A TON IN A MATCHBOX

Taranaki Daily News, 9 August 1930, Page 1 (Supplement)

A TON IN A MATCHBOX

MECHANISM OF-THE STARS

(Rev. B. Dudley,

F.B.A.Sj

A recently-read issue of “The Proceedings of-the Institution of Mechanical ■Engineers” contains a contribution en,t'itfed- Engineering in the Maehiner.y- of ; the StaTs; - by Profe-ssbr A. S. Eddington. ALA.,' D.Sc., LL.D., -F.-R.S-, being the Fifteenth? Thomas -Hawksley- Lecture. The author’is one of the outstanding astronomers of the day, a man with versatile mind,-whose, interests' range' between practical ■ ser■vice. for - humanity,- according Vto the tenets of the denomination to which he. ’belongs (the ’Society of • .Friends); • and scientific theory and/research. ' 1

- With’’- regard'to the sun’s compesition the professor points out that it has no definite’surface,-a lid that 'when we study the- solar- body by ■ means [of the proper instruments,-' -“we look downwa’ds .through its atmosphere towards -the i.iteribr° until the ..opacity becomes too -dreat for us to/penetfate farther; the cipectroheliograplv by selecting light of particular wavelength, has the pro; perty thaf. it shows us. what is .going cn at one particular level in this atmosphere, whereas the. ordinary, photograph gives merely the blurred impression of all layers superpesed. And, as he further shows, “the pressure at various depths in the suu can :be calculated without much difficulty, just as the stressor in a pillar or wall can bo calculated.”

Ayitli regard to the heat, of the great luminary, as the /professor states, there is--less data to go -upon. The nearest to exactness possible at present is to the effect that the 'solar temperature is 40 million degrees centigrade at the centre. This as mentioned by Eddington concides. generally with the temperature of the majority of stars, which arc suns situated at enormous distances. The sun is taken, as a typical star, “just about as ordinary a star,” says he, “as you could find, though the stars have great variety, and range widely on cither" side of this type.” While the stars differ in luminosity, tint and mass, they .are practically alike in the matter of central temperature. The lectuic goes on to demonstrate that, owing to the terrific rushing about of atoms and electrons in the interior of the sun, only n feeble proportion of the enei gy within it can escape and reach us, “The atoms dam up this store, and only a slight .leakage dribbles out to illuminate and warm the earth and other planets.” Durinor 1920-21 it was ascertained that some stars are “enormously swollen in bulk.” Though containing but little more material than the sun, ‘ they nevertheless fill a thousand, or a million times the volume.” Theprofessor quotes the instance of Betelgeuse, one of the stars .of ' the .constellation., of Orion, which is swollen to such an extent that the entire orbit of the earth could be put in-side it, leaving a wide margin beyond. Its density is so low in fact that it could be regarded as “a fairly good vacuum.”

Against’ this, the sun has a density rather greater than that of watei. Other stars are known to have the density of lead or iron. The bright star Sirius has revolving about it a comparatively dark companion whose gravitational influence was known long before it was seen in the telescope. This companion is so exceedingly dense that u match-box filled with an average sample of its materials would weigh a ton, the density being 60,000 times, that of water. The companion of Sirius is now regarded as an example of the extent to which matter can be compressed under conditions which though unknown to us on earth, are possible in stellar regions.

We have co right to judge the candldltions of matter throughout, space by what we know of it- here. _ An atom 01 matter as we know it is like a ballooii compared with what obtains in some ol the stars. “Dense materials such as I have been describing,” say.s the professor, “must appear to us at fiist almost as tin incredible fairy-tale. But 1 am sure we are looking at it fiom wrong attitude. ,You terrestrial engineers are concerned with matter in a very abnormal state. Nine-tenths of the matter of the universe is tucked away in the interior of stars under temperatures of more than a million, degrees. That is the normal condition of matter, and we must not take our experience or matter on this chilly little planet- as at all typical. We have at last realised the extreme emptiness of matter; a terrestrial atom is like a miniature solar system. If we eliminate that emptiness; if we pack the little electric charges close together (as they are packed elsewhere in the universe), a man's body m reduced to a speck just visible with a magnifying glass.”

A portion of the lecture was devoted to pulsating stars, special consideration beimr given’ Id a noted example of tins class’ of bodies, known as Delta Cephei, one of the stars in the constellation Cepheus. “It is,” says Eddington, “a rather large star, probably about 10 times as massive as the sun, and it is in a different condition with an average density less than that of air. This globe swells and contracts periodically so that the volume at maximum is about 20 per cent, greater than the volume at minimum.

“The variation Ims gone on regularly within a period of 5 1-3 days ever since the star was first observed 150 years ago. During, the contraction the inner material is "being compressed, and consequently rises ’in temperature” The star is famous for its variation in brightness, but that variability is not due’ to the movement of a dark companion revolving about it in a plane turned “'edge on” ’to us. and eclipsing the light of the brighter member of the pair, of which there are vast numbers m the heavens. Delta Cephei varies in luminosity owing to an actual pulsation going on*, for some unknown reason, within the star itself. Nor is Delta Cephei alone in this behaviour. As a matter of fact, there are hundreds of stars which behave like it. In a manner that would be appreciated by engineers, the lecturer suggests how these star-pulsations might possibly be caused, and acknowledges his wonder/ not that'stars’pulsate at all, but that they : do. hot do so on ft much larger scale than is evident at present.