THE KELBURN OBSERVATORY

Dominion, Volume 7, Issue 2214, 29 July 1914, Page 9

THE KELBURN OBSERVATORY

. : : (By:;Jas/R. Strachan.) ,i An v interesting.'object in the evening sky at the; present itime is the planet Jupiter and. his attendant moons, which on any clear Tuesday night may be seen, with-other heavenly bodies through the fine telescope in tho Kelburn Observatory, to whiob'Vtbe .public,have access upon payment : of:a6mall fee. .;.. ■ : ; Jupiter is-thb.largest of the planets, and since Galiles's time until 1892 it was' thought to havo'.fbur moons only, but up "to: the."present day :four'others, have been.;found''making,■ eight.-.in all; ■It was: the eclipses, of Jupiter's moons which first'showed that light travels at a speed of 186,0D0.i.miles.in. a.-.second., ' This ', unit : has r -;!gehorally.sbeoEH adoptedj when endeavouring to indioato. the distances of the various heavenly bodies from the earth. .uThus, the light from the raoonveould never take less than; about one and a fifth seconds to reach the earth.' The' light from Venus, our nearest plaiiet, which is an object of interest '..-in' 'the early evening in the western sky at the present time, coujel never take less than about two and a quarter minutes to reach tho earth. Alpha' Centauri,; the bigger of the two Pointers'to the Southern Cross, which .is--to.be seen here on any clear night throughout the year, is the nearest star to us, and the light from it would take about four years to reach the earth. In this connection w ( e see that no planet or star could thus interpose itself betweon the moon and the earth. The pbot Coleridge- was evidently unaware of this, for he says in "The An-'cierif'-'Mariner" :'-■■'..■■•:;,• ''■'■'' ' Till clqmb above the eastern bar . The horned Moon, with one bright :r ~y starv; ' Within the nether:tip.'.'■'. : - The Turks, too, were evidently unaware of .this fact, or they would not. have shown their merchant flag as a.crescent moon with "a star close to its'concave :«ide. ,; ;,...;.'. .-. _■• ' •■'■-._, ' ' Oh August 6 it will be interesting_to watch Jupiter, for about half-past nine in the evening it will disappear, for: a time behind the moon. . ~■ : . ■ •.'■.' On August. 1,- jlntares, the largest star in the Scorpion constellation, which is well overhead during the evening at the present;time, will.be hidden behind the.moon a few minutes before seven in the even'ing._ Arcturus is the largest star in ,the Bootes constellation, and is to be' seen at the present time during the evening.; It is so far away that the light from it takes about 136 years to reach us. . .Vega >is the largest star in the Lyre constellation, and is to be seen low .down at the present, time during the; evening. . The light from it takes' about. 50: years to; reach the_ earth. !•'-. Another.first magnitude star to bo seen in, the sky during the evening at tho: present ~time is the Alpha Aquilae, ! the Eagle constellation. • Astronomers, measure' the distances, of the stars, by a trianglo of which the apex is the star and tho base.a line joining'opposite sides of the earth's ! : orbit round tho sun. .This base is approximately 186 million miles in length, but so great is the distauce away'of somo-.of the;stars that even this long 'base as seen from them is a mere point. To-put the case hi- a. slightly, different way.: If the ..diameter of the earth's ■ orbil be represented by. a marble, one i'inch' in diameter, the nearest, star would be about 2 1-5 miles away. The interesting nature of this subject would j amply repay one for making a deeper: study of it.