WADHURST ASTRONOMICAL SOCIETY

APRIL NEWSLETTER 2008

INDEX: MEETINGS, OTHER NEWS, CONTACTS

MEETINGS

MARCH MEETING

The Magellanic Clouds

A talk given by Konrad Malin-Smith at the March meeting

The meeting was opened by Phil Berry welcoming back Konrad Malin-Smith whose talk this time was about the Magellanic Clouds visible from the southern hemisphere. Konrad began his illustrated talk with an astro-photograph of the area around the earth's celestial south pole.

There is no visible star that marks the pole like Polaris in the Northern sky but in this photograph we could see the Southern Cross, Alpha Centauri and the Large and Small Magellanic Clouds.

During the sixteenth century, a Portuguese maritime explorer called Magellan was in the service of the Spanish Crown and was asked to find a westward route via the tip of South America to the Spice Islands in Indonesia.  Magellan had visited the islands previously but by approaching from the opposite direction across the Indian Ocean.

For navigation purposes, he considered the South Celestial Pole to lie somewhere between the two misty clouds visible in the night sky.  These were to be named the Large and Small Magellanic Clouds in his memory after he had fallen out with the locals of Mactan and killed.

Astronomers later discovered that the clouds are not part of the Milky Way but are in fact irregular dwarf galaxies.  The next diagram Konrad showed us was of the Milky Way around which orbited material that formed the two clouds and by observing Cepheid Variables in them and measuring their proper motion it has been calculated that the clouds are in a huge orbit around our galaxy, taking 2.2 billion years to complete one orbit.  The Large Magellanic Cloud is at a distance of about 175,000 light years.

It has also been found that there is a stream of atomic hydrogen linking the orbit of the clouds with the Milky Way.

The next few slides showed a trip Konrad had made to Perth in Australia.  Using a Potterton Gas boiler clock drive, they were able to track their telescopes and take several film images.  From here, Sirius was more like a powerful searchlight and familiar Orion was now upside.

One of the images was of the Large Magellanic Cloud (LMC) taken with a 15-minute exposure using 1000 ISO film.  The image revealed much of the structure of the cloud with several blue stars ionising gas clouds.

One of the main features of the Large Magellanic Cloud is NGC 1910, a large star cluster with a definite "S" shape.  Inside this cluster is a variable star called S Deradus, which is a million times brighter than our own Sun.

Konrad showed RR Lyra stars, which are standard variables rather like Cepheid variables but far fainter, being used to calculate the distance of the Small Magellanic Cloud (SMC) as 210,000 light years away.  This cloud is much less evolved than our own galaxy and contains far more hydrogen than might be expected and we saw NGC 346 viewed through a hydrogen-alpha filter to reveal its delicate structure.

The SMC is rather like a huge tube and using radio astronomy, it has been shown that the SMC is spinning.  If it weren't spinning all the stars would collapse into the centre.  This has also been shown to be the case with the LMG as well.

At this point, Konrad described how The Small Magellanic Cloud became important in measuring astronomical distances.

A certain type of variable star had puzzled astronomers for some time.  These were known as Cepheid Variables after Delta Cephei in the constellation of Cephus.

In 1908 Henrietta Leavitt joined Harvard University in the USA and for a number of years studied Cepheid Variables in the SMC from an observatory in the Peruvian mountains, taking thousands of photographic plates.

Leavitt noticed that their period of fluctuation was related to brightness and since they were all in the same cloud it was reasonable to think they were at similar distances from us.

From this she worked out a mathematical relationship of brightness against period although no Cepheid variables were close enough to the Sun to calculate their distance using parallax.

Konrad introduced Hertzsprung who, in 1913 suggested using the average proper motion of Cepheid variables near the solar system since by then there were enough photographic plates taken over many years.  He calculated, incorrectly as it happened, the distance of the SMC as 30,000 light years.

Harlow Shapley used Cepheids as distance indicators and determined the size of the Milky Way as 300,000 lys, although later corrections brought this to 100,000 light years in diameter.

To conclude Konrad's introduction to the Magellanic Clouds, he described a supernova in the LMC that was observed to take place in 1987, the closest in nearly 400 years.  It has been named SN1987A.

When astronomers looked at previous images of the same area it was found that the progenitor star was a blue super giant around which was a bright ring of material created from its stellar wind.

It is now understood that the plane of this ring slopes back as seen from earth.  It was ionised by the ultra-violet flash from the supernova explosion and consequently began emitting light once the UV reached it several months after the explosion

This light from the nearest part of the ring was detected on earth.  As time passed this light spread round to eventually ionise the entire ring, the delay being caused by the enormous distances involved around the ring and the speed of light.

The size of the ring is known, and using basic trigonometry the distance to SN1987A has found to be about 171,000 lights years.

An excellent talk as one has come to expect from Konrad.

COMMITTEE MEETING

The Committee met on Monday 31st March when the Treasurer announced that at present we have 28 paid-up members, which are down on last year, although the funds remain healthy with £554-62 in our current account and £1,147-73 in the reserve account.

It was proposed that we try and share member's skills and with this in mind the "Help List", which is available at each meeting could be partly used for this purpose.

Phil Berry has written a comprehensive letter on behalf of, and signed by the Committee with regard to objections to the proposed evening lighting of the Wadhurst Tennis Club.  This letter has been forwarded to Wealden District Council.

APRIL MEETING

Wednesday 16th April 2008 Greg Smye-Rumsby gives a talk he has entitled "Astronomical Bits and Bobs".

Greg is a member of the Orpington Astronomical Society and in addition narrates presentations at the Greenwich Planetarium.  He is also well known through his many contributions to the Astronomy Now magazine.

The meeting begins at 1930 although members are invited to arrive anytime after 1900.  This is a good time to exchange ideas and discuss problems.

FUTURE MEETINGS & EVENTS

Wednesday 21st May 2008 Our own Brian Mills who contributes the excellent Sky Notes each month is giving a talk about "Occultations".

During June:  A trip is being arranged to visit the Great Transit Circle at Greenwich Observatory.  This will be either Friday 13th or 20th of June.

Wednesday 18th June 2008 Because this is one of the shortest nights of the year and in recent years this has become a members evening when we can bring telescopes, binoculars and other aids to amateur astronomy to chat about their use and discuss problems.  There will also be a short video on an astronomical subject.  More info. nearer our June meeting.

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  OTHER NEWS

SUBSCRIPTION FOR THE CURRENT YEAR

The current session of the Society began on 1st of January.

The Treasurer, Mike Wyles, is ready to accept subscriptions, which are the same as previous years at £15 per member and £20 for two members in the same family.

Mike prefers to receive a cheque payable to "Wadhurst Astronomical Society" although he will willingly take cash.  If it is more convenient, subscriptions can be sent direct to him at:

Mr. M. Wyles, 31 Rowan Tree Road, Tunbridge Wells, Kent TN2 5PZ

THE "HELP LIST"

At the monthly meetings, Phil Berry has introduced a clipboard with a sheet headed "Help List" intended for anyone asking advice.  It has been used successfully and members are reminded to use the list as much as possible.  It can be useful for discussion purposes as well as hopefully providing answers.

THREATENED CLOSURE OF JODRELL BANK

Jodrell Bank was first used by Manchester University for astrophysics in 1945 and since then has contributed considerably to astronomy, particularly after the building of the Lovell stearable radio telescope in 1957.

The early achievements are well documented but more recently it has obtained distinction worldwide through its research in Long Base Line Interferometry with ongoing MERLIN: Multi-Element Radio Linked Interferometer Network.

Research work that cannot be done successfully at present elsewhere is being made on Pulsars, Background Radiation and astro-chemistry.

SAGAS (The Southern Area Group of Astronomical Societies) has sent the following note:

Jodrell Bank costs approximately £2.5 million a year to operate.  Putting this into perspective, Cabinet Ministers are said to have claimed that amount in expenses during 2007.

The article below gives some information:

http://www.timesonline.co.uk/tol/news/uk/science/article3492504.ece

Should you feel strongly about the proposal and its significant implications for damage to UK Radio Astronomy's high profile around the world, we have been asked to encourage people to write to their local MPs, local newspapers and national broadsheets.

Not everyone will have the time to do that.  However I would urge you to sign the Downing Street petition. (The recent Road Charging petition gained a massive number of signatures and appears to have affected government policy, so this is worth the small effort)

The link to the PM petition is here:

http://petitions.pm.gov.uk/jodrellfunding/

A second petition also aiming to reverse funding cuts proposed for UK Radio Astronomy has also begun.  This could have the effect of splitting the signatures between the two petitions, so you may wish to sign both petitions to ensure maximum impact.

The second petition is: http://petitions.pm.gov.uk/RadioAstronomy/

SKY NOTES FOR APRIL

  Planets

Mercury will only become visible at the very end of the month, very low down in the north west after sunset. Remember never to sweep this area of the sky with optical aid until after the sun is below the horizon. As I mentioned in the February sky notes, the best evening views of Mercury this year will occur in May.

Venus is too close to the Sun for observation this month.

Mars still lies in the constellation of Gemini (the twins) as its magnitude continues to decrease to +1.2. By the end of the month it will set at around 01.30 (02.30 BST).

Jupiter is a morning object low down in the south east at magnitude -2.2 in the constellation of Sagittarius (the archer). By the middle of the month it rises at around 02.00 (03.00 BST).

Saturn is still in Leo (the lion) and is excellently placed for observation at magnitude +0.5. It is on view almost all night, setting at around 03.45 (04.45 BST).

Lunar Occultations

Phases of the Moon for April

Meteors

The Lyrid meteor shower is active from April 19th to 25th with maximum occurring on the 22nd. The radiant in the constellation of Lyra (the harp) is almost circumpolar from the UK, but sadly this year the moon is just past full at the time of maximum when we would expect a zenithal hourly rate (ZHR) of around 10 meteors per hour.

ISS

Graze Occultation

The graze occultation on March 14th that I mentioned in the last newsletter turned out to be a non-event due to almost total cloud cover. Thanks to Geoff who had agreed to accompany me to the sites I had chosen near Headcorn.

Kelling Heath Star Party

Just a reminder for anyone interested, that the annual event at Kelling Heath in Norfolk takes place from Friday 4th April to Sunday 6th April.

Advance Warning

There is a daylight occultation of Mars by the Moon on May 10th at 13.43 BST.

Brian Mills

NASA SPACE PLACE

Tracking Wildlife from Space

by Patrick Barry

It's 10 o'clock, and do you know where your Oriental Honey Buzzard is?

Tracking the whereabouts of birds and other migrating wildlife across thousands of miles of land, air, and sea is no easy feat. Yet to protect the habitats of endangered species, scientists need to know where these roving animals go during their seasonal travels.

Rather than chasing these animals around the globe, a growing number of scientists are leveraging the bird's-eye view of orbiting satellites to easily monitor animals' movements anywhere in the world.

The system piggybacks on weather satellites called Polar Operational Environmental Satellites, which are operated by the National Oceanic and Atmospheric Administration (NOAA), as well as a European satellite called MetOp. Sensors aboard these satellites pick up signals beamed from portable transmitters on the Earth's surface, 850 kilometers below. NOAA began the project-called Argos-in cooperation with NASA and the French space agency (CNES) in 1974. At that time, scientists placed these transmitters primarily on buoys and balloons to study the oceans and atmosphere. As electronics shrank and new satellites' sensors became more sensitive, the transmitters became small and light enough by the 1990s that scientists could mount them safely on animals. Yes, even on birds like the Oriental Honey Buzzard.

"Scientists just never had the capability of doing this before," says Christopher O'Connors, Program Manager for Argos at NOAA.

Today, transmitters weigh as little as 1/20th of a pound and require a fraction of a watt of power. The satellites can detect these feeble signals in part because the transmitters broadcast at frequencies between 401 and 403 MHz, a part of the spectrum reserved for environmental uses. That way there's very little interference from other sources of radio noise.

"Argos is being used more and more for animal tracking," O'Connors says. More than 17,000 transmitters are currently being tracked by Argos, and almost 4,000 of them are on wildlife. "The animal research has been the most interesting area in terms of innovative science."

For example, researchers in Japan used Argos to track endangered Grey-faced Buzzards and Oriental Honey Buzzards for thousands of kilometers along the birds' migrations through Japan and Southeast Asia. Scientists have also mapped the movements of loggerhead sea turtles off the west coast of Africa. Other studies have documented migrations of wood storks, Malaysian elephants, porcupine caribou, right whales, and walruses, to name a few.

Argos data is available online at www.argos-system.org, so every evening, scientists can check the whereabouts of all their herds, schools, and flocks. Kids can learn about some of these endangered species and play a memory game with them at spaceplace.nasa.gov/en/kids/poes_tracking.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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CONTACTS

Chairman   John Vale-Taylor 

Phil Berry  01892 783544

Treasurer  Mike Wyles  01892 542863

Publicity & Website  Michael Harte  01892 783292

Any material for inclusion in the May 2008 Newsletter should be with the Editor by April 28th  2008

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