MEETINGS

 

NOVEMBER  MEETING

 

        The meeting began with the sad announcement by our Chairman, John Vale-Taylor that one of our members, Angus Macdonald had died after a long illness.  Angus was an inspiration and will be sadly missed.  There is an obituary to Angus later in this Newsletter.

        Phil Berry led the rest of the meeting and introduced a talk by one of our members, Trevor Grey.

 

It is Rocket Science

 

        Trevor has been a member of the Society for quite some now and gave a good explanatory talk about flight from its origins to Man’s venture into the future of travel and into space.

        He said an alternative title for his talk was “To Infinity and Beyond”, suggesting he would talk about some of the most recent innovations with regard to “flying” into space.

        He began by telling us that he designs and builds free flying model aircraft, not radio controlled, and he said that most space rockets have to negotiate the Earth’s atmosphere to enter space so a certain amount of aeronautical science has to be considered as a prelude to space travel.

        We looked at ancient Chinese rockets, then at Goddard’s early experiments in the 1920s despite very basic knowledge of aerodynamics.

        Early experiments in manned flight were carried out in Russia by German born Lilienthal although they eventually lead to his death.

        Trevor related the story of an Englishman, Sir George Caley who made his coachman fly his experimental airplanes although they were gliders; apparently after one flight, the coachman survived but was never seen again.

        Then we heard about a Frenchman, Oscar Chanute and a Brazilian, Santos Dumont before coming to the Wright Brothers who are generally accepted as the first to achieve conventional flight.  Their significant advance was using powered flight with the ability to control the aircraft.

        Trevor gave a very clear explanation of the fundamentals of aerodynamics beginning with a flat plate moving through an atmosphere.  If the plate is angled upwards in the direction of movement we get lift although very inefficiently.  As the angle increases so does the lift until the stall point is reached and lift fails dramatically.

        Making the plate streamlined and then adding camber greatly improves the efficiency and stability.

        Then we looked at the factors involved in flight; weight, thrust, drag and lift.

        We were told that gliding is the same as powered flight.  By tilting the wing towards the ground, some of the weight begins to provide thrust.

        Designing an aircraft was Trevor’s next consideration where these basic principles are put together.

        Starting with a wing and adding a power source isn’t sufficient as we need to consider pitching moment where there is nothing to hold the wing in steady flight.  We need to add a second wing either behind or in front. In the former case this is called a tail.

        If the overall aerodynamic centre can be made to be behind the overall centre of gravity then there is a tendency towards dynamic stability.

        Other flying examples were shown such as the swept back wing where the tips of the wing are set at a lower angle of attack and act as an effective tail, although making it more difficult to achieve stability.

        The delta wing shape was another example.

        The final consideration was to provide lateral control, the ability to turn left and right, and this is provided by a vertical fin.

        Before Trevor moved on he mentioned in passing the biplane and triplane which were used to overcome the limitations in early engine power.

        Supersonic flight brings new problems to be encountered.  Both lift and drag change with the square of the speed.  Double the flying speed produces four time the lift and four times the drag so a plane flying at 400 mph would have 16 times the lift and drag at 1600 mph; Mach 2.1.

        With a rocket, aerodynamic design still applies whilst in the Earth’s atmosphere and as Trevor pointed out, for a rocket to counteract the Earth’s gravitational field it needs to reach escape velocity, a speed of 16,500 mph.  This is reflected in the rocket’s design.

        We now looked at the Space Plane.  Speeds encountered here are generally above Mach 5 and this lead to a discussion by Trevor of the different forms of propulsion utilised such as the Supersonically Compressed Ram Jet and the Hybrid Rocket Motor, combining liquid and solid fuels.

        But as he says, whatever comes to final practical fruition the ultimate flying machine still has to go through the atmosphere to get out of it; – and land back on Earth if to be reused, so aerodynamics still features in the future of Earth launched space travel.

 

 

DECEMBER  MEETING

 

        Wednesday 15th December 2010 – There is to be a very appropriate talk by our Director of Observations, Brian Mills, who talks about “The Star of Bethlehem”.  This will be followed with hot drinks and mince pies.

        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 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)

 

 

FUTURE  MEETINGS

 

        Wednesday 19th January 2011 – The January meeting is the start of a new session of the Wadhurst Astronomical Society and begins with the Annual General Meeting.  Following this there is a talk by long time member Bob Seaney.  Bob continues his fascinating look at ancient and forgotten megalithic structures in his talk called “Forgotten Circles”.

 

        Wednesday 16th February 2011 – This month member Jan Drozd updates us with a further talk about the environment from an astronomical perspective in his presentation; “Life, the Earth and the Universe”.

 

OTHER NOTES AND INFORMATION

 

 

ANGUS MACDONALD OBITUARY

 

        Angus Macdonald has been an active member of the Society for over five years but had been fighting cancer for some time and sadly lost his battle a few weeks ago.

        Although a distinguished medical consultant by profession he was very much a practical man and in his workshop in Mayfield he produced many innovative ideas such as a method of driving a Dobsonian telescope he had made.  He had an intuitive eye for anything he found lying around, and on this particular occasion he used the controllers from an electric drill to provide the telescope’s drives.

        Shortly after becoming a member of the Society, Angus suggested forming a practical “hands-on” group where members could meet to discuss their practical problems and look for solutions.  This group became known as “The Angus Group” and meets every so often.

        More recently he had been working on a method of using a telescope for observation of the sky from a prone position.  He proposed cleverly driven mirrors allowing an observer to still view the night sky even though disabled or whose movement was severely restricted.

        As a keen amateur astronomer Angus will be greatly missed by members of the Wadhurst Astronomical Society.

 

 

SKY NOTES FOR DECEMBER

 

Planets

 

Mercury is an evening object reaching greatest eastern elongation on the 1st of the month. Sadly for observers in the UK it is far too low in the sky to be observed easily, setting as it does only a few minutes after the Sun.

 

Venus rises nearly four hours ahead of the Sun on December 4th, the day it reaches its maximum brightness of -4.7. In the early morning of December 2nd Venus, Saturn and the Moon are all close together in a small area of the south eastern sky as shown in the diagram.

 

 

 

Mars will suffer a superior conjunction early next year and so, for now, it is too close to the Sun to be seen.

 

Jupiter is still a brilliant evening object at magnitude -2.5 below the square of Pegasus on the border between Pisces and Aquarius. It has completed its retrograde loop and has resumed its direct motion from west to east. It is on the meridian at 21.00 on the first day of the month.

 

Saturn is a morning object (at magnitude +0.8) as mentioned above but by the end of the month it rises just before 01.00. It will technically be an evening object by the end of January 2011.

 

Uranus and Jupiter are again drawing closer as the planets near their conjunction on January 4th 2011.

 

Lunar Occultations

        In the table below I’ve only listed events for stars down to magnitude 7.0 that occur before midnight although there are others that are either of fainter stars or occur  in the early hours.

DD = disappearance at the dark limb whilst RD = reappearance at the dark limb. Times are in GMT.

 

Dec

Time

Star

Mag.

Ph

PA °

7th

16.07

SAO 187080

5.8

DD

116

7th

16.29

SAO 187088

6.7

DD

50

13th

17.03

GSC00578 01213

4.9

DD

75

13th

17.04

SAO 174092

4.9

DD

87

19th

17.13

SAO 76588

7.0

DD

127

 

Phases of the Moon for December

 

New

First ¼

Full

Last ¼

5th

13th

21st

28th

 

ISS

        Below are details of passes of the ISS as seen from Wadhurst that are brighter than mag. -1.5. The details of all passes including those visible from other areas can be found at www.heavens-above.com Please remember that the times shown below are for when the ISS is at it’s maximum elevation, so you should be able to see it for a few minutes before and after these times.  Times are in GMT.

 

Dec.

Mag

Time

Alt°

Az.

27th

-1.7

17.53

19

SSE

28th

-2.1

18.17

30

SSW

29th

-1.7

17.08

19

SE

29th

-1.2

18.41

24

WSW

30th

-2.8

17.32

40

SSE

31st

-1.6

16.21

20

SE

31st

-3.7

17.56

74

SSE

 

Iridium Flares

        The flares that I’ve listed are brighter than magnitude -3 although there are a lot more that are fainter or occur after midnight. 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 often possible to see the satellite in advance of the “flare”, although of course it will be much fainter at that time.  Times are in GMT.

 

Dec

Time

Mag

Alt°

Az.

3rd

18.12

-8

34

SSE

4th

16.49

-6

20

SSW

6th

16.46

-6

17

SSW

7th

17.57

-5

33

SSE

8th

17.33

-6

14

WNW

9th

17.18

-5

17

WNW

10th

17.03

-6

20

WNW

14th

16.21

-4

28

W

15th

17.27

-7

28

S

26th

16.58

-5

17

SSW

30th

17.24

-5

18

WNW

 

Lunar Eclipse

        There is a total eclipse of the Moon on Tuesday December 21st which is unlikely to be widely observed because it occurs in the early morning as the Moon is setting. The partial phase begins at 06.32 with totality lasting from 07.40 until 08.53, though unfortunately for us the Moon sets at 08.14. How much you will be able to see of the event will depend on local conditions - haze and mist etc and how low a horizon you have to the north west.

 

Meteors

        The Geminid meteor shower lasts from December 7th to the 16th with maximum predicted for the early hours of the 14th when the ZHR could be as high as 100.

 

        There is a first quarter Moon that will interfere but it is well into the west even at 22.00 on the night of maximum. Watches are worthwhile earlier in the shower as the Moon will be even further to the west and will also have a slightly smaller phase.

 

The Ursids are active from December 17th to the 25th with maximum on the night of the 22nd. The ZHR is only 10 and with the Moon just past full, observations are likely to be limited.

 

 

The Night Sky in December

        Looking east at 22.00 around the middle of the month sees Leo just rising whilst Orion and his retinue are all now readily on view. The two dogs, Canis Major and Minor, along with Taurus and Gemini dominate the south eastern sky. The South is much less crowded with the large and relatively faint constellations of Cetus and Eridanus still on the meridian. In the west the stars of the Summer Triangle take their last bow. Altair has already set, Vega is close to the horizon and only Deneb is easily visible. The Square of Pegasus is also in the west meaning that it too will soon be lost from the evening skies. In the north Ursa Major is “standing on its tail” whilst its smaller companion is pointing down towards the horizon. Cassiopeia on the opposite side of the pole has passed the overhead point and is just west of the meridian.

 

Advance Warning for January

Partial eclipse of the Sun on the morning of January 4th.

Conjunction of Jupiter and Uranus on January 4th.

Quadrantid meteor shower at maximum around midnight on January 3rd.

 

What’s Happening in 2011

Apart from the events mentioned above the following are some of the more important dates:-

 

Early January - Good morning apparition of Mercury.

Late March to early April - best evening apparition of Mercury.

11th May - Grouping in the dawn skies of Mercury, Venus and Jupiter.

15th June - Total lunar eclipse - the Moon rises during totality.

Late August to early September - Good morning apparition of Mercury.

8th October - Possibility of a meteor storm from the Draconids.

10th December - Total lunar eclipse - at moonrise totality is already over.

 

Brian Mills

 

 

DEFINITIONS OF TERMS USED IN ASTRONOMY

 

Lunar Eclipse

        An eclipse of the Moon occurs when the Sun, Moon and Earth are all aligned, with the Earth in the centre so that the Moon passes into the shadow cast out into space by the Earth. When this alignment is precise the Moon becomes fully immersed in the Earth’s shadow (the umbra - position B in the diagram) to give us a total eclipse but if only part of the Moon moves into this central shadow then we see a partial eclipse. On occasions the alignment is such that the Moon only passes through the outer (penumbral) part of the shadow (position A in the diagram) and at these times the change in the Moon’s appearance is so small that it could easily be overlooked.

 

 

        A total eclipse only occurs when the Moon is full because at that time it is opposite the Sun in the sky. If there is a full Moon every month then surely it follows that there should be an eclipse every month? As we know that isn’t the case and the reason is that the orbital planes of the Earth and Moon do not quite coincide. In fact the differ by only just over five degrees but this is enough to allow the Moon to pass either above or below the Earth’s shadow cone.

 

 

 

 

        During a lunar eclipse it is normal to be able to see the Moon throughout the event as it turns a red/copper colour particularly during the total phase. This is caused by sunlight falling onto the Moon after it has been refracted (bent) by the Earth’s atmosphere which tends to scatter longer wavelengths of light more, leaving the red light to pass through. The depth of colour of the eclipsed Moon is dependant on the state of the Earth’s atmosphere, so that at times of volcanic eruption for example when there is more dust in the air, the shorter wavelengths of light are scattered even more leaving red as the predominant colour. However there have been times when the atmosphere was heavily polluted and the Moon was invisible even in a telescope. It follows that if the Earth had no atmosphere then the Moon would always disappear during a total eclipse although of course we wouldn’t be here to see it!

 

Solar Eclipse

        An eclipse of the Sun occurs when the Moon passes between the Sun and Earth so that all three are in a line. If the conditions are just right the Moon will exactly cover the Sun to give a total eclipse - a very rare phenomenon for any given location on Earth. Sometimes though we see a partial eclipse which is when the Sun looks as if a chunk has been taken out of it, and this occurs when the Moon passes just above or just below the point of perfect alignment (as on January 4th 2011). The reason is as I said earlier is that the orbits of the Earth and Moon do not quite coincide. Solar eclipses always occur at new Moon when it’s sunlit side is turned fully towards the Sun (and fully away from us) although in most instances of new Moon it will pass either above or below the Sun and be invisible at that time.

 

 

        Solar eclipses happen because of a mere coincidence - the Sun is 400 times more distant than the Moon but the Sun is 400 times larger than the Moon. This means in approximate terms they appear the same size in the sky. However, the orbits of both the Earth and the Moon are not circles but ellipses meaning that the Moon and Sun both vary in distance and therefore in apparent size. Due to this variation sometimes the Moon does not appear large enough to completely hide the Sun, leaving a thin ring of sunlight shining around the Moon. This type of eclipse is called “annular”.

        One of the highlights of a total solar eclipse is being able to view the Corona - the Sun’s outer atmosphere - because this is the only time that it is visible apart from with specialist equipment. The shape of the corona varies depending on where the Sun is in its eleven year cycle of activity.

 

Please remember that you must never look at the Sun with any kind of optical aid - if you do you risk permanently blinding yourself. The safest way to view a solar eclipse is to use the “glasses” that became popular during the 1999 total eclipse. They are normally made of cardboard and have filters made from special material that cuts out almost all of the light and heat from the Sun.

        If you have a telescope or binoculars you can try the “projection” method as shown in the diagram but you must take care that no-one else can use them who doesn’t realise the dangers. If you use binoculars, you need only use one half of them but cover the lens that is not in use. This method is possible without the instrument being mounted but you will find in much easier if you have a tripod that you can fix the telescope or binoculars too. Bear in mind that you will need to constantly move them to keep up with the Sun as it rises. Remember also that if your telescope has a “finder” (a smaller telescope attached to it) that will also need to have a cover over the front lens.

 

 

 

 

        Of course you could revert to the simplest method of all - the pinhole. This is where you make a small hole in a piece of card and allow the sunlight to pass through it onto another piece of card held behind it. The card with the hole in casts a shadow onto the second card which helps to make the Sun’s image easier to see. The image will be upside down exactly as it would in a pinhole camera.

 

 

 

 

Brian Mills

 

 

NASA’S SPACE PLACE

 

Blue Rings around Red Galaxies

by Trudy E. Bell and Dr. Tony Phillips

 

        Beautiful flat rings around the planet Saturn are one thing—but flat rings around entire galaxies?

        That is the astonishing discovery that two astronomers, Samir Salim of Indiana University at Bloomington and R. Michael Rich of UCLA described in the May 10, 2010, issue of The Astrophysical Journal Letters.

        “For most of the twentieth century, astronomers observing at visible wavelengths saw that galaxies looked either ‘red and dead’ or ‘blue and new,’” explained Salim. Reddish galaxies were featureless, shaped mostly like balls or lentils; bluish ones were magnificent spirals or irregular galaxies.

        Elliptical galaxies looked red, astronomers reasoned, because they had mostly old red giant stars near the end of their life cycles, and little gas from which new stars could form. Spiral and irregular galaxies looked blue, however, because they were rich in gas and dust that were active nurseries birthing hot, massive, bluish stars.

        At least, that's how galaxies appear in visible light.

        As early as the 1970s, though, the first space-borne telescopes sensitive to ultraviolet radiation (UV) revealed something mysterious: a few red elliptical galaxies emitted “a surprising ultraviolet excess,” said Rich.  The observations suggested that some old red galaxies might not be as “dead” as previously supposed.

        To investigate, Salim and Rich used NASA’s Galaxy Evolution Explorer satellite to identify 30 red elliptical galaxies that also emitted the strongest UV. Then they captured a long, detailed picture of each galaxy using the Hubble Space Telescope.

        “Hubble revealed the answer,” says Salim. The UV radiation was emitted by enormous, flat bluish rings that completely surrounded each reddish galaxy, reminiscent of the rings of Saturn. In some cases, the bluish rings even showed a faint spiral structure!

        Because the bluish UV rings looked like star-forming spiral arms and lay mostly beyond the red stars at the centres of the elliptical galaxies “we concluded that the bluish rings must be made of hot young stars,” Salim continued. “But if new stars are still being formed, that means the red-and-dead galaxies must have acquired some new gas to make them.”

        How does a galaxy “acquire some gas?”  Salim speculates that it was an act of theft. Sometimes galaxies have close encounters. If a gas-rich irregular galaxy passed close to a gas-poor elliptical galaxy, the gravity of the elliptical galaxy could steal some gas.

        Further studies by Galaxy Evolution Explorer, Hubble and other telescopes are expected to reveal more about the process.  One thing is certain, says Rich: “The evolution of galaxies is even more surprising and beautiful than we imagined.”

        The press release is available at:

http://www.galex.caltech.edu/newsroom/glx2010-03f.html

        The full published article is “Star Formation Signatures in Optically Quiescent Early-Type Galaxies” by Samir Salim and R. Michael Rich, The Astrophysical Journal Letters 714: L290–L294, 2010 May 10.

        Point the kids to the Photon Pile-up Game at :

http://spaceplace.nasa.gov/en/kids/galex/photon

where they can have fun learning about the particle nature of light.

 

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

 

 

 

Caption:

The Galaxy Evolution Explorer UV space telescope helped to identify red elliptical galaxies that also emitted the strongest UV. These are detailed, long-exposure Hubble Space Telescope images of four of these galaxies that capture the UV-emitting rings and arcs indicative of new star formation.

 

CONTACTS

 

Chairman     John Vale-Taylor

                                                      pjvalet1@btinternet.com

 

Secretary & Events                 Phil Berry             01892 783544

                                                      phil.berry@tiscali.co.uk

 

 

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

 

Wadhurst Astronomical Society website:

                                                      www.wadhurst.info/was/

 

SAGAS web-site                        www.sagasonline.org.uk

 

Any material for inclusion in the January 2011 Newsletter should be with the Editor by December 28th 2010