Page:Popular Science Monthly Volume 12.djvu/58

48 stop in its flight; but the feeblest outward influence would be felt, throwing it either into the sphere of attraction of our sun or into that of Alpha Centauri.

This sun called Centaurus is located in the southern sky, near the antarctic pole. It appears to us in the form of a bright star of the first magnitude. The sun nearest to us, next after this, is situated in the northern sky, in the constellation Cygnus, or the Swan. It is famous as 61 Cygni. Its distance is 400,000 times the radius of the earth's orbit, or about fifteen trillions of leagues. I have often observed this star: it is just visible to the naked eye, but to the telescope it is double, as the preceding, only its components do not move around each other, a conclusion which has much surprised me, although arrived at by comparing all the observations made during the last hundred years; its mass, therefore, cannot be determined. But, however that may be, the fact which should impress us is that the distances which separate the suns of the universe are reckoned not by millions, nor by billions, but by trillions of leagues.

The most brilliant star of our sky, Sirius, is a sun whose volume, judging from its light, should be 2,600 times larger than that of our sun. Its distance is about 897,000 times thirty-seven millions, that is about thirty-three trillions of leagues.

Let us mention again among "our neighbors" the sixty-second of Ophiuchus, situated near the equator. I have calculated that it weighs about three times as much as our sun, that is, 900,000 times more than the earth. Its distance is 1,400,000 times the semi-diameter of the earth's orbit, that is, fifty-four trillions of leagues.

Astronomers, since the time of Kepler, agree in admitting that each of the countless suns that fill infinite space is the centre of a system analogous to the planetary system of which we form a part. Each of these suns that we see in the sky shows to us a luminous fireside around which other human families are gathered. Our eyes are too feeble to see these unknown planets. The most, powerful of our telescopes do not yet reach down to these depths. But Nature concerns itself neither with our eyes nor with our telescopes, and so, beyond the boundaries that stop the flight of our tired conceptions, she continues to display her boundless and magnificent works.

However, the hour has come when these planetary systems different from ours cease to slumber in the domain of hypothesis. In spite of the telescope, celestial mechanics have already revealed the existence of obscure stars, invisible in the rays of these distant suns, but which affect them in their proper movements across immensity; and already powerful telescopes have contemporaneously recognized several among the stars known before to exist only in hypothesis.

One of the most splendid conquests of sidereal astronomy has been the discovery of the system of Sirius, made some fifteen years since. For a long time, from careful measures of its position, it has been