Elementary Astronomy, or Notes and Questions on the Stars and Solar System (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 9. As light travels at the rate of one hundred and eighty-five thousand miles in a second of time, it would take three and a half years for a ray of light to pass from the nearest fixed star to our globe. 10. It is computed that Sirius, the brightest of the fixed stars, is about twenty thousand times as large as our sun, and yet at so enormous a distance as to appear a point in space. Sir John Herschel concluded from observations by Dr. Wollaston that the intrinsic splendour of Sirius is equal to sixty-three times that of the sun; if therefore Sirius occupied the position of the sun, its light would be increased in the same proportion. 11. Fixed stars, when seen through a telescope, do not appear in the shape of globes, but only as points of light; this is owing to their enormous distances. 12. Many stars, which appear to be single when seen with the unaided eye, have been found to be double; triple, quadruple, and even eight have been detected when they were seen through a telescope. 13. Optical couples are those which appear as one, when one star is nearly behind the other, probably at a great distance. 14. In the case of many double stars one star is found to revolve round the other. chapter{Section 4These are sufficiently near to attract each other, and are known as binary stars or physical couples as distinguished from optical couples. 15. The two stars which form a binary are mostly of different colours?for example, one being red, the other green; and on applying the test of concealing one while the other only is looked at, it is found that the colours really belong to the stars themselves, and are not complementary (as when a piece of green paper is placed by the side of a white piece, and the white piece appears of a pink hue). Some stars have been fou...