Easton is of opinion that the annular hypothesis of the Milky Way is inconsistent with our present knowledge of the galactic phenomena, and he suggests that its actual constitution resembles more that of a spiral nebula.
Wilczynski thinks that the age of a spiral nebula may be indicated by the number of its coils; those having the largest number of coils being the oldest, from the point of view of evolution.
The result would be the formation of a spiral nebula in which the motion of the ejected particles--planetesimals--would be across the spiral arms, toward and away from the passing star.
It must be borne in mind that a spiral nebula formed by the close approach of two suns would resemble in form only the great spiral nebulae that are known to exist by hundreds of thousands in the heavens.
The real product of the cooling process in such a nebula would undoubtedly be something in the nature of a spiral nebula, in which the matter would revolve around the nucleus the more rapidly the nearer it was to the nucleus.
They postulate that the materials now composing the Sun, planets, and satellites, at one time existed as a spiral nebula, or as a great spiral swarm of discrete particles, each particle in elliptic motion about the central nucleus.
If the collision is a grazing one, they say, a spiral nebula will be formed.
However, a fairly close approach of two stars will occur in vastly greater frequency and the effect of this approach will also be to form a spiral nebula or two such nebulae.
Then another astonishing change happened: in August photographs taken at the Yerkes Observatory and at Heidelberg showed that the ``nova'' was surrounded by a spiral nebula!
Such, then, is the mechanism of the first phase in the history of a spiral nebula according to the Planetesimal Hypothesis.
Laplace was one of the ablest mathematicians that ever lived, but he had never seen a spiral nebula; if he had, he might have invented a hypothesis to suit its phenomena.
Some astronomers, indeed, now reject Laplace's hypothesis in toto, preferring to think that even our solar system originated from a spiral nebula.
The above list will hopefully provide you with a few useful examples demonstrating the appropriate usage of "spiral nebula" in a variety of sentences. We hope that you will now be able to make sentences using this group of words.
