nce from the sun. The sun
itself removed to that distance would appear to our eyes only as a star
of the first magnitude. But Zoellner has shown that the sun exceeds
Jupiter in brilliancy 5,472,000,000 times. Seen from equal distances,
however, the ratio would be about 218,000,000 to 1. This would be the
ratio of their light if both sun and Jupiter could be removed to about
the distance of the nearest stars. Since the sun would then be only as
bright as one of the stars of the first magnitude, and since Jupiter
would be 218,000,000 times less brilliant, it is evident that the latter
would not be visible at all. The faintest stars that the most powerful
telescopes are able to show probably do not fall below the sixteenth or,
at the most, the seventeenth magnitude. But a seventeenth-magnitude star
is only between two and three million times fainter than the sun would
appear at the distance above supposed, while, as we have seen, Jupiter
would be more than two hundred million times fainter than the sun.

To put it in another way: Jupiter, at the distance of the nearest stars,
would be not far from one hundred times less bright than the faintest
star which the largest telescope is just able, under the most exquisite
conditions, to glimpse. To see a star so faint as that would require an
object-glass of a diameter half as great as the length of the tube of
the Lick telescope, or say thirty feet!

Of course, Jupiter might be more brilliantly illuminated by a brighter
star than the sun; but, granting that, it still would not be visible at
such a distance, even if we neglect the well-known concealing or
blinding effect of the rays of a bright star when the observer is trying
to view a faint one close to it. Clearly, then, the obscure objects seen
by Dr. See near some of the stars, if they really are bodies visible
only by light reflected from their surfaces, must be enormously larger
than the planet Jupiter, and can not, accordingly, be admitted into the
category of planets proper, whatever else they may be.

Perhaps they are extreme cases of what we see in the system of
Sirius--i.e., a brilliant star with a companion which has ceased to
shine as a star while retaining its bulk. Such bodies may be called
planets in that they only shine by reflected light, and that they are
attached to a brilliant sun; but the part that they play in their
systems is not strictly planetary. Owing to their great mass they bear
such sway over the