Posts Tagged ‘telescopes’

LO WOLTJER’S TELESCOPE; THE VLT

March 11, 2021

Francis Bacon, a very wise old bird, wrote; “By far the greatest obstacle to the progress of science and the undertaking of tasks and provinces therein is found in this — that men despair and think things impossible“.[Novum Organon, 1604]. But sometimes a man has the imagination, or effrontery, to see beyond his fellows, and so to build a marvel which they all thought impossible. Such a man was Lo Woltjer who built the VLT, now the most powerful optical telescope on Earth.

In 1976, during a conference in Italy I overheard him say over lunch ‘It’s time for Europe to take back the lead in Astronomy from America’. At the time I thought that idea preposterous but overnight I changed my mind and went to talk to him . I had spent spent several years analysing the Scaling Laws of telescopes, that is to say how their effectiveness and cost scale with their mirror diameter D. Naively I had imagined all would scale with the mirror area, that is to say with D2 , but that turned out to be very far from the truth. Big mirrors also collect unwanted sky light (noise) while some major costs could rise as fast as D4 . Why? Because if they are to focus the light, telescopes cannot afford to bend, and bending moments scale as D4 — that’s why big trees are so much stouter in proportion than saplings. And in engineering, costs tend to rise in proportion to weight. I had thus concluded (1972) that large telescopes were disproportionately expensive and should be replaced by arrays of smaller ones which could add their signals together.

When I went to talk to Lo he was sitting under a tree reading Tacitus’ “The Agricola and the Germania” because he was an historian at heart, son of an eminent Dutch historian. He took the long view, saw the big picture, and realised that America’s huge lead was a temporary consequence of finding better telescope sites in its own back yard. But the coming of the jet airliner Woltjer saw as a chance for Europe to catch up, indeed overtake America in mankind’s race to decipher the Cosmos. He asked me to spend 6 months at his European Southern Observatory (ESO) headquarters, then in Geneva, and help with his visionary plan — which I afterwards did.

In 1977 Woltjer organised a huge conference on Big Telescope Design in Geneva at the end of which he announced his vision of a 16-metre class European telescope at a time when the largest was the 6 metre Russian instrument. 21 years later his his vision bore fruit when the VLT (‘Very Large Telescope’) saw First Light high up in the Chilean Andes. This is now recognised to be the most powerful astronomical facility on Earth, generating even more research papers than the Hubble Space Telescope, which cost ten times as much.

vlt

The VLT up at La Paranal up in the Chilean Andes. It looks nothing like a conventional telescope because the mirror area is equally divided between 4 largely identical 8.2 metre units, each in its own rotating enclosure. The 4 smaller auxiliary telescopes in domes combine with the 4 monsters for the purposes of optical interferometry. Such a single image can convey little of the ingenuity going on inside. For that see later

I played only a minor roll in the VLT’s eventual evolution and confess I’ve never used it because my primary interests turned in other directions, such as Hidden Galaxies for which it wouldn’t be useful. But I would like to celebrate what seems to be a most extraordinary personal , as well as a European-wide, achievement. So many challenges had to be met, so many stubborn minds had to be persuaded, so many co-workers had to be inspired to realize a dream built out of glass, electronics and light. Whereas one can marvel at other great constructions like Stonehenge and Agia Sophia we know almost nothing of how they were built , or even who built them, but the VLT story is still acccessible , not least in Woltjer’s own modest book “Europe’s Quest for the Universe” [2005]. Fascinating episodes include:

Deciding on its fundamental configuration , which had to be a series of tricky trade-offs between performance, politics and cost.

Finding the very best site when cloudlessness and atmospheric steadiness do not necessarily go together.

Building huge mirrors which are very light, yet optically and thermally stable. Eventually the Schott company cast the 8.2 metre monoliths out of its proprietry Zerodur which took months and months to cool as they were spun into shape. Lo Woltjer’s chief optician, Ray Wilson from Brum, devised active support mechanisms which thereafter kept those mirrors in perfect shape as they were tilted to follow the sky. Not least was the challenge of moving such huge but fragile structures via the waterways of the world to their eventual home atop the Andes.

Any telescope’s performance can be ruined by turbulent air bubbling anywhere near it, hence its housing is vital. The VLT housings, while protecting the telescopes from wind and weather, leave them largely out in the pristine night air. This novel design was proof-tested on ESO’s smaller NTT and appears to work remarkably well.

The demands of near-infrared astronomy on a telescope are different from the optical variety. For instance the massive secondary mirrors have to be wobbled at 10 Hertz or more to subtract off the much brighter infra- red sky. At some considerable cost this was achieved by building them out of light but very tricky Beryllium.

Any telescope is only as good as the Instruments fitted to it to analyse and record its light. Here Woltjer took a leaf from Space Astronomy. Such Instrument’s specifications were sent out to tender across Europe, with the winning teams not only paid but rewarded with large grants of telescope time to do their own Science. This not only challenged the best of European brains but built up invaluable infrastructure across the continent.

Last, but not least, Woltjer and his chief lieutenant Maximo Tarenghi had to deal with a Chilean government which was traumatized by the brutal Pinochet coup. They had to sup with some real devilsL

Last but not least , Woltjer and his chief lieutenant Maximo Tarenghi had to deal with a Chilean government rocked by Pinochet’s very violent coup. At times that meant supping with some pretty vile devils.

But in the end, somehow everything came together and worked superbly, so that, in my opinion, the VLT is one of mankind’s greatest achievements, reminding us of what we humans, at our best, can do.

No blog or image can possibly do justice to Lo Woltjer and his great achievement but, as you might expect, ESO runs a quite wonderful website at eso.org and if you look there under ‘Movies’, or on You-Tube, you can find ‘VLT trailer’ , a stirring evocation of this magnificent project, fanfare and all.

THE LOVELL RADIO TELESCOPE

March 8, 2021

is surely the most spectacular telescope on Earth and definitely worth a family visit to the visitor centre at Jodrell Bank near Macclesfield in Cheshire. Remarkably it can tip all the way down to to the horizon and if you can get close to it you can watch its wheels very slowly turn as it follows a radio source across the sky. In other words you can see the Earth actually turn — which fascinated me when I was privileged to observe with it.

Lovell Radio Dish at Jodrell Bank Cheshire

The 250 foot Lovell Radio Telescope completed in 1957 and named after Sir Bernard Lovell of Manchester University who built her largely out of war surplus, is still the only big dish which can tilt all the way down to the horizon. She has numerous scientific discoveries to her credit including gravitational lenses.

The old girl’s getting on a bit but she’s definitely had her moments. The first pictures back from the Moon’s surface, taken by the Russian Luna 2 spacecraft in 1966, were beamed back to Earth using her unique capabilities at the time. The local Manchester University staff decoded them and rushed them down to a Royal Astronomical Society meeting in London where I was lucky enough to be amongst the audience as a student. We all had to pinch ourselves to make sure we weren’t dreaming.

Much later in 2004 my colleague Jon Davies and his team used it to discover a Hydrogen source Virgo HI 21 in the Virgo Cluster, which is, in my opinion, the first Dark Galaxy. It’s massive, it’s spinning and it’s invisible. What else could it be?

The source Virgo HI 21 first discovered by a team from Cardiff University who were searching for Dark Galaxies in the 21-cm Hydrogen Line using a multi-beam receiver specially designed for that purpose. Higher resolution radio observations by the same team with the radio interferometer at Westerbork in Holland are shown above superposed on negative optical images. On the left you can see that the source has interacted with and disturbed the massive Spiral Galaxy NGC 4254, the most luminous in the huge cluster. The velocity map on the right reveals that Virgo HI 21 is spinning at about 200 kilometres a second, about what you would expect of a massive disc. But very deep Hubble Space Telescope images of the mysterious disc revealed no light.

The claim that Virgo HI 21 is a Dark Galaxy gave rise to titanic refereeing battles and vicious arguments which are described in Chapters 12 and 13 of my novel ‘Beyond the Western Stars.’ [ see this site under Category ‘My Books’]. They illustrate that cutting edge astronomy is definitely not for the faint hearted. If you ask me, from a distance of 12 years, much of the opposition was motivated by sour grapes. But why not make up your own mind and look at some of the evidence. Science can be tough, very tough.

HIDDEN GALAXIES, HIDDEN UNIVERSE

November 6, 2020

Hidden Galaxies were Tom Morgan’s passion (and mine). We both fell under their spell when we were young and spent our lives, and other people’s too, searching for them. Were we mad, as many sensible astronomers thought, or were we lucky? After all, searching for a vast continent whose existence could only be inferred from coincidences and equations, seems close to insanity. But then Christopher Columbus had been driven to his own folly by finding tropical beans washed up on the wester shore of Ireland, and by scraps of manuscript written in Egypt but then left forgotten for a thousand years on a library shelf in the great dome of Byzantium — Agia Sofia.

The saga of of Morgan’s life-long obsession ( and mine) is the spine of my quartet of novels Written in the Stars, starting with Against the Fall of Night (AFN) and ending with Beyond the Western Stars (BWS), a sort of Sidereal Odyssey I won’t retell here. But what I can do for non-astronomers is add some scraps of the evidence, the tropical beans if you like and the pieces of parchment which kept Morgan and his comrades going when all the Odds looked to be against them.

The Wigwam diagram showing the Visibilty of any galaxy (upwards) plotted agains its dimness, plotted horizontally, dimmer to the right. It is the consequence of two plunging curves and so is very sharp and very thin, which surprised everybody. It is utterly unintuitive, yet entirely dominates our ability to see the extragalactic universe. It turns out that virtually all the galaxies we can measure lie right under the peak. That is either a miraculous coincidence or a warning that most galaxies are hidden out of sight.

Let’s begin with the calculation Morgan made back in 1975 in that caravan on the Teifi Estuary (AFN). Above we see it in the form of a graph. It shows the Visibility of a galaxy — that is to say how easy it will be to see, plotted upwards, against its dimness, plotted towards the right along the bottom. And what Morgan found, to general consternation and surprise, was an extremely sharp, narrow peak. The inference was that only galaxies of a very particular dimness (or ‘surface brightness’ in the jargon) would be visible to mankind. Those ones to the right (‘Icebergs’ Morgan called them) would be sunk too far below the night sky, whilst the ones to the left (‘Brilliants’) would be so small in apparent size as to be mistaken for background objects And here was the killer-coincidence: all the galaxies known to science at the time fitted exactly underneath Morgan’s peak. That is why the paper, with its implicit challenge, was published in the journal ‘Nature’ in 1976. What the diagram The ‘Wigwam diagram” as we came to call it, cannot convey is just how narrow the Wigwam really is. It is ten thousand times narrower than the total range over which the occasional galaxy has turned up by accident. Ten thousand times! Even Morgan sometimes couldn’t believe that. Apparently we are looking at the universe through a mere crack in the shutters. It was the Wigwam diagram which kept Morgan and his crew sailing on, through doldrum and tempest, for the next forty years.

Astronomy is beset by what are called “Selection Effects”. That is to say we build our picture of the cosmos selectively out of what we can observe down here, pretending that what we cannot observe, which might be much the greater portion, is not significant. What else could we do? Morgan’s wigwam was thus a rude shock, for it suggested, very directly, that Astronomy must be missing much of the extragalactic cosmos. What could be done about that? We had to try and devise alternative observing strategies which might enable us to see through one window, what could not be seen through another.

ICEBERG GALAXIES

Using that approach Morgan and his colleagues decided to survey the sky in the radio band, and when they found a source, check what was there in the optical. The next figure shows some typical results, with a radio spectrum superposed on a negative image (easier to see) of the corresponding area of the visual sky..

Here are radio scans of the sky made with the Parkes Radio Telescope superposed on negatives of the optical sky behind. The receiver is tuned to the frequency of gaseous Hydrogen receding from the Earth at the velocities ( in Km/sec) shown at bottom. The two upper spectra corresponded to giant spiral galaxies, bottom left to a dwarfish Irregular galaxy, and bottom right to a dim galaxy barely visible above the sky. The area under each spectrum is a measure of the total amount of gas present while the width derives from the internal motions within the galaxy ,such as rotation. Much can be inferred from these measures. Copyright Monthly Notices of the Royal Astronomical Society.

Usually there is indeed a galaxy to be seen there. But of course the team were hoping to find cases where the optical counterparts were invisible — i.e. true ‘Hidden Galaxies’

A montage of galaxies found at Parkes and then observed in several colours with the Sloan Survey Telescope in New Mexico. The six bottom right are all colossal giants more massive than our Milky Way. Nevertheless, as you can see, some are very dim. This all ties in with the Wigwam diagram and indicates just how treacherous a purely optical survey of the Universe might be. Courtesy of Professor Julianne Dalcanton, University of Washington, Seattle

The figure above shows that, from time to time they came close. Each postage stamp in the montage shows the optical image corresponding to a radio signal found in a blind survey of the sky made with the Multibeam Receiver fitted to the Parkes Radio Telescope in Australia. As you can see some are almost invisible, lying in the very wings of the Wigwam diagram. It is important to emphasise that the Luminosity of a galaxy (which corresponds to the number of stars it contains — generally billions) and its surface-brightness (dimness) are entirely different concepts, the latter depending on how its Luminosity is spread out across the sky. Although the six galaxies bottom right are all luminous giants, some are nevertheless, extremely dim.

There is another trick though in astronomy for finding something invisible in Space: observe an object behind it and look for tell-tale gaps (‘spectral ghosts’) in its spectrum where specific atomic species in the invisible object have absorbed out the light coming from behind. That is what Frank Cotteridge and his like found, albeit by accident, when they observed the spectra of very distant Quasars — lots and lots of inexplicable absorption lines (‘spectral ghosts’). “What else could they be”, Morgan argued, “If not my Hidden Galaxies?” Thus the bitter battle over QSOALs or ‘Quasi Stellar Object Absorption Lines’ began (see especially “Crouching Giant“).

The spectra of Quasars showing the many absorption lines (spectral ghosts) etched into them. Measurements show they are caused by clouds of atoms like Hydrogen and Nitrogen lying in the foreground along the line of sight to the quasar. But what form could those clouds take? Morgan claims they are the numerous Hidden Galaxies you would expect. Opponents who don’t like that idea are forced to postulate that visible galaxies must have absolutely vast gaseous halos surrounding them. Controversy continues [see Whispering Sky and Crouching Giant in particular]. As you go down the montage one is looking at higher and higher redshift quasars. Out there, back in time, the absorbing clouds appear to have been crowded closer and closer together. The humps are features in the spectra of the Quasars themselves. Copyright The European Southern Observatory (eso.org).

In 1987 the whole field was electrified by a paper written by Greg Bothun, Chris Impey and colleagues who were then based in California. Quite by accident, while observing dwarf galaxies in the nearby Virgo Cluster, they noticed that one wasn’t a dwarf, but the nucleus of a “Crouching Giant”, that is to say of an absolute monster of a spiral galaxy 25 times further away than the cluster but too dim to show much of itself above the sky. Here was unequivocal evidence that Hidden Galaxies of the most dramatic kind actually existed.

The Crouching Giant found by Greg Bothun, Chris Impey and co. by accident in 1987. The bright nucleus (this is a negative) was thought to be a dwarf galaxy in the nearby Virgo Cluster. But some very smart detective work revealed that it was instead the core of an absolutely colossal but dim giant spiral 25 times further away, whose spiral arms you can just pick out. It is no less than half a million light years across, ten times the extent of our own colossal Milky Way. Because of the accidental way it was found, finding others like it would be infernally difficult. Copyright Astronomical Journal 1987

That might have been that — except that nobody could find another such. The sceptics could, and did, write it off as a freak. If Hidden Galaxies were to become ‘significant’ they needed to make up a healthy fraction of the cosmic light and mass. In other words astronomers needed to find lots of Crouching Giants.

And how we all tried! But even when Jon Davies & co. did find one at Jodrell Bank (below) the opposition was fanatical.

Theoreticians who’d ‘proved’ that Hidden Galaxies couldn’t exist were furious; observers with even bigger telescopes than Jodrell were adamant that if they hadn’t found one then certainly we could not. And then there were the computer modellers who, at the drop of a hat, could prove or disprove anything, often without acknowledging the manifold frailties of their craft.

The putative Dark Galaxy VirgoHI-21 in the Virgo cluster. Left shows the radio contours superposed on a negative optical image. (Data obtained with the Westerbork Array in Holland) The giant spiral NGC4254 has obviously been disturbed by an encounter with a massive object which could only be Virgo HI-21, which is Dark, but note the bridge of gas between them. But the dynamical map (Right) shows it is spinning rapidly which can only mean that it is indeed massive. Massive, dark, spinning; what else could it be but a Dark galaxy? Copyright The Astrophysical Journal, 2007.

So although , after titanic refereeing battles, Virgo HI-21 did eventually get published in the prestigious Astrophysical Journal, most of the self appointed ‘experts’ stubbornly refused to acknowledge it as the first Dark Galaxy. But, in my opinion, if you read all the arguments carefully enough, it cannot be anything else.

In Big Science the problem is very often Lack of Breadth, rather than Lack of Depth. The clues are here and there but who has the breadth to spot them all, and assemble a coherent picture? Often we fail because no one individual in the field has the required breadth. And then there are the Systematic Errors that can bedevil any ambitious undertaking, errors held on to fanatically, especially by those who do not appreciate the frailty of The Scientific Method, and the need for caution in applying it (See my book Thinking for Ourselves) . This is highlighted in the following image based on observations we made with the Jansky Telescope in New Mexico, much the most powerful radio telescope on Earth at present. It reveals a huge cloud of hydrogen, the signature you would expect of a Dark Galaxy, but with a giant but optically visible galaxy to the South, receding away from us at the exactly the same speed as the Hydrogen. Previously the Parkes team, to which I then belonged, had mistakenly identified that as the source of the Hydrogen, and so overlooked what appears to be a true dark galaxy. Galaxies, Dark or Light, cluster so gregariously together that one needs a very powerful beast like the Jansky, to distinguish between them. None of us fully appreciated that, certainly not the Quasar observers with their spectral ghosts, who could always postulate, around visible galaxies, ‘gaseous haloes’ of unlimited size, to discount the invisible ones, which is what most of them choose to do.

What a Dark Galaxy ‘looks like’. Parkes 0039+03 was first discovered as a massive Hydrogen source out at 5,300 km/sec recession-velocity by Morgan and co. using the Parkes dish. They mistakenly associated it with the luminous optical galaxy (marked ‘cont’ here ) which happened to have an almost identical radial velocity, even though it is rather far away on the sky. But much later these more precise observations with the colossal Jansky array revealed that the Hydrogen and the bright galaxy are unassociated, as you can see. Even later a much deeper optical observations of the cloud made with the William Herschel 4.2 metre telescope in the Canary Islands revealed that it has tiny patches of light in it, but that is all. The strong clustering of galaxies together, both in space and in velocity, makes the search for Dark galaxies far harder than anyone had imagined. But if this isn’t a dark galaxy then what is? We found more like this out there.

BRILLIANTS

Thus far I have spoken entirely of Icebergs, hidden below the sky on the right hand (dim) side of the Wigam; what about the ‘Brilliants’ on the other? They would be even harder to find so Morgan and co almost forgot them altogether. Apart from anything else, being compact, they would be largely shrouded in their own smoke, disguising their true brilliance, appear like ordinary galaxies, but far far in the background, and therefore of no particular interest.

It was only after WFC-3 was operating on Hubble (2009) that Morgan began to worry about the extremely high redshift galaxies dotted all over the background in deep Hubble images (see below). If the universe were really expanding they oughtn’t to have been there — dimmed out of visibility by the so called ‘Tolman Effect’. And they turned out to be very small physically, much smaller than galaxies of the same luminosity situated close by to us in Space. Then the penny dropped with a clang for Morgan. Here were his Brilliants but at very high redshift, dimmed just enough by expansion to place them in the Visibility Wigwam where they became possible for us to see. The implications though were startling: Space must be inhabited by vast numbers of Brilliants , just as it probably was by Icebergs. And together all their extra radiation would have sufficed to re-ionise the Universe — otherwise a major problem for Cosmology. So it all fitted together: Hidden Galaxies, Expansion, Brilliants, the Wigwam diagram, Reionisation…….if Morgan was right. If…….. This was the theory which obsessed him towards the end of Beyond the Western Stars.

The Hubble Ultra Deep Field, the deepest image ever taken. In an expanding universe distant galaxies ought to be dimmed to the point of invisibility by straightforward physical effects. Yet here they are, dotted all over the place. Either the universe isn’t expanding or these are normally invisible Brilliants, shifted into the Wigwam by redshift so as to be visible. Courtesy ESA/NASA

Who was right, and who was wrong can only be decided by posterity . But in my story of Hidden Galaxies I have tried to convey, above all, just how engrossing it all was: the tournament of ideas, the clashes of personality and ambition, the conflicts of evidence, the camaraderie, the bravery and the cowardice, the wild misunderstandings and the hazards of fortune……. They make science such an exciting career; though not one for the faint-hearted.

PS. I have actually left out the biggest reason for mystery here, because it has a post of its own entitled HOW DARK IS THE NIGHT?

Professionals who would like to see a fairly up-to-date review of this subject can look at my opening address to the International Astronomical Union symposium No.355 held at the IAC in Tenerife in 2019 entitled “The Realm of the Low Surface Brightness Universe” (Procs. edited by David Valls- Gabaud to appear soon in CUP) at:

https://mjdisney.org/wp-content/uploads/2020/11/hgreview7sept.pdf

THE HUBBLE SPACE TELESCOPE

November 5, 2020

Given that there are roughly ten tons of turbulent murky atmosphere above every square metre of the Earth’s surface it is a wonder that we can see the Cosmos at all. Thus the urge to orbit a big telescope above that atmosphere was irresistible. So in 1976 NASA and ESA put together a joint mission , which was eventually to be christened ‘The Hubble Space Telescope’ (HST) after Edwin Hubble. If, and it was a very big if at the time, all went according to plan, the prospects were breathtaking. The machine would image the Cosmos in a thousand times more detail, and across an eight times greater colour range than its ground based counterparts. Because of its accuity it would begin to see the Universe actually moving for the first time. Furthermore it ought to detect objects a hundred times fainter and thus ten times further away, and because light has a finite speed that meant it would be a Time Machine able to observe the Universe as it was long before the Earth and Sun were born. No wonder some suggested it would become “the most exciting project ever undertaken by mankind”.

This illustration shows the NASA/ESA Hubble Space Telescope in its high orbit 600 kilometres above Earth. It’s about the size of a bus while the ‘wings’ are solar panels

But if it was to succeed there were huge challenges to overcome. How was a mirror of the required precision ever to be made? How could the telescope take pictures up there and then return them to Earth? Given that there would be no crew (too clumsy), how was it first to find its targets and then hold steady on them with unheard of precision? How could it be serviced, or repaired if things went wrong, as they were bound to do on on a spacecraft far more complex than any nuclear-powered aircraft carrier?

Nobody knew the answers. But that was half the point. Like JFK challenging the Apollo Mission to get to the Moon in the 1960s “……not because it is easy, but because it is hard” so NASA and ESA were throwing down the gauntlet to their successors. “Here” they said to their selected teams “Here’s a problem we can’t solve. You go crack it. But you’ve only got so long!” And that of course was the very kind of challenge which inspires scieneers.

Astronauts installing WFC-3 camera on Hubble Space Telescope in 2009

Teams, committees, call them what you will, were the secret, and the Camera Teams were at the very heart of the entire enterprise. Only the cameras on board could exploit the full power of the telescope, and so deliver its most ambitious science. But what was that science to be? Before they designed a single lens it was those instrument teams , and those alone , which had to peer far into the future and try to imagine the most exciting questions that the telescope would be called upon to answer.

I was lucky enough to attend the first meeting of the Faint Object Camera team in 1977, and the last meeting of the Wide-Field-Camera-3 team, in 2010. So I feel well placed to describe our long voyage of discovery, as one of the on-board crew. I have chosen to tell it in novel form because what was to happen had to first germinate in the human heart and mind, the drivers of everything else. It also allowed me to cut many a tedious corner while keeping the true cast of thousands to less than Tolstoyian size. I hope readers, and in particular fellow members of the crew, will forgive me for that, and certainly for omitting episodes and heroes they feel should have been included. But this is meant to be a human story of a very human endeavour, not the synoptic history which will no doubt emerge when we have all gone.

Since The HST story occupies much of my three novels:

The Whispering Sky ( 1976 to 1983)

Crouching Giant (1983 to 1995). and

Beyond the Western Stars (1996 to 2011)

all Amazon Publishing (2020)

I won’t say more here. However I intend to add, from time to time , images and scraps which could enrich the reader’s experience of the adventure. and I would be grateful if readers, or ex-comrades, could suggest more.

Here is the recent Ultraviolet Ultra Deep Field image taken with Hubble WFC-3, the deepest picture of the universe ever taken, and illustrating its capability as a Time Machine. Apart from the odd spikey star all the objects are galaxies vast distances away. The tiniest reddest ones have redshifts as large as 7 indicating that we are seeing them as they were over ten billion years ago. The Sun is only 5 billion yeas old. Copyright NASA/ESA/stsci.

Hubble would have been a disaster without the Space Shuttle, which not only launched it back in 1990 but visited it 5 times thereafter, to adjust for the flawed mirror, make innumerable repairs, and install new instruments like WFC-3, the camera which is still up there working perfectly after 11 years in orbit. Man seldom gets things right first time; we do our best by tinkering, by Evolution. Without Shuttle that would not have been possible, and I fear that HST’s successor, the James Webb Space Telescope, whose launch has been postponed at least a dozen times already, could be a disaster because it has no such means for repair. Anyway below you will see a panoramic view of the Cape Canaveral launch-site in 2009 with Shuttle Atlantis on Pad 39-A about to go up on its final mission STS 125 to the telescope, carrying WFC-3, along with its brave crew. In the background is Shuttle Endeavour on Pad 39-B, standing by to act as a Lifeboat to bring the crew back should Atlantis experience a serious failure, as happened with Columbia. In the background is Merritt Island nature reserve. If you zoom in enough, you might spot Morgan swimming up one of the alligator infested creeks to get as near to Atlantis as he could.

Those interested in following up the treasury of wonderful Hubble images and what they signify, can go to websites such as stsci.edu, nasa.gov, eso.org , http://www.cosmos.esa.int, and http://www.spacetelescope.org.

THE PARKES RADIO TELESCOPE

October 8, 2020

Parkes Radio Telescope New South Wales

The Parkes Radio Telescope in New South Wales Australia after it had been fitted with the new Multi-beam receiver system designed to pick up the Hydrogen signals from galaxies with about a thousand times the speed of any previous instrument. It has 13 separate dual-beams and 26 receivers cooled down close to absolute zero (minus 273 degrees C) up in the receiver cabin which is the size of a small house. Up there the very weak signals are mixed with a maser and the lower frequency output signals are sent down to the tower where they are processed by specially designed and very powerful digital correlators to look for the characteristic 21- centimetre wavelength signal of Cosmic Hydrogen. With it Morgan and his Australian colleagues surveyed two thirds of the sky and found over 5,000 such sources among which they hoped to find Dark Galaxies.[See Written in the Stars quartet of novels under ‘My Books’ Category]

The Dish has a romantic background. It was built by Taffy Bowen who, together with Hanbury-Brown, devised the night-fighter radar system which put an end to the Nazi blitzes in 1942. Starting at Bawdsey Manor in 1936 they devised means to cram radar systems into aircraft — which was fiendishly difficult to do in those days when radar waves were 10 metres long. But somehow, supported by Air Marshall Dowding, the head of RAF Fighter Command, they eventually did so.

In 1941 Bowen was sent to the US with his notorious ‘Suitcase Full of Secrets’ to teach the Americans how to build effective radars [See my book ‘History of the Brits‘ for that story ]. Later Bowen came to Sydney to direct the CSIRO Radiophysics Lab and the grateful Americans gave him half the money to build the Parkes dish which was completed in 1961. In 1962 Cyril Hazard from the University of Sydney used it to locate the first Quasar when the radio source 3C-273 passed behind the Moon. The disappearance and re-appearance of the radio-signal enabled Hazard to get a very precise position for it — which corresponded to that of a moderately bright star. An optical spectrum of that star showed it to have a high redshift and so to be an enormous distance away. The first Quasar Stellar Radio Source, or ‘Quasar’ had been discovered — starting off a whole new branch of Astrophysics — leading eventually to the discovery that they are Super Massive Black Holes.

Hanbury-Brown — after whom the term “Boffin” was coined, also made his name later as an astronomer in Australia. He it was who completed the night-fighter radar system which did for the Blitz and saved Britain [He features extensively in my Second World War scientific novel ‘Strangle‘ described in ‘My Books’ Category] .

The main weakness of radio telescopes is the non-existence of a ‘radio-camera’ which can look in more than one direction at once. The big box you can see at the focus was the first successful attempt at one. It has got 26 receivers looking in 13 adjacent but different directions at once — which allowed us to survey two thirds of the entire sky for Hydrogen gas in deep space — in the hope of locating Hidden Galaxies (see our Post ‘Hidden Galaxies‘). Unfortunately we then totally cocked things up by mis-identifying all the 5000 such sources we found with conspicuous optical galaxies , which is all too easy to do when galaxies are so highly clustered together in Space. Actually many of the Parkes sources are indeed dim or dark galaxies or gas clouds. Astronomy is hard….but very exciting!