CHAPTER 16
Type II Supernovae
The derivation
of the principal characteristics of objects moving at ultra high speeds
in the preceding chapter gives us a foundation on which we can construct
a theoretical picture of the nature and properties of astronomical objects
of this class. Before so doing, however, it will be appropriate to give
some attention to the process by which the ultra high speeds are generated.
As explained
in Volume II, the continued existence of matter is subject to two limits,
one related to the temperature, and therefore to the mass of the star
in which the matter is located, and the other related to the age of the
matter itself, subject to some modification by reason of its location
We have seen that when the temperature limit is reached in the center
of a star, that star explodes in an event known as a Type I supernova.
Arrival at the age limit results in a similar explosion, which is called
a Type II supernova. While these explosions are basically alike, in that
each results from the sudden conversion of a substantial portion of the
mass of the star into energy, and each produces some products that move
with speeds greater than that of light, as well as slow moving products,
there are also some significant differences that we will want to explore.
The upper
destructive limit of matter is actually a limiting value of the magnetic
ionization, but this is a function of age, because the magnetic ionization
level continually increases under normal conditions. This ionization is
equalized when atoms come into effective contact All components of a solid
aggregate are therefore at the same ionization level. In the fluid states—liquid,
gas, and condensed gas—the equalization process proceeds more slowly.
Where the material aggregate is as large as a star, and there is a substantial
inflow of matter from the environment, an ionization gradient is produced,
extending from the lower level of the accreted material to the higher
level of the older matter in the interior. When the ionization level in
the interior reaches the destructive limit, and the explosion occurs,
the matter that is still below the destructive ionization level is dispersed
in space and in time in a manner similar to the dispersion of the products
of the Type I supernova.
Reliable information
about supernovae is very limited. Unfortunately, observations of the individual
explosive events can only be made under some rather severe handicaps.
No supernova has been observed in our galaxy for nearly 400 years, and
information about the active stage of these objects can be obtained only
from extragalactic observation, aside from such deductions as can be made
from imprecise eyewitness accounts by observers of the supernovae of 1604
and earlier. The most meaningful information comes from examination of
certain astronomical objects, a few of which are known to be remnants
of old supernovae, and others that are similar enough to justify including
them in the same category. Even at best, however, hard evidence is scarce,
and it is not surprising that there is considerable difference of opinion
among the astronomers as to classification and other issues. As might
be expected under these circumstances, our deductions from physical theory
conflict with some current astronomical thought.
The Type I
explosion, according to our findings, originates in a star that has reached
the size and temperature limits. This is a hot, massive star at the upper
end of the main sequence, a member of a group of practically identical
objects. Thus our theoretical conclusion is that all Type I supernovae
are very much alike. The observers concede the validity of this conclusion.
Here are some typical comments:
Type I supernovae
display a fascinating homogeneity of photometric and spectroscopic properties.170 (David Branch)
Supernovae
of Type I form a fairly homogenous group with relatively little variation
between the spectrum of one star and that of the next . . . Supernovae
of Type II constitute a much less homogenous group than those of Type
I.31 (Robert P. Kirshner)
The supernovae
other than those of Type I are actually so diverse that serious consideration
has been given to defining several additional types. In the light of our
findings it is apparent that a substantial degree of variation in the
Type II events can be expected by reason of the differences in the masses
of the exploding stars, and in their physical condition; that is, in the
stage of the evolutionary cycle in which they happen to be at the time
when they arrive at their age limits. Some of the observations show indications
of mass differences. For instance, R. Minkowski reports that ”The
supernova of 1961 in NGC 4303 which Zwicky designates as Type III, shows
properties that suggest strongly a supernova of Type II with unusually
large ejected mass.“ 171 Massive objects are, of course,
relatively rare in a sample drawn at random from the general run of stars,
the great majority of which are small.
The astronomers
have not been able to find a satisfactory explanation for the difference
between the two classes of supernovae. Shklovsky, for instance, points
out that this is one of the things that a theory of stellar explosions
should explain:
Why, for
instance, are the light curves of Type I supernovae so similar to one
another? And why are the light curves of Type II supernovae so diverse?“
Theoreticians have found these questions very difficult indeed.172
The principal
roadblock in the way of arriving at an answer to these questions is the
prevailing commitment to the upside down evolutionary sequence, which
is the basis for the current belief in astronomical circles that the Type
II explosions are the ones that originate from the hot massive stars.
Again quoting Shklovsky:
As for the
stars that become Type II supernovae, it is logical to infer that they
are young objects. This conclusion follows from the simple fact that
they are located in spiral arms, where stars are formed out of a gas-dust
medium.173
The lack of
force in this argument can be appreciated if it is recalled that this
same author characterized the current theory of star formation as ”pure
speculation.“ This is another of the places where the uncritical
acceptance of the physicists' assumption as to the nature of the stellar
energy generation process has diverted the astronomers' thinking into
the wrong channels, and induced them to close their eyes to the direct
astronomical evidence. When the correct age sequence is recognized, all
of the observations fall into line without difficulty.
Type I supernovae
are found to be distributed among all of the various kinds of galaxies.
This is consistent with our findings, as the limiting mass may theoretically
be reached early in the life of a star, under appropriate circumstances.
Age, on the other hand, is inconsistent with an early type of galaxy (with
the usual exception that some old stray stars may be picked up by a young
galaxy). A Type I event, if it occurs at all, must precede the Type II
event that marks the demise of the star. Since the Type II supernova is
a result of age, the explosions of this type are primarily phenomena of
the older galaxies. The absence (or near absence) of Type II supernovae
from the Magellanic clouds, for instance, is easily understood on the
age basis, as these Clouds are clearly much younger than the Galaxy, according
to the criteria that we have developed. On the other hand, this is a distinct
embarrassment for the prevailing ”massive star“ theory of Type
II supernovae. As explained by Shklovsky,
The fact
that only Type I supernovae appear in irregular galaxies such as the
Magellanic Clouds would seem inconsistent with the picture we have outlined,
for these galaxies contain a great many hot, massive stars. Why is it
that Type II supernovae are not observed there?173
What needs
to be recognized is that when the observed facts are ”inconsistent
with the picture,“ then they are telling us that the picture is wrong.
This is the same message that we get from a whole assortment of astronomical
observations that were discussed item by item in the preceding pages of
this volume. All agree that the objects—stars, clusters, galaxies—characterized
by astronomers as the older members of their respective classes are, in
fact, the younger. This is to answer the Shklovsky's question, and to
a wide range of similar problems.
In spite of
the absence of observed events, Type II supernovae are not totally
excluded from small elliptical or irregular galaxies, or even from globular
clusters. As pointed out earlier, all of these aggregates contain a few
old stars that have been picked up from the environment during the formation
and subsequent travel of the aggregates. When these old stars reach their
age limits, supernova explosions take place. The absence of observed events
of this kind is due to their scarcity. The Large Magellanic Cloud does
contain a few supernova remnants that can be identified with Type
II events, indicating that at least a few Type II supernovae have occurred
in this galaxy within the last 100,000 years.
The observed
Type II events are largely in the arms of the spiral galaxies, as indicated
in one of the quotations from Shklovsky, but we find from theory that
the great majority of the Type II supernovae occur in the unobservable
inner regions of the giant spheroidal galaxies and the largest spirals.
This is where the oldest stars are concentrated. The number of stars that
undergo Type II explosions is considerably greater than the number that
undergo Type I explosions, since all must eventually meet the Type II
fate. This is offset in part by the fact that many stars repeat the Type
I explosion at least once, in some cases several times. Aside from occurring
much later in the life span of the star—at the very end—the most distinctive
feature of the Type II explosion is that the intensity of the explosion,
relative to the stellar mass, is much greater than in Type I. The total
mass participating in the explosion is, in most cases, less than that
of the massive star that becomes a Type I supernova, as the mass of the
star involved in the Type II event may be anywhere between the maximum
and minimum stellar limits. But the Type II explosion converts a much
larger proportion of this mass into energy, and the ratio of energy to
unconverted mass is therefore considerably higher, increasing the proportion
of the mass going into the products with upper range speeds, and the maximum
explosion speed of these products.
The optical
emission from the explosion products comes mainly from the low speed component,
the material that is expanding outward into space. Since the amount of
this material is much smaller in the Type II events than in those of Type
I, the optical magnitude of the Type II supernova at the peak is considerably
less than that of the Type I events. One investigation arrived at average
magnitudes of -18.6 for Type I and -16.5 for Type II.174 The Type II Supernovae 221
emission from Type II also drops off more rapidly at first than that from
Type I, and the light curves of the two types of explosions are thus quite
different. This is one of the major criteria by which the observational
distinction between the two types is drawn.
In view of
the limited optical activity and the relatively small mass of the remnants,
there has been some question as to what happened to the energy of these
Type II events. Poveda and Woltjer, for instance, comment that they find
it difficult to reconcile current ideas as to the energy release in the
Type II supernovae with the present state of the remnants.175 This question is answered by
our finding that the great bulk of the energy that is generated goes into
the upper range explosion products, most of which are not optically visible.
These products
include some that are moving at intermediate speeds, and are unobservable
because their radiation is widely dispersed by the motion in time, and
others moving at ultra high speeds and therefore optically visible only
during the linear stage of their expansion. The ultra high-speed matter
moves outward with the low speed products during this early stage. The
intermediate speed matter has no spatial motion component of its own,
but much of it is entrained with the outward-moving products. As a result
this outward-moving cloud of matter contains local aggregates in which
there are substantial amounts of material with the speeds and other characteristics
of the white dwarf stars.
The long-continued
radio emission of the remnants of the Type II supernovae is due to the
presence of these upper range products. It was noted in Chapter 6 that the early white dwarf product of the Type
I supernova is not visible optically, and manifests itself only by its
radio emission. The same is true of the local concentrations of intermediate
speed matter in the remnants, which are the equivalent of small-scale
white dwarfs, and pass through the same evolutionary stages. Because of
their small size, their evolution proceeds more rapidly, and even in the
relatively short time during which the remnants are observable there are
portions of the intermediate speed matter in all stages, including small
aggregates with the outer shell of condensed gas that is characteristic
of the white dwarfs in the visible stages. Thus the radiation from the
remnants is not limited to dissipation of the kinetic energy imparted
to the explosion products by the supernova. There is a continued generation
of energy within the remnants. As the observers concede, the brightness
of the supernova remnants decreases much less rapidly with increase in
radius than conventional theory predicts.176 The supplemental energy
generation is the answer to this problem.
Continued
generation of energy in the remnants is manifested not only by the persistence
of the radio emission, but also by direct evidence of energetic events
within these structures. Inasmuch as conventional astronomical theory
provides no means of generating energy in the explosion products, the
prevailing view is that any emission of energy exceeding that, which can
be ascribed to the initial explosion, must be introduced into the remnant
from some separate source. In the case of the Crab Nebula, the remnant
of a supernova observed in 1054 A.D., it has been estimated that an input
of energy ”of the order 1038 erg/see“ is required to maintain
the observed emission.177 The current belief is that this
energy is derived from a dwarf star located in the center of the nebula,
but this is purely hypothetical, and it depends on the existence of a
transfer mechanism of which there is no evidence, or even a plausible
theory.
The explanation
that we derive from the theory of the universe of motion is that the continued
supply of energy is due to radioactivity in the local concentrations of
upper range matter in the remnants. It is the existence of this secondary
energy generation in the Type II remnants that accounts for the great
difference between the maximum period of observable radio emission in
the Type I remnants, perhaps 3000 years, and that of the Type II remnants,
which is estimated at more than 100,000 years. As an example of this difference,
there is a nebulosity in the constellation Cygnus, known as the Cygnus
Loop, which is generally considered to be a remnant of a Type II supernova,
and is estimated to be about 60,000 years old. After all of this very
long time has elapsed, we are still receiving almost twice as much radiation
at 400 MHz (in the radio range) from this remnant as from all three of
the historical (1006, 1572, and 1604) Type I supernova remnants combined.178
There are
a number of other remnants with radio emissions that are far above the
magnitudes that can be correlated with Type I. Also there are some remnants
whose radio emission is within the range of the Type I products, but whose
physical condition indicates an age far beyond the Type I limit. These
must also be assigned to Type II. In general, it is probably safe to say
that unless there is some evidence of comparatively recent origin, all
remnants with substantial radio emission can be identified with Type II
supernovae, even though Type I events may be more frequent in the observable
region of our galaxy.
The conclusions
as to the relative magnitude of the radio emission enable us to classify
the most conspicuous of the remnants, the Crab Nebula, as a Type II product.
The radio flux from this remnant is about 50 times that of the remnant
of the Type I supernova that appeared in 1006, and is therefore of practically
the same age. The Crab Nebula was originally assigned to Type I by the
astronomers, mainly on the basis of the differences between it and Cassiopeia
A, the remnant of a supernova that occurred about 1670 A.D., which was
regarded as the prototype of the Type II remnant. More recently it has
been recognized that the differences between the Crab Nebula and the Type
I remnants are more significant. Minkowski, for instance, reports that
”an unbiased assessment of the evidence leads to the conclusion that
the Crab Nebula is not a remnant of a supernova of Type I.“ 171
This nebula
consists of two physically distinct components, ”one is an amorphous
distribution of gas . . . and the other is a chaotic network of filaments.“
179 In the center of the nebula there
is a dwarf star of the Type II class, the nature and characteristics of
which will be discussed in the next chapter. The presence of a star of
this type definitely identifies the nebula as a product of a Type II supernova
large enough to produce maximum speeds in the ultra high range.
On the basis
of the theoretical considerations discussed in the preceding chapter,
the presence of ultra high speed matter in the inward-moving product of
the Type II supernova implies the existence of an observable outward-moving
ultra high speed component, which should consist of one or more jets of
material. Instead, as indicated above, the observers report the presence
of a ”chaotic network of filaments.“ So let us take a look at
the nature of these filaments.
The dictionaries
define the word ”filament“ as a ”slender, threadlike object.“
We are accustomed to the way in which astronomical magnitudes dwarf those
of our ordinary experience. Indeed, we commonly use the term ”astronomical“
in the sense of ”extremely large.“ But even so, it comes as
somewhat of a shock when we are told that ”on the average the bright
filaments are 1.4 arc sec. in diameter, which corresponds to a width of
2.5 x 1012 km.180 The ”slender“ object
is more than a hundred billion kilometers in diameter. But this does give
us an answer to the question as to the nature of the filaments. These
”slender“ filaments are clearly the same kind of entities that
we call jets in a different context. Their erratic courses are undoubtedly
due to the resistance that they meet as they make their way through the
clouds of matter moving at lower speeds.
There is also
a problem in connection with the so-called ”amorphous“ component
of the nebula. It must consist in part of the low speed products of the
supernova explosion, but the properties of this component do not resemble
those of a hot gas and dust mixture. In fact, even though it is identified
as a ”gas,“ its spectrum is continuous, like that of a solid.
This seeming anomaly gives us the clue that points the way to an explanation
of the observations. An explosion that is powerful enough to give some
of its products speeds in the ultra high range also accelerates other
portions of its products to speeds just below the ultra high level; that
is, the upper part of the intermediate range. These intermediate products
are moving in time only, and have no capability of independent motion
in space, but most of them are entrained in the moving components. Those
that mix with the low speed matter are carried along until the particles
individually drop out of the stream. This settling out process begins
immediately after ejection. The outward motion of the products of the
Crab supernova has therefore left the volume of the nebula filled with
scattered particles of intermediate speed matter concentrated toward the
center,181 rather than toward the periphery,
as in the shell structures that are typical of supernova remnants in general.
As we saw
in our examination of the theoretical aspects of the upper range speeds
in the preceding chapter, particles moving with speeds in the upper portion
of the intermediate speed range radiate in the same manner as those in
the lower portion of the range below unity; that is, with a continuous
spectrum. The physical state of this material is the temporal equivalent
of the solid state: a condition in which the atoms occupy fixed positions
in three-dimensional time, and the emission is modified in the same manner
as in the solid state. Here we have another concept that is totally foreign
to conventional physical thought. For that reason it will undoubtedly
be difficult for many persons to accept. But it is clearly the kind of
a result that necessarily follows from the general reciprocal relation
between space and time. The two speed ranges with continuum emission are
symmetrically related with respect to the natural datum level: unit speed.
Furthermore, the intermediate range continuum radiation is not limited
to supernova remnants. We will meet the same kind of radiation from matter
in the same temperature range later, under different circumstances.
The theoretical
presentation in Chapter 15 also explains why
the filaments, which are in a still higher speed range, have a line spectrum.
As brought out there, motion in a second scalar dimension is incapable
of representation in the conventional spatial reference system, but the
elimination of the gravitational effect by this motion does cause an observable
change of position in that system. This indirect result applies to the
thermal motion as well as to the unidirectional translational motion previously
considered, but in both cases the magnitude of the observed motion is
subject to the limitations on the gravitational speed in one dimension;
that is, it is confined to the range below unity. Thus, even though the
speeds of the particles in the filaments are in the ultra high range,
the observable thermal effect is in the low speed range, and the radiation
that is produced has a line spectrum like that of an ordinary hot gas.
It has not
been possible to extend the present investigation to an analysis of the
spectra of astronomical objects because of the amount of time that would
be required for such an undertaking. Some aspects of these spectra that
are of special significance in connection with the subjects under discussion
will, however, be noted briefly as we proceed. In the case of the Crab
Nebula much stress has been laid by the astronomers on two points: (1)
that the radiation is non-thermal, and (2) that it is polarized. It will
therefore be appropriate to point out that, according to our theoretical
findings: (1) all radiation from objects with upper range speeds,
except that generated by indirect processes such as the one explained
in the preceding paragraph, is non-thermal, and (2) all such radiation
is polarized as emitted. Where a lower polarization is observed, this
is due to depolarizing effects during travel of the radiation. A three-dimensional
distribution of radiation is impossible in a two-dimensional region.
As noted earlier,
the observed characteristics of Cassiopeia A, the other very conspicuous
(at radio frequencies) supernova remnant, are quite different from those
of the Crab Nebula, even though it is now conceded (not without dissent)
that both are Type II remnants. Here again, there are two components of
the remnant, but neither resembles a component of the Crab Nebula. Both
appear to consist mainly of local concentrations of ordinary matter distributed
in the volume of space occupied by the remnant. The objects of one class
are moving rapidly, and are located mainly at the periphery of the remnant
in what is commonly described as a shell. The other objects are larger,
more evenly distributed throughout the remnant, and nearly stationary.
The shell is no doubt composed of the outward-moving low speed explosion
products. The problem of accounting for the quasi-stationary objects in
the context of conventional astronomical theory has been very difficult;
so difficult, in fact, that there is a tendency to try to dodge the whole
issue, as in the following statement:
The only
possible interpretation of the stationary filaments in Cas A is that
these filaments were present before the supernova outburst.182
Here again
we meet the assumption of omniscience that is so curiously prevalent among
the investigators of the least known areas of science. From the very start
of the investigation whose results are being reported in this work, the
answers to outstanding problems have almost invariably been found in areas
in which the adherents of orthodox theories have claimed that they have
examined all conceivable alternatives. The Cassiopeia A situation is no
exception. The explanation that these authors characterize as impossible
can be obtained from a consideration of the theory that is being discussed
in this work.
There is no
indication of the existence of a Type II dwarf in the remnant. We can
conclude from its absence that the Cassiopeia A supernova was not energetic
enough to produce significant amounts of ultra high-speed products. On
this basis, the two components of the remnant can be identified as low
speed and intermediate speed products This raises another issue, because
intermediate speeds in the dense central core of an exploding star would
normally cause inward motion and production of a Type I dwarf. No such
product is observed. From its absence we can conclude that the star of
which Cassiopeia A is a remnant did not have a dense core; that
is, it was a star of the giant, or pre-giant, class, in an early stage
before there was much central condensation. The Type II explosion can
take place at any stage of the stellar cycle. If it happens during a diffuse
stage, the explosion involves the entire structure the explosion forces
are predominantly outward, and they are distributed so widely that they
d`, not reach the ultra high levels. In this case the intermediate speed
products are entrained in the outgoing low speed matter, and are distributed
in the remnant in much the same manner as the amorphous mass in the Crab
Nebula, but in local concentrations because of the lower density of the
moving matter in which they are being carried.
Explosion
of a relatively cool and extremely diffuse star would not be as spectacular
an event as an ordinary supernova. This is probably the reason, or at
least a major part of the reason, why there is no record of an observation
of the supernova that produced Cassiopeia A. The explanation of the strength
of the radiation now being received from this remnant, and the rather
rapid decrease in the amount of this radiation, will become apparent when
the process by which the radiation is generated is described in Chapter
18.
From the explanations
that have been given, it can be seen that the unique characteristics of
both Cassiopeia A and the Crab Nebula are due to the youth of these objects.
These are features of the very early post-explosion stages. Within a few
thousand years these early phases of the evolutionary development will
be completed. The optically observable activity in the remnant will then
be confined almost entirely to the outer shell, where the outward-moving
low speed component is concentrated. Radio and x-ray emission will continue
on a reduced scale for a considerable period of time. The Vela remnant,
estimated to be about l0,000 years old, has already reached this more
advanced age.
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