Page:In the high heavens.djvu/213

 considered to be the sun's nearest neighbour in our sidereal system.

The proper motion and the distance of 1830 Groombridge being both assumed, it is easy to calculate the velocity with which the star must be moving. The velocity is indeed stupendous and worthy of a majestic sun; it is no less than 200 miles a second. It would seem that the velocity may even be much larger than this. The proper motion of the star which we see is merely the true proper motion of the star foreshortened by projection on the surface of the heavens. In adopting 200 miles a second as the velocity of 1830 Groombridge, we therefore make a most moderate assumption, which may and probably does fall considerably short of the truth. But even with this very moderate assumption, it will be easy to show that 1830 Groombridge seems in all probability to be merely travelling through our system, and not permanently attached thereto.

The star sweeps along through our system with this stupendous velocity. Now there can be no doubt that if the star were permanently to retain this velocity, it would in the course of time travel right across our system, and after leaving our system would retreat into the depths of infinite space. Is there any power adequate to recall this star from the voyage to infinity? We know of none, unless it be the attraction of the stars or other bodies of our sidereal system. It therefore becomes a matter of calculation to determine whether the attraction of all the material bodies of our sidereal system could be adequate, even with universal gravitation, to recall a body which seems bent on leaving that system with a velocity of 200 miles per second.