There were a few differences this year. Firstly, because of work commitments Mark was unable to travel and therefore notes on the lectures were made by both Andy Lawrence and Andi Ye, so these will be a vast improvement on years gone by!
Secondly, only four lectures were given allowing a little more time for taking in the trade stalls (and lunch) and allowing an early finish. As two versions of the lectures have been submitted to Mark he has done a ‘mash up’ job including parts of both.
Dr Chapmans talk will be included in next month’s notes.
Six WDAS members attended the Leeds Astromeet at the University of Leeds this year. Arriving around 9:30am, we spent 20 minutes or so perusing the various trade stalls.
Lectures:
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"The Amateur's Moon" Subtitled "British Selenography and the BAA Lunar section involvement"
By Prof. Bill Leatherbarrow, BAA president. -
"DECAM: The Dark Energy Survey Camera"
By Peter Doel; University College London. -
"Planetary Magnetic Fields"
By Professor Richard Holme; Earth, Ocean and Ecological Sciences; University of Liverpool
The raffle was drawn and as usual WDAS members were triumphant with Mike Welham winning a 7.5 Super Plossl eyepiece, Andy Lawrence winning a telescope cover and John Lamb winning a book entitled "The Night Sky Month by Month". Not a bad haul.
Prof. Bill Leatherbarrow, BAA president:
"The Amateur's Moon" Subtitled British Selenography and the BAA Lunar section involvement.
Bill started by explaining that Selenography was the study of the lunar surface. He went on to state that the BAA had studied this field the longest. Many had taken part in this over the years including Patrick Moore, and although much of this field (data) is collected by spacecraft, amateurs still play a role in the study of the Lunar surface.
Thomas Harriott was the first to study and map the moon’s surface by telescope in July 1609, but he did not publish his observations;- Galileo did, and that's why he gets all the credit for this ground breaking research.
In the early days German and British amateurs took the lead in this field because of the quality of their telescopes. A variety of anecdotes from early British speculations about the moon were given, for instance William Herschel's lunar work, has largely been forgotten, which may be a good thing, as he expounded on forests of vegetation akin to trees, and said that that lunar life is a great possibility if not an absolute certainty”. Herschel also claimed to have discovered "3 glowing volcanoes" on the lunar surface.
Bill told us that British lunar study has been characterised by three concepts:
- A focus on cartography
- A romantic fascination with the idea of lunar change (and the possibility of life)
- A preference for volcanic theories of crater formation.
These concepts turn out to be related. If you're keen on the idea of finding life, you'll look for change. A succession of changes was believed to have been observed, but to demonstrate whether these changes were real required a decent map. And a volcanic explanation of craters painted a picture of a living system, rather than of a dead, unchanging moon.
This theory was cherished by many British astronomers who believed that the Lunar surface was a result of Volcanic action, and thus more interesting to study. The first Director of the BAA; T.G. Elgar was a Lunar observer and cartographer and he believed the Lunar surface was due to volcanic action rather that impact.
According to Bill, although Patrick Moore would reluctantly accept the impact theory (a result of meteor impacts forming craters ) he still believed in volcanism as a mechanism by which the moon's surface has been shaped. Mapping the Moon therefore became important, especially after Percival Lowall's study and mapping of the Martian surface. Successive directors of the BAA Lunar Section were transfixed with the ambition of getting ever greater detail on the moon, rather than taking a wider view. This obsessive pursuit of minute detail culminated in Hugh Percy Wilkins (Director of the Lunar Section 1946-1956) making a 300-inch map, crammed with too much detail to be of any use, and much of that detail didn't even exist in reality. Eventually lunar mapping and exploration was left to spacecraft with the BAA switching to more scientific studies.
One feature of the moon which could not be mapped from Earth and which has seen endless speculation is the ‘far side’. Today, we have the benefit of tremendous images from the Lunar Reconnaissance Orbiter.
Bill concluded by saying some BAA members still carry out mapping work but that is a subject for a future lecture.
Peter Doel; University College London:
"DECAM: The Dark Energy Survey Camera"
Peter talked about a multi-country project to build a very powerful CCD camera to fit onto an existing telescope in Chile, to carry out the Dark Energy Survey (DES). Peter was one of the scientists involved in the British arm of the project, which was in building the housing.
At first he gave an insight into the project objectives:" The DES is a 525 night project to survey 5000²° of the Southern sky in 5 different colour filters, to get information on 300 million galaxies, covering:
- Photometric red shift
- Galaxy shape (in Q&A, Richard explained that we can use a statistical analysis to compare average changes to galaxies in a particular region against each other and the norm)
o Clustering" A fraction of the project time will be used to observe smaller patches of sky every few days, to discover and study thousands of supanovae.
Type 1a Supanovae: to measure universe expansion
- Baryon Acoustic Oscillations: periodic fluctuations in density of visible matter of the universe caused by acoustic waves from the early universe.
- Galaxy Clusters: counting numbers of galaxy clusters of a given mass within a given volume of the universe to determine how their quantity has changed over time.
- Weak Gravitational Lensing: up to 1% distortion in a galaxy's shape by dark matter. Next we were told about the camera's specs. "It is to be fitted to an existing scope - an old scope built in the 1960s, which is a positive thing because it was over-engineered and has consequentially lots of space and strength to hold a very big camera.
It is a 4m telescope with an equatorial mount, and based in Chile. "The camera is a 570 megapixel red sensitive CCD array, with very wide field optics. It's not possible to make a CCD that big, so they have used 62 individual 5cm x 3cm CCDs. Together they make a 486.2mm diameter (Field of View) array. It can cover an area of sky equivalent to about 8 full moons. "The CCD’s are "fully depleted", which means they are sensitive to infrared.
Peter gave a great deal of detail about the tight tolerances to which the components had to be manufactured, and showed us pictures of the process. The component for the camera were delivered in December 2010 and assembled in January 2012. Installation was completed in August 2012. The first exposure was taken in September 2012 and was of the Fornax Cluster NEC1365. This image was carried in 258 publications in 36 countries. The camera’s field of view could actually take in the whole of the small magellanic cluster in one exposure.
Work is now getting under way relating to constraints in measuring Dark Energy with multiple images of locations with a very slight movement to fill in the spaces between the CDs in the array.
Professor Richard Holme:
"Planetary Magnetic Fields"
Richard is the head of Department of Earth, Ocean and Ecological Sciences at the University of Liverpool and opened with an apology for not been an astronomer. He went on to explain that his studies concentrated on the planets of our solar system.
Richard told us that the common "bar magnet pictures" of planets' magnetic fields lining up with the rotational North and South Poles are not accurate. For one thing, the magnetic and rotational axes often do not align (as with Uranus and Neptune). He showed us a cut-away diagram of earth, showing that layers of atmosphere and parts of the earth (crust, mantle, core) all have their own magnetic field, though the Earth's Core is the main field. A hydrodynamic dynamo in the earth's core of molten iron is driven by the earth's cooling.
In 1980 MagSat became the first satellite to study the Earth's magnetic field. There are now many satellites orbiting Earth that are devoted to this field of study. There is currently a project called Swarm with which Richard is involved that was launched on the 24th November 2013. While satellites can only measure data for around 10 years, ground stations (starting in 1840) provide long-term measurements.
Richard went onto explain that the Earth's magnetic field constantly changes and that Magnetic North and true North were getting closer together. This is caused by the movement in the Earth's liquid core. Richard is currently working on why Martian rocks have such a strong Magnetic field. Why Mercury is too small to have a magnetic field, yet it does, and why Saturn's magnetic field is symmetrical; which is impossible. The magnetic fields of the Galilean moons are believed to be induced from much bigger Jupiter. A mission to Jupiter is planned which is called Juno and Juice Richard is involved in the planning stage of the Juice portion of the mission, which is going to Ganymede. The results of which are expected by 2033. Ganymede was chosen because it has a strong internal magnetic field as well as an induced one.
Finally Richard told us that there's a move for planetary magnetic field researchers to jump aboard the recent (funded) enthusiasm for exoplanets, wondering what we might learn about their magnetic fields. But there's so much we don't understand about magnetic fields in planets close at hand in our own solar system, he doesn't hold out much chance of success in the foreseeable future.
During the final break of the day and just before the final lecture, we bumped into Paul Money with our 22 copies of "Night Scenes 2014" which again has been expanded by another 4 pages. The exchange was made, so these will be available for purchase by members and friends.
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