, whose light intensity would, however, owing to strong radiation, diminish with comparative rapidity.

Such an extensive nebular system, in which gravitation, on account of the enormous distances, would act feebly and very slowly, would yet, in spite of the extraordinary attenuation of matter in its outer portions, and just on account of its vast extension, be able to stop the movement of the particles of dust penetrating into it.

If the gases of the nebula are not to escape into space, notwithstanding the infinitesimal gravitation, their molecules must be assumed to be almost at a stand-still, and their temperature must not rise by more than 50 or 60 Cent, above absolute zero.

At such low temperatures the so-called adsorption plays an enormously important part (Dewar).

The small dust particles form centres about which the gases are condensed to a remarkable degree.

The extremely low density of these gases does not prevent their condensation; for the adsorption phenomenon follows a law according to which the mass of condensed gas will only be reduced by about one-tenth when the density of the surrounding gas has been decreased by one-ten-thousandth.

The mass of dust particles or dust grains will thus be augmented, and when they collide they will be cemented together by the semi-liquid films condensed upon them.

There must, hence, be a relatively energetic formation of meteorites in the nebula, and especially in their interiors.

Then stars and their satellites, migrating through space, will stray into these swarms of gases and meteorites within the nebulae.

The larger and more rapidly moving celestial bodies will crush through this relatively less dense matter; but thousands of years may yet be occupied in their passing through nebulae of vast dimensions.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

An extraordinarily interesting photograph obtained by the celebrated Professor Max Wolf, of Heidelberg, shows us a part of the nebula in the Swan into which a star has penetrated from outside.

The intruder has collected about it the nebulous matter it met on its way, and has thus left an empty channel behind it marking its track.

Similar spots of vast extent, relatively devoid of nebulous matter, occur very frequently in the irregular nebulse, they are frequently called "fissures," or by the specifically English term "rifts," because they have generally a long-drawn-out appearance.

The presumption that these rifts represent the tracks of large celestial bodies which have cut their way through widely expanded nebular masses (Fig. 54) has been entertained for a long time.

The smaller and more slowly moving immigrants, on the other hand, are stopped by the particles of the nebulae.

We therefore see the stars more sparsely distributed in the immediate neighborhood of the nebulae, while in the nebulae themselves they appear more densely crowded.

This fact had struck Herschel in his observations of nebulae; in recent days it has been investigated by Courvoisier and M. Wolf.

In this way several centres of attraction are created in a nebula; they condense the gases surrounding the nebula, and catch, so to say, any stray meteorites and collect them especially in the inner portions of the nebula.

We frequently observe, further, how the nebular matter appears attenuated at a certain distance from the luminous bright stars (compare Figs. 52 and 55).

Finally, the nebulae change into star clusters which still retain the characteristic shapes of the nebulae; of these the spiral is the most usual, while we also meet with conical shapes, originating from conical nebulae, and spherical shapes (compare Figs. 56, 57, and 58).

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

This is, broadly, the type of evolution through which Herschel, relying upon his observations, presumed a nebula to pass.

He was, however, under the impression that the nebulous matter would directly be condensed into star clusters without the aid of strange celestial immigrants.

It has been known since the most ancient times, and has been confirmed by the observations of Herschel and others in a most convincing manner, that the stars are strongly concentrated about the middle line of the Milky Way.

It is not improbable that there was originally a nebula of enormous dimensions in the plane of the Milky Way, produced possibly by the collision of two such giant suns as Arcturus.

This gigantic nebula has gathered up the smaller migrating celestial bodies which, in their turn, have condensed upon themselves nebular matter, and have thereby become incandescent, if they were not so before.

The rotational movement in those parts which were far removed from the centre of the Milky Way may be neglected.

At a later period collisions succeeded between the single stars which had been gathered up, and it is for this reason that gaseous nebulae, as well as new stars, are comparatively frequent phenomena in the plane of the Milky Way.

This view may some day receive confirmation, when we succeed in proving the existence of a central body in the Milky Way, evidence of which might possibly be deduced from the curvature of the orbits of the sun or of other stars.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

As regards the ring-shaped nebula in the Lyre (Fig. 50), the most recent measurements made by Newkirk point to the result that the star visible in its centre is distant from us about thirty-two light-years.

As it appears probable that this star really forms the central core of the nebula, the distance of the nebula itself must be thirty-two light-years.

From the diameter of the ring-shaped nebula which Newkirk estimates at one minute of arc, this astronomer has calculated that the distance of the ring from its central bodly is equal to about three hundred times the radius of the earth's orbit that is to say, the ring is about ten times as far from its sun as Neptune is from our sun.

There is a faint luminescence within this ring.

The nebular matter may originally have been more concentrated at this spot than in the outer portions of the ring itself.

But this mass was probably condensed on meteors which immigrated from outside, and when these meteors coalesced dark planets were produced which move about the central body, and which have gathered about them most of the gases.

If that central body were as heavy as our sun, the matter in the ring should revolve about it in five thousand years.

That rotation would suffice to wipe out the original spiral shape, enough of which has yet been left to permit of our distinctly discerning the two wings of the spiral.

The central body of this ring-shaped nebula gives a continuous spectrum of bright lines which is particularly developed on the violet side.

The star would therefore appear to be much younger and much hotter than our sun, and its radiation pressure would therefore be much more intense.

The period of rotation of the nebula may, for this reason, have to be estimated at a considerably higher figure.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

The eminent Dutch astronomer Kapteyn has deduced from the proper motions of 168 nebulae that their average distance from the earth is about seven hundred light-years and equal to that of stars of the tenth magnitude.

The old idea, that the nebulae must be infinitely farther removed from us than the fainter stars, would therefore appear to be erroneous.

According to the measurements of Professor Bohlin, the nebula in Andromeda may indeed be at a distance of not more than forty light-years.

The "new stars" form a group among the peculiar celestial bodies which on account of their variable light intensity have been designated as "variable stars," and of which a few typical cases should be mentioned, because a great scientific interest attaches to these problems.

The star Eta, in Argus, may be said to illustrate the strange fate that a star has to pass through when it has drifted into a nebula filled with immigrated celestial bodies.

It is one of the most peculiar variable stars.

The star shines through one of the largest nebular clouds in the heavens.

Whether it stands in any physical connection with its surroundings cannot be stated without further examination.

The star might, for instance, be at a considerable distance in front of the nebula, between the latter and ourselves.

Its frequent change in light intensity suggests, however, a series of collisions, which do not appear unnatural to us when we suppose that the star is within a nebula into which many celestial bodies have drifted.

As this star belongs to the southern hemisphere, it was not observed before our astronomers commenced to visit that hemisphere.

In 1677 it was classed as a star of the fourth magnitude; ten years later it was of the second magnitude; the same in 1751.

In 1827 it was of the first magnitude, and it was found to be variable that is to say, it shone with variable brightness.

Herschel observed that it fluctuated between the first and second magnitudes, and that it increased in brightness after 1837, so that it was by 1838 of magnitude 0.2.

After that it began to decrease in intensity up to April, 1839, when it had the magnitude 1.1.

It remained for four years approximately at this intensity; then it increased rapidly again in 1843, and surpassed all stars except Sirius (magnitude 1.7).

Afterwards its intensity slowly diminished once more, so that it remained just visible to the naked eye (sixth magnitude); by 1869 it had become invisible.

Since then it has been fluctuating between the sixth and seventh magnitudes.

TO BE CONTINUED ...
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

The last changes in the intensity of this star strongly recall the behavior of the new star in Perseus, only that the latter has been passing through its phases at a much more rapid rate.

It appears to be certain, however, that Eta, in Argus, was from the very beginning far brighter than Nova Persei, and that at least once before the great collision in 1843 (after which it was surrounded by obscuring clouds of increasing opacity) namely, in January, 1838, it had been exposed to a slight collision of quickly vanishing effect.

This lesser collision was probably of the kind which Mayer imagined for the earth and sun.

It would give rise to heat development corresponding to the heat expenditure of the sun in about a hundred years.

As it had been observed that the star was variable in an irregular manner before that, we may perhaps, presume that it had already undergone another collision.

According to the observations of Borisiak, a student in Kief, the new star in Perseus would have been, on the evening of February 21, 1901, of 1.5 magnitude, while a few hours previously it had been of magnitude 12, and the following evening of magnitude 2.7; afterwards its intensity increased up to the following evening, when it outshone all the other stars in the northern sky.

If this statement is not based on erroneous observations, the new star must have been in collision with another celestial body two days before its great collision, perhaps with a small planet in the neighborhood of the sun, with which it later collided.

That would account for its temporary brilliancy.

TO BE CONTINUED …
thelivyjr
Site Admin
Posts: 73424
Joined: Thu Aug 30, 2018 1:40 p

Re: ARRHENIUS, WORLDS IN THE MAKING

Post by thelivyjr »

VI - END OF THE SUN ORIGIN OF NEBULA, continued …

New stars are by no means so rare as one might perhaps assume.

Almost every year some new star is discovered.

By far most of these are seen in the neighborhood of the Milky Way, where the visible stars are unusually crowded, so that a collision which would become visible to us may
easily occur.

For similar reasons we find there also most of the gaseous nebulae.

Most of the star clusters are also in the neighborhood of the Milky Way.

This is in consequence of the facts just alluded to.

The nebulae which are produced by collisions between two suns are soon crossed by migrating celestial bodies such as meteorites or comets, which there occur in large numbers; by the condensing action of these intruders they are then transformed into star clusters.

In parts of the heavens where stars are relatively sparse (as at a great distance from the Milky Way), most of the nebulae observed exhibit stellar spectra.

They are nothing but star clusters, so far removed from us that the separate stars can no longer be distinguished.

That single stars and gaseous nebulae are so rarely perceived in these regions is, no doubt, due to their great distance.

Among the variable stars we find quite a number which display considerable irregularity in their fluctuations of brightness, and which remind us of the new stars.

To this class belongs the just-mentioned star Eta, in Argus.

Another example (the first one which was recognized as "variable") is Mira Ceti, which may be translated, "The Wonderful Star in the Constellation of the Whale."

This mysterious body was discovered by the Frisian priest Fabricius, on August 12, 1596, as a star of the second magnitude.

The priest, an experienced astronomer, had not previously noticed this star, and he looked for it in vain in October, 1597.

In the years 1638 and 1639 the variability of the star was recognized, and it was soon ascertained to be irregular.

The period has a length of about eleven months, but it fluctuates irregularly about this figure as a mean value.

At its greatest intensity the star ranks with those of the first or second order.

Sometimes it is weaker, but it is always of more than the fifth magnitude.

Ten weeks after a maximum the star is no longer visible, and its brightness may diminish to magnitude 9.5.

In other words, its intensity varies about in the ratio of 1 : 1000 (or possibly more).

After a minimum the brightness once more increases, the star becomes visible again that is to say, it attains the sixth magnitude and after another six weeks it will once more be at its maximum.

We have evidently to deal with several superposed periods.

TO BE CONTINUED ...
Post Reply