We have no positive knowledge of dead stars; which is not surprising
when we reflect that a dead star means an invisible star! But when we
see so many individual stars tending toward death, when we behold a vast
population of all conceivable ages, we presume that there are many
already dead. On the other hand, there is no reason to suppose that the
universe as a whole is "running down." Some writers have maintained
this, but their argument implies that we know a great deal more about
the universe than we actually do. The scientific man does not know
whether the universe is finite or infinite, temporal or eternal; and he
declines to speculate where there are no facts to guide him. He knows
only that the great gaseous nebulæ promise myriads of worlds in the
future, and he concedes the possibility that new nebulæ may be forming
in the ether of space.
The last, and not the least interesting, subject we have to notice is
the birth of a "new star." This is an event which astronomers now
announce every few years; and it is a far more portentous event than the
reader imagines when it is reported in his daily paper. The story is
much the same in all cases. We say that the star appeared in 1901, but
you begin to realise the magnitude of the event when you learn that the
distant "blaze" had really occurred about the time of the death of
Luther! The light of the conflagration had been speeding toward us
across space at 186,000 miles a second, yet it has taken nearly three
centuries to reach us. To be visible at all to us at that distance the
fiery outbreak must have been stupendous. If a mass of petroleum ten
times the size of the earth were suddenly fired it would not be seen at
such a distance. The new star had increased its light many hundredfold
in a few days.
There is a considerable fascination about the speculation that in such
cases we see the resurrection of a dead world, a means of renewing the
population of the universe. What happens is that in some region of the
sky where no star, or only a very faint star, had been registered on our
charts, we almost suddenly perceive a bright star. In a few days it may
rise to the highest brilliancy. By the spectroscope we learn that this
distant blaze means a prodigious outpour of white-hot hydrogen at
hundreds of miles a second. But the star sinks again after a few months,
and we then find a nebula round it on every side. It is natural to
suppose that a dead or dying sun has somehow been reconverted in whole
or in part into a nebula. A few astronomers think that it may have
partially collided with another star, or approached too closely to
another, with the result we described on an earlier page. The general
opinion now is that a faint or dead star had rushed into one of those
regions of space in which there are immense stretches of nebulous
matter, and been (at least in part) vaporised by the friction.
But the difficulties are considerable, and some astronomers prefer to
think that the blazing star may merely have lit up a dark nebula which
already existed. It is one of those problems on which speculation is
most tempting but positive knowledge is still very incomplete. We may be
content, even proud, that already we can take a conflagration that has
occurred more than a thousand trillion miles away and analyse it
positively into an outflame of glowing hydrogen gas at so many miles a
second.