February 2006 | Megan's Blog

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The Blue Book - a piece of history

As I might have mentioned before, next year marks the 50th anniversary of the completion of the Lovell telescope. Over the last few weeks I have been talking about this with various members of staff at the Observatory as some of us feel that we really need to mark the event in a big way. When doing "Ask an Astronomer" I usually tell the audience a bit about the history of the Observatory, why we came to be here in the first place. Today, after some digging, I found some important pieces of that history.

After working on the development of radar during the war years, Bernard Lovell, a member of staff in the physics department of the University of Manchester, wanted to carry on his research. When he tried to use his radar equipment in the physics department in Manchester he found that there was too much interference from the trams which, at that time, ran up Oxford Road, right through the middle of the campus. He began looking for another site he could use temporarily while he used his equipment to search for radar echoes from cosmic ray air showers. When he discovered that the botany department owned a site at Jodrell Bank in Cheshire, he sought permission to take his equipment there.

What Lovell and his fellow researchers soon realised was that the signals they were detecting came not from the cosmic rays which they were trying to detect but from the ionised trails left by meteors as they streaked through the upper atmosphere. Over the next few years they aquired and built various other telescopes around the site to continue their research, not least of which was the 218-foot transit telescope, a giant wire construction which (as it was constructed on the ground) could only see the sky in a 30 degree wide stip as it drifted overhead. This telescope was used to survey what they could see of the sky at a variety of low frequencies at which the telescope was capable of operating (one of the factors which determines the highest frequency at which a telescope can realistically operate is the accuracy of its surface; the smoother the surface, the higher the maximum operating frequency).

Eventually Lovell came up with his plan to build a 250-foot fully steerable radio telescope. In his book "The Story of Jodrell Bank" he describes the early years and the process of constructing the telescope, both in terms of the political, financial and personal stuggles involved. Chapter 8 of that book describes the decision of a committee of the Royal Astronomical Society to endorse his proposals for construction of the telescope. The Council of the RAS passed a resolution to this effect and Lovell and Blackett (Professor of Physics at the University of Manchester) then went to the DSIR (Department of Scientific and Industrial Research) to ask for funding to carry out a design study. This was granted and so Husband, the consulting engineer on the project, began to draw up detailed engineering proposals. To accompany the engineering study, Blackett told Lovell to put together a detailed report on the scientific aspects of the project which included the researches carried out at Jodrell up to that point, what the telescope was intended to observe and the scientific reasons for the design of the telescope. These reports, together with information on the beam shape, gain, and control system, were typed up as a memorandum to be passed to the DSIR before any further decisions were to be made on whether the project would actually be given permission to go ahead. As the memorandum was bound in blue cloth it became known as the "Blue Book".

This afternoon, while looking through a wooden cabinet trying to find the original negatives of the photographs of the construction of the telescope used in Lovell's books, I came across an original copy of the Blue Book. When I took it back over to the main building I had fun showing people what I had found. I don't now how many copies were made, but I don't think there are many copies left now. Several people who have worked at the Observatory for many years (decades in some cases) said that they had never seen a copy before! Rather than leaving it in the damp of the archives it is now safely locked away in a warm room. It really amazes me how a lot of the old archive material is treated. Someday soon I plan on going up to the archives in the Rylands library in Manchester as a lot more of Lovell's records are up there. It's all useful for next year's anniversary...

Posted by Megan on Wednesday 22nd Feb 2006 (22:39 UTC) | Add a comment | Permalink

Busy week

While I've been busy visiting schools, teaching undergraduates and fighting with the wonderful public transport system in my part of the world, lots of far more exciting things have been happening in the rest of the Universe.

For a start, there have been some quite exciting supernovae, not least of which was SN 2006X in M100. This explosion was of the sort known as "type Ia" supernova. These occur in binary systems. When one star in the pair reaches the end of it's life and runs out of fuel in the core it throws off it's outer layers and leaves behind a small, cooler object known as a white dwarf. When the second star in the pair reaches the end of it's life, it swells up to become a red giant. If the stars are close enough, the outer layers of the second star fill what is known as the Roche lobe and the material starts to fall onto the white dwarf. As material falls onto the surface, it gets compressed and heats up. When enough material has accreted (been collected) on the surface an explosion will occur. This is what we see as a type Ia supernova. Why are these interesting? Well, cosmologists love them. Each type Ia explosion has the same absolute brightness, that is, if they were all placed at the same distance from the Earth, they would all have the same brightness. Thanks to this fact, if we can measure how bright they appear to us, then we can calculate how far away they are and so get a handle on how big the Universe is.

Around the same time that 2006X was discovered, another supernova was seen in UGC9265. This explosion, SN 2006W, was of a different sort known as a type II. These are the result of catastrophic collapses of stars greater than about eight times the mass of our Sun. When they run out of hydrogen (the main constituent of stars, the fusion of hydrogen nuclei to make helium is what produces all the heat and light which keeps us alive) in the core, they start to collapse. As the core shrinks, the pressure and temperature increases until it gets hot enough for the fusion of helium. When all the helium is used up the core shrinks again until carbon begins to fuse. This continues all the way up the periodic table as far as iron. Iron is pretty stable so, even though the temperature and pressure goes up, it can not fuse in the core. The collapse continues until the core is so dense that the outer layers still falling in can't go any further, effectively they hit a solid surface and rebound. This is what causes the explosion we see as a type II supernova. These are the kind of explosions that I study as they tend to be seen in active starforming regions such the cores of interacting galaxies. By watching the explosions and the resulting expanding shells of gas we can tell a lot about the interstellar medium - the "stuff" between the stars.

There was another exciting explosion spotted of February 12th. A nova known as RS Ophiuchi has begun another outburst, the first since 1985. Again, these explosions occur on the surfaces of white dwarf stars, due to the accretion of material, but they are less energetic that supernovae. RS Oph has exploded a number of times before and this time appears to have gone from a magnitude of 10.5 to 4.5 over a couple of days. That's naked eye visibility! If you have the skies for it, go take a look.

Posted by Megan on Friday 17th Feb 2006 (21:48 UTC) | Add a comment | Permalink

The end of the world

This last week has been manic. Next week is half term here so the local schools will be on holiday and the Visitor Centre will be busy (I've got two groups of visitors coming myself). One of my jobs this week has been to organise Ask an Astronomer helpers again. Unfortunately, most of the usual helpers have either left the Observatory and gone onto other jobs, are out of the country, or are really busy themselves. Not a single student has volunteered to help out, so I'm going to be doing three out of five sessions at this rate! You'd think half an hour wasn't too much to ask...

On Tuesday I gave my first school's talk. Twice. It would have been three times, but a university admissions person showed up to speak to the entire lower sixth (17-yr olds) during the last lesson of the day, so I got to finish earlier than planned. (I didn't mind too much, even though it took nearly two and a half hours to get there, as it meant I could stop off at the model shop in Manchester on my way home, I now have a rocket with a camera mounted in the nose cone!) It was quite scary though, as I've never given a talk to this sort of audience before. Normally, the people I'm speaking to had chosen to be there, this lot were told to come. I was even more nervous when the teacher decided to leave me to it! Bear in mind that I have no training in this sort of thing at all. I'm still not sure that it was a good idea. When we take out the planetarium the teachers sometimes see it as an hour off so they sit there in the dark and let the kids run riot, but at least they are there and can step in if things really do get out of hand. I'm going back in two weeks to do the same thing for some other classes, hopefully it will go a bit better. This is all part of the Researcher in Residence scheme which gets young researchers in science and engineering into schools to try and show that it can be fun and you don't have to be a geek with a lab coat and a comb-over to be good at it. Not sure I'm the best role model...

Thursday was another lab day in Manchester. It took over two hours to get there, and three to get back. I arrived at Jodrell at half seven in the eveing, had a cup of tea with Kim, that evening's duty controller, and then went home for some sleep. After ten hours solid I woke up feeling quite good, but I was yawning again by this afternoon. Thank goodness I don't have to do that again.

There are plenty more events coming up that I really have to start thinking about. In March there is a solar eclipse for which I'm putting on an event for local schools. Even though it is only partial here, it's a good excuse to teach them about how eclipses work. I've been asked to give a talk to some primary school children in National Science Week. I'm also organising an Astronomy & Space challenge day for Girl Guides in May, this is part of the preparation for a Go For It! pack which I am helping to write. These are challenge packs for patrol groups to do over a few weeks at their normal meetings and this one is based around astronomy. After that there is the flower show at Tatton Park where the Spaced Out group are going to have a garden. They've asked for some astronomers to be there to talk to people about the science behind it, so I'll probably be there for a couple of days. There's also going to be a star party in August to coincide with the Perseids, if I can get it organised.

On top of all that, I have work to do and observations to take care of as well! During February and March I have a total of seven telescope sessions which I have to schedule. Two have been observed already, the next run is on Tuesday, and today I finished off the schedules for the rest of them. Hang on, this is what I'm supposed to be doing, right?! Crumbs, my thesis has to be finished by September, so I'd better get a move on :-)

Posted by Megan on Friday 17th Feb 2006 (21:40 UTC) | Add a comment | Permalink

Moon

What with funding applications, telescope schedules to write, the Macc Astro workshop to sort out and random schools phoning me to ask if I can give them talks, it has been a busy week. Still, most of the urgent stuff is done now so, as it was clear, I made time to get out the telescope this evening before I left the Observatory. The Moon looks fantastic. The terminator always fascinates me as it is so different each time you look. It's fun to put in a high power eyepiece and jut watch it drift through the eyepiece. You could almost pretend you were in one of the Apollo command modules, flying over the cratered landscape while your fellow astronauts are somewhere down on the surface. I could watch it for hours :-)

Posted by Megan on Wednesday 08th Feb 2006 (22:33 UTC) | Add a comment | Permalink