Archive for the ‘Meetings’ Category
Prof Alan Aylward – “From Daedalus to Dan Dare to Daedalus: Can we go to the stars and what would we find if we get there?”
Wednesday, January 12th, 2011
The New Year got off to a good start with a talk from Professor Alan Aylward (shown on the right in the photo above) who kindly came all the way from Surrey to visit us. Alan is head of the Atmospheric Physics Laboratory at University College London and gave us an overview of intergalactic space travel coupled with some of his research on the atmospheres of extrasolar planets (hence the atmospheric physics). He started by reminding the older club members about the spaceships used by Dan Dare in the Eagle comics of the 1950s. The idea of travelling the gigantic distances between our planet and other stars seems fanciful, but the comic book rocket actually has features that make it possible to do this, at least in theory. The basic concept involves the use of nuclear detonations to create a massive thrust that propels a spacecraft up to around 12% of the speed of light. This would be sufficient to send astronauts to a nearby star within a fifty year time frame. This idea was seriously considered by the British Interplanetary Society in the 1970s and NASA up to, and including, the present day. The project was seen to be feasible in engineering terms, but the original idea of using nuclear fusion by lasers has been subsequently shown to be impractical (at least for now). There are of course all sorts of unanswered questions, not least those relating to the fate of the astronauts who may be travelling on a one way ticket to the stars.
Other propulsion systems were described, including a giant earth-based laser that would be shone onto a lightweight sail attached to a spacecraft. These and many other ideas are being actively considered by NASA who stipulate that any proposal must keep to the laws of conservation of energy and of momentum; this is apparently something that even the best scientists get caught out with!
So having discussed travel to the stars, Alan described how it might be possible to detect habitable planets around these stars. His research group in London studies the atmospheres around exoplanets (of which most appear to be smaller than Jupiter-sized objects). The number of such planets is increasing on an almost daily basis and it is possible to observe their effects on their parent star even using the venerable telescope at the Mill Hill Observatory in North London. This is quite a testimony to the equipment and data analysis capabilities of the exoplanet research group, since this part of the UK suffers from serious light pollution. Nevertheless, data are being gathered that allow astronomers to make inferences about the types of molecules (including the all-important water) that is present in the atmospheres of possible earth-like planets. The discussion about extraterrestrial life is now getting sensible, as experiments are underway to get real evidence, rather than just rely on speculation about what might be. Maybe this is a good omen for astronomy in 2011.
The meeting was publicised as part of the BBC’s Stargazing Live programmes that were broadcast in early January. We were delighted to see several new faces at the meeting as a result of the publicity and we hope to be able to be of assistance to several members who have bought a telescope for the first time.
Leonard Honey – “Sundials, ancient and modern”
Wednesday, November 3rd, 2010
This month’s talk was by Leonard Honey from Science Replicas based in North London. His interest in antique scientific instruments was reflected in a talk about sundials and their construction. Like many people, I thought that sundials were only found as static objects attached to walls or on plinths in the garden; this is clearly not the case, as apparently portable sundials were available after the twelfth century for use by the wealthy. Prior to that point the ancients used sticks to cast a shadow onto the ground or a hemispherical hollow carved in stone.
Leonard described the various types of portable sundial produced between the 16th to 18th Centuries (an activity known as dialling). Only when mechanical clocks became more reliable in the 19th Century did the use of sundials decline. We were shown some beautiful pictures of pillar dials which have a fixed pointer (gnomon) that casts a shadow down the outside of a tube marked with specific dates. Its use is limited to a particular location, so the introduction of the ring dial with a device to measure the sun’s height in the sky meant that the instrument could be used anywhere on the planet. The very attractive diptych dials were also described – these are folded into a small case like a closed book, with a small wire passing down across two faces acting as the gnomon. These portable sundials are very ornate, some in ivory cases, and covered in markings, including the names of European towns as reference points. Lastly we were shown pictures of a series of portable flat sundials with an enclosed compass.
Although these instruments are no longer in use, they have enormous aesthetic value as well as historical interest. Leonard and his wife brought along a display of replica dials and other astronomy related material which generated a lot of interest. These items can be purchased from Green Witch in Dry Drayton, or directly from Science Replicas.
Prof Anthony Hewish – “Radio-astronomy, inflation and the design of the Universe”
Wednesday, October 6th, 2010
We were very honoured to have Professor Tony Hewish talk to us about some of the outstanding problems raised by modern cosmology. He of course has a long and distinguished career in radio astronomy and is a Nobel laureate in physics, so his audience was treated to an authoritative review of cosmology since the beginnings of his research career in Cambridge after WWII.
Working with Martin Ryle and colleagues, Tony used ex German radio equipment to build a radio telescope at Lords Bridge off the A603 and before that, an array on the playing fields behind Grange Road in Cambridge. The purpose of this was to identify strong radio sources in the sky and match them to their optical counterparts. Having achieved this with the intense radio source Sagitarius A, many other radio galaxies were identified along with quasars and pulsars as the years went on.
After this historical overview of the Cambridge research, attention was turned to the first of the two main problems with our understanding of the universe, namely the nature of dark matter. An audit of mass in the universe based on the motions of galaxies and the phenomenon of gravitational lensing implies that there must be a much larger percentage of as yet unidentified mass that has no interaction with normal matter. This ‘dark matter’ comprises about 23% of the universe, with normal atoms being only 4.6%. The remainder is a mysterious ‘dark energy’ that pervades the universe and is involved in inflation. This is the idea developed by the physicist Alan Guth that the universe rapidly expanded an infinitesimally small time after the Big Bang that started the universe. Tony Hewish had some success in explaining the complex quantum theory behind Guth’s theoretical prediction of how inflation works, but it isn’t easy for the novice. The idea that a perfect vacuum still contains energy is hard to get the head around, but it does explain the source of energy that drives inflation. We were shown a remarkable graph with data from the WMAP space observatory that measures changes in the microwave background. This was remarkable because Guth’s theoretical calculations of the expected values overlapped the experimental data to an extraordinary degree.
The talk was concluded with a discussion of String Theory in which space and time are in eleven dimensions rather than four. The theory attempts to explain gravity and dark energy, but seems to be more in the realms of mathematical philosophy. We were left with the feeling that much has happened since Tony’s first radio astronomy experiments over fifty years ago, but that actually more problems have been raised than solved. This is part of the appeal of science as well, as the challenge!
Dr Andy Martin – “Beware Invisible Cows”
Wednesday, September 1st, 2010
Wednesday 1st September 2010
Andy works in the Faculty of Modern & Medieval Languages, but is also a surfer, writer and historian with an interest in science and philosophy. These latter interests prompted him to write a book called “Beware Invisible Cows” in which he describes a philosophical journey towards understanding how the universe began. This led him to visit the twin 10 metre telescopes at the Keck observatory in Hawaii. The mountain access road to the top of the mountain has limited visibility at times, as well as roaming cattle, hence the road sign which prompted the title of his book and talk to us.
We were presented with a sort of ‘stream of consciousness’ about the different ways of seeing back in time – the mirrors on telescopes do this, because the light falling on them has a history; it’s the same as a person looking at their reflection in a mirror, they are looking at history, even though it is only a few nanoseconds back. Punctuating these reflections (no pun intended) were comments about Andy’s physicist twin brother who tried to build a device that could communicate with the ‘flying saucer’ that Andy had seen over his house! I didn’t understand the physical principles of this device, let alone believe in flying saucers, but it was an interesting (if somewhat bizarre) departure from the main theme of the talk. The mirrors of the Keck telescopes are used to look back in time, but they can only reach so far- there is a limit of about 380,000 years after the Big Bang where no electromagnetic radiation can be observed. However, Einstein predicted the existence of gravitational waves in his General Theory of Relativity and these should be detectable further back in time.
These musings prompted Andy to visit the Laser Interferometer Gravitational-Wave Observatory (LIGO) based in Washington State, USA. This consists of an L shaped tube four kilometres long on each side that contains lasers and mirrors designed to detect the impact of a gravitational wave by changing the phase of two light beams interacting together (see http://www.ligo.caltech.edu/ for a proper explanation). Andy pointed out the problems caused by background vibrations from activities on earth, including large waves crashing on the shore miles away in California (prompting the surfers at LIGO to pack up for the day!). No gravitational waves have been detected so far, but the LISA space mission is in the offing which will increase the detection sensitivity by orders of magnitude.
Andy concluded his talk with the words of Sartre and Wordsworth on the origins of the universe and finally with a piece of music by Ligeti (music used in 2001 A Space Odyssey) to illustrate the ‘noise’ of the universe.
“Beware Invisible Cows” is published by Simon & Schuster. Andy Martin’s website is http://www.andymartinthewriter.com/
Prof Paul Murdin – “Secrets of the Universe”
Wednesday, May 5th, 2010
Wednesday 5th May 2010
We were very pleased that Professor Paul Murdin was able to make our May meeting as he had to dash off to London immediately afterwards for an appearance on ‘In Our Time’ the following morning on BBC’s Radio 4. Paul is a senior fellow at the Institute of Astronomy in Cambridge and visiting Professor at Liverpool John Moore’s University. He is Editor of the Encyclopaedia of Astronomy and Astrophysics as well as a prolific book author. He gave us the opportunity to hear about his latest book ‘Secrets of the Universe – How We Discovered the Cosmos’.
The theme of the book is scientific discovery in its various forms as related to astronomy and cosmology. Seventy case histories have been covered in the book and Paul recounted a selection of these, ranging from the first telescopes to computer simulations of galaxy clusters. Discovery can happen when an unusual observation is picked up and explored further, rather than discarded. As Paul pointed out, the great science fiction writer Isaac Asimov wrote that “The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’, but ‘That’s funny…’”. Some of these moments in astronomical history include the observation of planets by Galileo, in which the phases of Venus and the moons of Jupiter implied that the Earth goes round the Sun and not vice versa.
Jumping several centuries, Paul described how chance observations of radio pulses led to the discovery of neutron stars in the 1960s. Moving back again in time, he recounted the classic stories of the discoveries of Uranus by William Herschel and Neptune by LeVerrier and Adams. Although both involved planetary discovery, they were quite distinct in that the existence of Neptune was predicted purely from theoretical calculations, an astonishing achievement!
While the background to these older discoveries is fairly well known, that relating to more modern advances in cosmology and planetary science are less so, like the volcano on Io. The Voyager 1 mission imaged this moon of Jupiter in 1979. Linda Morabito was an engineer on the mission and wanted to examine the images in more detail for navigational purposes. She increased the gain on the images and noticed a plume of material on one side of the disc. Subsequent investigations showed that it was an active volcano, one of what is now known to be around 700 such features on a moon that is subject to huge stresses from Jupiter’s gravitational field. This was another neat example of serendipitous discovery brought about by the “prepared mind favoured by chance” to paraphrase Louis Pasteur.
All in all, this was a most thought provoking and enjoyable talk that prompted many questions for Paul, and much discussion over coffee and biscuits afterwards!
Paul’s book, published by Thames and Hudson, retails at £24.95 and is available from all good bookshops.
Peter Howarth – “Radio astronomy for the slightly nervous”
Wednesday, April 7th, 2010
Wednesday 7 April 2010
Peter explained the background to radio transmission and the position of radio frequencies in the electromagnetic spectrum. These frequencies vary according to the wavelengths used particular transmissions. Long wave radio, for example, uses wavelengths measured in meters, but the one of interest to astronomers is the shorter wavelength radio detected from outer space. This was first detected as a background hiss by Karl Jansky in 1933. Further radio astronomy was carried out by Grote Reber and others, particularly driven by the Second World War and its aftermath, when there was a large amount of surplus equipment available for research. Martin Ryle, Tony Hewish and colleagues used some of this surplus radar to build radio telescopes at Lords Bridge near Cambridge leading to pioneering work on extragalactic radio astronomy. In 1961, Penzias and Wilson used a radio telescope to observe the microwave background left over from the Big Bang.
What about amateur radio astronomy? Peter suggested a few examples of what amateurs could build using simple electronic circuitry to listen in on solar flares or even the radio noise of Jupiter. The simplest suggestion was to place a two meter wire in the sound card of a computer and listen to radio noise created by lighting bouncing of the ionosphere. There will be some interference from the 50Hz mains supply, but this project seems well worth a try. Maybe we’ll use it on one of the Papworth observing evenings to complement the optical astronomy?
Observing Evening
Wednesday, March 3rd, 2010
Wednesday 3 March 2010
Although attendee numbers were a bit on the low side (suspected competition from the football!) the sky was clear enough to allow those who did turn up to do some observing.
We had the opportunity to compare the performance of a basic Meade refractor with a 6” Celestron Nexstar brought along by Lee Sproats from Green Witch. Mars was high up in Gemini, but the disc size was small compared with its close apparition a few years ago. Despite this, it was possible to see surface features on Mars using the Nexstar in conjunction with a low power but high quality eyepiece. This was literally a real eye opener to what good optics can achieve.
Orion was conveniently placed for a view of the much observed nebula, M42/NGC1976 (pictured above). The Nexstar provided a strikingly clear and bright view of the nebula, demonstrating once again the high quality of its optics.
Lee showed us some new CCD cameras and a filter wheel from Atik which, although not cheap, are very good value for money. More information can be obtained from the Green Witch website.
Dr Richard Salisbury – “Infrared cameras and the LCROSS mission”
Thursday, February 4th, 2010
Thursday 4 February 2010
We don’t often get detailed background information on instruments that are carried in spacecraft, but this was put right in a fascinating talk by Richard Salisbury the CEO of Thermoteknix in Waterbeach. His company produces sophisticated infrared cameras that have attracted the attention of the space community in the USA. Richard explained how the cameras were built to withstand very high (for example in cement kilns) and very low temperatures, as well as vibrations and strong G forces. The latter were apparent in applications of their technology to Formula 1 and Indy racing cars. It was through Indy car racing that the camera’s potential for use in space was brought to the attention of the space physics department at Johns Hopkins University. After successful application to imaging exhaust debris in their rocket testing programme, the camera was fully certified for use in space. As a result, the near infrared imaging camera was chosen to be part of a suite of instruments on the LCROSS mission to crash a spent rocket into the Moon and image the resulting plume of debris. LCROSS (Lunar CRater Observation and Sensing Satellite) was designed to confirm observations by other spacecraft that hint at the presence of water on the Moon. The craft consisted of a rocket stage that had spent its fuel which crashed into a crater on a side of the moon in permanent shadow. A companion craft with imaging cameras for different wavelengths followed closely behind to record the impact and take spectroscopic measurements of the resulting debris before itself crashing into the Moon. Although the plume of debris was much smaller than expected (to the disappointment of many earth bound observers) the Thermoteknix camera recorded a clear flash of released heat from the lunar surface at the point of impact. Spectroscopic observations indicated that water was indeed present, along with a significant amount of sodium which is, as yet, unexplained.
There were a couple of messages from this talk: one was that scientific progress is often made when different fields come together in unexpected ways (cement kilns, racing cars and space!) The other is that costs of space missions can be kept relatively low by using commercially available instruments that have been extensively tested under extreme conditions, rather than developing new instruments from scratch.
This isn’t the last adventure of Thermoteknix in space as a camera will be visiting Saturn’s moon Titan in a few years time. We hope to be around long enough to hear what Richard Salisbury has to say in another visit!
Keith Tritton – “Extrasolar Planets”
Wednesday, January 13th, 2010
Wednesday 13 January 2010
It is important to know how our own solar system was formed in order to understand how planets may form around other stars. Keith showed diagrams of the large clouds of gas circling the early sun in spirals that slowly condensed into the rocky Earth-like planets and the gas giants such as Jupiter. The division between these two types of planet is known as the Frost Line. In our solar system, the giant planets are kept at a healthy distance from the sun. However, as was pointed out later, there are many extra solar planets of Jupiter mass that are significantly closer to their parent star.
How were these planets discovered? Keith creatively used a number of “props” to show us how these objects have been detected by inference rather than direct observation which is very challenging. Any object that orbits a star will induce a slight wobble in the star (illustrated with a small rubber ball and football respectively). The star’s wobble will cause a shift in its spectrum due to the Doppler effect – modern spectroscopy is highly sensitive and can detect this slight movement without too much difficulty. So the first extra solar planet (orbiting 51 Pegasi) was detected in 1995. Many more have been discovered using this technique since then. Another approach is to measure the slight dimming of the star’s light when a planet transits. This requires extremely accurate observations to detect a tiny drop in starlight, but it works and has even been reproduced by amateurs. It would of course be desirable to image the planets directly and there have been some reports of just that, with convincing movement of tiny dots of light around artificially obscured starlight detected by imaging over several months. This is more readily achieved using infrared light where the balance between the brightness of the planet and star is more favourable than in visible light.
As mentioned before, the number of discoveries is increasing almost daily and can be checked on the Extrasolar Planets Encyclopaedia website, which is a rich source of information on extra solar planets.
The launch of NASA’s Kepler space telescope last year has already yielded a new crop of extra solar planets with many more to come. Most importantly it will be possible to detect planets with a similar mass to our earth. Currently most of the planets have been Jupiter sized or greater and as mentioned earlier, are sometimes found very close to their parent star. This is in stark contrast to our own solar system, prompting some discussion about how typical we are in this respect. It also raises the question of whether our model of solar system formation is actually correct.
This talk certainly gave us food for thought. Since this is such a hot area of astronomy, we fully expect there to be many more fascinating discoveries by this time next year.
Observing session
Wednesday, December 2nd, 2009
Wednesday 2nd December 2009
With observing a literal washout due to rain in Papworth, we fully expected a much reduced turnout of Club members to the second observing evening of the year. In fact we had a good number of regulars who enjoyed an evening discussing practical astronomy in an informal and friendly atmosphere. This was helped by the presence of Lee Sproats from Green Witch Telescopes in Dry Drayton. The world of astronomy is continually developing, with new equipment being introduced by specialist manufacturers on a regular basis. This was highlighted by some of the new products that Lee brought along from the Green Witch showroom.
New cost effective telescopes are always of interest. The Heritage 76p is a 3” mini-Dobsonian reflector specially designed to celebrate the 400th anniversary of Galileo’s first observations together with the International Year of Astronomy. Its compact size and ease of use make it suitable for a young person to handle alone. Its decorated tube certainly looks very attractive and the optical quality will be significantly better than that of the toy telescopes being offered to the same market. In fact there was some discussion about whether such an inexpensive reflector could compete with the much more expensive refractors of the same aperture.
Lee then showed us the Heritage Explorer 130, a 130mm (approx 5½”) compact Newtonian with an innovative mechanism for collapsing the tube size for increased portability. This instrument is decorated with the names of significant astronomical figures from the past.
Telescopes are obviously the centre-piece of most practical astronomy, but it’s important to know where to look in the night sky and understand what you are seeing through the eyepiece. The practical observing books written by Stephen James O’Meara are of interest to those who want to deep sky objects from different catalogues. O’Meara has written guides to the Caldwell objects compiled by Sir Patrick Moore in addition to the well known Messier collection. We were able to browse a copy of this well illustrated book and one covering the less familiar Herschel 400 deep sky objects. To make up for not being able to see astronomical objects for ourselves that evening, we were shown books of amazing celestial photographs by amateurs; Star Vistas, by Greg Parker and Noel Carboni and Capturing the Stars by Robert Gendler.
Finally we had a demonstration of two quite different products; one was the Bresser Planetarium, an interesting educational toy that projects different vistas of the night sky onto the ceiling. The other was a Celestron LCD microscope. While not strictly astronomy related (except for meteor samples?) this was of interest to those who have peered through microscopes without the benefit of the LCD screen like the one fitted to this instrument. It provides a very clear view of what is normally seen through an eyepiece.
Although we would have liked to use the observing evening to try out our various telescopes in the Papworth night air, we had a very enjoyable and productive evening all the same!