WADHURST ASTRONOMICAL SOCIETY

SEPTEMBER NEWSLETTER 2005

INDEX: MEETINGS, OTHER NEWS, CONTACTS

PLEASE READ THE SECRETARY'S IMPORTANT NOTICE AT THE END OF THE NEWSLETTER

MEETINGS

THE JULY MEETING

  Pulsars

  By Konrad Malin-Smith 20th July 2005

      Konrad Malin-Smith arrived with a suitcase full of aids for his demonstrations.  He began his talk by showing an analogy of the twinkle of a star by passing a large torch through rippled glass, the effect being slight undulations in brightness.  Using a point source through the same piece of glass we could see a very obvious twinkle, demonstrating the relative effect of source size.

      Jocelyn Bell, a graduate student at Cambridge University was working towards her Ph D under Anthony Hewish when in 1967 she was operating the huge 81.5 MHz radio aerial she had helped construct using 9,000 wooden poles which supported the receiving wire used to observe radio signals from distant Quasars.  Her job was to analyse the radio signals received as the earth rotated since the array itself was fixed.  As the array scanned the sky she noticed a period of very rapid pulses amongst the data.  Jocelyn Bell had detected the first pulsar although at the time it was christened LGM - "Little Green Men"!

      The rapid pulses suggested that the source must be a rapidly rotating neutron star that had collapsed under enormous gravitational pressure.  The resulting fast spin being similar to that of a spinning skater drawing her arms in to her sides.

      The giant Aricibo telescope in Porto Rico was used to observe the pulsar since this aerial could be steered up to a point and then subsequently the fully steerable Jodrell Bank radio telescope in Cheshire was used.

      In 1968, Jocelyn Bell looked in the general direction of Perseus using 21.5 MHz, the absorption radio frequency of hydrogen and observed CP3028, a pulsar calculated to be 6,000 light years away with a diameter of 6 miles.  The pulsar had to be a neutron star to withstand so many rotations per second without flying apart.

      Molonglo radio observatory near Sydney used a Mills Cross array to observe an object in the southern end of the Veil Nebula.  A pulsar was discovered at its core, rotating at 11 times a second.  It was estimated to be a young pulsar resulting from a supernova that had taken place about 50,000 years ago.

      A more recent supernova occurred in 1054 and was recorded by Korean astronomers.  It was so bright that it was even visible during the day.  Modern astronomers have identified the event as that which created M1, the Crab Nebula as we see it after nearly a thousand years.

      Konrad demonstrated the effect of polarized light using two polarizing filters and rotating them so that light through both reduced to nearly zero when at 90 degrees.

      It was discovered that the Crab Nebula radiates polarised light and it was also noted that the light from the Veil Nebula was 90 % polarised.

      The pulsar in the centre of M1 rotated at 30 times a second and Lick Observatory made a light-intensity-graph through a rotating shutter that revealed the regular pulse.

      To demonstrate the way in which we "see" a pulsar Konrad returned from his suitcase with a model built by one of his students.  The pulsar was represented by a sphere about the size of a tennis ball with projecting pipe cleaners on opposite sides to represent the narrow beams.  A light inside shone out in line with the two sets of cleaners.  The whole fitted on to the end of a battery screwdriver that slowly rotated the model so that we could see how we would only "see" the pulsar when we were in line with the beams.

      The outer crust of a neutron star would have to be very strong to prevent it flying apart, and it has been calculated that this would be in the region of ten-to-the-eighteenth times the strength of steel.

      An over exposed photograph of the Crab revealed the wispy structure as a cylinder of hydrogen with the pulsar at its centre.  The Crab was the result of a Type 2 supernova.  A Type 1 supernova has no hydrogen.

      A slide of The Crab Nebula taken in X-ray radiation revealed further structural details and further research is still uncovering yet more information.

      After the talk was over, a question of the rotation of a neutron star was put by one of our members, and amazingly Konrad went to his suitcase and produced a box of 6 eggs!  He explained that one of the eggs was hard boiled and the others were fresh and proceeded to demonstrate a way in which the odd egg could be determined by spinning each egg on its longest axis in turn.  The hard-boiled egg spun for some time but the raw eggs wouldn't spin.  He explained that the glutinous contents dispersed the energy inside the egg leaving little or none left in a coherent direction to spin it.

      The question of why he had eggs in his case that he hadn't intend to use in our talk never got asked...

      It was an excellent talk presented in a way that only Konrad Malin-Smith could have done.

SEPTEMBER MEETING  

      The next meeting of the Society is on Wednesday 21st of September 2005 when the speaker will be Alan Drummond talking about "Perception in Astronomy".

      The meeting takes place in the Drama Studio at Uplands College starting at 7.30 pm.  The entrance to the studio is the first door on the left through the College gates.  This will be the last time we meet at this venue!  (See the Secretary's notice later in the Newsletter)

FUTURE MEETINGS

      Future meetings will be held at the Upper Room at Wadhurst Methodist Church opposite Uplands College.

Wednesday 19th October 2005.  Peter Parish introduces us to "Planets and Small Telescopes"  

Wednesday 16th of November.  The speaker will be Gilbert Satterthwaite talking about nineteenth century instruments with a particular interest in Sir George Airy.  The talk is called "Positional Astronomy".

 

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OTHER NEWS

THE ASTRO BARBECUE  

      The Astro Barbecue on Saturday 27th August and hosted very kindly by Michael Harte and his wife at Greenman Farm was great fun.  Several members brought telescopes and the sky was exceptionally clear with virtually no light pollution.  The Milky Way was very clear with the dark lanes being prominent.

      Two very bright meteors occurred and judging by their origins looked as though they could have been late runners from the Perseid meteor shower.

PROPOSED VISIT TO HERTFORD UNIVERSITY ASTROPHYSICS FACILITY

      As mentioned in the Summer Notices sent to members on the 10th of August, Ian King has very kindly offered to arrange a guided tour of Hertford University's astronomical facilities at the Bayfordbury complex, just over a mile outside Hertford town, provided enough members are interested in going.  The visit would take place on Friday 21st October 2005, meeting at the site at around 7.30 pm.  Members would need to make their own travel arrangements or share cars to the centre.  We can discuss this at the September meeting.

      Our guide would be Nik Szymanek who has talked to the Society before and is also featured in the August edition of Astronomy Now, so it can't help but be a very interesting and informative evening.

      Ian would like to know the names of interested members by, or at the September meeting of the Society on Wednesday 21st September 2005.  If you need to contact Ian, his telephone number is 01892 836288 and his email address is ianking2112@hotmail.com

THE NIGHT SKY IN SEPTEMBER

      The nights are lengthening and the sight of the Pleiades means that the winter constellations are not too far away.  But there is still a chance to try and find M57, the Ring Nebula in Lyra to be found just 6 degrees south of Vega midway between the two magnitude 3 stars, Sulafat and Sheliak.  Worth a look.

      Mars is not far from the Pleiades rising soon after nine, although until the beginning of October its orbit appears to be retrograde.

LIGHT POLLUTION AROUND WADHURST  

      Phil Berry, one of our members, alerted other members in the Wadhurst area about proposed lighting over a private tennis court that would have been quite intrusive during the evenings.  As a result many local members wrote to the local council and I am delighted to say that the protest was successful and it has just been announced that the proposal was rejected.

AN IMPORTANT  NOTICE FROM THE SECRETARY

      The Society meetings have been held in the Drama Studio at Uplands Community Centre (UCTC) since 1997 at no cost until 2000 when cost of hire was set at 137.50.  Since then it has risen to 316!

      We have also been very fortunate indeed to have enjoyed, through Chairman Tim's generosity, 5 years of refreshments and during the past 2 years Amina and Chris Green have made all the arrangements to ensure that we were refreshed at each meeting.

      The time arrived to seriously review the high cost of the meeting room and to take the pressure off Amina and Chris.  Following the Committee meeting on 11th July enquiries were made to try and lower hiring costs in accommodation where there were existing catering facilities.

      The Committee has arranged to move our meetings to the Upper Room at Wadhurst Methodist Church COMMENCING 19TH OCTOBER 2005.

      Entrance to The Room is situated on the OPPOSITE SIDE OF THE ROAD about half way between UCTC and the Greyhound pub.  The Secretary will endeavour to have the Society Banner on display outside the premises.  Parking is available behind the Greyhound if St. James Square is full.

      The room is centrally heated and there is wall-to-wall carpeting.  It is clean, tidy and devoid of extraneous theatre props and clothing.  Catering equipment is installed including a warming oven (for AGM mince pies).  What is more the cost is 53% less that UCTC.

      DO REMEMBER that our meeting will be held at UCTC as usual, yes Uplands, on 21st September so that any members who are on holiday or miss this first advice of a change of venue do not get hopelessly lost.

Ian Reeves

 

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CONTACTS

Chairman          Tim Bance                   01732 832745                                  timbance@hotmail.com

Secretary         Ian Reeves                        01892 784255

Treasurer         Mike Wyles                   01892 542863                                 mikewyles@globalnet.co.uk

Publicity         Michael Harte                       01892 783292

& Web site                                                                                                    michael@greenman.demon.co.uk

Editor            Geoff Rathbone                01959 524727                                 Geoff@rathbone007.fsnet.co.uk

Any material for inclusion in the October Newsletter should be with the Editor by September 27th  2005

 

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