A German astronomer recently counted 1528 on one
photographic plate. Many of them, moreover, are so vast that they
must contain the material for making a great number of worlds.
Examine a good photograph of the nebula in Orion. Recollect that
each one of the points of light that are dotted over the expanse
is a star of a million miles or more in diameter (taking our sun
as below the average), and that the great cloud that sprawls
across space is at least 10,000 billion miles away; how much more
no man knows. It is futile to attempt to calculate the extent of
that vast stretch of luminous gas. We can safely say that it is
at least a million times as large as the whole area of our solar
system; but it may run to trillions or quadrillions of miles.
Nearly a hundred other nebulae are known, by the spectroscope, to
be clouds of luminous gas. It does not follow that they are
white-hot, and that the nebula is correctly called a "fire-mist."
Electrical and other agencies may make gases luminous, and many
astronomers think that the nebulae are intensely cold. However,
the majority of the nebulae that have been examined are not
gaseous, and have a very different structure from the loose and
diffused clouds of gas.
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