27th January 2015
This talk, prompted by Voyager 1 leaving the solar system, was given by the Lucie Green, a well-known astronomer and broadcaster.
The heliosphere is the volume within which the Sun’s magnetic field and the solar wind dominate the interplanetary medium. Lucie talked about many of the features on and near the Sun’s surface, including sun spots, the corona and magnetic field lines. We have a number of spacecraft studying the Sun, including in particular the ESO’s Ulysses, which has a polar orbit, and the STEREO pair of spacecraft. These give us unprecedented views of what’s going on there.
We had many video clips of activity, with explanations of how that fits with what’s going on in the Sun’s magnetic field. For example, the differences in outflow characteristics between solar minimum and solar maximum can be explained by looking at the magnetic field has increased complexity at maximum.
There has been lack of understanding of how charged particles can leave the Sun’s surface when they are following magnetic field lines which loop up and back down to the surface. Models explained how the magnetic field can make “chimneys” that the particles can flow up.
Further out, the heliosphere is shaped a bit like a wind sock as the Sun moves through then interstellar medium. Contrary to expectation there are a large number of magnetic field “bubbles” near the heliopause, which are explained by twisty bundles being forced up from the Sun and moving to the edge of the solar system. The field structure is so complex the field lines look rather like a ballerina’s fluffy tutu!
Lastly Lucie talked about the ESA Solar Orbiter which will be launched later this decade. It has 10 instruments on board, and its orbit will move out of the ecliptic to give some polar observations, as well as approaching the Sun inside Mercury’s orbit: at 600⁰C heat shielding is of paramount importance. It has been in development for many years, and we have high hopes for what it will tell us.
An excellent and well-attended lecture: a very technical subject that Lucie explained with great clarity.
The Apollo Missions Science Packages
25th November 2014
This talk was given by the Keith Wright, who was an engineer working on all the science packages that were included in the Apollo missions.
Keith started by reviewing his career, stating with making model rockets at school, and on through working on “Blue Streak” to Apollo in 1966. He then joined ESA in 1972.
We looked at the various packages that were attacked to the lunar lander, starting with Apollo 11 which had laser ranging reflector, a passive seismometer and a dust analyser. After that we looked at the instruments that were additional to what was brought by earlier landings, though many of the experiments were repeated.
Apollo 12 had a magnetometer, a solar wind detector, an ion detector and an atmospheric pressure meter. All these were connected to a central station. As Keith discussed each bit of equipment, he also told stories about training the astronauts, problems, etc., e.g. tripping over cables on the Moon.
Apollo 14 had an active seismometer with a small mortar and astronaut operated thumper, and a charged particle detector. Apollo 15 included a heat flow detector, but it proved very difficult to drill into the surface to install it, so only one of the two sensors was installed. Apollo 16 had no new items, and Apollo 17 had a gravimeter and an atmospheric composition spectrometer.
Keith concluded by telling us how much our understanding of the Moon has been added to by the information these experiments gave us. For example, the internal structure of the moon is now known to be very different from what we thought it was before all the seismology experiments.
An excellent talk on a subject which the audience found most interesting.
The Story of Radio Astronomy
25th October 2014
This talk was given by the Chairman, and covered various subjects. Firstly we looked at the electromagnetic spectrum and what we can observe from the ground, with optical and radio “windows”.
History started with the 19th century, moved on to Jansky’s detection of the centre of the Milky Way and Reber’s home made dish. The war interfered with developments in this field, but radar expertise was one of the drivers behind J Stanley Hey setting up the Cambridge group, and Bernard Lovell setting up the Jodrell Bank observatory.
We then looked at various types of telescope and how things have developed since then, using ever more effective forms of interferometry, culminating in the LOFAR observatory and the square kilometre array.
The subject then switched to what people are looking at today, included the Cosmic Microwave background (CMB) radiation, Pulsars, Quasars, radio galaxies and Active Galactic Nuclei (AGNs).
Finally we looked at the 21 cm hydrogen line, and a lot of the things studying this “cold hydrogen” line can tell us.
A to Z of the Solar System
16th September 2014
Bob Mizon came once again to entertain us with his whimsical list of objects in the solar system, running of course from A to Z.
You might expect “A” for “Asteroid”, “B” for “Bolide” etc., but no… “A” was for “Aurora”, as might be expected, but “B” was for “Binary Asteroid”, with Bob showing pictures of asteroid Ida with its tiny moon Dactyl and an aerial picture of a double crater in Canada.
Similarly other unexpected items included “F” for “Fallacy” where Bob pointed out common beliefs that are erroneous, and “M” for “Mont Blanc” where an observatory was constructed that failed to work from day 1 because of clouds and snow.
Bob revealed he was very grateful that one of the Kuiper belt dwarf planets has been called “Quaoar”, otherwise he’d have been stuck for a “Q”.
It was an amusing and very informative look around the solar system, and Bob as usual excelled himself.
After the break, Bob gave us a run around what’s in the sky at night at the moment, using the free planetarium software “Stellarium” to illustrate his points.
16th August 2014
We were very pleased to welcome back Allan Chapman who talked about William and Caroline Herschel and to a lesser extent William’s son John.
William Herschel was from Hanover, which had the same king as the United Kingdom, George II. He came needing to make money and was an extremely successful businessman. At that time science was not a funded activity, and if you wanted to study, e.g., astronomy, you paid for it yourself.
Both he and Caroline had formidable intellects, and he was also a most accomplished musician. Initially he earned money from music as an impresario, but soon moved on to making his own telescopes, which he sold for substantial sums.
He produced papers on the structure of the “universe”, i.e. the shape of the Milky Way, and was the discoverer of Uranus in 1781. His telescopes became bigger and bigger, moving up from a (length of) 7’ to 20’ to eventually 40’, which was somewhat unwieldy and with an 18.5” mirror probably not the best optically either.
As a serious scientist who wanted to understand the theory behind what he was looking at, he was well regarded and became an honorary fellow of the Royal Society in 1835.
Caroline is best known for having found up to 8 comets by “sweeping” the sky.
John was an extremely gifted linguist as well as a brilliant mathematician. His main achievement was charting the southern skies, which he did from the Cape of Good Hope.
15th July 2014
This talk was given by the Chairman.
The talk started with the question: what are comets? Usually called dirty snowballs, the examples looked at their structure including their albedo, nucleus and tails.
They originate far out in the solar system, and the talk looked at the solar system’s formation and the subsequent location of comets beyond the planetary realm. They are now found in the Kuiper belt, the Scattered Disc, and especially in the Oort cloud
We looked at what we see nearer to home, including Centaurs between Jupiter and Neptune. Most inner solar system comets are divided into 2 families, short-period and longperiod. There are also some main belt comets in the out reaches of the asteroid belt with fairly circular orbits.
We then looked at a bit of history, at myths and legends, which are mostly of woe, including Europe and China. Aristotle’s view of their origin and refutations of this were covered as well.
Some say the water on Earth comes from comets, but it’s perhaps more likely it comes from icy asteroids, based on isotopic ratios of hydrogen and deuterium.
As an origin of life the panspermia theory promotes comets as the vectors: the Wickramasinghe/Hoyle theory.
Lastly we looked at collisions with Earth and the energy yields from those, including Chicxulub and Tunguska. We looked at ways to divert a comet. Lastly it seems there may well be many invisible ex-comets with very low albedos, which could strike the Earth with no notice!