Page:Popular Science Monthly Volume 92.djvu/250

 Canopus — A Mighty Celestial Furnace

It is so far away that we see it by the Ught that left it in the 15th century, and it is 139 times bigger than our Sun

By Scriven Bolton, F. R. A. S., M. B. A. A.

��IF we took up our abode at a distance equal to one of the nearest stars, say Alpha Centauri, long before arriving there our world would be totally invisible, even if we carried with us a powerful telescope. The ratio which it bears to the visible universe of stars is incon- ceivably less than that which a single drop of water bears to all the oceans of the world united.

The immensity of the stellar universe will never be comprehended by our finite intelligence. Let us, however, contem- plate the intervals of time required for light to bridge the awful gulfs of space around us. Traveling at the rate of at least 188,000 miles per second, light takes four years to reach us from the nearest bright star. Yet the velocity of that light is sufficient to circuit the earth at the equator no less than seven and a half times in a single second. The light from many stars occupies hundreds and even thousands of years in the journey; hence we gaze upon them to-day as they were centuries ago, and if at the present mo- ment they ceased to shine, our senses would remain unnotified of the fact till centuries hence. Further, it has recently been ascertained that stars in the Magel- lanic star cloud are so very distant that their light requires 30,000 years to reach us! A striking witness to the inconceiv- able dimensions of what may be termed a microscopic corner of the heavens was forthcoming in 1901, when the new star Nova Persei suddenly burst forth. The rays of light thus propagated took many months in reaching and finally illuminat- ing the nebulous region situated "locally" one might say.

The question of the size of different bodies poised in this infinite space is one which frequently arises, and the slumber- ing sense is startled on learning of the existence of spheres hundreds, thousands, millions of times larger than our globe. Situated as we are near the center of the Milky Way, that beautiful soft track of

��light which forms a complete circle of light round the earth, we hold a position in the heavens favorable to an inspection of our neighbors. We are apt to be mis- lead by the assumption that the brightest stars represent those nearest us. As- tronomers have found that distances vary quite irrespectively of brightness, for throughout space we find big and httle stars strewn alike in haphazard fashion.

How Small Is Our Mighty Sun!

As in many things common to our- selves, appearances are often decidedly misleading. We might say that our sun is larger than other suns. Careful measurement, however, tells us that our luminary represents just an average sized member of the celestial host. But to say that it attains a diameter of 865,000 miles is a bare statement which fails to awaken an adequate conception of its vastness. If a track were laid along its equator, and a train were to travel thereon at the rate of sixty miles an hour day and night without intermission, five years would be occupied in completing a single journey. The sun's comparative diameter might be illustrated by placing 109 marbles in a rov/, each one represent- ing the earth. A colossal globe no doubt. But we have only to look around at some of the well-known stars to find the sun's dimensions surpassed many times. Take Sirius, the Dog Star, whose diameter is six times that of the sun. At a more remote distance, so remote that its dis- tance cannot be correctly ascertained, is Spica, a first magnitude star, which, judging from its bright light, must be a sphere at least "fifty-five times greater in diameter than our sun. At a similarly in- conceivable distance is the well-known star Rigel, which Sir David Gill stated must possess a minimum diamtter of seventy-five times that of our luminary.

What is the Biggest Star? In ascending to greater dimensions the

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