September 18 1964 - Vesta

Very little is heard about the minor planets, apart from the few whose exceptional orbits bring them relatively close to the Earth. Of these minia­ture worlds, the brightest, though not the largest, is Vesta; and this was the subject of our programme for September 1964.

One of the less-familiar members of the Solar System is now ex­cellently placed for observation in the evening sky. This is Vesta, the brightest of the swarm of asteroids or minor planets. It is far from spectacular, and even in large telescopes it appears as nothing more than a star-like point, but keen-sighted observers may be able to glimpse it without optical aid provided that they know exactly where to look for it.

Vesta is of the sixth magnitude, which means that from the viewpoint of the naked-eye observer it is hidden by the slightest trace of mist in the Earth's atmosphere; a dark, transparent sky is essential. Telescopically it looks exactly like a star, so that its nature is not evident at a glance. The only way to identify it with certainty is to observe the whole area from night to night; the stars will remain in the same relative positions, but the minor planet will move. This is brought out by Acfield's photograph. The date of the photograph itself was 8 September 1964, at 0.30 hours; the cross well to the right of Vesta shows the position of the minor planet in the early morning of 13 September. The five-day interval has been quite enough to reveal a decided shift.

Since Vesta is on the fringe of naked-eye visibility, even a very keen-sighted observer will be hard pressed to identify it without optical aid; binoculars, however, should suffice. Its faintness is by no means surprising in view of its small diameter and its con­siderable distance from Earth. Vesta is a mere 241 miles across, and moves round the Sun in a period of 3.6 years at a mean distance of 219,300,000 miles. A drawing showing Vesta and Eng­land to the same scale would demonstrate that we are indeed dealing with a dwarf world; yet only two of the minor planets - Ceres and Pallas - are larger.

The existence of at least one body moving in the region be­tween Mars and Jupiter was suspected long before the first asteroid was discovered. The Solar System is divided into two distinct parts. First come the four terrestrial planets (Mercury, Venus, the Earth, and Mars), after which there is a wide gap. Then follow the four giants (Jupiter, Saturn, Uranus, and Nep­tune) together with Pluto, a curious little world which may not be a true planet; according to some authorities, it is merely an ex-satellite of Neptune which has moved off in an independent path. A striking mathematical relationship, known as Bode's Law, led astronomers of the late eighteenth century to suppose that an extra planet might exist between Mars and Jupiter, and in 1801 the missing world war duly found. The Italian observer Piazzi, who discovered it, named it Ceres. It never attains naked-eye visibility, but with its diameter of 427 miles it remains the senior member of the asteroid swarm.

Further discoveries followed: Pallas in 1802, Juno in 1804, and Vesta in 1807. Number 5, Astrsea, came to light almost forty years later, due to the systematic labours of a German amateur named Hencke, and since 1847 no year has passed without the discovery of several new minor planets. Several thousands have now had their orbits worked out. On the other hand, very few are of appreciable size; most have diameters of under fifty miles, and the smaller members are probably not even approximately spherical.

Most asteroid discoveries have been made by means of photo­graphy. With a time-exposure, a star will appear as a sharp point, provided of course that the telescope is clock-driven to compensate for the east-to-west movement due to the rotation of the Earth; a minor planet will crawl across the sky, and will appear as a short trail on the photographic plate. Astronomers are not always glad to see these trails. Plates exposed for quite different reasons are often found to be crowded with asteroids, all of which have to be checked and eliminated. To make matters worse, some of the minor planets have high orbital inclinations - over 34 degrees in the case of Pallas, for example - so that they do not keep within the bounds of the Zodiac in the same way as the true planets. One infuriated observer referred to the asteroids as 'vermin of the skies'.

Most of the asteroids keep to the main zone between the paths of Mars and Jupiter, but some have eccentric orbits which carry them into other parts of the Solar System. No. 433, Eros - dis­covered in 1898 - may pass within 15,000,000 miles of the Earth ; No. 1566, Icarus, has a curious path which carries it closer to the Sun than Mercury, the innermost of the main planets, while No. 944, Hidalgo, swings out almost as far as the orbit of remote Saturn. In 1937 a dwarf body now known as Hermes approached the Earth to within 500,000 miles, and there were suggestions that it might even collide with our world. Such an event is most unlikely, but in any case Hermes can be little more than a mile in diameter, so that it could cause only local damage; it could certainly destroy a city, but it could not produce world-wide devastation.

Vesta appears the brightest of the minor planets because it is appreciably closer to the Sun and Earth than its two seniors, Ceres and Pallas. Even so, its distance from us is never as little as 100,000,000 miles, and to study details upon its surface is quite out of the question, even with the most powerful telescopes in existence. We can only speculate as to what it may be like, but we have at least a few concrete facts to guide us.

First, its small size means that it must have a very low escape velocity. The most important result of this is that it can retain no vestige of atmosphere, while its surface temperature must be very low indeed. No precise value for the escape velocity can be given, since we have no information about its density, but its gravita­tional pull is certainly very feeble. An astronaut who managed to land there would find that he would be able to jump an im­mense distance above the ground, and his subsequent descent would be extremely gradual. Yet it is not correct to say, as some writers have done, that a man could jump clear of Vesta by the power of his leg-muscles alone. This would not be possible except with an asteroid less than about two miles in diameter, assuming normal density; and Vesta, though small, is very much larger than that.

Probably, too, Vesta is more or less spherical, which means that its surface must be sharply curved; the 'horizon' would be strangely close. Minor variations in its light have led to the con­clusion that its rotation period is about 10 3/4 hours - slightly longer than the periods of either Ceres or Pallas, and three hours longer than that of Juno. This may indicate either that its shape is not entirely regular, or that some parts of its surface are more reflec­tive than others. _

When we come to consider the nature of the surface, we have to confess our complete ignorance, but Vesta seems to be a better reflector of sunlight than its companions. Its albedo, or reflecting power, has been estimated at 25 per cent as against 3 per cent for Ceres, 5 per cent for Pallas, and 11 per cent for Juno; the value for the Moon is considerably less than 10 per cent. Vesta, therefore, may have a smoother surface, but one cannot be sure, and moreover the albedo estimates - due to the German astronomer N. Richter - are bound to be somewhat arbitrary.

The origin of Vesta is similarly uncertain, but it was certainly formed in the same manner as the other members of the asteroid swarm. There are two main theories. It may be that the asteroids resulted from the break-up of an old planet or planets which used to move round the Sun between the orbits of Mars and Jupiter, in which case they are the visible remains of a tremendous out­burst which took place thousands of millions of years ago. Alter­natively, it has been supposed that the asteroids, together with meteoroids, were produced from material which was 'left over', so to speak, when the major planets were born.

The first of these theories is attractive, and has met with wide support, but it is not easy to see how a former planet could have met with disaster; a direct collision between two smaller bodies seems to be the only real possibility, and it is worth noting that the total mass of the asteroids is relatively small. There is no definite information as to the total number of members; R. S. Richardson, in the United States, has suggested 44,000, while Russian astronomers tend to believe that the true number may be as large as 100,000. Yet even if all the asteroids could be lumped together, the prove difficult to solve, and for the moment, at least, the nature of Vesta and its companions is not known.

It is worth noting, incidentally, that some of the smaller satellites _of the main planets may be captured asteroids. This applies to /Photos and Demos, the dwarf attendants of Mars, both of which appear to be less than a dozen miles in diameter, while the same may be true of the seven outer satellites of Jupiter and the smallest satellites of Saturn and Neptune. There is also a possibility that a second asteroid ring exists in the outer regions of the Solar System, though to observe small bodies at such a distance would be impossible with our present-day telescopes.

Science-fiction writers have put forward the idea that in the far future, when interplanetary travel has become commonplace, navigational beacons may be set up on Vesta and other asteroids. It would be rash to say that this will never be done, but at least it is not likely to be attempted for many centuries, even if it proves to be desirable! It is pointless to speculate about the pos­sibility of finding valuable minerals upon worlds such as Vesta, and we need spend no time upon another science-fiction idea, that of wrenching small asteroids free from their present orbits and steering them into more convenient paths to serve as natural space-stations. This remarkable scheme has been seriously dis­cussed by American scientists during the past few years, but it is quite impracticable. The energy needed to alter the path of an asteroid would be so great that there is no chance of anything of the sort being attempted.

If an astronaut could in fact go to Vesta, he would find him­self on a strange world. The temperature would be very low; there would be no atmosphere, and the Sun would appear relatively small and pale in the black sky. The constellation-patterns would of course seem the same as those we know, but there would be many additions to the sky, since Vesta lies within the main minor planet belt, and many of the other members of the swarm would appear as conspicuous naked-eye objects. From time to time, passing asteroids might even appear as distinct disks, and they would not add up to a body as massive as our Moon. The problem of the formation of the asteroids is likely to chances of collision certainly could not be ruled out. The pull of

gravity would be slight, though persistent; an Earthman would have very little weight.

There is one fact about which we may be quite positive: Vesta, like its companions, is utterly without life; no living organism of the kind known to us could survive under such conditions. In its way, Vesta is just as hostile as the Moon. Whether it will ever be reached seems extremely doubtful - and yet it is certainly not devoid of interest. If we knew how Vesta came into being, we should be well on the way toward solving the problem of the origin of the Solar System.

August 21 1964 - Colour in the Universe

During the television coverage of the ig6y lawn tennis championships at Wimbledon, the BBC started putting out programmes in colour. Of course, tests had been made much earlier, and colour television had begun in some countries ; but Wimbledon marked the start of a new era so far as Britain is concerned.

I can see that in the future, this change-over will cause some complica­tions in The Sky at Night programme. Colours in the sky are not strong, except with rare phenomena, and how they will show upon a television screen I do not know. However, it may be interesting to look back to a programme I devoted to this topic as long ago as the summer of 1964, when colour television still seemed to lie a long way in the future.

What is the colour of the night sky? Most people would probably answer this question by saying 'Black, with white stars' - but in fact the situation is not nearly so simple. There is plenty of colour in the universe, provided that the observer knows where to look for it. The planets, for instance, have their own distinctive hues, though only in the case of Mars is the colour really conspicuous to the naked eye.

Saturn, the outermost of the planets known in ancient times, is now visible in the south-east after sunset, and remains above the horizon all night. It has a dull, leaden aspect, and the astrolo­gers of past ages regarded its influence as baleful. It appears in the guise of a moderately bright star, lying well below the prominent Square of Pegasus; there should be no difficulty in finding it, since the only possible confusion is with the first-magnitude star Fomalhaut in Piscis Austrinus (the Southern Fish). Fomalhaut, however, is lower down and not so bright.*

Saturn, like the other three giant planets, is made up of gas, and this gas is known to be largely hydrogen. This means that the details on its surface are constantly changing, and it is im­possible to draw up permanent maps, though the main cloud belts have persisted since the start of serious telescopic observation. Spots are rare, but now and then something really spectacular is seen - the last occasion being in 1933, when W. T. Hay dis­covered a brilliant white spot near the planet's equator. Of course, Saturn is less easy to study than Jupiter, partly because it is smaller and partly because it is farther away. Its equatorial dia­meter is just over 75,000 miles, while at the date of opposition 24 August 1964) its distance from us was no less than 816,000,000 miles.

The general colour of Saturn's disk is yellow, as any small :telescope will show. During 1964 there were interesting changes there. For much of July the whole equatorial zone of the planet appeared to be tinged with brown or deeper yellow; I detected :his aspect on 9 July, and it has since seen confirmed by Ameri­can observers, while in Britain it has been recorded by A. W. Heath, Director of the Saturn Section of the British Astronomical Association. By mid-August the unusual hue was less pronounced, though it had not quite disappeared. The cause of this sort of phenomenon is not known.

The real glory of Saturn lies in its ring-system. The rings, made up of large numbers of small particles moving round the planet in the manner of dwarf moons, are of great extent, but are also very thin; their thickness can hardly be more than ten miles. The appearance of Saturn therefore changes markedly according to the angle at which the rings are placed with respect to the Earth. The rings are creamy, and are actually more brilliant than Saturn itself.

Jupiter, too, is predominantly yellow, but since 1959 its appearance has been unusual. Generally there are two distinct cloud belts, one to either side of the planet's equator, together - with other belts in higher latitudes. In 1959 the whole equatorial region turned an extraordinary orange or brownish hue; this persisted, with variations, until 1963, when the two equatorial belts had run together to form a continuous 'wedge of colour' right across the disk. It now seems that things are reverting to normal, and by August 1964 the separate belts were again identi­fiable. The remarkable feature known as the Great Red Spot has also been very much in evidence - and it really has been decidedly reddish in hue, though it has lost the brick-red colour which, from all accounts, it showed for a few years following 1878. It must be admitted that, so far, we have no real idea of the nature of the Great Red Spot, and neither do we know why Jupiter exhibits these peculiar changes in colour.

A small telescope will suffice to show the yellowness of Jupiter, together with the main belts and the four large satellites. Venus, which is a fine object in the eastern sky before dawn, is even more brilliant than Jupiter, but is less spectacular telescopically. It is a very different sort of world, since it is slightly smaller than the Earth, and is closer to the Sun than we are. Like the Moon, it shows phases, and at present it is 'gibbous', i.e., between half and full. Unfortunately no details are visible on its disk, since Venus is permanently covered with a dense, obscuring atmosphere which, according to recent results obtained from balloon-borne instruments sent up from the United States, con­tains a considerable amount of water vapour. Venus is slightly yellowish, though the naked-eye observer will probably call it pure white.

Through a powerful telescope, Mars is brilliantly coloured. Most of the surface is reddish-ochre, and is thought to be coated with some sort of mineral, possibly felsite or limonite. The polar caps, which are probably made up of some icy or frosty deposit, are glittering white, while the dark patches are said to have a greenish hue at times. H. Strughold has paid great attention to Mars, and has called it 'the Green and Red Planet', but to my eyes the dark markings generally seem grey. At any rate, it seems possible that they are due to living organisms, even though doubts have arisen lately.

Of the remaining planets, Mercury is somewhat pinkish, Uranus green, and Neptune bluish, while it has been claimed that Pluto is on the yellow side of white. However, these colours are not striking, and only experienced observers will be able to detect them. Mercury is always elusive; Uranus is on the fringe of naked-eye visibility, and both Neptune and Pluto are much too faint to be seen without optical aid.

In discussing the colours of the stars, it is natural to begin with our own particular star - the Sun - which, of course, is yellow. Its surface temperature is 6,000 degrees Centigrade, and it is in every way unremarkable. There are many similar stars in the Galaxy, and no doubt plenty of other stars are attended by in­habited planets. The only sensible way to observe the Sun telescopically is to project its image on to a white screen; to look straight at the Sun, even with a very small telescope, is extremely dangerous even when a dark filter is used. By projection, however, any sunspots which may be present are well seen. These spots appear dark, but this is an effect of contrast; if they could be seen shining by themselves they would be very brilliant, but they are less luminous than the rest of the Sun's surface because they are some 2,000 degrees cooler. During the summer of 1964 sun- spots were scarce, and there were long periods when the disk was completely blank. However, this was only to be expected; the Sun exhibits a roughly regular 'cycle' of eleven years, and from now on it is likely that spot-groups will become more frequent again. The next period of maximum activity is expected around 1969.

Stars which are hotter than the Sun will be white or bluish, while cooler stars will appear red. Binoculars are powerful enough to show these various colours well, while there are some stars whose hues are evident without any optical aid. A good example of this is Vega, in the small but interesting constellation of Lyra, the Lyre or Harp. Vega is extremely bright. It cannot match Venus or Jupiter, but of the so-called 'fixed stars' visible from Britain only Sirius is its obvious superior. Moreover, Vega is almost directly overhead during summer evenings, so that there should be no trouble in identifying it. It is definitely blue; it is fifty times as luminous as the Sun, and its distance from us is twenty-seven light-years, so that we are now seeing it as it used to be twenty-seven years ago.

The blueness indicates high temperature, and in fact the sur­face temperature of Vega is about twice as hot as the Sun. There is an interesting contrast with Arcturus, which now lies in the west, more or less in line with the curve of the 'tail' of the Great Bear. Arcturus shines about as brilliantly as Vega, and is actually twice as luminous, but its surface temperature is lower; only about 4,000 degrees. This means that its colour is a glorious orange. Vega is one of three first-magnitude stars making up what is unofficially termed the 'Summer Triangle'. The other two members are Deneb in Gygnus (the Swan), which is yellowish and Altair in Aquila (the Eagle), which is pure white. Deneb, apparently the faintest of the three, has been found to be a re­markably luminous supergiant, equal to at least 10,000 Suns and lying at a tremendous distance from us.

The best example of the Red Giant star is, undoubtedly, Betelgeux in Orion. Orion is a winter constellation, but now rises before dawn, and the contrast between its two leading stars is very marked; the redness of Betelgeux is as obvious as the pure white light of Rigel. Another Red Giant is Aldebaran in Taurus (the Bull), which lies in line with the three stars of Orion's belt, and is associated with the V-shaped cluster of stars known as the Hyades.

With the naked eye, only a few of the brightest stars are strongly coloured; with fainter objects, optical aid is needed before the hues can be well seen. A good example of this is Herschel's 'Garnet Star', Mu Cephei, not very far from Polaris. To the naked eye it appears unremarkable, but any small telescope makes it look like a tiny glowing coal. The surface temperature in this case is only about 3,000 degrees.

Observers who have access to binoculars or small telescopes will find it interesting to look from star to star and note the various colours; it will not take more than a few minutes to find that the stars are utterly unlike each other. There are lovely colours, too, among double stars, of which Albireo in Gygnus is an outstanding example. Albireo is the faintest of the five stars making up the •.veil-known cross of Gygnus, and to the naked eye it seems white, but a telescope will show that it is made up of a golden-yellow primary together with a much fainter companion which some people term green and others blue. And there are bright red stars, such as Antares in Scorpio (the Scorpion) which have green com­panions. The greenness of the small attendant of Antares is accentuated by contrast, but this does not make it any the less beautiful.

Not all double stars show contrasting colours. Look, for instance, at Epsilon Lyra:, which lies close to Vega. Keen-sighted observers will note that it is made up of two; a 3-inch refractor will show that each component is again divided, so that Epsilon Lyra; is a double-double or quadruple system. All four of its suns are white.

Very faint stellar objects show colours which cannot be de­tected except by photography. There is a good example of this in Messier 57, the Ring Nebula in Lyra, which also lies near Vega. The Ring is a 'planetary nebula', but the name is a bad one, since planetary nebulae are neither planets nor nebulae. Messier 57 consist of a faint central star surrounded by a tremendous en­velope of tenuous gas, so that it looks rather like a very dim, luminous bicycle-tyre. Moderate telescopes will show it clearly, and it is easy to find, but no colour will be detected. A famous photograph taken some years ago with the largest telescope in the world, the Palomar 200-inch reflector, showed that the Ring has a bluish central area with the outer parts yellowish and red.

Star-colours are important because they provide a key to the surface temperatures, though detailed analysis is carried out with the aid of spectroscopic equipment rather than by visual estima­tion. Yet the colours are spectacular, too, so that the casual ob­server who uses binoculars to look at the orange Arcturus, the glittering blue Vega, and the dull yellow planet Saturn can hardly fail to be impressed. We live in a coloured universe; the skies are anything but drab.

June 26 1964 - Astronomy Old and New

Astronomy is a fast-developing science; it has altered more in the past hundred years than it did in the previous thousand. But despite the modern emphasis upon vast telescopes, refined photographic techniques and space probes, it is always worth while to pause for a moment and look back at some of the ideas current in past ages. This was what we did for the July 1964 programme, in which I was joined by Henry Brinton. Following it, I had some amusing letters.

There is one point that should be made. During the programme, I ex­pressed serious doubts about Professor Hawkins' theory that Stonehenge is an ancient computer. My viewpoint was that people who possessed enough knowledge to build anything of the sort would not need to do so; they could manage excellently by calculations, without going to the trouble of constructing a huge monument. Since then, the evidence seems to indicate that Professor Hawkins was right and that I was wrong, so that I hereby retract my scepticism even though I have not altered the article as it appeared in 1964.

Astronomy is the oldest science in the world. The earliest men must have looked up at the heavens and wondered at what they saw there; it was not until later that the pseudo-science of astrology arrived upon the scene to confuse men's minds and hold up progress.

Observational records of celestial phenomena go back for thousands of years. For instance, the ancient Chinese observed eclipses of the Sun and Moon, although they did not know why an eclipse occurs and they would have found it impossible to believe that the Earth is a planet moving round the Sun. At the time of a solar eclipse, the Chinese believed the Sun to be in danger of being eaten by a dragon, so that they used to bang pots and pans and make as much noise as possible in order to scare the dragon away.

Solar eclipses, caused when the Moon passes between the Earth and the Sun, are indeed highly spectacular. When the Moon passes into the Earth's shadow, at a lunar eclipse, the usual result is to make the Moon turn a dim and somewhat coppery colour. The only light reaching the lunar surface during the total phase of the eclipse has been refracted through the Earth's atmosphere, and it is obvious that the state of the atmosphere will affect the look of the eclipsed Moon. Quantities of volcanic dust in the upper air will produce a 'dark' eclipse, such as seen in 1816, following the Tamboro eruption of the previous year; the eclipses following the eruptions from Krakatoa (1883), Katmai (1912), and Mount Agung, on Bali in the East Indies (December 1963), were also very dark.

There is strong evidence that a lunar eclipse was recorded by the Chinese as long ago as 1136 b.c. The Greeks, however, were the first to raise astronomy to the level of a true science, because they did their best to interpret their observations; by using the so-called Saros Period, they were able to predict eclipses with fair accuracy. Thales of Miletus, the earliest of the great Greek philosophers, knew that any solar or lunar eclipse will be followed by a similar eclipse 18 years 10J days later; the relationship is only approximate, but for lunar eclipses, in particular, it works quite well. By 450 b.c. another Greek, Anaxagoras of Clazomenaj, was able to explain the cause of an eclipse of the Moon, and to state that because the Earth's shadow was curved, the Earth itself must be spherical.

Recently, Professor Gerald Hawkins, of Harvard, has suggested that the early Britons, too, were able to predict eclipses. Accord­ing to Hawkins, Stonehenge is nothing more than a primitive computer, the outer circle of fifty-six pits being used as a form of protractor. For instance, eclipses are likely to occur when, to an observer standing in the centre of the monument, the mid-winter Moon rises over the large block known as the Heel Stone.

This fascinating that it may be regarded as a form of observatory as well as a lemple. Midsummer ceremonies are always associated with it, and it is also popularly linked with the ancient Druids. In point of fact, the monument existed long before the Druids were active in England, and there is no evidence that the Druids ever used it, while there is a great deal of indirect evidence that they did not. The same applies to the other stone circles found all over Britain - at Roll right in Oxfordshire, for instance, and Callanish on the Island of Lewis. G. Henderson considers that they could be used as 'star markers' to check the march of the seasons, and this is certainly possible, since the observations themselves would be very simple and straightforward.*

Undoubtedly the old star-gazers were skilled at what may be termed positional astronomy; Egyptian observations, for instance, were very precise, and the later Greeks drew up remarkably good star catalogues. Subsequently, however, some strange theories were put forward. One of the most curious relates to the Egyptian pyramids, with special reference to the Great Pyramid of Khufu. Here again there is no doubt about the astronomical alignment. This is related to the north celestial pole, now marked by Polaris to within one degree, but in Egyptian times situated near the much fainter star Thuban in Draco; the slow shift is due to the phenomenon of precession, or change in direction of the Earth's axis.

The great pyramid

In 1859 John Taylor, an eccentric London publisher, issued a book called The Great Pyramid.: Why was it Built? And Who Built it? Taylor never visited the pyramid, but he believed that he had found various mathematical truths in its measurements which showed him that the Egyptian priests knew most, if not all, of the secrets of the universe, but had prudently decided to keep these truths to themselves. Taylor was, therefore, the founder of the cult of pyramidology, but his speculations would soon have been forgotten but for the fact that he found a strong supporter in Charles Piazzi Smyth, Astronomer Royal for Scotland. Smyth's theory may or may not be correct, but in any case Stonehenge has certainly an astronomical significance, so subsequent book, Our Inheritance in the Great Pyramid, is a classic of crank science.

Smyth began by taking Taylor's discovery that if you divide the height of the monument into twice the side of a base, you obtain a fairly close approximation to the value of pi (the ratio of diameter to circumference of a circle). The square of the height, moreover, is equal to the area of one face of the pyramid. On these and other similar grounds Smyth claimed that the Egyptians were able to 'square the circle'. By juggling with the length of the diagonals, he also considered that he had proved that the pyramid builders had worked out an exact figure for the preces­sion of the equinoxes - the movement of the celestial Pole which revolves once in about 26,000 years. From this Smyth went on by ingenious but rather arbitrary calculations to derive the unit of measure which the builders used. This he believed to be a little more than two feet, and he associated the unit with the cubit of the Bible. He then divided the cubit into twenty-five 'pyramid inches', which were very slightly different from the English inch. Smyth attributed the discrepancy to carelessness on the part of later artisans. This, of course, proved that the pyramid inch was sacred, and in 1879, in Boston, U.S.A., a movement was started for outlawing the 'atheist' metric system. The movement actually had the moral support of President James Garfield.

The possibilities are endless. For instance, the number of pyramid inches in the height of the pyramid, multiplied by a thousand million, yields 91,840,000 miles, which was close enough to the Earth's distance from the Sun (rather less than 93 million miles, on the average) to make Smyth sure that he had found another sacred relationship. But it was in connection with the pyramid's internal passageways that Smyth rose to his greatest heights. When these passages are measured in pyramid inches, counting one inch to the year, and the symbolism is properly interpreted, then - said Smyth - the principal dates in the Earth's past and future are plainly indicated. These include the creation of the world in 4004 b.c., the birth of Christ and of course the end of the world, which has been predicted so often in so many different ways.

When many measures are available, a dextrous mathemati­cian - as Smyth was - can make a judicious selection to prove almost anything. It was a great pity that Smyth himself, who made many valuable contributions to astronomy, should have become a convert to eccentricity of this sort; it damaged his reputation, and also led to a positive craze for pyramidology which lingers on even today. It is perfectly harmless, but it can hardly be re­garded as scientific. Sir Flinders Petrie, the great archaeologist, once caught a fervent pyramidologist filing down a projecting stone to make it conform with his theories.

One feels that the builders of the pyramids were rather more logical than some of the nineteenth-century theorists. Yet the Egyptians made little effort to interpret their astronomical ob­servations; this was left to the Greeks, who made amazing pro­gress in all fields of physical science. Had they realized that the Earth moves round the Sun, instead of lying at rest in the centre of the universe, astronomy would have developed quickly. A few of the Greek philosophers (Aristarchus, for example) did take this vital step, but met with little support, and the reality of the Earth's movement round the Sun was not properly demonstrated until about 400 years ago.

On the other hand, the Greeks knew that the Earth is a globe. The form of the shadow on the eclipsed Moon was only one of their many proofs. For instance, ships disappear below the horizon when sailing out to sea, which would be impossible on a flat Earth. And Aristotle, in about 350 b.c., pointed out that the stars appear to alter in height above the horizon according to the observer's position on Earth; Canopus, a brilliant southern star, can be seen from Egypt, but never from Greece. This is easy to explain on the assumption that the Earth is a globe, but cannot be accounted for by supposing the Earth to be flat. Moreover, yet another Greek scientist, Eratosthenes, measured the circum­ference of the globe with remarkable accuracy. The value which he obtained was much better than that used by Christopher Columbus on his pioneer voyage so many centuries later.

It is rather surprising, then, to find that even in the modern age there are still some people who doubt the spherical form of the Earth. The International Flat Earth Society flourished up to a year or two ago, and issued pamphlets as well as holding meetings. Their 'proofs' were fascinating, though hardly con­vincing. They pointed out, for instance, that a time-exposure of the night sky will produce a photograph showing star trails, which are hard, sharp lines. Astronomers attribute this to the rotation of the globe. The Flat Earthers, however, considered that the sharpness of the trails showed the world to be stationary - otherwise the trails would have been blurred. And in the town of Zion, Illinois, on the shores of Lake Michigan, may be found the remnants of a religious sect known as the Christian Apostolic Church, founded in 1895 and ruled for thirty years by Wilbur Glenn Voliva, who regarded the Earth as flat, with the North Pole in the centre and the South Pole distributed round the circumference. Voliva held that a huge wall of ice and snow prevented ships from sailing off the edge and tumbling into Hades. He added, as an aside, that the Sun was a mere 32 miles across, and not more than 3,000 miles away.

Other theories have been put forward. In 1818, an American officer, Captain John Cleves Symmes, claimed that the Earth was made up of five concentric spheres, with openings several thousand miles in diameter at the poles; sea flowed through both polar openings, and plant and animal life abounded on the con­cave interior as well as on the convex surface of the next sphere. Later, he petitioned Congress to finance a trip to the North Pole in order to check his theory. Congress did not agree, though it must be recorded that on the second petition Symmes found twenty-five supporters.

Perhaps the strangest theorists of all are those who maintain that the Earth is the inside of a hollow globe, with the Sun in the middle of the structure and Australia above our heads, and then he obtained was much better than that used by Christopher Columbus on his pioneer voyage so many centuries later.

It is rather surprising, then, to find that even in the modern age there are still some people who doubt the spherical form of the Earth. The International Flat Earth Society flourished up to a year or two ago, and issued pamphlets as well as holding meetings. Their 'proofs' were fascinating, though hardly con­vincing. They pointed out, for instance, that a time-exposure of the night sky will produce a photograph showing star trails, which are hard, sharp lines. Astronomers attribute this to the rotation of the globe. The Flat Earthers, however, considered that the sharpness of the trails showed the world to be stationary - otherwise the trails would have been blurred. And in the town of Zion, Illinois, on the shores of Lake Michigan, may be found the remnants of a religious sect known as the Christian Apostolic Church, founded in 1895 and ruled for thirty years by Wilbur Glenn Voliva, who regarded the Earth as flat, with the North Pole in the centre and the South Pole distributed round the circumference. Voliva held that a huge wall of ice and snow prevented ships from sailing off the edge and tumbling into Hades. He added, as an aside, that the Sun was a mere 32 miles across, and not more than 3,000 miles away.

Other theories have been put forward. In 1818, an American officer, Captain John Cleves Symmes, claimed that the Earth was made up of five concentric spheres, with openings several thousand miles in diameter at the poles; sea flowed through both polar openings, and plant and animal life abounded on the con­cave interior as well as on the convex surface of the next sphere. Later, he petitioned Congress to finance a trip to the North Pole in order to check his theory. Congress did not agree, though it must be recorded that on the second petition Symmes found twenty-five supporters.

Perhaps the strangest theorists of all are those who maintain that the Earth is the inside of a hollow globe, with the Sun in the middle of the structure and Australia above our heads, and the Earth itself extending infinitely in all directions. This is still the view of a German society, and in 1933, at Magdeburg, a rocket was sent up to test the hypothesis, the idea being that if the ascent were vertical the rocket would inevitably crash-land in the Antipodes. The first rocket rose to a height of six feet and ex­ploded ; the second vehicle was launched horizontally instead of vertically, and after that the experimenters ran out of money.

There are many other eccentric theories which would have seemed strange even to our ancestors. Dr Velikovsky, Russian- born but now resident in the U.S.A., has published some large books in which he claims that the planet Venus is an ancient comet (!) which once stopped the Earth's rotation for a while, causing the Red Sea to divide precisely at the time when the Children of Israel wanted to cross it. The universal ice theory of Hans Horbiger, who regarded the Milky Way as being composed of ice blocks which periodically hit the Sun and produced sun- spots, became so popular in Nazi Germany that the Propaganda Ministry actually had to issue a statement that it was possible to be a good National Socialist without believing in Horbiger's doctrines. The cult spread to Britain, mainly through the writings of H. S. Bellamy, and still exists. Finally, there is astrology, which retains a considerable following even though it has long since been shown to be as baseless as pyramidology or universal ice.

Most of these strange ideas are innocuous enough, and they have their amusing side - yet their continued existence shows that we cannot afford to laugh at the understandable mistakes made by theorists of long ago. Moreover, there is every prospect that the astronomers of, say, a.d. 3000 will look back at us in the same light as we ourselves regard the early star-gazers who be­lieved the Earth to be the centre of all things.

Author's Preface to Book 1 & Video Interview from 2000

(C) Journeyman Pictures

In April 1957 BBC Television invited me to present a series of astronomical programmes under the general title of The Sky at Night. Some time later, Mr Maurice Ashley, Editor of The Listener, invited me to contribute articles on the same theme, based entirely on the programmes, though not verbatim reports (which would have been impossible in any case, since I never use a script when I am 'on the air'; I cannot broadcast that way). It has now been decided to issue some of these in book form, but I feel that one thing should be made clear at the outset: the articles have been published before - the dates are given - and so are not new contributions. Moreover, there is a certain inevitable overlap with other books that I have written. I have done my best to select the articles in which overlap is cut to a minimum, but I would not wish anyone to buy the present book under a false impression!

At this point I should express my sincere thanks to Mr Ashley; it has always been a pleasure to write for The Listener.

The method adopted here has been to reproduce the articles in the original form, though in one or two cases I have added foot­notes to bring them fully up to date, and there are a couple of instances in which I have made deletions so as to avoid including anything which has now been superseded. The articles have been arranged in chronological order, which seemed to be the best way. It is very pleasant to think that the articles have caused sufficient interest to warrant their being issued in a book, and I am most grateful to all those who have given me help in both the television programmes and in the present production.

PATRICK MOORE

East Grinstead August 1964

August 8 1964 - Close-Up of the Moon

This last article — written after the rest of the book had gone to press — differs from the others inasmuch as it has not been published before. When the U.S. rocket Ranger VII was dispatched toward the Moon on 28 July 1964, there was considerable excitement everywhere, plus a general feeling that this time the programme of taking lunar photographs from close range would be carried through successfully. I made a fleeting appearance on television after News Extra on 29 July, and said that in my view the interesting problems likely to be solved were (1} whether the lunar seas were in fact deep dust-drifts, and (2) whether there were many small craterlets too tiny to be seen from Earth. I also said that I had the most serious doubts about the existence of dust, and that I expected large numbers of minor craterlets.

The landing-point of Ranger VII was known, and when it duly hit the Moon on 31 July, after having sent back more than 4,000 photographs, it was clear that we would have to present a Sky at Night ''special'. This was duly broadcast after the end of normal programme time. I was joined by Peter Stewart, the rocket expert, and we tried to call up the Jet Pro­pulsion Laboratories in Pasadena, California. Unfortunately we were unable to establish two-way communication. I could hear Pasadena, Pasa­dena could hear the control centre in London, and control centre could hear both of us, but that was all. Finally, some thirty seconds before trans­mission was due to begin, I rapped out a series of questions which were repeated from control centre and answered by Pasadena.

Half a dozen of the Ranger VII pictures had been sent across to us, so that we were able to put them on the screen less than twelve hours after they had been taken. It was all most interesting, and quite different from our abortive effort with Lunik IV over a year earlier! On that occasion (April 1963) we undertook a similar Sky at Night special as the Soviet probe, launched on 2 April, neared the Moon. The general consensus of opinion was that the Lunik would either make a 'soft landing' or else deposit a package of some kind on to the Moon. During the vital period I carried out a live transmission from Lime Grove; I had a telephone link with Moscow, a radio link with Jodrell Bank (where Colin Ronan was stationed, and where Professor Sir Bernard Lovell generously gave up some of his time to join in), and cameras fixed to the large telescopes at Edinburgh (with Dr Peter Fellgett commenting) and Patcham (where George Hole was in readiness). The idea was to get the latest news from Moscow, listen to the signals from Jodrell Bank, and observe the impact from Edinburgh and Patcham. What actually happened was that nobody in Moscow seemed to know anything, Jodrell Bank could not hear anything, it was raining in Edinburgh and cloudy at Patcham, and in any case Lunik IV missed the Moon by four thousand miles. The programme provided a perfect instance of the workings of Spode's Law.

At 13 hours 25 minutes on 31 July 1964 - that is to say, at 2.25 p.m. British Summer Time - the American rocket Ranger VII hit the Moon. For the previous quarter of an hour it had been transmitting pictures of the lunar surface taken from close range, and when the first photographs became available they proved to be of amazingly good quality. Features much too small to be visible from Earth were clearly shown, and several outstanding problems of the Moon were cleared up at once.

The success of Ranger VII ended almost six years of frustrating failure by the American scientists. The moon-shot programme had been started as long ago as 1958, but it had been dogged by ill-fortune from the outset, and the plan of setting a man on the lunar surface before the end of 1970 had begun to look very over- optimistic. Now, perhaps, the tide had turned.

The first United States moon-rockets were the Pioneers. Five were launched between 17 August 1958 and 3 March 1959, but with somewhat depressing results. The original vehicle reached i2i miles, but then its lower stage exploded and the flight came to a premature end. The next rocket, officially known as Pioneer I, was sent up on October 11 and reached an altitude of slightly over 70,000 miles, but then fell back to Earth and burned up in the atmosphere (at least, this was presumably its fate; no trace of it was ever found). Pioneer III, launched on 9 November, was a total failure, since its third stage failed to ignite, while the fourth attempt, made on 6 December, attained 66,200 miles before it too fell back. The last Pioneer, No. 4, went up on 3 March of the following year; it weighed 13 lb and passed within 37,000 miles of the Moon during the night of 4-5 March. Signals from it continued to be received until it had receded to some 400,000 miles and had entered an orbit round the Sun, so becoming a tiny artificial planet. That, for the moment, ended the series, but meanwhile the Russians had been far from idle; during 1959 they launched their three celebrated Luniks, the second of which landed on the Moon, while the third went on a 'round trip' and sent back photographs of the area of the lunar surface always turned away from Earth.

It was not until 1961 that the Americans were ready to try again. The Ranger programme was initiated on 23 August, but the first two vehicles failed to go anywhere near the Moon. Ranger III, launched on 26 January 1962, seemed much more promising, and for a while hopes ran high; it looked as though the attempt to photograph the Moon from close quarters would be crowned with success. Unfortunately, errors then became apparent. The first stage of the launcher, an Atlas rocket, had been slightly too effective, so that the vehicle moved at more than its planned velocity and never approached the Moon to within less than 23,000 miles. Even so, it was still hoped that photographs would be received, and Ranger III was positioned by remote control, but the ill-luck was still there; further faults developed, so that only the extreme edges of the television pictures could be picked up, showing no details whatsoever.

The story was continued in April, with Ranger IV. The vehicle is thought to have reached the Moon on 26 April, but this time the photographic equipment failed as well as the guidance system, so that no data of any sort were obtained. Ranger V, of 18 October, was even less successful; it missed the Moon by a wide margin, and contact with it was lost at a relatively early stage.

The next attempt came from Russia. On 2 April 1963 the Soviet space-researchers launched Lunik IV, which was said to weigh over 1 1/4 tons and to carry complex equipment. Very few details about it were released, and even now nobody outside the USSR scientific circle seems to know just what it was meant to do. In the event, it merely went past the Moon and continued its journey into space, so that it was clearly a failure.

When 1964 opened, the situation appeared somewhat depress­ing; all in all, very little obvious progress had been made for four years so far as moon-shots were concerned. I think that the news of the launching of Ranger VI, on 29 January, was received with resigned pessimism - and the fears were justified. At least the Americans brought the vehicle down exactly where they had hoped, in the Mare Tranquillitatis, but the photographic equip­ment failed completely. Neither has any trace of an impact-scar been detected, though the exact position of the landing is known.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Photographs of the Moon taken from Ranger VII

Left: The moon from 34 miles the area covered is 16 miles square. Right the Moon from 3 miles; takes 3.2 seconds before Ranger VII hit the Moon.

With the ascent of Ranger VII, on 28 July, the total bill for the American lunar programme passed the £90,000,000 mark, and so far there had been remarkably little to show for it. Yet somehow or other there was a feeling that the new launching would be different - and so it proved.

Ranger VII took 67 hours 35 minutes to complete its journey of 243,665 miles. There were no communication troubles; the probe was tracked from America and also from Jodrell Bank, though the last stages of the flight could not be followed from Britain because the Moon had dropped below the horizon. When the vehicle was some 1,300 miles above the lunar surface, the cameras were turned on, and for the next 16minutes worked perfectly; 4,316 pictures were received, the last of which was still being transmitted when Ranger VII smashed itself to pieces on the Sea of Clouds.

There have been reports that on this occasion the impact was actually observed. Astronomers at Gape Kennedy, using power­ful equipment, described a small black speck about twenty seconds after the crash-landing; this speck mushroomed into a small white cloud 'resembling a three-leaf clover', which rapidly diffused and disappeared. The reports are not conclusive, but they are at least plausible. Whether any permanent scar will be detected seems rather doubtful. If it is visible at all, a giant telescope will be needed to show it.

Before going into further details about the photographs them­selves, it is important to say something about their purpose. It would be pointless to spend over £90m. in doing no more than show fine details on the Moon unless they would add materially to our knowledge of the lunar world, but in fact there were several urgent problems which could not be solved in any other way. The main question concerned the nature of the surface layer.

In 1955 a revolutionary paper had been published by T. Gold, well known for his work in helping to formulate the steady-state theory of the universe. According to Gold, the lunar craters were produced by meteoritic bombardment, while the maria were filled with dust - so that any astronaut unwise enough to land there would be comprehensively swallowed up in a dust-ocean more treacherous than any quicksand. Practical lunar observers were, in general, unimpressed,* but the theory could not be rejected out of hand, and it had to be checked before the more ambitious programmes, involving manned craft, could be worked out in every detail.

Another point concerned the numbers of very small craters scattered over the Moon. From Earth, it is difficult to see any crater with a diameter of less than 1,600 feet or so; in fact, we can examine only the coarser details. It was essential to find out whether any truly level ground existed, or whether the surface were pitted even in those regions which seem smooth and mirror like in Earth-based telescopes. For this reason, Ranger VII was aimed at a mare-surface rather than a bright upland area. It came down in the Mare Nubium, in the general neighbourhood of the low-walled, 36-mile crater Guericke - and the aiming was incredibly precise. A mid-course correction was made, on schedule, but no terminal correction was necessary.

Of the first pictures to be made available, two were particu­larly informative. From an altitude of 3 miles, 3.2 seconds before impact, craters less than a dozen feet across are shown; the last picture, still being transmitted at the moment of landing, covers an area comparable with that of a tennis-court, with craters 3 feet across and a mere 12 inches or so deep. These tiny objects are sharp and clear-cut, which would be out of the question in a surface of soft dust. Moreover, it was stated that some of the other photographs showed rather larger craters (that is to say, over 100 feet in diameter) containing isolated rocks which had been presumably hurled out during the formation of still larger craters — and yet were obviously not dust-covered. In fact, Gold's whole idea was wrong. Any dusty or ashy layer on the Moon could hardly be more than a few inches deep, so that basically the surface would be strong enough to bear the weight of a landing vehicle, even if unsafe areas existed here and there.

Associated with the dust problem was the old, much-discussed argument about meteors versus volcanism as the main force in crater production. Gold had been a strong supporter of the impact theory, and so had many other professional astronomers, such as G. P. Kuiper, H. Urey and F. Hoyle. Urey had even stated that the evidence was so overwhelming that there was no need to talk about it further. Others were not so sure, and at the New York lunar conference held in May 1964, at which I read a paper, I found that the meteor idea had come under heavy fire from geologists as well as practical lunar observers. For instance, J. Green of the United States and G. J. H. McCall of Australia drew attention to a possible analogy between lunar craters and terrestrial volcanic calderas. My own views were quite clear-cut; as I said at the conference, I have always been an 'unrepentant vulcanist', though no doubt numerous small meteor pits exist.

It cannot be said that the Ranger VII pictures give a final answer, but it looks very much as though vulcanism has, after all, been the main factor. At any rate, there can be no doubt that the Moon has been the site of tremendous volcanic activity at some stage in its history. Many of the minor pits in the area where Ranger landed may well be due to impact - but in all probability the bodies producing the pits were hurled out from lunar craters of greater size instead of coming from space.

One photograph, taken from a height of 34 miles, showed what Kuiper called 'a whole nest' of small craters, some of them no more than 15 feet in diameter, said to have rounded crests potentially dangerous to astronauts. This particular area was crossed by one of the bright rays from the 56-mile crater Coper­nicus, and it was evident that some connection existed between the craterlets and the ray, so that the craterlets looked as though they must be secondary pits due to the eruption of Copernicus itself. As for the rays, it was claimed that they were sizeable rocks thrown off during the production of the focal craters - but to me this idea does not seem to be at all convincing, and the rays remain enigmatical.

Moreover, there is at least a chance that some of the rays shown in the photographs do not come from Copernicus at all, but from Tycho. Of course, Tycho, in the southern uplands of the Moon, is a long way from the point where Ranger VII landed — but the Tycho ray-system is more extensive than that of Copernicus and the alignment seems to fit the general Tycho pattern well. Further studies of the photographs will certainly clear up this and other points. Meanwhile, Ranger VII has at least disproved the dust-drift theory, and it now seems likely that the mare surfaces are made up of some material such as hardened lava.

Of course, only a very limited part of the Moon was covered; even the first pictures, taken about i6| minutes before impact, showed an area of no more than 180,000 square miles, appreciably less than that of France. Really level ground was lacking, and it does not seem probable that other mare-surfaces are much smoother; astronauts of the future cannot hope to find any mirror-like expanses big enough to be pressed into service as landing-grounds.

It cannot be said that the photographs have provided any major shocks for those astronomers who have always disbelieved in Gold's dust theory, and who have regarded the lunar surface as essentially volcanic in character. However, it has been pointed out that there seem to be few small cracks or fissures. Fissures of such a kind may be absent, or else they may simply not have shown up; this is a problem for the future, but since there are so many crater-chains, clefts and valleys on a larger scale, it would be distinctly strange to find that small cracks do not exist.

There is one more point which has already been brought up, though not by the American scientists concerned in the experi­ment. It has long been thought that the Moon is utterly without life; even lowly vegetation is improbable to the highest degree. The Ranger photographs have shown nothing that could be interpreted as being due to living organisms, and nobody had had the slightest expectation that they would. The Moon is a sterile world, and probably has always been so.

The success of Ranger VII means that plans for the future can be continued with high hopes. Two more vehicles of the same sort are planned for early 1965; Ranger VIII will go up in January, all being well, and Ranger IX will follow in February. No major modifications to the probes or launchers are expected, but different areas of the Moon will come under study, and it may well be that one of the rockets will be aimed at a bright upland instead of a dark plain. I rather hope that one Ranger will land near Aristarchus, the brilliant crater near which observers at the Lowell Observatory, Flagstaff, reported red patches in October and November of 1963.

This will complete the Ranger series. Next will come vehicles of the Surveyor type, involving soft landings, and 1966 should see the launching of Orbiter vehicles, which will go round the Moon taking high-resolution photographs from heights of 30 miles or so. Whether the Americans will manage a manned flight to the Moon before 1970 remains to be seen. Incidentally, we must not forget the Russians, who have had no real successes with their lunar or planetary probes since 1959, but who are certainly making plans of their own. A soft landing on the Moon by a Soviet space-craft may be imminent.

At present Ranger VII lies wrecked in the Mare Nubium, but I doubt whether it will stay there for ever. At some future date an expedition from Earth will surely collect its shattered remnants and carry them off to a museum. America's lunar probe accom­plished its task more brilliantly than its makers can have dared to hope, and it has certainly earned its place in history.

July 24 1964 - The Brightest Objects in the Universe

One of the most important astronomical discoveries of recent times, if not the most important of all, was that of the objects known variously as quasars, quasi-stellar objects, or simply as QSO's. Thousands of millions of times more luminous than the Sun, if present evidence is to be trusted, they look like faint and unspectacular stars, but they are in fact infinitely more dramatic. Despite our lack of knowledge as to their true nature, it was clear that a programme would have to be devoted to them, and on this occasion I was again joined by one of the regular visitors to The Sky at Night, Colin Ronan.

Our knowledge of the universe has progressed amazingly during the past half-century. In 1920, for instance, it was still not defin­itely established that the 'resolvable nebulae', now known as galaxies, lie well beyond the boundaries of our own system; leading astronomers of that time considered that they were contained in the Milky Way, and there was certainly no thought of an expanding universe. The present position is very different. There can be no doubt that the galaxies are separate objects, some of them considerably larger than the Galaxy in which we live, while there is not much reasonable doubt that all the galaxies apart from those in our Local Group are racing away from us at tremendous speeds. 3C-295, a faint galaxy in the constellation Bootes, is in the order of 5,000 million light-years away, and is receding at almost half the velocity of light, as was established by Minkowski in 1960.

Very recently, objects of a completely new type have been identified. They have been called quasars, quasi-stellar objects, or (for short) QSO's, and the evidence indicates that they are the brightest things in the whole universe. Yet they are not normal galaxies, and the source of their energy is still unknown.

A recent illustration of Quasar 3C120

The detection of QSO's would have been almost impossible s been found that galaxies of certain types are strong emitters of radio waves. According to Minkowski, over 90 per cent of these 'radio galaxies' are giant ellipticals. In some cases it has been supposed that the radio emission must be caused by collisions between galaxies, as with the famous Cen- taurus A, unfortunately too far south in the sky to be visible in Europe. When photographed with a large telescope, Centaurus A is a spectacular object, and there seemed every reason to suppose that it was in fact made up of two separate systems which were passing through each other; individual stars would seldom or never collide, but the gas and dust spread between them would be in collision all the time, so producing the radio waves picked up by the instruments at Jodrell Bank and elsewhere.

Like so many other plausible-sounding ideas, this theory has been tested, and has been found to be inadequate. The intensity of the radio emission is simply too great to be explained in this way, and it now looks as though the whole notion of galaxies in collision must be given up. Some other energy-source is in­volved, though at the moment we have to confess that we do not know what it is.

Detailed surveys carried out during the past year or two showed that there were some radio sources not associated with normal galaxies. One of these was numbered 3C-48, since it was the forty-eighth object in the third Cambridge catalogue of radio sources. The radio position could be fixed with fair accuracy, and it appeared that the waves could come only from what looked like a faint star, with a wisp of nebulosity close by. Astronomers were keenly interested, and subjected this 'star' to close examin­ation, with remarkable results. It became clear that instead of being a star, 3C-48 was something very much more dramatic. Studies of its spectrum showed that it was extremely remote, and moving away from us at high velocity. Also, it was very blue.

The real surprise came when the luminosity was worked out. 3C-48 must shine as brightly as 1,000,000,000,000 Suns put together, so that it is much more luminous than the Andromeda Spiral, the most brilliant galaxy known (twice as luminous as the Milky Way system)". Yet it gave the impression of nothing more than a 16th-magnitude star, and it was certainly much smaller than a galaxy - unless, of course, we were seeing only the brightest part of it.

Since then, eight more of these QSO's have been identified, one of which, 3C-273, far outshines even 3C-48. It is of visual magnitude 12-7, so that it is not difficult to see in an average amateur telescope, but at first sight there is nothing to single it out. In fact, it must be over 1,500 light-years away, with a luminosity 200 times as great as that of our Galaxy. Finally there is 3C-147, which lies at something like 6,000 million light- years, and has the distinction of being the most remote object so far identified by visual means.

These distances are almost incredible in view of the apparent nature of the QSO's, and yet they seem certainly to be of the right order. The estimates depend, of course, upon the Red Shift of the spectral lines; according to the Doppler principle, a shift of this kind indicates recession, the velocity depending upon the extent of the shift. There is a definite relationship between the recessional velocity and the distance of the object concerned, as has long since been established by studies of normal galaxies, so that the distances themselves can be found.

The only loophole in this argument is to suppose that the Red Shifts in the spectra of QSO's are due to some other cause, but here we run into difficulties at once. If, for instance, the QSO's were relatively close, and yet were receding very quickly, they ought to show definite proper motions — that is to say, their movement against the starry background should be detectable over a period of a year or so - but this is not the case. It has also been suggested that the Red Shifts have nothing to do with velocity, but are due to strong gravitational fields at the surfaces of what may be termed 'super-stars'. However, the American astronomers Greenstein and Schmidt have shown that a field of this intensity would collapse the super-star's atmosphere, so that the spectrum would not correspond to what is actually observed. All things considered, it seems overwhelmingly likely that the QSO's really are immensely remote and immensely lumin­ous.

Another problem concerns the short-term variations in brightness shown by at least four of the QSO's, including 3C- 273. It must be emphasized that QSO's are not recent discoveries ; they have been known for a long time, since they are not parti­cularly faint when photographed with large telescopes - it is simply that not until now has it been realized that there is anything remarkable about them. A. Sandage and H. Smith, in America, have studied photographs of 3C-273 taken during the last sixty years, and have found that there are fairly regular changes of from 0-2 to 0-3 magnitude with a period of about thirteen years, with possible 'flashes' of more than half a magni­tude lasting for a few weeks. 3C-273 is a double object, each radio source being about 1,500 light-years in diameter, which is impossibly small for a normal galaxy and impossibly large for an ordinary star. It is hard to see how a QSO can virtually double its luminosity in a few days, when light takes several hundred times as long to travel from one part of it to another. In fact, most of the light from a QSO must be coming from a body whose diameter is less than half a light-year.

Clearly, a QSO cannot be simply a galaxy with more than its fair quota of highly-luminous supergiant stars. In this case, the angular diameters of the objects would be much greater than they actually are, and they would not appear as stellar points. Rather more rational, but profoundly unconvincing, is the idea that the energy source may be due to chains of supernovae.

A supernova is a star which suffers a cataclysmic outburst and destroys itself, shining for a brief period with a luminosity millions of times that of the Sun. Only three have been recorded in our own Galaxy - the stars of 1054, 1572, and (probably) 1604; the first of these has left the mass of gas known as the Crab Nebula. Supernova wrecks are known to be radio emitters, and the Crab Nebula itself is a particularly strong source. On the other hand, it would need a good many supernovae to produce as much energy as is sent out by a QSO. No mechanism is known whereby one supernova could 'trigger off' another, and in any case the period of brilliance would be relatively brief. There is no reason to suppose that the QSO's are temporary features, and few authorities have much faith in the supernova theory. It is worth noting, however, that G. Field has proposed that star formation would occur suddenly in the case of a non-rotating mass of gas which is condensing into a galaxy, so that many supernovae might explode at much the same time several millions of years after the main period of star formation.

More plausible, though highly tentative, is the idea of gravi­tational collapse. Here we begin with a 'star' of fantastic size, perhaps 100 million times as massive as the Sun, and lying inside a galaxy. If it collapsed under its own gravity, the collapse would be catastrophic, so that the super-star would explode inwards. Immense quantities of energy would be produced, certainly enough to account for the strong radio emissions received from QSO's. Significantly, F. Hoyle and A. Fowler had actually discussed the properties of such collapsing heavy bodies about a year before the first QSO's were identified.

This is all very well, but it leads to further difficulties. Though the normal stars show a great range in size and luminosity, they are much more uniform in mass; generally speaking a large star is rarefied, while a small star is dense. A star 100 times as massive as the Sun must be classed as a real freak. If the gravitational collapse theory of QSO's is valid, the original bodies must be entirely different from anything previously suspected, and we can have no clue as to their origin, so that in trying to explain one set of peculiar facts we have merely introduced another. It follows, incidentally, that on this hypothesis a QSO would be comparatively short-lived, and after a period of from 100,000 to 1,000,000 years would evolve into an as yet unknown state. (In itself this would not, of course, be an obstacle, since the changes would still be much too slow to become evident over a great many generations of astronomers!)

It would be much more straightforward to suppose that a QSO is nothing more than the nucleus of a strange sort of galaxy. This is quite possible, since the great distances involved would mean that the fainter parts of the system would be too dim to be observed. Yet as we have seen, there are indications that the majority of the light comes to us from a body which is relatively small, and which may well be gaseous. If this is so, there is no escape from the conclusion that the energy is being produced in some way that we cannot yet visualize. Ordinary nuclear processes, such as those which operate inside stars, are hopelessly inadequate.

The identification of QSO's has come as an astronomical bombshell, and may lead to a drastic revision of many of our cherished ideas about the universe. The problem is obviously linked with that of the origin of the galaxies. At present, the arguments between the supporters of the 'steady-state' and 'evolutionary' theories continue unabated; some authorities consider that the universe has always existed, and that new matter is being continually created out of nothingness, while others hold that the universe began at a set moment in time, is now evolving in a definite pattern, and will eventually die. Radio astronomy holds out the greatest hope of deciding between these rival theories, but up to now it has been supposed that all the very faint and presumably remote radio sources must be galaxies of some sort or other. If a QSO is not a galaxy in the proper sense of the word, then the situation may be very much altered.

At least there can be little doubt that the QSO's are the most extraordinary objects ever discovered. Apparently small by cosmical standards, extremely remote, and of incredible lumin­osity, their nature remains a mystery. Further studies of them may provide at least some of the answers, but the detection of a whole new class of objects, previously unsuspected, brings home to us how little we really know about the universe.

May 1 1964 - The Clouds of Magellan

Among the most fascinating objects in the sky are the two Clouds of Magellan, or Nubecula. They are too far south to be visible from Europe, but European observatories have been co-operating in studies of them. Actual photographs are taken from southern hemisphere stations, and the theoretical work is being undertaken on an international scale.

A great deal of this work is being carried out at the Armagh Observ­atory, in Northern Ireland. Armagh Observatory is extremely interesting in many ways, and so we decided to go there for a Sky at Night pro­gramme. Dr E. M. Lindsay, the Director, could not have been more helpful - indeed, he joined in the broadcast, and showed himself to be an expert in television technique as well as in his own sphere of astro­physics. I must also pay tribute to Mrs Lindsay and to the Armagh staff, who made our stay at the Observatory so very pleasant.

In the southern hemisphere of the sky, the famous sixteenth-century explorer Magellan noticed two strange luminous patches. They looked almost like two detached portions of the Milky Way, and both were easily visible to the naked eye. Today, these objects are known as the Magellanic Clouds or Nubecula, even though Magellan himself was not their actual discoverer.

The Clouds never rise in our own latitudes. They are therefore permanently out of view from great observatories such as Palomar and Mount Wilson. However, they are of great importance in astronomical study, and intensive research into their nature and characteristics has been going on during the past half-century or so. The visual work must naturally be done from a southern station, but much of the theoretical work is carried out in the north, and a part in the investigations has been played by the Observatory of Armagh.

Armagh Observatory, in Northern Ireland, has a long and honourable history. Indeed, it is the oldest British observatory still operating from its original site (Greenwich Observatory is now at Herstmonceux in Sussex). The founder was Lord Rokeby, better remembered as Archbishop Robinson, a great man in the history of Armagh; memorials to him are to be found all over the city. During the closing years of his life, Archbishop Robinson was anxious to found an Ulster university. This project was never realized, but the founding of the observatory, due entirely to Robinson, was probably connected with the university scheme. The Archbishop's generosity led to the setting-up of the observa­tory in 1790, and in July of that year the Rev. Dr James Hamilton was appointed Director. Since that time Armagh has maintained a fine record of observational and theoretical work. There have been seven Directors, including Dr E. M. Lindsay, the present holder of the office; special mention should be made of Dr Romney Robinson (no relation to the Archbishop) whose regime extended from 1823 to his death in 1882, and Dr J. L. E. Dreyer, who is particularly remembered for his work in connection with the New General Catalogue of star-clusters and nebulae.

There are many historical exhibits in the present observatory. There is, for instance, a mirror made by Sir William Herschel, discoverer of the planet Uranus and 'explorer of the heavens', together with letters written by his sister Caroline. Herschel was well acquainted with Archbishop Robinson, and the two used to visit Bath Spa together from time to time even after Herschel had ceased to be organist there and had begun to devote all his time to astronomy. Equally interesting is a small reflector which was owned and used by no less a person than King George III, who was keenly interested in astronomical science.

Together with this historical material, there are modern instru­ments in regular use. There is, for instance, a Schmidt telescope - better known, perhaps, as a Schmidt camera, since its use is entirely photographic. The Armagh Schmidt is employed mainly on variable star research. Another telescope is a 10-inch Grubb reflector, with which double star measures are being carried out.

Moreover, Armagh is a meteorological station as well as an observatory, and continuous weather records have been kept ever since 1790.

Excellent though they are so far as quality is concerned, the Armagh telescopes are small compared with the American giants such as the Palomar 200-inch reflector. Moreover, conditions in Ireland are not ideal for astronomical observation, although admittedly they are no worse than over many other parts of Europe (including England). For these reasons, a link was formed with the famous Harvard Observatory in the United States and with the Dunsink Observatory at Dublin. The result was the setting up of the 'A.D.H.' (Armagh-Dunsink-Harvard) telescope at the Boyden Station of the Harvard Observatory, near Bloemfontein in South Africa, with the set intention of studying objects which could never be seen from northern latitudes. The project dates from 1950. In 1955 the Swedish, Belgian, and West German Observatories joined with Harvard and the two Irish Observatories to form the Boyden Observatory, the Council of which consists of the Directors of Armagh, Brussels, Dunsink, Harvard, and Stockholm Observa­tories. Unlike most international projects, this scheme has been completely free from friction, and there has been full agreement in all respects.

The A.D.H. telescope at Boyden is a 36-inch reflector. Use is also made of other instruments at the observatory, notably the 60-inch reflector. Conditions are excellent, and the programme which has been undertaken is a very full one. Emphasis has been placed on the two Clouds of Magellan, and the results have been very encouraging, as Dr Lindsay has stressed.* There are two Clouds; the Large (Nubecula Major) and the Small (Nubecula Minor). They are not, in fact, detached parts of the Milky Way, but are galaxies in their own right. Each is about 180,000 light- years away, so that the Clouds are considerably nearer than any other external systems.

Our Galaxy is made up of perhaps 100,000 million stars, of which the Sun is one. The system is arranged in a flattened form, so that the familiar Milky Way effect is nothing more than an effect of perspective; when we look along the main axis of the Galaxy, we see many stars in much the same direction. Together with stars, the Galaxy contains huge clouds of gas (nebulas), and clusters of various kinds; there are open or loose clusters, of which the Pleiades group is the best known, and globular clusters, such as Messier 13 in Hercules. The two brightest globulars, Omega Centauri and 47 Tucanae, are, like the Clouds of Magellan, too far south to be seen in Europe or the northern United States. The closest of the really large outer galaxies is Messier 31m Andromeda, known as the Great Spiral, which is dimly visible to the naked eye on a clear night. This system appears to be considerably larger than our Galaxy, but is very remote, since it lies at a distance of more than 2,000,000 light-years. The Clouds of Magellan are seen, then, to be relatively near to us on the cosmical scale. To use Lindsay's analogy: if our Galaxy is represented by London, then the Clouds will be represented by Greenwich or Woolwich.

The Clouds are also relatively close to each other. The distance between their centres is about 75,000 light-years, and there is evidence that the two are actually connected, forming a twin system; for instance, radio astronomers have been able to show that the two Clouds are embedded in a common envelope of hydrogen gas. There have also been suggestions that the Clouds are satellites of our Galaxy, and move round it, taking an im­mensely long time to complete one revolution. This may or may not be the case - more information is needed - but at all events there is no doubt that the Clouds are true members of the so-called 'local group' of galaxies.

Broadly speaking, there are three main types of galaxies: elliptical, spiral, and irregular. In a spiral, such as Messier 31 in Andromeda, there is a central nucleus, relatively free from inter- stellar gas and dust, and with a high proportion of red giant stars, which are well advanced in their evolution. In the spiral arms there are many young, highly luminous, hot blue stars, together with clouds of gas and dust. Parts of the Nubecula Major are seen to be of the 'spiral-arm' type, and there is inconclusive evidence of an incipient spiral structure; there is certainly a main axis with a great concentration of stars. The smaller Cloud is different; there is no nucleus, no symmetry, and nothing in the nature of a spiral arm, so that Nubecula Minor is best classified as an irregular galaxy. There is one marked extension, but this is probably due to tidal effects caused by the Large Cloud. All things considered, efforts to find order and structure in the two Nubeculae have not, so far, proved very rewarding.

What is far more important is the fact that the Clouds contain objects of the same kind as are found in our own Galaxy, and to all intents and purposes we may assume that all objects in the Clouds are at the same distance from us. (To give a rough analogy; it is true that New York is closer to Southampton than to Portsmouth, but the difference is utterly unimportant.) It was by studying the short-period variables in the Small Cloud, fifty years ago, that Miss Henrietta Leavitt, at Harvard - using photographs taken from southern stations - made the discoveries that led on to the 'period-luminosity law' of Cepheid stars. These Cepheids brighten and fade regularly, and their behaviour can always be predicted. Miss Leavitt found that the longer the period of a Cepheid, the brighter it looked; since she could assume that all the Cloud Cepheids lay at the same distance, it followed that the longer- period stars were genuinely the more luminous. Without the Clouds, this far-reaching discovery would have been very difficult to make.

At Armagh, during the past few years, Dr Lindsay and his assistants have been completing a survey of various types of objects photographed in the Clouds with the A.D.H. telescope. There are clusters, both open and globular; there are planetary nebulae, and also gaseous nebulae. A planetary nebula consists of a central star surrounded by a ring or shell of gas, and is not appropriately named, since it is not, strictly speaking, a nebula - and is certainly not a planet. The brightest example in our own Galaxy, the Ring Nebula in Lyra (not far from the brilliant bluish Vega) is visible with a moderate" telescope. Planetary nebulae in the Clouds are too remote for their structure to be seen, but their spectra, as obtained with the A.D.H. telescope, reveal their true nature, and about 150 have now been found. Also to be seen are a few objects which look very much like the wrecks of supernovae, or stars which exploded long ago and never returned to their original state.

Of the gaseous nebulae, the most striking is known popularly as 'The Tarantula'. It is of basically the same type as the celebrated Orion Nebula in our own Galaxy, but is much larger. The Orion Nebula, which may be seen with the naked eye in the Hunter's Sword, is 1,600 light-years away and about 25 light-years in diameter; its mass is about 100 times as great as that of the Sun, and it seems to be one of the sites where fresh stars are being created from interstellar material. The Tarantula Nebula in the Large Cloud of Magellan, however, is 800 light-years across, and has a mass equivalent to 500,000 Suns. If it lay in our own system, it would indeed be a magnificent object. Embedded in it are clusters of hot, young, very luminous stars.

It is also interesting to note that the Large Cloud contains S Doradus, which has the distinction of being the most luminous star known. It is equal to about 1,000,000 Suns - and yet is so far away from us that without a telescope it cannot be seen at all. It is variable, and is using up its 'nuclear fuel' at a fantastic rate, so that it must have a relatively short expectation of life in its present form. The Sun will not change much for some thousands of millions of years to come; S Doradus can hardly continue squan­dering energy at its current rate for more than 1,000,000 years.

Great attention is being paid to the star-clusters in the Clouds, and by now many have been detected; about 120 in Nubecula Minor, almost 1,000 in Nubecula Major. Most of these are of the open type, though there are also numbers of globular clusters. From their distribution, it is possible to estimate the maximum dimensions of the systems, and it has been found that the diameters are 20,000 light-years for the Small Cloud and double this for the Large Cloud. Even the senior of the two is, therefore, much smaller than our Galaxy, which is about 100,000 light-years across: even so, the Clouds are certainly not dwarfs.

Astronomers consider that we are fortunate in having the two Nubeculae near at hand. Studies of them give us considerable insight into the anatomy or structure of galaxies in general, and also yield information about the evolutionary processes of the stars and star-systems. As Lindsay has commented: 'One of the aims of the astronomer, if not the ultimate aim, is .to find out how and when the universe began, how it is changing, and how and when it will end - if indeed there was a beginning or if there will be an end'.

It is probably true to say that without the Clouds our knowledge of the universe today would be markedly less than it actually is. There are no other comparable systems within range; the Andro­meda and Triangulum spirals are much more remote, so that they cannot be examined so easily, and the remaining galaxies of the local group are much less informative. There is an urgent need for a really large telescope in the southern hemisphere, since photo­graphs of the Clouds taken with a 150-inch or 200-inch reflector would be invaluable. Meanwhile, the A.D.H. telescope is playing its part well.

At Armagh, the 'old' meets the 'new'. The observatory itself is a charming old building set in picturesque surroundings, and the modern domes housing the Schmidt telescope and the 10-inch refractor fit well into the picture. Yet the work in progress there is extremely modern, and is of great scientific importance. Moreover, the complete success of the international project at Boyden augurs well for the future.