MEETINGS

FEBRUARY  MEETING

The February meeting was introduced by Phil Berry who told members that during the past month, he and our Chairman, John Vale-Taylor had been invited by the Parish Council to a gathering in order to thank the various local clubs and societies for their work in the Community.

Phil was able to ask about the council’s approach to street lighting with a view to talking about ‘Dark Sky’ friendly lights.  Many of the street lights are relatively good, but one of the problems in the centre of the town is that the street lights there not only light the public areas but are also designed to look aesthetically good and this meant that some of the classic lamps inevitably threw wasted light up into the sky.

He said that the Chairman of the council listened sympathetically and it was agreed that Phil would measure Sky Quality around various parts of the area and report back.

Phil introduced the meeting to our new digital projector which was now much sharper than the one we have been used to and it is now so bright that the lights in the room can be left on.

The first to use the new projector was our speaker Jan Drozd, a Society member, whose talk was called:

Revolutions in Astronomy Jan Drozd

We have had a number of very varied and enjoyable talks from Jan and this was no exception.  He began by saying that as a student he had been fascinated with the development and understanding of astronomy through the ages and was delighted to have this opportunity to give his talk when a previous speaker had to drop out for health reasons.

In ancient times, what we now call ‘science’ was referred to as philosophy which included the natural sciences, mathematics and astronomy; in fact the word ‘astronomy’ only appeared about 1200.

Jan said that although much had been written from the earliest times about the stars, and their positions mapped, it was the Greeks such as Ptolemy who first began to ask why the stars, planets and moon were as they were; even Ptolemy believed that the Earth was naturally the centre of everything.

But it was Francis Bacon who published a book in 1620 that developed the reasoning behind scientific enquiry.  The Scientific Method involved observation, hypothesis, experiment and analysis of the results, and if necessary, creating a new hypothesis, and then experimenting again, and so repeating the process.

We were told about an Arabic philosopher, Alhazan 965 – 1039 who had done a lot of work on optics.  After years of much experimenting, Alhazan arrived at the conjecture that light travels in straight lines.  He considered that the light from the sun could be focused with the use of a parabolic mirror placed on land to set fire to attacking ships in the bay.  Mainly he did a lot to establish the Scientific Method as did Galileo.

As Jan said, it is interesting to consider how the mind-set of thinkers in those far off times influenced beliefs.  Aristotle believed that the planets were perfect spheres and orbited the Earth in perfect circles.  This was well established and the Roman Catholic church believed these teachings to be correct and indisputable.

The retrograde motion of some of the observed planets such as Mars was explained through suggestions that the planets themselves moved in small epicycles.

Also at that time books written by the philosophers had to be hand printed and so very few copies were made and translations had to be prepared and then printed individually.

As Jan said, Copernicus asserted that it was the sun that was at the centre of our planetary system and this answered many questions although there was also great opposition from the church.

But these new suggestions led to historical changes in thought and belief and the Scientific Revolution began to take place from about 1550 and ended with Isaac Newton who proposed universal laws and a mechanical universe.

The Gothenburg printing press was invented in 1440 enabling works by such great thinkers as Galileo, Copernicus and Kepler to be distributed throughout Europe, and so the Age of Enlightenment began.

Then Jan introduced us to two very interesting modern scientific philosophers, Karl Popper and Thomas Kuhn.

According to Popper, one scientific theory was built from previous theories as more was learnt.  No theory is absolutely correct; if a theory cannot be falsified then it is adopted – for the time being.  Einstein once said “No amount of experimentation can ever prove me right but a single experiment can prove me wrong!”

On the other hand Thomas Kuhn argued that scientists work on small associated problems within a framework called a paradigm, although to change the paradigm becomes difficult because it may be in opposition to the thinking of their peers and may be against more orthodox understandings.

Jan said that Kuhn’s definition of a Paradigm drives as:

·          what is to be observed
·          what kind of questions should be asked
·          how these questions should be structured
·          how investigative results should be interpreted

Scientists working within a theory, progress in small steps as anomalies are found but after time, the whole theory becomes woolly and unstable.  Then someone will come along and view the whole theory from a different perspective and see a whole new approach.  The data is then used in a new way and this fresh approach to the theory is called a ‘Paradigm Shift’.

A beautiful way if illustrating this was to use the following sketch shown to us by Jan.

       http://upload.wikimedia.org/wikipedia/commons/4/45/Duck-Rabbit_illusion.jpg

Is this a duck or is it a rabbit?

We were given a number of examples of Paradigm Shifts that have occurred such as the acceptance of Lavoisier's theory of chemical reactions and combustion in place of phlogiston theory, known as the Chemical Revolution.  Another example is the transition between the worldview of Newtonian physics and the Einsteinian Relativistic worldview.

Was Karl Popper’s approach correct or was Thomas Kuhn’s?  Jan left us to judge for ourselves.

Finally, Jan showed this delightfully obscure picture of a cat ‘doing’ a crossword puzzle.

              Cats doing X-word.jpg

He said the cat could never ever understand what a crossword puzzle was, let alone try and solve it and he then said there are most likely things we humans will never know about; things that the human brain would never be able to comprehend.

Jan briefly mentioned Kepler but felt he would leave this for now and from the meeting’s feeling we would welcome a separate talk on Kepler from him in the future if he is willing.

Sky Notes

        This month our Director of Observations, Brian Mills, talked about the Leo region of the sky.  He used the star-hopping method between easily recognised stars to locate objects.

        Brian showed how star-hopping from Castor and Pollux to Regulus at the bottom of the backward ‘question mark’ in Leo made it possible to find M44 about half way between.  This is a loose open cluster about 1.5o across and 590 light years away and containing about 50 members.

        He also talked about a faint star called Groombridge 1830 close to Canes Minor, discovered by Stephen Groombridge from Goudhurst in 1830.  At the time it was thought to have the greatest proper motion.

        Close by is Xi Ursa Major, the first binary system, discovered by William Herschel in 1780, with a period of about 60 years.

        A little further to the east is a binocular object, M3, a globular cluster at 34,000 light years away with half a million stars in it and with a collective magnitude of 6.3.

        Finally Brian talked about Tau Boötes around which one of the first exoplanets to be discovered was found.  It was discovered measuring the wobble of the parent star and looking at the Fraunhofer lines.  It was found to be orbiting in just 3.3 days!  This meant it was a hot planet about 3.7 times the mass of Jupiter.

        The rest of his Sky Notes are covered later in the Newsletter.

MARCH MEETING

        Wednesday 21st March 2012 – There will be a talk by Ben Ritchie called “In Search of the Most Massive Stars”.  This title is a slight change from the one previously advertised.

        Meetings begin at 1930 although members are invited to arrive anytime after 1900 as this is a good time to exchange ideas and discuss problems and also relax before the meeting.

        The venue as always is held in the Upper Room of the Methodist Church at the east end of Wadhurst Lower High Street, opposite the entrance to Uplands College.  (For those with SatNav – the post code is TN5  6AT)

        Anyone is welcome but non-members are asked if they wouldn’t mind contributing £2 towards costs.

FUTURE  MEETINGS

        Wednesday 18th April 2012 – Steve Richards talks about “Making Every Photon Count”.  He has written a book of the same name and it is a beginner’s guide to Deep Space Astro –photography.

        Wednesday 16th May 2012 – To be arranged.

        Wednesday 20th June 2012 – The Society’s Telescope Evening.

OTHER NOTES AND INFORMATION

SUBSCRIPTIONS FOR 2012

        We have now entered the Society’s new session, and again, the subscriptions remain the same as in recent years.  Membership for the year is still £15.00 and £20 for two members within the same family at the same address.  Children and students are free and always welcome.

        Subscriptions can be made at the meetings, preferably by cheque payable to “Wadhurst Astronomical Society” or can be posted to our Treasurer, Michael Wyles at:

31 Rowan Tree Road,  Tunbridge Wells Kent TN2  5PZ

        Visitors to meetings are asked if they wouldn’t mind contributing £2 towards costs.

SPACE ELEVATOR

        We recently had a talk about the possible development of a space elevator using tethers.  Paul Walsh found the following interesting link which shows just where we have progressed to in such a short time:

http://designtaxi.com/news/351720/Japanese-Company-To-Build-World-s-First-Space-Elevator/

SKY NOTES FOR MARCH

Planets

Mercury reaches greatest eastern elongation on the 5th and provides us with the best evening apparition of the planet for this year. The map shows the position of Mercury relative to the western horizon for the first half of March and at the end of civil twilight (the time when the centre of the Sun is minus six degrees). On the evening of the 5th it is at an elevation of 11° at 1820 and shines at magnitude -0.5. It brightens to -1.9 by the 15th although by then it is (apparently) much closer to the Sun as it moves towards inferior conjunction on the 21st. Please remember that you should never “sweep” for Mercury using optical aid whilst the Sun is above the horizon.

Venus is a brilliant evening object at magnitude -4.3 reaching greatest eastern elongation on the 27th. During March its phase decreases from gibbous to fractionally below half whilst its brightness and apparent diameter both increase. Venus moves swiftly eastwards from Pisces, through Aries and into Taurus and on the 13th it is around 3° away from Jupiter. On the 25th, 26th and 27th the slim crescent Moon joins them to provide an excellent photo opportunity.

Earth reaches the Vernal (spring) Equinox on March 20th when day and night are of roughly the same length. The Sun’s apparent path across the sky is called the ecliptic whilst the line of the Earth’s equator projected into space is called the celestial equator. The equinoxes occur where these two great circles on the celestial sphere cross each other as shown in the diagram. Initially this intersection occurred in the constellation of The Ram and was known as “The First Point of Aries”. However, because of the precession of the equinoxes, this point (travelling approximately 1.4° per century) has moved into the neighbouring constellation of Pisces. It takes roughly 26,000 years for one circuit to be completed.

The action of precession is sometimes compared to a spinning top that is running down, but in the case of the Earth, both axes are describing a circle in space. Over time this causes the celestial pole to shift with relation to the stars so that in time Polaris will no longer qualify as the “Pole Star”. 5,000 years ago the star Thuban in the constellation of Draco held that title whilst in 12,000 years time Vega will be the closest star to the north celestial pole.

Mars at magnitude -1.2 comes to opposition on the 3rd in the constellation of Leo when its disk has an apparent diameter of 13.9 arc seconds. The “Red Planet” is currently moving retrograde and does so until April 14th when it begins direct motion (west to east) again. Its position on the first and last days of March are shown in the diagram with the dotted line indicating how to find Leo from Ursa Major.

Jupiter at magnitude -2 lies in Aries where it will stay until after its solar conjunction on May 13th. It is still a brilliant object in the west but now sets before 2300. After its conjunction it moves into neighbouring Taurus where it stays for the remainder of this year and the first half of 2013.

Saturn at magnitude +0.4 is moving retrograde (east to west) in the constellation of Virgo. It remains there until the end of the year when it crosses over the border into Libra. As it moves so slowly I have only indicated its position once, and have used the “Mars” map above to do so. On the 1st it rises just before 2200 but by months end this has become 2045 (BST).

Lunar Occultations

In the table below I’ve listed events for stars down to magnitude 7.0 that occur before midnight although there are many others that are either of fainter stars or occur at more unsociable hours.  DD = disappearance at the dark limb and RB = reappearance at the bright limb.  Times are in GMT unless otherwise stated.

Mar

Time

Star

Mag

Ph

Alt °

%

illu

2nd

1813

SAO 77983

7.1

DD

57

67

4th

2001

SAO 97429

6.1

DD

53

85

5th

2324

Alpha Cancri

4.3

DD

47

92

29th

1231 BST

Zeta Tauri

3.0

DD

20

38

29th

1335 BST

Zeta Tauri

3.0

RB

30

38

The occultation of Zeta Tauri on the 29th should be interesting as it occurs around lunchtime. The star is magnitude 3 but the Moon will be easy to find at an altitude of 20 degrees above the eastern horizon. The star reappears just over an hour later on the bright limb. The diagram shows the position of the star just before disappearance.

Phases of the Moon for March

First ¼

Full

Last ¼

New

1st

8th

15th

22nd

30th

 

ISS

Below is the only evening pass of the International Space Station (ISS) this month that occurs before midnight and is of a reasonable magnitude. The details of all passes including those visible from other areas can be found at:

www.heavens-above.com

Please remember that the times and directions shown below are for when the ISS is at it’s maximum elevation, so you should go out and look a few minutes beforehand . Time is in GMT.

March

Mag

Time

Alt°

Az.

1st

-1.5

1758

28

SSW

Iridium Flares

The flares that I’ve listed are magnitude -3 or brighter although there are a lot more that are fainter, occur after midnight or at a lower altitude. If you wish to see a complete list, or obtain timings for somewhere other than Wadhurst, go to:

www.heavens-above.com

Remember that when one of these events is due it is sometimes possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time. The event on the 27th should be worth watching as -8 is about as bright as Iridium flares can get. Times are in GMT unless otherwise stated.

March

Time

Mag

Alt°

Az.

2nd

1839

-3

51

NNE

13th

2009

-4

49

E

18th

1924

-7

38

N

18th

1949

-6

55

ESE

19th

1918

-3

39

N

19th

1919

-4

39

N

23rd

1928

-4

62

ESE

NEXT

FOUR

ARE

IN

BST

27th

2146

-8

42

ENE

30th

2248

-6

13

NE

31st

2130

-3

47

E

31st

2236

-6

14

NE

The Night Sky in March (Written for 2200 GMT mid month)

In the south the constellations of Leo and Cancer are either side of the meridian whilst below them the long straggling line of stars that make up Hydra (the Water Snake) twists and turns as it makes its way towards the horizon in the south east. On the back of Hydra sit the two small constellations of Crater and Corvus.

Turning to the west, the familiar winter constellations are moving closer to the horizon although the brilliant Capella in Auriga is still 50° high and almost due west. Orion and his retinue are still visible but not for very much longer.

Looking north, the Plough is almost overhead whilst two stars of the Summer Triangle, Vega and Deneb can be seen skimming the horizon. The summer constellation of Hercules has now risen in the north east and Draco is now suitably placed to follow its tortuous shape as it winds between the two bears.

In the east, Boötes, with the brilliant Arcturus, and Corona Borealis have cleared the horizon, as has Virgo with Saturn still within its boundaries.

Advanced Warning for April

3rd - Venus passes close to the Pleiades cluster.

15th - Saturn at opposition.

Brian Mills

DEFINITIONS OF TERMS USED IN ASTRONOMY

Dichotomy

This refers to the moment when exactly half of the planet that is turned towards Earth is illuminated, having the same appearance as a first quarter Moon.

Schröters Effect

When the Earth, Sun and Venus are all in the right geometric positions Venus (as seen from Earth) should be exactly half illuminated. However this is not the case in practice with the phase appearing slightly different to that expected. Dichotomy occurs early at evening elongations and occurs late at morning elongations with the difference being in the region of four days. This is thought to be a phenomenon associated with the atmosphere of Venus.

Ashen Light

This is a very faint light that can be see on the night side of Venus and is similar to Earthshine as seen on the Moon but is much fainter and far less distinct. One suggestion as to its origin is that lightening in the atmosphere of Venus causes illumination across all the globe but it is more obvious on the night side than it would be on the day side.

Don’t forget that GMT ends on Sunday 25th March at 0100 when clocks are advanced by one hour.

Brian Mills

NASA’S SPACE PLACE

The Hidden Power of Sea Salt, Revealed

Last year, when NASA launched the Aquarius/SAC-D satellite carrying the first sensor for measuring sea salt from space, scientists expected the measurements to have unparalleled sensitivity. Yet the fine details it's revealing about ocean saltiness are surprising even the Aquarius team.

"We have just four months of data, but we're already seeing very rich detail in surface salinity patterns," says principal investigator Gary Lagerloef of Earth & Space Research in Seattle. "We're finding that Aquarius can monitor even small scale changes such as specific river outflow and its influence on the ocean."

Using one of the most sensitive microwave radiometers ever built, Aquarius can sense as little as 0.2 parts salt to 1,000 parts water. That's about like a dash of salt in a gallon jug of water.

"You wouldn't even taste it," says Lagerloef. "Yet Aquarius can detect that amount from 408 miles above the Earth. And it's working even better than expected."

Salinity is critical because it changes the density of surface seawater, and density controls the ocean currents that move heat around our planet. A good example is the Gulf Stream, which carries heat to higher latitudes and moderates the climate.

"When variations in density divert ocean currents, weather patterns like temperature and rainfall are affected. In turn, precipitation and evaporation, and fresh water from river outflow and melt ice determine salinity. It's an intricately connected cycle."

The atmosphere is the ocean’s partner. The freshwater exchange between the atmosphere and the ocean dominates the global water cycle. Seventy-eight percent of global rainfall occurs over the ocean, and 85 percent of global evaporation is from the ocean. An accurate picture of the ocean's salinity will help scientists better understand the profound ocean/atmosphere coupling that determines climate variability.

"Ocean salinity has been changing,” says Lagerloef. “Decades of data from ships and buoys tell us so. Some ocean regions are seeing an increase in salinity, which means more fresh water is being lost through evaporation. Other areas are getting more rainfall and therefore lower salinity. We don't know why. We just know something fundamental is going on in the water cycle."

With Aquarius's comprehensive look at global salinity, scientists will have more clues to put it all together. Aquarius has collected as many sea surface salinity measurements in the first few months as the entire 125-year historical record from ships and buoys.

"By this time next year, we'll have met two of our goals:  a new global map of annual average salinity and a better understanding of the seasonal cycles that determine climate."

Stay tuned for the salty results. Read more about the Aquarius mission at:

aquarius.nasa.gov

Other NASA oceanography missions are Jason-1 (studying ocean surface topography), Jason-2 (follow-on to Jason-1), Jason-3 (follow-on to Jason-2, planned for launch in 2014), and Seawinds on the QuikSCAT satellite (measures wind speeds over the entire ocean). The GRACE mission (Gravity Recovery and Climate Experiment), among its other gravitational field studies, monitors fresh water supplies underground. All these missions, including Aquarius, are sponsors of a fun and educational ocean game for kids called “Go with the Flow” at:

spaceplace.nasa.gov/ocean-currents

Description: aquarius-salinity-map.jpg

Caption:

Aquarius produced this map of global ocean salinity. It is a composite of the first two and a half weeks of data. Yellow and red represent areas of higher salinity, with blues and purples indicating areas of lower salinity.

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

CONTACTS

Chairman     John Vale-Taylor

                                                      pjvalet1@btinternet.com

Secretary & Events                 Phil Berry             01892 783544

                                                      philberryemail@gmail.com

Treasurer            Mike Wyles                          01892 542863

                                                      mike31@madasafish.com

Editor            Geoff Rathbone                         01959 524727

                                                      geoff@rathbone007.fsnet.co.uk

Director of Observations       Brian Mills    01732 832691

                                                      Brian@wkrcc.co.uk

Paul Treadaway                       01342 313799

                                                      paul_treadaway@btinternet.com

Wadhurst Astronomical Society website:

                                                      www.wadhurst.info/was/

SAGAS web-site                        www.sagasonline.org.uk

Any material for inclusion in the April 2012 Newsletter should be with the Editor by March 28th 2012