| N.B. Change to published programme. The first lecture of the New Year on January 18 by Prof. Paul Barrett has once again had to be cancelled due to the lecturer being abroad working on a research project. We are grateful to Mike Howgate FLS. MSc. who will continue the dinosaur theme with a talk entitled: The Myth of the Pack-Hunting Dinosaurs. |
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Doug Daniels
During the ‘cold war’ era, when the USA and the USSR competed to produce more and more destructive atomic weapons, surveillance satellites were put into orbit to monitor atomic weapon testing. These satellites scanned our planet looking for the tell-tale emission of gamma rays which would have been released by any clandestine nuclear explosions. It came as something of a shock when these satellites began to record very frequent random bursts of gamma rays coming, not from our planet, but from deep space. These bursts were of very short duration, typically a few milliseconds and vanished without a trace before a telescope could be trained on the possible source. They were given the name ‘Gamma Ray Bursters’.
Gamma rays occur at the far short wavelength end of the electromagnetic spectrum and they are the most energetic of all particles. As these gamma ray bursts seemed to be coming from immense cosmological distances, it was reasoned that whatever was causing them must be a colossal explosion of energy equivalent to the energy of trillions of Solar masses. It would be very useful if the ‘afterglow’ of such an event could be studied to see if other radiations, such as x-rays, or even visible light was emitted. Plotting the light curve for such an event could give astronomers valuable information as to the mechanism which might be responsible for it.
Peter R Wallis
The date of 17th August is important to me personally because it happens to be the 93rd anniversary of my birth. But it is of greater importance to astronomers as it was the gravity-wave detection of the merger of two neutron stars, GW 170817. You will recall the gravity wave detection in 2016 at the Laser Interferometer Gravity-wave Observatory (LIGO) in the US of the merger of two black holes that demonstrated the new technique for observing the universe. But black holes have event horizons which limit our ability to see them. Neutron stars have no event horizons and we can see their mergers using optical, infra-red and X-ray telescopes. Moreover, there is now a second gravity-wave observatory (Virgo) near Pisa in Italy and this has allowed a reduction in the location uncertainty from 600 square degrees to 30 square degrees.
The GW 170817 event was announced in Nature Vol 551 of 2nd November 2017 by M Coleman Miller. The event was first observed by NASA s Fermi Gamma-Ray Space Telescope just 2 seconds after the time of merger. There are also five papers published in the same issue covering x-rays, optical and infra-red light. It has been possible to locate the source close to galaxy NGC 4993 at a distance of 40 million parsecs (130 million light-years). This is quite close in galactic terms and 10 times nearer than any previously measured gamma-ray bursts. The gamma-ray burst from this event is rather weak, but probably because the polar jet is seen only obliquely. Recent theoretical work has predicted that some of the neutron-rich matter would be ejected in the orbital plane and combine to form new elements, perhaps heavy ones, leaving a signature glow for a few days. Three of the papers report such a glow, called “kilonova”. There is a possibility that the mix could involve the manufacture of very heavy elements such as gold and platinum, but this is not yet generally agreed. However, it is now agreed that neutron star mergers are responsible for the mysterious Short Gamma-Ray Bursts.
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Simon Lang
We’d been closed for a year from July 2016 as Thames Water had to re-cover the reservoir with an impervious ‘smart’ membrane that would sense future leaks and hence prevent contamination of the water supply. We managed to get in at the end of July this year and hoped to quickly restore the Observatory to be ready to re-open in September as usual but sadly found we needed to do far more than hoped.
On regaining access, we found the Observatory had been broken into, this was going to require replacing the lock and some door repair, it’s been decided that we are going to make the door thicker and much stronger than before, Demonstrators, don’t leave your keys inside in future! The risk of damage to the new membrane meant that our barrier separating the Met. Station could not be put back as before and the instruments themselves are proving difficult to re-locate; sadly there’s rumour that the Met Office may abandon the site if alternatives to their normal set ups can’t be found. This would be sad and I’m lobbying to press them into a technical solution. We had removed the mains power and lighting supply but tests on the old cable suggested replacement, and the old electrical intake to the site also needs attention. Thames Water and UK Power Networks need to track down and install a new supply to the reservoir, in the meanwhile we need to replace much of our electrical installation but at least we have an advisor in a volunteer from UK Power Networks to assist!
As part of the works we have looked into extending the viewing area outside the dome with paving slabs but discovered we need permission to do this. This is now pending. These issues are sadly taking a while to resolve and will continue to do so.
We got on with what we could manage with the building being rather weather beaten! We held about 10 Sunday sessions with volunteers where we concentrated on removing bad timbers and replacing them, sealing as many cracks to the base of the dome building and annexe and resealing the dome coverings. Most filling and painting has been completed.
With the weather turning cold and or, wet, we’re now in limbo to continue and with the Christmas season coming it is unlikely we’ll be open until well into the New Year now. One positive note is that we have no planets of interest we can see and so apart from the Moon we’re not missing much. When we have better weather the paving and electrical work will proceed.
During slightly better periods and when I have time, I’ll finish repairing the door, front gate lock and with luck start to reinstall our side of the power supplies to the building and step lighting. Unfortunately we have particularly complicated, time consuming things to deal with but only one skilled person whose health could be better and is very busy elsewhere. We’d quickly use up our funds to employ others to do this and so the wait continues.
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Jim Brightwell
I became interested in balloons as a child watching them being released at a fete. They were using hydrogen then with lots of balloons in a bunch near children. No spoilsport health and safety then! I was fascinated to know where they went and what the view from the balloon would be. In 1962 I was filling balloons with coal gas which was not only explosive but poisonous as well. It was not health and safety that put an end to this project but conversion to natural gas in 1971. Natural gas does not have enough lift and would no doubt get investigated if I used it now. The project restarted in 1985 when I was working with helium. It is now an ongoing project with cameras.
At the start of the project I was using different colour balloons and one colour had much better response than others – guess which? I found the best meteorological condition to get them in to the continent and received German letters, Dutch letters and letters from France. The rate of return using the best colour was about 1 in 25.
A return rate of 4% would be too expensive using cameras but camera balloons are larger and designed to come down in an area with better chance of a find which turned out to be about 1 in 8. I have two ways of bringing the balloon down. One is to attach a 2nd balloon to provide the extra lift with a fuse to release it after about 2 minutes. The fuse is made of paper treated with potassium nitrate from ebay. I could have brought a large amount with no questions asked. It seems most people buying it on ebay have also brought flowers of sulpher, I wonder why? The 2nd way is to have one balloon inside the other with a hole in the outer balloon, to leak heliumNow for some results if you search for HAMPSTEAD FLIGHT on youtube you will see it passes over Fitzjohns Avenue at 8.50, Finchley Road at 9.50, South Hampstead High School sports ground at 10.45 and lands in Hampstead cemetery at 13.30. The first 5 minutes of this video are very unstable. The release for this flight was one balloon inside the other. The video MOAT MOUNT FLIGHT used a 2nd balloon with a fuse and the separation takes place at 2.00. It passes over the A41 at 5.15, M1 at 6.20 and Barnet Way at 10.40 Barnet Way has much more traffic.
The videos are shaky as I am using cheap cameras which have a very narrow angle of view, so why not use a better camera? Well the camera I use costs about £3 and the ideal camera costs £60! Add an SD card, balloons and helium and each launch costs about £10. With a better camera it would be about £100 per launch! A GPS tracker has been suggested which would also add weight and cost and just knowing where it has landed would not help much if it is in a river, smashed on a motorway or most likely stuck up a high tree.
I fly well within CAA regulations – which are a limit not a target! The reason is I use a toy balloon about 12” in diameter and the CAA regulation limit for a free balloon in civil air space is 6 foot diameter. My balloon is far less than the weight of a pigeon and aircraft engines are designed to cope with a small bird. I read a report of a pigeon that got into a jet engine and it did no harm, but you should have seen what the jet engine did to the pigeon! I also do not launch if the wind direction is towards Heathrow in the interests of discretion as questions could be asked if it landed there.
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Last updated 27-Jan-2018