Astronomical Notes.

Evening Post, Volume L, Issue 36, 10 August 1895, Page 1 (Supplement)

Astronomical Notes.

(Specially written for the EyeninoPost.) The distance of the stars is a more difficult problem to solve, as they are so distant that no base-line drawn upon the earth will be long enough to show any parallax, or apparent change of place in the star, from the observer's thift from one end of the base-line to the other. The base-line chosen here is the diameter of the earth's orbit. As the earth revolved it was soon found that the star, a Centauri, chosen by Henderson, the astronomer at the Cape, for the purpose, varied in its position from small stars near, and that at the end of the year the star had apparently revolved in an orbit two seconds aoross, nearly, and this meant that the earth's orbit, seen from the star, if that were possible, would be of that size. Draw a circle with the earth in the centre and the star's orbit in the circumference, and the elliptic orbits of the earth and star are very nearly circles. The circumference of a circle is a little over three times ' the diameter, a ratio shewn by fraction 1-3 1416. The number of times the star-circle will occur in the circumference will be shown by fraction 860 x 60 x 60 2 and the value of this circle by 2192,000,000,2 1 92,000,000, or twice the earth's distance from the sun. Another divisor, 2, must be placed in the fraction to gain the radius of the large circle, or the star's distance, bo that the whole fraction becomes 360x60x60x21 92,000,000 x 1 2 x 2 x 3-1416 The result would be, if true measures had been used, 20 billions of miles, and light, travelling at the rate of 185,000 miles in each second of time, would require four years to reach us from the star, or we see tho star each night as it was four years ago. Her.chel illustrates our system thus: — The Sun a globe 2ft aoross ; Meroury will then be a mustard seed, at 82ft away; Venus, a pea, at 142 ft; Earth, a little larger pea, 2 loft; Mars, a large Bhot, 327 ft ; Asteroids, sand - grains, 600 f t; Jupiter, an orange, at ; Saturn, a small orange, at 4- lOths of a mile ; Uranus, a large cherry, J -mile ; Neptune, a large plum, 1} miles ; a Centauri, 8000 miles. The spectroscope, which splits up a ray of white light into a coloured band, called a spectrum, buows what the stars are made of. Light from different stars shows different bands of light in different places of the spectrum when passed through a speotroscope. The stars, when also thus examined, show different bands of light in different places, and it is a, fair conclusion that, if in any instance bands like those due to a gas are found in the star, the star-bands are produced by the presence in the star of the testing gas. It has also been discovered lately that if the star-bands are shifted nearer the blue end of the spectrum, the star and the earth are approaching one another ; that if there is no shift, their distance is constant ; and that, if the shif C"is nearer the red end, the Btar and earth are separating. These notes are now ended. They were written in answer to a letter to the Evenino Post, and were intended to serve as an introduction only to the wonders of astronomy, and to induce would-be learners to study the pleasant books on this science to be found in our Free Library ; but all has been stated with the further intention that something might be understood of tho order and intelligence that is here revealed, and that there might be gained, also, a fuller knowledge of the words of the Psalmist— "The heavens declare the glory of God, and the firmament showeth his handiwork." A. Stock.