NEW STAR DISCOVERED

Te Awamutu Courier, Volume 53, Issue 3783, 17 July 1936, Page 10

NEW STAR DISCOVERED

THE SMALLEST KNOWN. A valued correspondent has drawn my attention (writes K.G. in the Melbourne Age), to letters recently appearing in the columns of the London “Times,” written by Sir Joseph Larmor, late professor of mathematics in Cambridge, and Dr W. M. Smart, of the Cambridge University Observatory, discussing a certain obscure star which has recently blazed into notoriety in the astronomical world by reason of the enormous density of its material surpassing perhaps a million-fold that of any substance known on earth, and far exceeding even that attributed to the densest celestial objects hitherto known, stars of the “White Dwarf” class, of which the best known example is the famous companion of the giant' star Sirius, brightest star in the heavens. It was on this star that Brunton Stephens based his allegorical poem “The Dark Companion”:—

There is an orb that mocked the lore of sages, Long time with mystery of vague unrest; The steadfast law that rhunds the starry ages Gave doubtful token of supreme behest.

But they who know the ways of God unchanging, Concluded some far influence unseen— Some kindred sphere through viewless ethers ranging, Whose strdng persuasions spanned the void between.

And knowing it lone through perturbation And vague disquiet af another star, They named it, ’til the day of revelation, “The Dark Companion”—darklyguessed afar.

Although observation with powerful telescopes has shown this star as the poet truly says, to be “no Dark Companion, but a thing of light,” it yet held a remarkable secret in its keeping, namely, that matter, under certain conditions could exist in a form unknown on earth, in which its density was many thousand times greater than that of the densest substance we know. Space will not permit me to narrate this fascinating “detective story” of the heavens—as Sir Arthur Addington (himself the chief detective) has termed it—in full. It must suffice to say that the mass of the Companion can be fairly accurately estimated, from that very perturbation of motion which it produces in its giant neighbour, to be

about four-fifths of the mass of the sup; while its diameter can, not quite so accurately perhaps, be calculated from its observed brightness or “magnitude” (it is a star of the eleventh magnitude), the quality of spectrum of the light it emits—which shows it to have a temperature far higher than that of the sun, and, finally, its distance, which is known from the angle of “parallax” of Sirius itself. The diameter of Sirius minor works out at about 22,000 miles, only three times that of our diminutive planet, and about onefortieth that of the sun. The volume of this star is accordingly less than one fifty-thousandth of the sun’s volume, and, combining this with the mass given above, we see that the density of the matter in it must be more than 50,000 times that in the sun, which we know to be somewhat heavier than water. EXTRAORDINARY FIGURES. In other words, a cubic inch of the stuff of which Sirius minor is made would weigh nearly a ton! Such stuff, you might say, as astronomers' dreams are made of. In fact, astronomers themselves might have boggled at accepting the result of their own observations and reasoning had not confirmation been found in a totally different line of argument, which we owe to Einstein.

It was he who first showed that the gravitational pull of a celestial body would act to retard the escape and reduce the energy of light-rays from its surface in much the same way as it would that of a flying bullet, and gave a formula to compute this pull from the energy-loss or change of wave-length—for the two go hand in hand.

Applied to the light that comes from the companion of Sirius, this led to a result in very close agreement with that abovestated, and a density of the matter in the star 3000 times greater than that of the heaviest metal we know of. Several other stars of the same abnormally high density as the companion of Sirius are now known. They are called “White Dwarfs.” But the star referred to in my opening paragraph—which has as yet no name, but only a catalogue number—outdwarfs and out-classes them all. Its remarkable character has been revealed as a result of the attention devoted to it by Dr Gerard "Kuiper, who hails from the Dutch University of Layden, but who was carrying out research work during 1935 at the Lick Observatory of the University of California.

According to the brief report in the “Observatory,” this star is of the thirteenth magnitude—for, of course, below the limit of human vision—yet the colour and spectral quality of its light indicate a surface temperature of 28,000 degrees. (Compare our own sun’s 7000.) Its distance is roughly known from measurement of its parallax—or half-yearly shift in position due to the earth’s motion in its orbit. SMALLEST KNOWN STAR. From these data Kuiper calculates a diameter about half that of our planet, a value which makes this star absolutely the smallest known. Unfortunately, this star is not a member of a binary system, and, therefore, its mass cannot be obtained in the same direct way as that of Sirius minor. But an Indian mathematician has developed a formula connecting the mass of a White Dwarf star with its radius and the mean molecular weight of its material. Making a reasonable estimate for the latter, Kuiper finds the mass 'of his star to be 2.8 times that of the sun, which would make its density about 620 tons to the cubic inch, or nearly 1000 times as great of that of Sirius B. It is thus perfectly evident that such a figure as this, or even of one ton per cubic inch, can be accepted only if we take the view that the matter in these stars is in a condition entirely from that of any substance known to us on earth. What that condition is modern knowledge of the constitution of material atoms makes pretty clear. An atom of whatever kind is far from fulfilling the implication of its name. Each atom is a structure of far smaller particles built on‘ an extremely spacious plan, as spacious relatively to the size of these constituent particles, as is the solar system iii relation" to its individual members. STRUCTURE BROKEN DOWN. And what happens in stars of the White Dwarf type and to a greater or less extent in stars of all types is that this structure becomes more or less completely broken down, permitting the individual nuclei and electrons to pack together in a space a hundred, a thousand, or, as in Kuiper’s star, many million times less than that which the same number of complete atomic structures would occupy. In stars like the smaller of the iSrius pair this process of breaking down has gone far, far further than in the larger Sirius or in our own sun; in the star in which this property has just been revealed we can scarcely escape the conclusion that is has reached its utmost limit and that in its interior at least such temperatures prevail that matter as we know it cannot exist at all, but only a dense-paeked mass of nuclei and electrons’.