To count the stars involves a task which lies beyond the power of man
to accomplish. Even without the aid of any telescope, we can see a
great multitude of stars from this part of the world. There are also
many constellations in the southern hemisphere which never appear
above our horizon. If, however, we were to go to the equator, then,
by waiting there for a twelve-month, all the stars in the heavens
would have been successively exposed to view. An astronomer, Houzeau,
with the patience to count them, enumerated about 6000. This is the
naked-eye estimate of the star-population of the heavens; but if,
instead of relying on unaided vision, you get the assistance of a
little telescope, you will be astounded at the enormous multitude of
stars which are disclosed.
[Illustration: FIG. 82.--The Great Bear and the Pole.]
An ordinary opera-glass or binocular is a very useful instrument for
looking at the stars in the heavens. If you employ an instrument of
this sort, you will be amazed to find that the heavens teem with
additional hosts of stars that your unaided vision would never have
given you knowledge of. Any part of the sky may be observed; but, just
to give an illustration, I shall take one special region, namely, that
of the Great Bear (Fig. 82). The seven well-known stars are here shown,
four of which form a sort of oblong, while the other three represent
the tail. I would like you to make this little experiment. On a fine
clear night, count how many stars there are within this oblong; they
are all very faint, but you will be able to see a few, and, with good
sight, and on a clear night, you may see perhaps ten. Next take your
opera-glass and sweep it over the same region; if you will carefully
count the stars it shows, you will find fully 200; so that the
opera-glass has, in this part of the sky, revealed nearly twenty times
as many stars as could be seen without its aid. As 6000 stars can be
seen by the eye all over the heavens, we may fairly expect that twenty
times that number--that is to say, 120,000 stars--could be shown by the
opera-glass over the entire sky. Let us go a step further, and employ
a telescope, the object-glass of which is three inches across. This is
a useful telescope to have, and, if a good one, will show multitudes
of pleasing objects, though an astronomer would not consider it very
powerful. An instrument like this, small enough to be carried in the
hand, has been applied to the task of enumerating the stars in the
northern half of the sky, and 320,000 stars were counted. Indeed,
the actual number that might have been seen with it is considerably
greater, for when the astronomer Argelander made this memorable
investigation he was unable to reckon many of the stars in localities
where they lay very close together. This grand count only extended to
half the sky, and, assuming that the other half is as richly inlaid
with stars, we see that a little telescope like that we have supposed
will, when swept over the heavens, reveal a number of stars which
exceeds that of the population of any city in England except London. It
exhibits more than one hundred times as many stars as our eyes could
possibly reveal. Still, we are only at the beginning of the count; the
very great telescopes add largely to the number. There are multitudes
of stars which in small instruments we cannot see, but which are
distinctly visible from our great observatories. That telescope would
be still but a comparatively small one which would show as many stars
in the sky as there are people living in this mighty city of London;
and with the greatest instruments, the tale of stars has risen to a
number far greater than that of the entire population of Great Britain.
In addition to those stars which the largest telescopes show us, there
are myriads which make their presence evident in a wholly different
way. It is only in quite recent times that an attempt has been made to
develop fully the powers of photography in representing the celestial
objects. On a photographic plate which has been exposed to the sky in
a great telescope the stars are recorded by thousands. Many of these
may, of course, be observed with a good telescope, but there are not a
few others which no one ever saw in a telescope, which apparently no
one ever could see, though the photograph is able to show them. We do
not, however, employ a camera like that which the photographer uses who
is going to take your portrait. The astronomer’s plate is put into his
telescope, and then the telescope is turned towards the sky. On that
plate the stars produce their images, each by its own light. Some of
these images are excessively faint, but we give a very long exposure
of an hour or two hours; sometimes as much as four hours’ exposure
is given to a plate so sensitive that a mere fraction of a second
would sufficiently expose it during the ordinary practice of taking a
photograph in daylight. We thus afford sufficient time to enable the
fainter objects to indicate their presence upon the sensitive film.
Even with an exposure of a single hour a picture exhibiting 16,000
stars has been taken by Mr. Isaac Roberts, of Liverpool. Yet the
portion of the sky which it represents is only one ten-thousandth part
of the entire heavens. It should be added that the region which Mr.
Roberts has photographed is furnished with stars in rather exceptional
profusion.
Here, at last, we have obtained some conception of the sublime scale on
which the stellar universe is constructed. Yet even these plates cannot
represent all the stars that the heavens contain. We have every reason
for knowing that with larger telescopes, with more sensitive plates,
with more prolonged exposures, ever fresh myriads of stars will be
brought within our view.
You must remember that every one of these stars is truly a sun, a
lamp, as it were, which doubtless gives light to other objects in its
neighborhood as our sun sheds light upon this earth and the other
planets. In fact, to realize the glories of the heavens you should try
to think that the brilliant points you see are merely the luminous
points of the otherwise invisible universe.
Standing one fine night on the deck of a Cunarder we passed in open
ocean another great Atlantic steamer. The vessel was near enough for
us to see not only the light from the mast-head but also the little
beams from the several cabin ports; and we could see nothing of the
ship herself. Her very existence was only known to us by the twinkle
of these lights. Doubtless her passengers could see, and did see, the
similar lights from our own vessel, and they probably drew the correct
inference that these lights indicated a great ship.
Consider the multiplicity of beings and objects in a ship: the captain
and the crew, the passengers, the cabins, the engines, the boats,
the rigging, and the stores. Think of all the varied interests there
collected and then reflect that out on the ocean, at night, the sole
indication of the existence of this elaborate structure was given by
the few beams of light that happened to radiate from it. Now raise your
eyes to the stars; there are the twinkling lights. We cannot see what
those lights illuminate, we can only conjecture what untold wealth of
non-luminous bodies may also lie in their vicinity; we may, however,
feel certain that just as the few gleaming lights from a ship are
utterly inadequate to give a notion of the nature and the contents of
an Atlantic steamer, so are the twinkling stars utterly inadequate to
give even the faintest conception of the extent and the interest of
the universe. We merely see self-luminous bodies, but of the multitudes
of objects and the elaborate systems of which these bodies are only
the conspicuous points we see nothing and we know very little. We are,
however, entitled to infer from an examination of our own star--the
sun--and of the beautiful system by which it is surrounded, that these
other suns may be also splendidly attended. This is quite as reasonable
a supposition as that a set of lights seen at night on the Atlantic
Ocean indicates the existence of a fine ship.