If some appalling explosion occurred in this star, and the sound in its flight of 340 meters (1,115 feet) per second were able to cross the void that separates us from it, the noise of this explosion would only reach us in 3,000,000 years.
A train started at a speed of 106 kilometers (65 miles) per hour would have to run for 46,000,000 years, in order to reach this star, our neighbor in the celestial kingdom.
The distance of some thirty of the stars has been determined, but the results are dubious.
The dazzling Sirius reigns 92,000,000,000,000 kilometers (57,000,000,000,000 miles), the pale Vega at 204,000,000,000,000. Each of these magnificent stars must be a huge sun to burn at such a distance with such luminosity. Some are millions of times larger than the Earth. Most of them are more voluminous than our Sun. On all sides they scintillate at inaccessible distances, and their light strays a long while in space before it encounters the Earth. The luminous ray that we receive to-day from some pale star hardly perceptible to our eyes—so enormous is its distance—may perhaps bring us the last emanation of a sun that expired thousands of years ago.
If these methods have been clear to my readers, they may also be interested perhaps in knowing the means employed in weighing the worlds. The process is as simple and as clear as those of which we have been speaking.
Weighing the stars! Such a pretension seems Utopian, and one asks oneself curiously what sort of balance the astronomers must have adopted in order to calculate the weight of Sun, Moon, planets or stars.
Here, figures replace weights. Ladies proverbially dislike figures: yet it would be easier for some society dame to weigh the Sun at the point of her pen, by writing down a few columns of figures with a little care, than to weigh a 12 kilogram case of fruit, or a dress-basket of 35 kilos, by direct methods.
Weighing the Sun is an amusement like any other, and a change of occupation.
If the Moon were not attracted by the Earth, she would glide through the Heavens along an indefinite straight line, escaping at the tangent. But in virtue of the attraction that governs the movements of all the Heavenly bodies, our satellite at a distance of 60 times the terrestrial half-diameter revolves round us in 27 days, 7 hours, 43 minutes, 111⁄2 seconds, continually leaving the straight line to approach the Earth, and describing an almost circular orbit in space. If at any moment we trace an arc of the lunar orbit, and if a tangent is taken to this arc, the deviation from the straight line caused by the attraction of our planet is found to be 11⁄3 millimeter per second.