To study and encourage popular interest in all branches of Science.

Newsletter Christmas 2008

Dear Member,

FROM THE PRESIDENT............................................................Doug Daniels

I have just about recovered from the surprise of discovering that Council decided to elect me as your President, following the retirement of Professor Robert Weale. Since the foundation of the Society in 1898, this is the first time that the President has no formal scientific qualifications, other than 'A' levels. Mind you, they were 'proper' 'A' levels, circa 1959! As many of you will know, I am an amateur astronomer, in the true sense of the word 'amateur' - from the Latin Amo - love of the subject. But this does not mean that astronomical subjects will dominate the lecture programme. As ever, your Council will strive to produce a balanced programme with topical subjects covering the wide spectrum of scientific discovery. In this endeavour, I am well supported by an enthusiastic team - your Council, all of who work long and hard for the Society, and I take this opportunity to thank them on your and my behalf.

My first action, in Council, was to propose Dr. Julie Atkinson, our General Secretary, to the position of Vice President. This proposal was ratified, as per the constitution, by members at the first general meeting in September. I am sure that everyone is aware that in any society, it is the general Secretary who does most of the work! Julie has been working hard for the Society for many years and her 'elevation' is scant reward. Nevertheless, she will be the first female Vice President in the history of the Society, reinforcing our intention that this should be an equal opportunities Society.

I now take the opportunity to pay tribute to our retiring President, Robert Weale who has served the Society diligently for some twenty years. In this respect, his was the second longest Presidency in the history of the Society, only just exceeded by Sir Flinders Petrie - 1910 - 1933. It is proposed that we offer Robert, Honorary life membership and Vice Presidency at the next Annual General Meeting. We must also recognize the contribution of Betty Weale, who for well over a decade, missed the last ten minutes of every lecture to attend to the tea urn and who generously made her home available for Council meetings for two decades.

Council is also sad to lose the services of our Membership Secretary, Elisabeth Fischer. Elisabeth has served the Society for thirty years - a working lifetime and the Society owes her an enormous debt of gratitude. In the future, the roles of Membership Secretary and Treasurer will be combined as Peter Wallis has also decided to retire at the next A.G.M. After that time, John Tennant will be our Treasurer and Membership Secretary. Members can greatly assist our Treasurer by making sure that their subscriptions are paid on time, better still, by bankers order.

As you can see from the foregoing, there are many changes taking place in the administration of the Society. These changes are the direct result of the second law of thermodynamics - entropy (disorder) increases with time! Your council is ageing and it is vital that we recruit younger members if the Society is to continue to thrive. There are still vacancies on Council, so why not take a more active role in your Society - many hands make light work.

Finally, I wish all members a very merry Christmas and a prosperous and interesting New Year.



How many planets in the Solar System? Well, that's an easy one, at least it used to be! Prior to January 29th 1930, the answer was eight but then the American astronomer Clyde Tombaugh developed the photographic plate that revealed the tiny image of Pluto; and then there were nine. This was not an accidental discovery. Years earlier it was found that the then furthest planet, Neptune, was not orbiting quite as it should. It was as if some unseen force was acting upon it, tugging it out of position and the logical explanation was that there must be another more distant planet waiting to be discovered. Percival Lowell, the astronomer best known for his eccentric ideas about life on Mars, was convinced of the existence of a trans-Neptunian planet and in 1905 he began to calculate a possible orbit and to begin an organized search for it at the Lowell Observatory. Lowell's calculations were not completed until 1914 and they predicted that the 'new' planet would be about 6 times the size of Earth and lie at about 4000 million miles from the Sun. Lowell did not live to see the fruits of his labours. He died in 1916 and the 9th planet had still not been detected.

The search was resumed in 1919 by Humason at Mount Wilson, but he was also unsuccessful, so in 1929 Clyde Tombaugh returned to the problem at Lowell Observatory and just a year later, Pluto was finally discovered. It must be said that Pluto was a bit of a disappointment. It was much smaller and less massive than expected. Also, its orbit was a bit odd in that when Pluto is nearest to the Sun, it lies within the orbit of Neptune. Its distance from the Sun varies from 4,400 - 7,400 million kilometres. It orbits the Sun once every 248 years and has a diameter of just 2,300 km

Little more was discovered about Pluto until 1978, when J. Christie discovered that Pluto had a moon, subsequently named Charon. Charon turned out to be peculiar as well. It was quite large in relation to Pluto, being about 1/3 of Pluto's diameter and orbits at a distance of 17,000 kilometres every 6 days, which is the same time as Pluto's axial rotation. This means that an observer on Pluto would see Charon permanently stationary in the sky from one hemisphere, but totally invisible from the other hemisphere.

The fact that Pluto's size and mass were insufficient to account for the observed perturbations of Neptune's orbit indicated that there must be something else out there that was responsible, so the search has continued and since 1992 over 1000 Trans-Neptunian Objects (TNOs) have been discovered. Of these, only 132 have well defined orbits and only the seven largest have been observed in any detail. The largest of these, Eris, named after the Greek Goddess of discord and strife, is actually larger than Pluto with a diameter of around 2,500 km.; it was discovered by Mike Brown at Palomar in 2003-5. Its 45 degree orbit takes it out to 96.7 AUs from the Sun, nearly three times Pluto's mean distance and it has a tiny satellite named Dysnomia. Eris was at first categorized as a Scattered Disk Object (SDO) - yet another confusing category, and there are even more of those - Plutinos, KBOs (Kuiper Belt Objects) or Cubewanos and Centaurs to name but a few.

Five of the other major TNOs have been given names: Sedna, Orcus, Quaoar, Varuna and Makemake, formally 2005 FY9, pronounced Makimaki, named for the Polynesian God of fertility. This was another discovery by messers Brown, Trujillo & Rabinowitz in 2005. One more has yet to be named, that is 2003 EL61. Its shape is highly elliptical due to its rapid axial rotation of slightly less than 4 hours, and it has two small moons, so far also unnamed. Sedna and Makemake have diameters of around 1,700 km and Orcus and Varuna barely reach 1000 km. But at these distances, accurate sizing is difficult, relying on occultation timings and infrared measurements by the Spitzer Space Telescope.

The discovery of these TNOs, and the fact that Eris, is actually larger than Pluto, led to the recent demotion of Pluto to the status of 'Dwarf Planet' and the upgrading of Eris from an SDO to that of 'Dwarf Planet' as well, causing a certain amount 'discord and strife' in the process.

These recent re-classifications have caused astronomers to re-examine the qualities that define a planet. This might, at first glance, appear to be a simple task but in practice has proved to be much more difficult. The word 'planet' means 'wanderer' and was originally applied to any body 'wandering' against the background of the 'fixed' stars and at one time included the Sun and the Moon. More recently, the term has been applied to 'large' bodies that orbit the Sun in elliptical orbits that lie more or less in the same plane. But then one must be a little more specific about the term 'large'. Pluto is not that large and several of the TNOs are not much smaller. And what about the asteroids? The largest, Ceres is a fair size with a diameter of 900 km, considerably larger than the rest of the asteroids and only slightly larger than Varuna. Asteroids have also been called 'minor planets'. The problem becomes more difficult when we pass Neptune and enter the realm of the TNOs because at these distances it is easy to mistake a dormant comet nucleus for a TNO. This in fact has already happened to Chiron, an object found orbiting the Sun between Saturn and Uranus - formerly described as a Centaur (neither man nor beast!). Chiron was discovered in 1977 by T. Kowal but it soon became evident that Chiron was in fact a comet, when it underwent a flare up in 1988. As we probe further into the far reaches of the Solar System we are very likely to encounter more bodies from the Kuiper-Edgeworth belt - the distant reservoir for periodic comets.

Faced with the problem of classifying these new members of the Solar System, the International Astronomical Union met in Prague in August 2006 to re-define the term 'Planet' and they decided on three main categories, albeit less than 500 members (4% of the total membership), turned up to vote on the resolution. The three categories that they finally came up with are as follows:

  1. Planets - The eight major planets from Mercury to Neptune are 'true' planets
  2. Dwarf Planets - Pluto and any other 'round' body that has not cleared the neighbourhood around its orbit
  3. Small Solar System Bodies - all other objects orbiting the Sun.

It seems to me that this classification is less than satisfactory. I have no objections to (1). But regarding (2), the condition 'round' worries me. How then do we categorize TNO 2003 EL61? This body is quite elliptical in shape. And few planets can be described as truly 'round'- not even the Earth satisfies this condition. I am also unhappy about the 'clearing the neighbourhood' bit. Jupiter, for example, which is also not 'round', has at least 50,000 Trojan asteroids within its orbit! I have no real objections to category (3), but I feel that there is perhaps a better definition.

I should like to propose a new taxonomy for Solar System components called: 'The Hampstead Scientific Society Classification of Solar System Components' -- the HSSCSSC for short.

  1. Major Planets - The eight major planets from Mercury to Neptune
  2. Minor Planets - Any body greater than 2000 km. in diameter orbiting the Sun in an elliptical orbit not covered in (1).
  3. Asteroids - Solid bodies of less than 2000 km. in diameter in orbit around the Sun.
  4. Periodic Comets

Using the HSSCSSC system of classification, the answer to the question: How many planets in the Solar System? Is: eight major planets and two minor planets. All the rest being either asteroids or comets. But as the exploration of the Solar System continues, I am sure we can look forward to discovering even more new members of the Sun's greatly extended family and experience yet more 'discord & strife' attempting to classify them.

Doug Daniels (HSS President & Astronomical Secretary, August 2008)


I Know His Face

Peter R Wallis.

In recent years the technique of functional Magnetic Resonance Imaging (fMRI) has discovered interesting things about how our brain works. The technique originated as NMR imaging but the letter N stood for nuclear and was later dropped to avoid any connection with nuclear radiation, energy or weapons. But it still refers to the nucleus of the atoms which make up our bodies, in particular to the hydrogen atoms present in enormous numbers in our soft tissue. The nucleus of hydrogen is a proton and has 'spin'. In a strong magnetic field their spin axes can be aligned with the direction of the field. If disturbed, however, they precess like a spinning top around that direction; this can be detected as a small radio signal. In a field of 10,000 gauss the signal is at 42.65 MHz. If we apply a radio signal to the protons we can detect the resonance at this frequency. It can be as precise as 1c/s.

To use this for imaging of the body, we introduce a small extra magnetic field so that protons on one side have a slightly different resonant frequency to those on the other; the resulting spectrum shows the density of protons across the body. Repeating this in other directions allows us to measure the number in any specified position. MRI provides a non-invasive way of imaging the soft tissues of the body which are virtually transparent to X-rays.

But the technique of functional MRI goes much further than simple body-scanning. It is used to determine which neurons in the brain are active when we think or receive sensory inputs. Now neuron activity in the brain depends greatly on the supply of blood and we are able to determine which part of the brain is active by seeing where the blood is flowing.

As an example of what can be done, I shall report on some recent work on face recognition. We are remarkably good at recognising faces, even though they are all much the same: one nose, one mouth, two eyes and two ears. We are also good at discriminating emotions: anger, hate, sympathy or love. How do we do it?

About ten years ago brain imaging studies revealed that certain discrete regions of the temporal lobe fired up more strongly when people looked at faces rather than other objects. More recently Doris Tsao at Harvard Medical School and her colleagues located certain patches of neurons in monkeys which were dedicated to faces, in that they only fired when the monkey observed a face.

She has continued her studies on monkeys at Bremen University and reports that such 'face patches' are to be found in many places in the brain. She has used direct electrical stimulation and finds that stimulation in one face patch seems to cause reactions only in other face patches. The interconnectivity between them appears to be very strong.

She has also located 3 discrete patches in the frontal lobe, a region of the brain involved in goal-directed behaviour. One of the patches reacted particularly to emotional faces, unlike patches in the temporal lobe.

The picture emerging is that primate brains including ours have built-in face recognition capability. It seems that this must have evolved. Why? Because we are social creatures. Faces are important for our survival. We need to know who is a friend and who is an enemy.


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