Fusion Day and AGM 2006

Held 28 January concurrently with the S207 Preparation Weekend

The Christoloudu Rooms on the OU campus proved an excellent venue for both our events. After registration at 10.30 am, the two groups, AGM and S207 attendees, had a chance to meet up and chat before going off to their separate events.

The first AGM lecture, given by Dr. Anita Dawes, was entitled "Cosmic Chemistry: Icy Molecular Factories in Space and in the Laboratory", and Fred Muir has written us an excellent summary below. Dr. Dawes also told us about NASA's Stardust mission which will collect samples of comet-dust particles, and that the OU will receive some of these particles for analysis. The general public have also been invited to help analyse this data on their home computers - see stardustathome.ssl.berkeley.edu.

The subsequent lab tour demonstrated how Dr. Dawes and her colleagues are reproducing the conditions necessary for the formation of molecules on dust grains in the interstellar medium (ISM). The team have designed and assembled equipment to simulate the ISM, which involves firing bursts of radiation into special vacuum chambers at very low temperature and pressure and then detecting the molecules that have formed.

The AGM started after lunch, with an annual report from each Committee member for their area of responsibility - see January 2006 AGM Minutes. Following a question by Bill Willows, the Committee subsequently looked into the current fee structure and made the decision that fees should be increased by £1.00 per membership year.

After the AGM we enjoyed a tour of the OU's telescope, courtesy of John Tanner. At 6.00 pm everyone went to the nearby Hilton Hotel for dinner, relaxing with a well deserved beverage of their choice! Those who were made of sterner stuff then enjoyed Paul Ruffle's lecture 'Out at the Edge', which described his research into molecular clouds at the far edge of the Milky Way's disk.

S207 Preparation Weekend

Report by John Pollard

During a cold January weekend twenty OU students met at Walton Hall for two days to take part in the first Fusion S207 Preparation Weekend. For many, this was their first visit to the OU campus and the first Fusion event that they had participated in. Under the guidance of Doctors Ian Saunders and David Keen, both active Fusion members, they brushed up on their basic science and maths skills and were introduced to new material from S207 - The Physical World, the OU's main level two physics course. We hope that this will give them a head start in physics.

The Preparation Weekend ran concurrently with the 2006 Fusion AGM, and on Saturday evening, while some students took advantage of one to one maths tutoring, others joined AGM attendees for a presentation by Paul Ruffle, before congregating in the bar to unwind.

We thank both the Institute of Physics and the OU's Department of Physics and Astronomy for their generous financial support for this Weekend; this was particularly important for jump-starting the first presentation of what, we hope, will become an annual event. Planning is already underway for the next Preparation Weekend (which will benefit from feedback from this year's participants), which will be held on 20 - 21 January 2007 at Yarnfield Park Training and Conference Centre, Stone, Staffordshire. The event will run alongside Fusion's 2007 AGM, which will feature interesting activities in science and astronomy. For more details email s207@oufusion.org.uk or visit s207 Preparation Weekend.

Molecules in Space

AGM Lecture Report
by Fred Muirhead with Albert Nummelin and
Dr David Whitehouse

During Fusion Day 2006 we had the pleasure of a lecture on Interstellar Ices by Dr Anita Dawes, which has prompted me to write on a topic which is very much related to them, interstellar molecules.

Molecules have been found in the interstellar medium (ISM) by searching the radio frequencies of the electromagnetic spectrum. Many simple molecules such as CO, CN and OH have been detected, but to many people it is the discovery of complex organic molecules, such as formaldehyde (H₂CO) and methanol (CH₃OH), which are of the most interest. Amino acids are the building blocks of life and all the reagents which are used in a laboratory to synthesise such molecules are available in the interstellar medium.

Most of these molecules are formed via a sequence of two-body, ion- molecule processes in the gas phase, using interstellar grains as a catalyst. The majority of molecules found in the interstellar medium are found in giant molecular clouds, where the density tends to be higher and the probability of a collision is appreciably higher. Another reason that molecule formation is favoured in large clouds is that the core of these clouds is protected from ultraviolet radiation by the molecules around the edges.

Molecular clouds are called such because they are cool and dense enough for most of the hydrogen to be in molecular form, H₂, except in their outer layer. Over 120 different chemical compounds have been identified in interstellar clouds, circumstellar matter, and comets. It is also clear that the surfaces of interstellar dust grains have the ability to act as catalysts for certain reactions. Molecular Hydrogen, for example, is formed only on dust grains. In the last decade or so it has also been shown that more complex molecules can be synthesised this way.

The discovery of the molecule glycolaldehyde (CH₂OHCHO) in a giant cloud of gas and dust near the centre of our own Galaxy was detected by its faint radio emission in Sagittarius B2, some 26,000 light-years away. Glycolaldehyde is an 8-atom molecule composed of carbon, oxygen and hydrogen. It can combine with other molecules to form the more complex sugars ribose and glucose. Ribose is a building block of nucleic acids such as RNA and DNA, which carry the genetic code of living organisms. Glucose is the sugar found in fruits. Glycolaldehyde contains exactly the same number of atoms, though in a different molecular structure, as methyl formate (C₂H₄O₂) and acetic acid (CH₃COOH), both of which have been detected previously in interstellar clouds.

Some scientists have suggested that earth could have been "seeded" with complex molecules by passing comets. These carry material from the interstellar cloud that condensed to form the Solar System.

Molecular clouds play a key role in the evolution of the galaxy since, according to current knowledge, every star and planetary system originally formed inside a molecular cloud. The other types of interstellar cloud, in which the hydrogen is atomic, are too warm and diffuse to allow stars to form. Since star formation occurs when deeply embedded clumps of interstellar gas and dust collapse, stars that are newborn or in the very process of forming are always obscured from direct optical view, and the only source of information from the inside of these clumps is provided by longer wavelength radio waves emitted by molecules. Because of this, star formation is one of the most important fields of study for molecular astrophysicists.

QUANTA AND CONTINUUM

New Fusion Sweatshirt

Our new Fusion sweatshirts are now available, priced at £12.00 each (including post and packing within the UK) and available in dark grey with a stitched logo. See full details at Fusion Sweatshirts.

Fusion Fees

At our AGM in January we agreed to review our fee structure, and as a result fees for new or renewing membership have gone up by £1.00 per year of membership, i.e. £7.00 for 1 year, £18.00 for 3 years and £25.00 for 5 years. We are also working on providing on-line membership services with payments for fees and/or T-shirts by credit card.

Quantum Leaps

Scientists sometimes get understandably angry when scientific expressions are used in inappropriate ways in non-scientific contexts, but why does the perfectly justified use of the term "quantum leap" for a large or sudden change in something often elicit the same response? Only recently, a well-known popular science writer was heard on BBC Radio 4 saying that the use of the term to mean something very big is "quite wrong", and that it "really annoys him", because a quantum leap is really "the tiniest jump you could possibly make".

Let's just leave aside the slight logical inconsistency in that argument, and instead remind ourselves of quantum theory's big idea - that the absorption or emission of arbitrarily small amounts of energy, allowed by classical theory, is not possible in the real world; instead it can only come in what Feynman called "lumps" of a certain minimum size. So, although quantum leaps might be small on a human scale, compared to the alternative, which is an infinitesimally small change, they are absolutely huge -
Jim Grozier.

5 years of Fusion!

Happy birthday to Fusion
Happy birthday to Fusion
Happy birthday to Fu-s-ion
Happy birthday to Fusion

Equations really ARE beautiful!

Fusion member Tamasyn Willbond recently bought a Fusion Schrödinger T-shirt; she chose the design in memory of a cat of the same name that she had whilst doing A-Level Physics. When her grandmother saw it, she commented that "the patterns on the front are very pretty". Proof that equations really ARE beautiful! (Taken from a post on the Fusion First Class conference)

EuroPhysicsFun

EuroPhysicsFun is an international network of physics outreach groups who travel around teaching physics primarily through demonstration experiments or "physics shows". Through discussion forums, seminars and conferences, the members of the network exchange knowledge about teaching experiences, demonstration experiments, "edutainment", fundraising, performing, etc. Apart from joining existing physics shows together, EuroPhysicsFun will also help initiate new shows at universities all over Europe. They invite interested physics students to their workshops in Aarhus, Denmark, where all required knowledge about how to start a physics show is taught. If you want to subscribe to the Newsletter visit www.europhysicsfun.org.

First Class

Join us on OUSA Fusion to chat about physics or exchange information on what's going on in your area. Find us in Science > Science OUSA Conferences or OUSA > Study Rooms > Science Room.

The Jodcast

The Jodcast is a podcast by astronomers at the University of Manchester's Jodrell Bank Observatory. It can be either downloaded directly from the website or you can subscribe to their RSS feed. More details at www.jodcast.net.

OU Astronomy Club

During our AGM tour of the OU's observatory in January, John Tanner told us that the on-campus OU Astronomy Club meets once a month and does some observing, as well as having talks from invited speakers. He told us that Fusion members would be welcome to come too, and that they can join the club for £7 a year.

Barrie Jones

Staff Profile by Lindsey Shaw-Greening

Barrie Jones will be a familiar name to many of you that have studied with the OU for a while, as his involvement with courses at every level has been great. Professor Jones' career started with a PhD in solid state physics during which he grew the purest potassium chloride crystal in the world at the time. After completion of his PhD, the new Dr Jones then changed path slightly and took a post doctoral research position in gamma-ray astronomy during which he spent much of his time recovering balloons from muddy fields in Wales. A lectureship in architecture (yes, you did read that correctly) followed when he was asked to teach the physics of materials, colour perception and acoustics, among other topics. There was then a move, with wife and child in tow, to Cornell University in the USA where he worked for a year on infrared astronomy missions and for two years with "Tommy" Gold, who died last year, on oscillations of powders in order to understand the seismic signals from the Apollo lunar landers.

Barrie Jones with Patrick Moore during filming for "The Sky at Night".

In 1972 Barrie Jones moved to the Open University, where he has continued to carry out research in a wide variety of different areas, but now more focused on astronomy than architecture! Barrie's research interests have included photo-voltaics, thermal collectors of solar energy, passive cooling mechanisms for telescopes, shadow bands (which recently took him to Libya for the eclipse), and from the late 1990s, extrasolar planets and habitable zones. In 2001 Barrie Jones was made Professor of Astronomy because of his commitment to teaching, excellence in research and his management of the department.

Professor Jones still expresses his surprise at his success in his research. His work on habitable zones and survival of Earth-like planets is highly cited and he has recently been awarded the Astrobiology Society of Britain's newly initiated award, The David Wynn-Williams Prize for Services to Astrobiology. He has also published three textbooks, two on the Solar System and one on life in the Universe.

We asked him a few questions over coffee.
Q: Looking back on your own careers which piece of advice would you give to aspiring researchers?
A: Do not change path too often! My career has been varied and I have enjoyed that but it can be hard going.
Q: Which one thing would most improve your working day?
A: Having the time to concentrate on a small number of tasks rather than lots of little tasks.
Q: Which new OU courses would you like to see?
A: Physics in medicine and heath, a 10 point Level 1 course on weather, and something related to the history of science.
Q: If you could be Prime Minister for the day what would you change?
A: I would get the government out of schools and give schoolteachers more power to deal with disruptive students.
Q: And finally, what are your top three holiday destinations?
A: I enjoy visiting semi-arid and desert countries so probably Namibia, Rajasthan in India and Northern Kenya would be in my top three.

The Weakness
of Gravity

Maths Quickie
by Paul Ruffle

Imagine the gravitational force between two bodies (for example you and me floating in space):

F_g = Gm_mem_you / r²

F_g is proportional to your mass multiplied by my mass and then all divided by the square of the distance between us. In Newton's Law of Gravitation (NG) G is the gravitational constant and it's a very, very tiny number:

6.672 × 10^-11 m³ kg^-1 s^-2,

which is what makes the gravitational force so weak.

Now imagine that we are floating about a metre apart, and in our space suits we each have a mass of around 120 kg. Plugging these numbers into NG gives

F_g = 10^-6 N.

This gives us a very small force (millionth of a Newton) attracting us to each other. Now if we use Newton's Second Law of Motion (N2):

F = ma, rearranged into a = F/m

we can work out our acceleration towards each other as:

a = 8.33 nm s^-2.

So as our masses are mutually attracted, we are accelerating towards each other at around 16 nanometres per second, per second. Now there are a billion nanometres in a metre, so that's not very fast, is it? In fact we can derive a formula from N2 to work out how long it will take to make contact:

d = ¹/₂ at²

can be rearranged into:

t = √(2d/a) = 11 180 s ∼ 3.1 hr

So it will take over three hours for us to make physical contact from a distance of just 1 metre. So you see, gravity really is very weak!

However, the above simple model overlooks the fact that the acceleration a will not be constant, but rather it will increase as F_g increases as r gets smaller. So, just how much quicker will we make contact? Send your worked solution to editor@oufusion.org.uk.

Fusion members visit UKAEA Fusion at Culham on Friday 7 April (left to right): Don Love, Terry Ockendon, Guest, Irfan Ali, Pam Fineberg, Charlie Fraser-Fleming, Graham Foyle, Dwyn Padfield, Matthew Wilcoxson, Mark Gallaway, Mike Nugent, Alison Jones, Nigel Hollinshead, David Bush, and Paul Ruffle.

IAPS Solar Eclipse

by Digby Tarvin

As I am sure most readers will be aware, March 29th this year saw a total solar eclipse which was visible within a narrow band extending from Brazil, across the Atlantic, northern Africa, and central Asia, and ending at sunset in western Mongolia.

Needless to say observing prospects are never good in the UK, even when we are not so far from the path of the Moon's umbral shadow. So it was clear that getting a reasonable view of the spectacle was going to require some travelling.

Fortunately an enterprising group of physics students at the Middle East Technical University (METU) in Turkey took it upon themselves to take advantage of their much more advantageous location to organise a viewing event for physics students from around the world. The event was organised through (and supported financially by) the International Association of Physics Students (IAPS), to which all Fusion members who have taken up the option of joining the Institute of Physics (IoP) with their membership will also be a member. As an added bonus, the IoP generously provided a £60.00 subsidy to each participating student member to help with travel and registration costs - thank you IoP!

As it turned out, last minute cancellations by a large number of people that had originally indicated an intention to participate meant that it ended up being an event held almost exclusively for the benefit of students of British universities. Fortunately there were quite a few of us - 13 from Bristol University, 17 from University College London and Imperial College, and yours truly from the OU.

Arrival

The event officially started on Sunday 26th, which was allocated for arrivals, registration and the opening cocktail. However my flight arrived the previous night, so I was the first to arrive. I was met at the bus station by one of the organisers - Ugur Gocen, who escorted me back to my accommodation at one of the METU dorms.

METU is an international university, with students from a wide range of countries and English as the official teaching language, so we were shielded from many of the complications of unfamiliar culture and language while on campus.

The first thing that strikes one on arrival at METU is just how big it is. After passing through security at the front gate there remained a substantial drive through the cultivated forest before arriving at the University buildings it surrounded. It reminded me a little of the forest that surrounds the Star City complex near Moscow, intended to shield it from prying eyes during the cold war.

A view of the campus from atop the physics building

I was helped to check into my accommodation, which was a basic but cosy room in one of the older buildings. Ugur explained that we were originally supposed to be accommodated in one of the new buildings, but that we had lost that reservation because of the last minute reduction in numbers. By now it was quite late, and there was just time to get a snack from the cafeteria before it closed, and then it was time to retire.

Prelude

Sunday started rather earlier than I had intended with the dawn arrival of the students from the University of Bristol, including the three room mates to be, who had travelled overnight by train from Istanbul.

Sunday Campus Tour

By 10:00am everyone had settled in and we were all enjoying a Turkish style breakfast at a nearby restaurant. The rest of the day was filled by a campus tour, a leisurely lunch, a welcome dinner and then a bus ride into town where a floor of a local bar had been reserved for our welcome drinks, and where would be joined by the participants from University College London and Imperial College who were arriving in the wee hours of Monday morning - poor things.

Gathering in front of our new dormitory on Monday morning

This was made a little more interesting by the surprise announcement during dinner that our hosts had managed to negotiate our relocation to the more luxurious new dormitories, and that we would have to pack up and move out of our current rooms right away and bring all of our baggage with us on the coach ride into town.

The coach returned to the university with the full complement of UK participants at about 2:00am on Monday morning, and it was then time to check in to our new rooms and retire.

Monday and Tuesday was filled with a grueling program of lectures, sightseeing and parties. The lectures covered not only background information on the solar eclipse, but also topics such as atmospheric gravity waves and timekeeping on Mars.

The Eclipse

Wednesday began with an early morning coach ride to our selected observing site - the town of Hacibektas in the central Anatolian region of Kapadokya. Unsurprisingly, we were not the only people at the university interested in seeing the eclipse, so there was quite a convoy of coaches leaving with us. Tension mounted as first contact approached and, due to a frustratingly long rest stop just short of our destination, we were still on the coach. At about 12:55pm we arrived at the base of the hill that was our designated observing point, with just a little over an hour to go before totality.

Totality Approaches

For the next hour we watched enthralled as the dark lunar disc slowly engulfed the brilliant solar disc, until at just after 14:02 local time the temperature suddenly dropped and we were bathed in the eerie twilight of totality. It was at last safe to remove our glasses and view the spectacle with the naked eye, and it was time to face the dilemma of how to divide the precious minutes between the competing demands of observing the spectacular solar corona, looking at our eerie surroundings, and trying to preserve the two with photography.

Awestruck Onlookers During Totality

Sadly it seems impossible to describe the event adequately in words, or to capture it fully in pictures, so if you haven't seen a total eclipse before and really want to know what it is like, you will have to try for the next one in 2008. At about 14:05 totality came to an end and the sun began to re-emerge from behind the moon. After about half an hour our lunch was distributed and then it was time to explore one of the most striking attractions of Kapadokya - the surreal landscapes, cave dwellings and churches built into the sides of mountains, including the Göreme Open-Air Museum. The tour was concluded with a visit to an onyx factory, followed by dinner at a local restaurant. Then at about 21:30 it was time for the long coach ride back to Ankara, arriving back at our dormitory at about 02:30am.

Aftermath

The original program had included a city tour on Thursday, but the UCL group were leaving early to spend a few days on the Mediterranean coast, so those of us that remained took the time to do some exploring of Ankara in smaller, independent groups. I spent my last night at dorm on Thursday night, and after a last day of sight seeing on Friday, was invited by three of our Turkish hosts to stay overnight with them at their flat. And then on Saturday morning it was time to make my way back home.

If you like the sound of this event and think you might be interested in doing something similar (without the actual eclipse) later in the year, don't forget the International Conference of Physics Students to be held in Romania from 14-21 August this year. If you are quick the IoP is offering to pay half of the £90.00 registration fee for the first thirty members to register.

A Hard Day's Night

by Michael McCabe

Michael McCabe spent a week on Mallorca in late September 2005 as a tutor for the Open University residential course SXR208 "Observing the Universe". This is his personal account of what went on at the Observatori Astronomic de Mallorca (OAM). Formal details of the course can be found at courses.open.ac.uk/sxr208. SXR208 is highly recommended for anyone wishing to study a university course and gain practical experience of astronomy and planetary science in a favourable environment.

There's no place like OAM

SXR208 is not the name of a supernova or a Kuiper belt object. It's the code for the Open University course "Exploring the Universe". The S stands for science, the R for Residential and the X for something else, maybe eXperiment or eXperience or eXplore. "Exploring the Universe" is a week long residential school, designed to give OU students practical experience of optical astronomy and planetary science at Observatori Astronomic de Mallorca.

Although I had been an OU associate lecturer/tutor for 22 years, I had not worked at an OU residential school before. I have taken University of Portsmouth astronomy students to Clanfield Observatory regularly for the past ten years, but the Hampshire observing conditions are not always favourable(!) and the opportunity to tutor astronomy and planetary science in a warmer climate was inviting. In Spring 2005 I had been a reserve tutor, on stand-by to go out to Mallorca at short notice. With a London marathon to run in April and the prospect of having my body clock shaken up, I was not too disappointed when the phone did not ring. In late September I was given the opportunity to be an SXR208 tutor.

It was warm, sunny and clear when I arrived one Friday lunchtime at Hotel Horizonte in Palma with its wonderful view of the harbour and the huge cathedral across the bay. Together with Axel, another tutor, I sought out the course director for the week, Prof. John Zarnecki. John was the Principal Investigator for the Surface Science Package on the Huygens spacecraft which had successfully landed on Titan in January 2005. Axel had been working with him on the Huygens data. Together with the other tutor arrivals, Amanda, John, Hara, Diana and David, we bundled into cars and headed for the OAM, an hours journey towards the centre of the island.

The OAM is a well-equipped observatory. The main professional telescopes form part of the Spaceguard programme and are used for the observation of asteroids, especially to detect near-Earth asteroids and determine their orbits. The seven teaching telescopes used for the SXR208 project work are 12-inch or greater Meade LX200 Schmidt-Cassegrain with computer-drive systems and hand controllers. Each has its own dome, quaintly named Schmidt, Mutus, Galileo, Kepler, Tycho, Clavius and Copernic after astronomers and lunar craters. Two of the domes have wheelchair access. Five of the telescopes are equipped with filter wheels and STL1001E CCD cameras and the other two have spectrographs. A small number of University of Portsmouth project students have been able to use CCD and spectrographic equipment at Clanfield Observatory, but the majority are restricted to making virtual observations with virtual telescopes and equipment in computer labs for practical purposes. Other OAM facilities include a modern 110-seat planetarium, a cafeteria/meeting area, and the laboratory in the main observatory building, used for non-observational projects and observational data reduction and analysis.

The original intention was for all residential school tutors to be trained at Milton Keynes on similar equipment beforehand. The relaxation of this requirement meant that new tutors, who were not full-time OU staff, had to learn quickly. Our preliminary visit was the first chance to see the telescopes and equipment before students arrived the next day! Those with past experience of the course could not relax either, because the equipment had to be prepared and checked ready for the week ahead. The school assistant, Rosie, and course assistant, Verena, were also busy setting up their office and preparing for every possible eventuality in the week that lay ahead.

SXR208 students work together in small groups of between four and six, either in the observing domes or in the laboratory. For the observing projects the group is normally split between the two locations. There are seven projects: Astronomical Spectroscopy, Colour-Magnitude Diagrams of Star Clusters, Stellar Photometry, Eclipsing Binary Star, Asteroid Light Curves, Chondrule Size Distribution in Chondrites and Planetary Landing Site Selection, from which each student selects four, according to their chosen balance of astronomy and planetary science, to be tackled on successive nights. An extra night on the first Sunday is for project induction and allows students to familiarise themselves with the equipment, particularly the CCD cameras and observational techniques, such as taking bias/dark/flat frames. A full account of the week would be too long, but here is a typical day's night from the tutor perspective. It's perhaps worth adding from the outset that it was the good humour and teamwork of all the staff that made the week a success.

3pm The seven tutors/demonstrators assemble at the hotel reception leaving behind the swimming pools and other holiday attractions. We pile into cars and head for the observatory.

4pm We arrive at the OAM at times dependent upon the route taken, and reassemble in the laboratory for a briefing from the course director. What is happening when? Who is doing what? What equipment needs attention? Which student has been causing problems? Which objects should we be observing? This afternoon I ask which asteroid my group should be observing and am met by blank faces around the table. A rummage around the project cupboard reveals a file with the necessary information on 714 Ulula and other asteroids. My heart rate returns closer to normal.

5pm The student coach arrives as we quickly review our notes and gather them together ready for the night ahead. This afternoon the course director, John Zarnecki, is giving a research lecture in the planetarium about the Cassini- Huygens mission and his work on the Surface Science Package. We join the 38 students in the planetarium and listen to John's account of events in January when he was at mission control in Darmstadt, Germany, and the Huygens 'craft descended through the Titan atmosphere. He holds up a fist- sized chunk of orangey-brown rock taken from outside the planetarium and declares: "This is just like what we see on Titan".

6pm While students are engaged in project preparation, there is a last minute chance to make sure that all the necessary information is ready. Where did I put those asteroid ephemeris tables? Which group am I working with tonight? Which dome are they in? What equipment are they using? What were the problems with it the previous night?

7pm It's now time to assemble for project planning with my student group. Who is doing what? They need to agree a group chair, secretary and sub-group leaders. Tonight the group will be observing an asteroid light curve. Do they understand what they have to do, how they will do it and who is doing what? I hold up another irregular, fist-sized chunk of orangey-brown rock taken from outside the observatory. This time it's an asteroid: "How does its appearance change as it rotates?", I ask. How do we choose a suitable asteroid to observe? How fast will our chosen asteroid move across the CCD frame? The group seems to be well organised and ready, but the night is yet young and anything can happen yet!

8pm Dinner brings project planning to a rapid end. Discussions don't overrun, otherwise you're at the end of the dinner queue and have to settle for the paella leftovers. The hour passes all too quickly.

9pm I switch regularly between watching over the observing group preparing the telescope and equipment, and the lab group preparing a finder chart for their target asteroid, 714 Ulula.

10pm Early efforts to locate the moving asteroid by blinking between frames are unsuccessful and a sense of frustration starts to build. Is it the tutor's fault? Who has made a mistake? Careful checking by the lab team reveals that the finder chart has inaccurate coordinates. A revised chart is hastily produced and, with some relief all round, asteroid 714 Ulula shows up. Meanwhile another group has posted a humorous finder chart on the lab door. It's postage stamp size with a single dot located in the middle, and nothing else!

11pm Regular CCD images are now being taken by the asteroid dome team, while the lab team starts to reduce the early data. I shuttle between the two sub- groups to check that all is going well. The lab team decide to look up asteroid "Zarnecki" on the Web. It's been recently named after our venerable course director. John Zarnecki looks crestfallen when he discovers that "his" asteroid is fainter than 21st magnitude!

12 midnight It's halftime and groups break off for a midnight meal. Conversations focus on what has gone right and wrong so far. There's still a long way to go. It's a couple of hours after my normal bedtime and there's at least 6 hours to go. I drink another coffee.

1am The dome and lab group swap around. Observations seem to be progressing well, but no-one really knows until the data reduction and analysis is done. The group gradually notice that the CCD images have become blurred. Does the telescope need refocusing? What has gone wrong? They realise that dew is condensing on the front of the telescope. A period of attention with the hair-drier and a potential problem is averted.

2am The observing has become more routine and conversations become more relaxed. A few isolated clouds threaten, but move away. The lab team are beginning to obtain relative magnitudes for the asteroid and start to plot a light curve. A pile of free newsletters about the Titan landings appear on the lab table. "Only £5 a copy - includes a picture of our beloved course director meeting Tony Blair", reads the accompanying student notice.

3am The observers gather some final CCD images before shutting down their dome. Furious activity in the lab is underway to complete processing of the night's observations in time. The light curve is imperfect, but there is clear indication of one and maybe two humps. They hastily calculate an asteroid axis ratio of 2.1 and a rotation period of 5+ hours. With 15 minutes to go, the group reassembles for a final discussion of their results. All around groups are hurriedly finalising their work and discussing their successes or failures.

4am The student coaches arrive and depart for Palma. Suddenly the whole observatory falls quiet. Tutors sit for a moment to recover, before comparing their experiences and problems during the night. Although some nights it has clouded over, tonight it is crystal clear. John suggests we go back out to one of the telescopes for some casual observing. For half an hour we simply enjoy the night sky and begin to relax!

5am It's back to the labs. Tutors must now get down to the necessary recording of assessment marks for each of the students in their group, not the easiest of tasks at this time of night. Rosie and Verena summon the seven tutors to the office for their special awards as the "Seven Dwarfs". In my mind we are the "Magnificent Seven". The night's job is done, but there's still the return journey to Palma.

6am We're on our way back to Palma. The exchange of funnier moments during the night helps to keep our driver awake. As we pass through Palma in the dark, night-club revellers are spilling out into the street at the end of their night activities. The lights of the ships in the harbour pass by our glazed eyes. Someone notes that one is owned by David Beckham. Do I care?

7am I collapse onto my bed and fall asleep immediately.

8am The sound of a jack-hammer in the building site adjacent to the hotel wakes me from my slumbers. They're working on the foundations of the neighbouring building site. The sun begins to appear through my curtains. I doze while the hammer bangs intermittently in my head.

9am I decide to cut my losses and go out for an early morning run down to the beach which lies a couple of miles away.

10am I find a sun-bed on the beach and fall asleep again in the sunshine.

11am The beach attendant wakes me up to pay for my sun-bed hire.

12 midday I go back to sleep.

1pm I have a swim to cool off.

2pm I run back to the hotel for some lunch. The course director tells me that he has located a 1990 paper on asteroid 714 Ulula, in accordance with my group results last night. I'm pleased.

3pm Tutors and course director reassemble at the hotel reception, ready for the next hard day's night. Have we really got to do all this again for 5 nights in succession?

Not every night's observing was 100% successful. Some nights it was frustrating to watch as mistakes were made and progress was painfully slow. Thankfully, most nights were clear and every night there was at least a few hours of adequate observing. It was a delight to watch even the weakest student groups working together to achieve their results. SXR208 is undoubtedly a wonderful learning experience not just for students, but also for tutors!

As I boarded my plane back from Palma to Bournemouth at the end of the week and my body clock struggled to return to daylight operation, my thoughts turned to the following week. It was the start of the new academic year at the University of Portsmouth and workbooks for astronomy students had still to be sorted out.

As a final postscript, all that running down to the beach to escape the jack- hammer could not have done that much harm. I won the Great South Run (for over fifties) round the streets of Portsmouth a couple of weeks later.

Michael McCabe is a National Teaching Fellow in the Department of Mathematics at the University of Portsmouth.

A Day at the Thames Barrier

Event Report by Fred Muirhead

I'd heard about the Barrier in the past but never thought that the public would be allowed to go and view it. So when the opportunity arose, I grabbed it. I was told it would be a bit cold so bring a warm jacket, which I did, and to wear flat shoes not high heels, which I was a bit disappointed about. Anyway, I arrived at the barrier to be faced with a man in a box and a big steel door which we managed to get through after answering many questions like "take me to your leader". Once inside we were directed to a small lecture room where we drank tea and coffee whilst waiting for other members of the group to arrive.

We were then treated to a very nice potted history of the Barrier and a long film which was really only a short film because the man operating the handle of the projector couldn't get it to start.

We were told in no uncertain terms how exhausting the tour was going to be because of the many steps (and narrow at that) there was to go up and down (90 steps down, long walk, 90 steps up), and how cold it was. A show of hands was then requested as to who would like to venture on the Barrier. After a lot of bribery and persuasion two hands went gingerly up. The first volunteer was Ralph Fiennes and then Pierce Brosnan.

Onto the Barrier we strode and then began the descent down the narrow stone steps, railings either side, and a nice view looking through the gratings (not for the fainthearted). On reaching the bottom we were actually beneath the bed of the Thames, and began walking down the connecting tunnel between the Barriers. On either side were power cables, services and drains. A 30 m walk brought us to the first Barrier and then began the climb to reach the level of the Thames and find ourselves on the Barrier platform.

During the climb we were shown the two hydraulic cylinders which work in opposite directions. Pulling on the upper linkage and pushing on the lower linkage raises the rocking beam. A connecting link between the tip of the rocking beam and gate arm transfers the beam movement and makes the gate rotate. Outside on the platform we took a few photographs, breathed some fresh air, marvelled at what we'd seen and then it was last up the stone steps was a sissy.

"There was last night the greatest tide that ever was remembered in England to have been in this river all Whitehall having been drowned". Thus wrote Samuel Pepys in his diary for 7 December 1663. Even in Pepys' day the menace of flooding on the Thames had a long established history. In 1236 the river was reported as overflowing "and in the great Palace of Westminster men did row with werries in the midst of the Hall". If this flood had reached central London's highly populated areas the result could have been horrendous indeed.

Tide levels are steadily increasing due to a combination of factors. These include higher mean sea levels, greater storminess, increasing tidal amplitude, the tilting of the British Isles (with the south eastern corner tipping downwards) and the settlement of London on its bed of clay. As a result tide levels are rising in the Thames estuary, relative to the land, by about 60 cm per century.

Royal assent to the Thames Barrier Act was given in 1972. Some 32 km of flood defences were built downstream of the Barrier with bank levels some 2 m higher than had previously existed. As an interim measure to improve London's defences against flooding, whilst the main defences were being constructed, 80km of banks were raised between Putney and Purfleet in 1971-72. Defences upstream of Putney on the south bank and Hammersmith on the north bank were also raised, to give the same degree of protection as in central London.

Basically the Barrier is a series of ten separate moveable gates positioned end to end across the river. Each gate is pivoted and supported between concrete piers that house the operating machinery and control equipment. Closing the Barrier seals off part of the upper Thames from the sea. When not in use, the six rising sector gates rest out of sight in curved recessed concrete sills in the river bed, allowing free passage of river traffic through the openings between the piers. If a dangerously high tidal surge threatens, the rising sector gates are moved up through about 90 degrees from their riverbed position and the four falling radial gates are brought down into the closed defence position. The gates thus form a continuous steel wall facing down river ready to stem the tide. Further rotation of the gates to the horizontal maintenance position renders them accessible for routine maintenance.

The width of the Barrier from bank to bank is about 520 m with the four main openings each having a clear span of 61 m The four main gates are massive. Each is constructed as a hollow steel-plated structure over 20 m high and weighing, with counterweights, about 3700 tonnes. Each is capable of withstanding an overall load of more than 9000 tonnes. There are two further gates of similar concept, albeit smaller, with 31 m navigation openings and the four falling radial gates have non-navigable openings adjacent to the river banks.

It has been known for some time that sea levels are rising, and the present defence system was designed for the tidal levels anticipated by 2030. Although that is still some time away owing to the time it takes to research, design and build tidal defences, the agency has started planning for flood risk management for the next hundred years, up to 2100.

Jodrell Bank Observatory

Event Report for Saturday 25 February by Mike Nugent

The Jodrell Bank Observatory, operated by The University of Manchester, has been at the cutting edge of British radio astronomy for some 60 years. Unusually for a research station, Jodrell Bank and its Director Bernard Lovell (he had not yet received his knighthood), became household names during the heady days of Sputnik and the space race in the 1950s, and when the first quasars and pulsars were discovered in the 1960s. So when Fusion arranged this event, it was an easy decision to put my name down for the visit.

Fusion members pose in front of the Lovell 76m telescope (left to right): Irfan Ali, Hammad Ali, Yumna Ali, Mike Nugent, Louise Heatley, Dwyn Padfield, Pat Wood, Pam Wood, Paul Ruffle and Srabani Datta.

I arrived a little before 11 am, when the visit was due to begin, and met the rest of the group in the Space Café in the Science Centre. After introductions, we were met by Ian Morison, who took us on a tour of the site, first to the oldest part of the grounds where Bernard Lovell set up his radar equipment next to Manchester University's Botanical Research Station in 1945 for research into cosmic rays. This area is now occupied by the Mark 2 Radio Telescope, and also the workshops, where various precision pieces of equipment such as the radio detectors and their cryostats are made. However, because of the wind conditions on our arrival, none of the telescopes were in operation.

We then went to the main research building (photo above). Astronomers are not without humour. Displayed in a window there were two notices visible from the outside: "Warning: may contain nuts" and "Don't feed the astronomers". Ian gave us a short introductory talk focusing on the history of the site and its facilities. I was pleasantly surprised to learn that Sir Bernard still comes in three times a week. We were then taken on a short excursion to the control room and one of the data processing laboratories. The control room houses, among other things, an atomic clock that is used to synchronise the telescope control systems and to provide precise timing signals for data acquisition. As an aside, Ian explained to us that GPS is one of the very few facilities used in daily life that needs to take into account the special and general theories of relativity, in order to retain accurate timing, and therefore position, information.

Ian then gave us a further short talk about the scientific research work currently underway at Jodrell Bank. He highlighted their research into: Pulsars (more of this later) - one telescope (photo above) continually tracks the pulsar at the centre of the Crab Nebula; Starburst galaxies - galaxies in which there is an unusually high rate of star formation; Quasars - point-like images due to beams of radiation from the centres of extraordinarily energetic galaxies at enormous distances; Gravitational lensing - the bending of light from a distance source by a massive object that lies on the line of sight, resulting in multiple images of the distant source; and the cosmic background radiation - the microwave radiation that is left over from the Big Bang from which the universe was born.

Much of this research is done as part of larger networks of radio telescopes, such as MERLIN, a network of six sites located across the UK, and VLBI, a network that stretches right across Europe. By training all the telescopes in the network simultaneously on to one celestial object, and combining the signals in the right way, observations can be carried out in much greater detail than by just using a single instrument. We were then given a guided tour of the laboratories where data are received and processed (photo above), not only from the Jodrell Bank telescopes, but also from MERLIN, VLBI and other international telescope networks.

During lunch there was an opportunity to walk around the base of the massive and hugely impressive 76 m (250 ft) Lovell Telescope. The original Mark 1 telescope began observing in 1957, was rebuilt in the 1970s, and was appropriately renamed the Lovell Telescope in 1987.

The afternoon was taken up with two talks which gave a more detailed flavour of the work currently being done in radio astronomy, including announcements of results that had been published only a few days earlier.

The first talk was by Albert Zijlstra on "Planetary Nebulae in the Interstellar Medium". With the aid of stunning computer models, he explained how planetary nebulae - the shells of ionised gas expelled from red giant stars - are formed and evolve.

The second talk, by Michael Kramer, was on "Pulsars", in which he explained their origin and behaviour. After a supergiant star explodes as a supernova, the core of the star collapses into a rapidly rotating neutron star - a pulsar. Michael also talked about more recent work, such as the discovery of binary pulsars and the huge velocities that pulsars can achieve as a result of the violent events from which they were created.

After a vote of thanks to the speakers, the visit closed at 4 pm. Just as we were leaving, we were pleased to note that the wind had dropped and the telescopes were able to resume their work. It rounded off the day nicely. I would also like to add my thanks to the speakers for giving up their Saturday for us and making the visit so informative and enjoyable. An excellent day.

Mike Nugent has been an OU student since 1997, taking mathematics and physics courses. He graduated last year and has now started an MSc. On the day after the visit, he located the JBO distance learning web site, and applied for one of their four courses in astronomy, and by the Monday his application had been accepted. Mike is now looking forward to the observation weekend at Jodrell Bank in November!

What they said about the JBO visit

"Thanks for organising the trip to Jodrell Bank - I enjoyed it, and found it quite accessible even with only a basic knowledge of physics. I'll look forward to coming along to future events." - Louise Heatley.

"I very much enjoyed Sat visit to JBO - well worth the journey. Many thanks to you and the three speakers for a very interesting day." - Dwyn Padfield.

"It was very enjoyable and interesting, my kids found it interesting and thought it was well worthwhile." - Irfan Ali.

Planetary Nebulae

by Paul Ruffle

The main reason for this edition of the Newsletter being a bit late, is that I am in the final stages of writing up my PhD thesis. To compensate, here is an extract from my introduction on PNe.

Planetary nebulae (PNe) consist of a glowing shell of gas and plasma that has been ejected from low to medium mass stars at the end of their lives. The name originates from a supposed similarity in appearance to giant planets. About 1,500 PNe are known to exist in our galaxy, out of around 200 billion stars. They are generally less than 50 thousand years old, compared to typical stellar lifetimes of several billion years. This short lifetime compared to stellar lifetimes accounts for their rarity. They are found mostly near the plane of the Milky Way, with the greatest concentration in the galactic Bulge. A typical PN is roughly 3 pc across, and consists of tenuous gas, with a density of ∼10³ cm^-3. Young PNe can have higher densities, ∼10⁶ cm^-3, but as they age, expansion causes their density to decrease. The central stars of PNe are very hot, but their luminosity is very low, implying that they must be very small. Spectroscopic observations show that all PNe are expanding.

PNe play a crucial role in the chemical evolution of galaxies. The early universe consisted almost entirely of hydrogen and helium, but successive generations of stars have created heavier elements via nucleosynthesis. When stars exhaust all their nuclear fuel they collapse to a small size, and for medium and low mass stars (< 8 M_sun) PNe are the end stage of their evolution. The gases of PNe contain a large proportion of heavy elements (or metals), and as they evolve they return material such as carbon, nitrogen, oxygen and calcium to the interstellar medium (ISM). Stars weighing more than a few solar masses end their lives in a catastrophic supernova explosion, and either become neutron stars or black holes.

A typical star like our Sun spends most of its lifetime fusing hydrogen into helium in its core. The energy released prevents the star from collapsing under its own gravity, making the star stable. After ∼10¹⁰ years, the star runs out of hydrogen in its core, so fusion ceases to support the outer layers of the star. The core then contracts and heats up from ∼10⁷ K to ∼10⁸ K. This results in the outer layers of the star expanding and cooling because of the very high core temperature, and the star becomes a red giant. However, the core continues to contract and heat up, and when its temperature reaches 10⁸ K, helium nuclei begin to fuse into carbon and oxygen, stopping further contraction of the core. The core then consists of inert carbon and oxygen, with a surrounding helium-burning shell. Helium fusion is extremely temperature sensitive, (r ∝ T⁴⁰), so a 2 per cent increase in temperature more than doubles the reaction rate. This makes the star very unstable - a small rise in temperature releases a lot of additional energy, increasing the temperature further. This causes the helium-burning layer to rapidly expand and therefore cool, which reduces the reaction rate again. These pulsations build up and eventually become large enough to eject the star's atmosphere completely. Up to 90 per cent of the progenitor star's mass is lost to the newly formed nebula.

The core of the star is now exposed as more and more of the ejected atmosphere moves away from the star. Deeper and deeper layers of the core at higher and higher temperatures are exposed, and when the temperature reaches about 3 × 10⁴ K, there are enough ultraviolet (UV) photons being emitted to heat the gas to the same temperature, ionising the ejected atmosphere and making it glow as a PN. The gas temperature is often seen to rise at increasing distances from the central star. This is because the more energetic a photon, the less likely it is to be absorbed, so less energetic photons tend to be absorbed in the inner regions of the nebula, while the higher energy photons tend to be absorbed in the outer regions.

The gases of a PN continue to move away from the central star at speeds of a few kilometres per second. As the gases expand, the central star cools, radiating away its residual energy. There are no further fusion reactions, because the remnant stellar core is not massive enough (∼0.6 M_sun) to generate the temperatures required for carbon and oxygen to fuse. Eventually the core cools to the point that it does not give off enough UV radiation to ionise the increasingly distant gas cloud. The star becomes a white dwarf (∼0.01 R_sun), supported by the degeneracy pressure of its closely packed electrons (ρ = 10⁷ - 10¹¹ kg m^-3), and the gas cloud continues to expand, and eventually merges into the ISM, enriching it with heavy elements such as carbon, nitrogen and oxygen, as well as organic molecules and refractory silicates and carbonaceous grains. The lifetime of a typical PN is ∼10⁴ years from formation to recombination.

HST images of planetary nebulae taken by Bruce Balick and his collaborators (www.astro.washington.edu/balick/WFPC2).

Hubble Space Telescope (HST) images reveal that many PNe have an extremely complex and varied morphology. Generally speaking, PNe are symmetrical and about a fifth are roughly spherical, but a wide variety of shapes exist with some very complex forms seen. Approximately 10 per cent of PNe are strongly bipolar, and a small number are asymmetric. One is even rectangular. The reason for the huge variety of shapes is not yet fully understood, but interactions between stellar winds moving away from the star at different speeds is believed to give rise to most of the shapes that are observed. Other explanations include: gravitational interactions with companion stars if the central stars are double stars; or a star's planetary system disrupting the flow of material as the nebula forms. One recent study has found that several PNe contain strong magnetic fields, something which has long been hypothesised. Magnetic interactions with ionised gas could be responsible for shaping at least some PNe.

The outflow features of He2-104 seen in the low intensity contours plotted by the author from images taken at the 3.5 m New Technology Telescope (NTT) in Chile.

As PNe are composed of extremely rarefied gas they show only a small number of emission lines. Some of the brightest of these are hydrogen, Hα, and doubly ionised oxygen, [OIII], at wavelengths of 6564Å and 5007Å respectively. These so-called forbidden lines can only be seen in very low density gases, because at such low densities, electrons can populate excited metastable energy levels in atoms and ions, which at higher densities would be rapidly de-excited by collisions.

PNe can be described as matter bounded or radiation bounded. In the former case, there is not enough matter in the PN to absorb all the UV photons, so the visible nebula is fully ionised. In the latter case, there are not enough UV photons to ionise all the surrounding gas, so an ionization front propagates outward into the circumstellar neutral envelope. As most of the gas in a typical PN is a plasma (i.e. ionised), magnetic fields can give rise to phenomena such as filamentation and plasma instabilities.

For most PNe distances are difficult to determine. For nearby PNe, it is possible to determine distances by measuring their expansion parallax: high resolution observations taken several years apart will show the expansion of the nebula perpendicular to the line of sight, while spectroscopic observations of the Doppler shift will reveal the velocity of expansion in the line of sight. Comparing the angular expansion with the derived velocity of expansion will reveal the distance to the nebula.

The angular diameter and flux of a PNe are much needed parameters when modelling the optical spectrum and evolution of the nebula and its central star. From these parameters the density and mass of the PNe can be calculated, as well as the extinction along the line of sight. PNe also provide an independent tracer of stellar populations and extinction in regions where visual tracers, such as hot luminous stars, are lacking.