THE STAR WORLD

Otago Daily Times, Issue 22743, 2 December 1935, Page 16

THE STAR WORLD

WORK OF ASTRONOMERS OBSERVATIONS OF THE SUN DISTURBED PERIOD. | It is a familiar saying that “ There is nothing new under the sun.” The astronomer can counter this, and with perhaps more justification, by saying “ There is always something new on the sun,” writes Dr Harold Spencer Jones, the Astronomer Royal, in the Daily Mail. During the next few years the Sun will be closely watched, for it is eratering on one of its disturbed stages. Just as a volcano has alternations of periods of quiescence and periods of violent eruption, so the sun has alternations of periods of relative inactivity and periods of great disturbance. For the sun these alterations occur with considerable regularity in a cycle of about 11 years. We can anticipate with reasonable certainty that the increasing disturbances on the sun will reach their peak in about three years’ time. Large spots are now frequently to be seen on the sun. They are violent cyclonic disturbances which ■ sometimes start very suddenly and develop with remarkable rapidity. For instance, on August 20 a spot was seen covering an area about one and a-half times the total area of the surface of the earth, where twenty-four hours previously there had been no trace of any spot. The next day the area of the spot was four times the area of the earth’s surface. The largest spots will cover an area of about 100 times that of the earth’s surface and extend over 150,000 miles. Associated with these disturbances are movements in the sun’s atmosphere having velocities as great as 100 miles a second. The recent depression that passed over England and did so much damage, with a wind velocity of 60 miles an hour, was a puny affair compared with the gigantic depressions that from time to time develop on the sun. BLAZING STARS. When the’sun is in its disturbed stated great jets of incandescent vapours, covering areas much greater than the earth, arc often thrown out from its surface to heights of many thousands of miles. Sometimes these jets are thrown out with such violence that they shoot off into outer apace like a gigantic fiery rocket. A few years ago, an enormous flame was seen, extending for more than 500.000 miles. It grew rapidly, and in five hours it had risen 375,000 miles. When it was last seen it was at a height of more than 500,000 miles above the surface of the sun, and was receding rapidly away, from it. Great as are these disturbances on the sun, they pale into insignificance when compared with the disturbances that take place now and then on some other stars. The appearance last December of a new star in the constellation of Hercules was due to a violent flare-up that caused the star to increase in brightness some 400.000 times. Before this flare-up, a long exposure photograph with a large telescope was needed to show the star; after the flareup it became a bright naked-eye object. The star faded slowly until about the end of March; its brightness then dropped rapidly. When at its brightest, its candlepower was about 40,000 times that of the sun; in April it decreased until it was about equal to that of the sun. The cause of such a, remarkable outburst is still very much of a mystery. It is not improbable that every star experiences such a flare-up during its lifetime. Some astronomers believe that our sun, which has not passed through this stage, shows incipient signs of doing so. CENTURIES AGO. Even if this were the case—and it is by no means certain —millions of years might pass before the outburst ensued. The flare-up of Nova Herculis actually occurred about 1200 years ago; it* is due to the great distance of the star that the light-waves, carrying the story of the star’s upheaval, have only just reached us. Contrasting with the new stars, which at the peak of their anthuss are of intensely high candle-power, are the small low candle-power stars that the astronomer calls “white dwarfs.” These stars are so faint that they are extremely difficult to detect. They are probably abundantly scattered throughout space, but we can only hope to detect those that are comparatively near. Until just recently only five of these very faint small stars were known; the new discovery of three more such stars is therefore a matter of satisfaction. One of these newly-discovered stars is of great interest for it Is probably smaller than any other star known. It is actually smaller than our earth, having only about half the volume of the earth. We may compare it with the sun, which could contain about 1.300.000 bodies the size of the earth, or with the giant star Antares, which could contain about 80,000,000 bodies the size of the sun. The newly-discovered small star, though smaller than the earth, weighs about as much as the sun, but the matter in it is so densely packed that a matchbox full would weigh about 1200 tons! HOTTER THAN THE SUN. When contrasted with such dense matter, even lead seems a light and airy substance. This star is hotter than the sun, but because of its small size its total candle-power is only about one 700th that of the sun. For studying such faint stars large telescopes are needed. The great project of constructing in America a 200inch telescope is being followed with interest all over the world. The 20-ton disc of pyrex glass, 17 feet in diameter, from which the mirror is to be made, was successfully east at the Corning Glassworks, New York, on December 2, 1934. After easting, the disc was placed in the electrically-heated annealing oven, the temperature being very gradually lowered to ensure that the disc cooled slowly and uniformly, and that it therefore remained free from strain.

The period of 10 months required for the annealing has ended, and we may expect soon to hear that the oven has been opened and the disc removed. Meanwhile, it is a matter for satisfaction that the British Empire is not altogether outdistanced in the matter of giant telescopes. Sir Howard Grubb, Parsons, and Co. have Recently completed a fine 74-inch telescope for the Dunlop Observatory, Toronto, and have just signed a contract for a telescope of the same size for the Radcliffie Observatory, which is being moved from Oxford to a site near Pretoria, in South Africa, where conditions are sufficiently good to e;.able a large telescope to be efficiently used. AEONS AGO. We cannot yet say what new avenues the observations with the 200-inch telescop j may open up. With the 100-inch telescope, a distant universe has recently been discovered that is so far away that the light from it has taken 230,000,000 years to reach us. While the light by which it was photographed was on its long journey,

dinosaurs and flying reptiles have appeared on our earth, have had their day, and have disappeared again.

Many of the great mountain ranges of the earth were formed long after the lig... sot out on its journey, and mankind only appeared on the earth when the light was on its last lap. This universe of some thousands of millions of stars, the most remote at present known, is moving away from us with the remarkable velocity of about 25,000 miles a second or, in other words, at such a rate that it could circle lUc earth’s equator in a second.

No other kflown celestial object can equal this for speed of motion. The 200-inch telescope will be able to probe much farther into space and may reveal yet more distant and more rapidly moving universes.