Because of the mandatory restrictions imposed on the revelators (1109), the science and cosmology of The Urantia Book is at the approximate level of current human knowledge for the mid-1930's. It also contains some statements that were prophetic at that time because the mandate allowed the revelators to supply vital information to fill gaps in our otherwise earned knowledge. One such gap-filler may have been:

"In large suns when hydrogen is exhausted and gravity contraction ensures, and such a body is not sufficiently opaque to retain the internal pressure of support for the outer gas regions, then a sudden collapse occurs.  The gravity-electric changes give origin to vast quantities of tiny particles devoid of electric potential, and such particles readily escape from the solar interior thus bringing about the collapse of a gigantic sun within a few days."(464)

No tiny particles devoid of electric potential that could escape readily from the interior of a collapsing star were known to exist in 1934. In fact, the reality of such particles were not confirmed until 1956, one year after the publication of The Urantia Book. The existence of particles that might have such properties had been put forward as a suggestion by Wolfgang Pauli in 1932, because studies on radioactive beta decay of atoms had indicated that a neutron could decay to a proton and an electron, but measurements had shown that the combined mass energy of the electron and proton did not add up with that of the neutron. To account for the missing energy, Pauli suggested a little neutral particle was emitted, and then, on the same day, while lunching with the eminent astrophysicist Walter Baade, Pauli commented that he had done the worst thing a theoretical physicist could possibly do, he had proposed a particle that could never be discovered because it had no properties. Not long after, the great Enrico Fermi took up Pauli's idea and attempted to publish a paper on the subject in the prestigious science journal "Nature." The editors rejected Fermi's paper on the grounds that it was too speculative. This was in 1933, the year before receipt of the relevant Urantia Paper.

An interesting thing to note is The Urantia Book statement that tiny particles devoid of electric potential would be released in vast quantities during the collapse of the star. If, in 1934, an author other than a knowledgeable particle physicist was prophesying about the formation of a neutron star (a wildly speculative proposal from Zwicky and Baade in the early 1930's), then surely that author would have been thinking about the reversal of beta decay in which a proton, an electron and Pauli's little neutral particle would be squeezed together to form a neutron.

Radioactive beta decay can be written...
1. neutron ----> proton + electron + LNP
where LNP stands for little neutral particle.  Hence the reverse should be:
2. LNP + electron + proton---->neutron

For this to occur an electron and a proton have to be compressed to form a neutron but somehow they would have to add a little neutral particle in order to make up for the missing mass-energy. Thus, in terms of available speculative scientific concepts in 1934, The Urantia Book appears to have put things back to front, it has predicted a vast release of LNP's, when the reversal of radioactive beta decay would appear to demand that LNPs should disappear.

The idea of a neutron star was considered to be highly speculative right up until 1967. Most astronomers believed that stars of average size, like our sun, up to stars that are very massive, finished their lives as white dwarfs. The theoretical properties of neutron stars were just too preposterous; for example, a thimble full would weigh about 100 million tonnes. A favored alternative proposal was that large stars were presumed to blow off their surplus mass a piece at a time until they got below the Chandrasekhar limit of 1.4 solar masses, when they could retire as respectable white dwarfs. This process did not entail the release of vast quantities of tiny particles devoid of electric potential that accompany star collapse as described in the cited Urantia Book quotation.

Distinguished Russian astrophysicist, Igor Novikov, has written, "Apparently no searches in earnest for neutron stars or black holes were attempted by astronomers before the 1960s. It was tacitly assumed that these objects were far too eccentric and most probably were the fruits of theorists wishful thinking. Preferably, one avoided speaking about them. Sometimes they were mentioned vaguely with a remark yes, they could be formed, but in all likelihood this had never happened. At any rate, if they existed, then they could not be detected."
    Acceptance of the existence of neutron stars gained ground slowly with discoveries accompanying the development of radio and x-ray astronomy. The Crab nebula played a central role as ideas about it emerged in the decade, 1950-1960. Originally observed as an explosion in the sky by Chinese astronomers in 1054, interest in the Crab nebula increased when, in 1958, Walter Baade reported visual observations suggesting moving ripples in its nebulosity. When sensitive electronic devices replaced  the photographic plate as a means of detection, the oscillation frequency of what was thought to be a white dwarf star at the center of the Crab nebula turned out to be about 30 times per second.

For a white dwarf star with a diameter in the order of 1000 km, a rotation rate of even once per second would cause it to disintegrate due to centrifugal forces. Hence, this remarkably short pulsation period implied that the object responsible for the light variations must be very much smaller than a white dwarf, and the only possible contender for such properties appeared to be a neutron star. Final acceptance came with pictures of the center of the Crab nebula beamed back to earth by the orbiting Einstein X-ray observatory in 1967. These confirmed and amplified the evidence obtained by prior observations made with both light and radio telescopes.

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The reversal of beta-decay, as depicted in (2) above, involves a triple collision, an extremely improbable event, unless two of the components combine in a meta-stable state--a fact not likely to be obvious to a non-expert observer which also indicates that the author(s) of the Urantia Paper was highly knowledgeable in this field.

The probable evolutionary course of collapse of massive stars has only been elucidated since the advent of fast computers. Such stars begin life composed mainly of hydrogen gas that burns to form helium. The nuclear energy released in this way holds off the gravitational urge to collapse. With the hydrogen in the central core exhausted, the core begins to shrink and heat up, making the outer layers expand. With the rise in temperature in the core, helium fuses to give carbon and oxygen, while the hydrogen around the core continues to make helium. At this stage the star expands to become a red giant.

After exhaustion of helium at the core, gravitational contraction again occurs and the rise in temperature permits carbon to burn to yield neon, sodium, and magnesium, after which the star begins to shrink to become a blue giant. Neon and oxygen burning follow. Finally silicon and sulphur, the products from burning of oxygen, ignite to produce iron. Iron nuclei cannot release energy on fusing together, hence with the exhaustion of its fuel source, the furnace at the center of the star goes out. Nothing can now slow the onslaught of gravitational collapse, and when the iron core reaches a critical mass of 1.4 times the mass of our sun, and the diameter of the star is now about half that of the earth, the star's fate is sealed.

Within a few tenths of a second, the iron ball collapses to about 50 kilometers across and then the collapse is halted as its density approaches that of the atomic nucleus and the protons and neutrons cannot be further squeezed together. The halting of the collapse sends a tremendous shock wave back  through the outer region of the core.

The light we see from our sun comes only from its outer surface layer. However, the energy that fuels the sunlight (and life on earth) originates from the hot, dense thermonuclear furnace at the Sun's core. Though sunlight takes only about eight minutes to travel from the sun to earth, the energy from the sun's core that gives rise to this sunlight takes in the order of a million years to diffuse from the core to the surface. In other words, a sun (or star) is relatively "opaque" (as per The Urantia Book, p.464) to the energy diffusing from its thermonuclear core to its surface, hence it supplies the pressure necessary to prevent gravitational collapse. But this is not true of the little neutral particles, known since the mid 1930's by the name "neutrinos." These particles are so tiny and unreactive that their passage from our sun's core to its exterior takes only about 3 seconds.

It is because neutrinos can escape so readily that they have a critical role in bringing about the star's sudden death and the ensuing explosion. Neutrinos are formed in a variety of ways, many as neutrino-antineutrino pairs from highly energetic gamma rays and others arise as the compressed protons capture an electron (or expel a positron) to become neutrons, a reaction that is accompanied by the release of a neutrino. Something in the order of 10⁵⁷ electron neutrinos are released in this way. Neutral current reactions from Z^o particles of the weak force also contribute electron neutrinos along with the 'heavy' muon and tau neutrinos.

Together, these neutrinos constitute a "vast quantity of tiny particles devoid of electric potential" that readily escape from the star's interior. Calculations indicate that they carry ninety-nine percent of the energy released in the final supernova explosion. The gigantic flash of light that accompanies the explosion accounts for only a part of the remaining one percent! Although the bulk of the neutrinos and anti-neutrinos are released during the final explosion, they are also produced at the enormous temperatures reached by the inner core during final stages of contraction.

The opportunity to confirm the release of the neutrinos postulated to accompany the spectacular death of a giant star came in 1987 when a supernova explosion, visible to the naked eye, occurred in the Cloud of Magellan that neighbors our Milky Way galaxy. Calculations indicated that this supernova, dubbed SN1987A, should give rise to a neutrino burst at a density of 50 billion per square centimeter when it finally reached the earth, even though expanding as a spherical 'surface' originating at a distance 170,000 light years away. This neutrino burst was observed in the huge neutrino detectors at Kamiokande in Japan and at Fairport, Ohio, in the USA. lasting for a period of just 12 seconds, and confirming the computer simulations that indicated they should diffuse through the dense core relatively slowly. From the average energy and the number of 'hits' by the neutrinos in the detectors, it was possible to estimate that the energy released by SN1987 amounted to 2-3 x 10⁵³ ergs. This is equal to the calculated gravitational binding energy that would be released by the collapse of a core of about 1.5 solar masses to a neutron star. Thus SN1987A provided a remarkable confirmation of the general picture of neutron star formation developed over the last fifty years. Importantly, it also confirmed that The Urantia Book had its facts right long before the concept of neutrino-spawning neutron stars achieved respectability...

References:

Hoyle, F., and J. Narlikar. "The Physics Astronomy Frontier." (W.H. Freeman & Co. San Francisco, 1980.)
Novikov, I. "Black Holes and the Universe." (Cambridge University Press, 1990)
Sutton, C.  "Spaceship Neutrino." (Cambridge University Press, Cambridge, 1992)