“WHITE DWARFS” OF THE SKY

Dominion, Volume 32, Issue 66, 10 December 1938, Page 5

“WHITE DWARFS” OF THE SKY

The Hottest Stars

THE DEPTHS OF SPACE

The story of the “white dwarfs” distant stars of such density that a piece the size of a pinhead would break a man’s back —was told by Sir Janies Jeans when he delivered the Lorimer Lecture under the auspices of the Atsronomical Society of Edinburgh in the Usher Hall, Edinburgh, recently. Speaking on “.The Depths of Space. Sir James Jeans said that all the stars that could be seen without a telescope lay inside a sphere' having a radius of about 3000 light-years —that was to say, the distance which light travelling at 11,000,000 miles a minute took 3000 years to cover. Judged by terrestrial standards, such a sphere seemed inconceivably great—the light by which we saw its farthest stars started o nfts journey long before the foundation of Rome, before the siege of Troy, and only reached us now. Yet this sphere was only one drop in the great ocean of space. The great wheel .of stars had a diameter of something like 200,000 dight-years; their light started on its journey through space long before man had become civilized at all. If they compared that wheel to the driving wheel of an express locomotive, tile sphere of stars seen with the unaided eye would be the size of a drop of steel one-eighth of an inch in diameter. Space was full of rotating stars; our own system was only one of many.

The central stars of the planetary nebulae were remarkable as being among-tbp- hottest stars known to astronomy—indeed, that was probably why they alone had these vast atmospheres round them. Their surface temperatures ranged up to about 60.OOOdeg. Centigrade, or 10 times the tenifierature of the sun. The fire in the fire-box of a locomotive was so hot that its few'square feet of surface sent out enough energy to run a train, but these stars were so hot that an area of surface the size of a postage stamp sent out enough energy to run a vast liner the size of the Queen Mary or Normandie.

The central stars of these nebulae were abnormally small as well as abnormally hot; they belonged to the class, of very compact stars known as white dwarfs. One of these stars bail recently been discovered with only about half the dimensions of the earth. In spite of its small size it probably; contained nearly 1.000.000 times as much substance ns the earth, so that its average density must: be about 36.000.090 times that of water. To put it in another way, a cubic foot of water on earth contained 1000 ounces, but I lie average cubic foot of matter in that star contained about 1.000,000 tons. A piece the size of n pinhead would break n man’s back. That, was an extreme ease, and the central stars of the planetary nebulae were mostly considerably larger, the majority having one-half or one-third of the diameter of the sun. Even the, nearest of these nebulae were many thousands of lightyears distant, so that they appeared as faint: objects in the telescope

Describing the nebulae lying outside

the wheel to 'which our sun belongs, Sir James said it was impossible to form any clear mental picture of such vast distances, but a small-scale model might, perhaps, provide some slight help.’ If we constructed a model on the scale of 1,600,000 light-years to the inch, all the stars we could see with our unaided eyes were contained in a sphere less than one-hundredth of an inch in diameter —a mere speck of dust. But the telescopic universe occupied a sphere 80ft. in diameter. In this model our whole galaxy was a small disk of the size of a pinhead ; our sun was a single electron, and the earth was one-millionth part of an electron. The Explorer’s Thrill. After discussing the theories of various scientists, Sir James concluded: As you will see, there is an absolute feast of hypotheses to choose from. You may pin your faith to any one you please, but you must not be certain about any. Personally. I' feel disinclined even to Pin my faith to any; it seems to me that it is still open to question whether space is finite or infinite, whether it is curved or -flat, whether the so-called constants of nature change in value or stand still—-if, indeed, any of these questions have any meaning. I know that in saying this I lay myself open to the charge that, haring led you into a maze. I do not even try to'show you the way out. In my defence, let me quote R. L. Stevenson- —"Little do ye know your own blessedness, for to travel hopefully is a better thing than to arrive.” Those, scientists who work at these problems; can still enjoy rhe explorer’s rhrill as they ever venture into new territory.