MEETINGS

 

MAY MEETING

 

        At the start of the May meeting Phil Berry welcomed new members and visitors to the Society and then reported on the Society’s visit to Herstmonceux on Saturday the 15th of May.  There is a report later in the Newsletter under “News and Information”.

        The June meeting is to be the Society’s Open Evening and Phil outlined what will be happening.  There will be a number of telescopes, binoculars and other astronomical equipment to see and discuss.  There will be short talks and demonstrations of computer software.  Members are also invited to bring along any equipment they wish to show or seek advice on.  We hold this meeting in June each year as it is amongst the shortest nights of the year.

        There is no Society meeting in August, but Phil announced that Michael Harte has very kindly invited us to hold an Astro-barbecue on Saturday the 28th August at Greenman Farm which is just to the west of Wadhurst Railway station from 1900.  All you will need is food to cook on his barbecue and drink and any telescopes if you wish to bring one.  In the past it has been successful and enjoyable and well worth putting in your diary.  More information in the August Newsletter.

        Phil then introduced the evening’s speaker, Simon Allen who is the Secretary of the East Sussex Astronomical Society based at Bexhill-on-Sea.  His talk was thought-provoking and generated quite a number of questions.

 

Space Elevator – Has everyone stopped Laughing?

Simon Allen

 

        Simon explained that the extension to the title of his talk was added because to most people the idea of a Space Elevator, where loads can be lifted into space up a tether is rather bizarre.

        Although the idea had been suggested in the nineteenth century, Arthur C. Clarke wrote about it extensively in 1979.

        To explain the idea Simon began by holding a piece of string on the end of which was a dried up tangerine.  The string was floppy until he whirled it around; the tangerine now acting as a weight and keeping the string taut.  This in essence is what the elevator is all about, but on a rather grander scale to say the least.  In passing, Simon did remind us that the International Space Station is closer than Manchester!

        In 1902 the Wright Brothers demonstrated that flight was possible after all the doubts.  We now take flight for granted, so perhaps we will feel the same about Space Elevators in the same way one day.

        At present, it costs NASA $20,000 per kilogramme to put something into space.  This could be done via an elevator for as little as $200.

        We were introduced to the definition of the Geo-Stationary Point; the height of an object above the Earth’s equator where an object will remain in synchronous orbit above the same point on the Earth’s surface.

        This point would be the centre of gravity for a tether and counter balance at the upper end.  Clarke suggested this counter balance could even be a captured asteroid.

        Apart from a problem of getting the tether established, the next question is what material to use to make the tether from.  Simon related that quite a bit of work has already been done and at present the most likely construction would be the use of Carbon Nano-tubes (CNTs) which are incredibly strong strands.  At present only very short lengths have been made but it is hoped that eventually they can be manufactured into very long structures.

       

 

The Space Elevator
Not to scale

        To produce a tether Simon said it would be necessary to make a ribbon made from carbon nanotubes that would be a metre wide and at present it would take a rocket to get one end up to the geostationary point.

        A continuation of the ribbon would be needed to reach the counterbalance on the other side of the geostationary orbit.

        Looking at the need for a powered lift meant combining some form of engine and a power source based else where.  Simon said the solution being considered was beamed power where the energy source was at ground level then beamed up to the rising lift using parabolic mirrors.

        At present, it is thought that at 200 Km/h it would take about 8 days to reach the geostationary point, but against this would be the fact that the lift would be reusable over and over again.

        The practical plan would be to use platforms on the equator at sea as the ground station.  The “pull” at the ground end of the tether would be very low.

        But one problem that may have to be addressed is the possible induction of electric currents into the ribbon due to carbon nano-tube’s low electrical resistance.  Also mechanical oscillations could develop leaving even more problems to be considered.

        Other setbacks could be radiation from space and the fact that oxygen will attack carbon.  Also, micro-meteorites could be an obstacle although Simon understood this to be quite a low probability of about 200-years.

        With 50 launches a year, the cost could be as low as £135 M.

        There is no re-entry heat to be considered and no escape mechanism would be necessary.

        The advantages would be low cost, no launch vibration, no pay-load envelope restriction, no explosive propellants and the system would be easily expandable having got the first tether in place.  Also, as the top of the lift would virtually always be in sunlight, solar power could be sent down to Earth.  The top station would be an excellent stage for telecommunications.

        Already development is taking place in the United States, Spain, the Netherlands and Japan.

        At the end of Simon’s excellent talk he gave the address of a website where more could be learnt  www.spaceward.org.

 

JUNE MEETING

 

        Wednesday 16th June 2010 - This is the Society’s annual Open Evening when there will be short talks and software demonstrations, together with photographs thought to be of interest.  A number of telescopes and other astronomical aids will also be present to see and hopefully there will be enough expertise to answer any questions.

        It is hoped to attract members of the public who have an interest in astronomy and we may even recruit new members.

        Society members are invited to bring anything along they think may interest others.

        It will be an informal evening and of course biscuits and coffee will be on hand.

        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 talk.

        The venue as always is 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 21st July 1020 – Steve Jackson from Ashford Astronomical Society will be visiting us and giving a talk on “An Introduction to Radio Astronomy”.

 

        Saturday 28th August 2010 – There is no meeting of the Society in August, but as mentioned earlier, Michael Harte is generously inviting us to hold an Astro-barbecue at Greenman Farm.  More details in subsequent Newsletters.

 

OTHER NEWS AND INFORMATION

       

THE SOCIETY’S VISIT TO HERSTMONCEUX

 

        On Saturday the 15th of May, the Society visited the Herstmonceux Observatory Space Centre. 

        Seventeen members and friends turned up which enable Phil Berry, who had organised the day, to obtain tickets with a discount.

 

WAS members in Dome B at Herstmonceux
Photo Brian Mills

        Members were able to spend some time looking round the Science Park and the permanent exhibition before lunching outdoors in the sunshine.

        In the afternoon they were taken on a tour of the facilities which included three domes not normally open to visitors.  All housed telescopes and the tour lasted a good hour and a half.

        Sadly, the historic Isaac Newton facility could not be entered because of the presence of asbestos; something the Park were looking at removing but since it would be self-financing, this would be some time in the future.

        At the conclusion of the tour it was suggested by Herstmonceux that the Society might return for an evening’s observing in one of the domes.

 

BEGINNER’S GUIDE TO OBSERVING THE SUN

 

        Air and light pollution are becoming serious problems in most areas in this country and the ease of observing the night sky has deteriorated dramatically over only a few years.

        One part of astronomy that has not been affected is observing our nearest star, the Sun.  It is still dependant on weather conditions of course but it can be a quite rewarding and is an ever changing subject and a lot can be achieved without spending lots of money.  In fact quite a bit can achieved without spending any money at all.

First of all, never look directly at the sun with the naked eye.  One second and the damage could be for life.  Even an overcast sun in the evening sky can cause permanent damage.

        The sun is a fascinating subject, but I am referring now to what can be seen from Earth.  Although at an average of 92 million miles, we orbit elliptically in 365.25 days a year.  The sun is also rotating and since its axis is at an angle of about 7.5 degrees to the plane of the Earth’s orbit, observing it provides an interesting challenge; added to this is the Earth’s own axial tilt of about 26 degrees.

        The Sun’s axial tilt means the Sun’s north pole is furthest away during the first week in March as seen from the Earth.

        The Sun’s rotation is very interesting.  If one was to observe a sunspot on its equator it would take 27 days to make one orbit but near the pole, it would take 39 days.  Added to this, sunspots in the northern or southern latitudes migrate towards the Sun’s equatorial belt.  These are just some basic facts about the Sun’s face as we see it from Earth.

        Perhaps the cheapest solar observing technique is to use a pin-hole and screen.  Take two pieces of thin card, one with a hole made by a pin and the other needs to be white and is used as a screen.  The size of the hole can be experimented with and the distance between the pinhole and the screen altered to find the most suitable combination.  Not all that good but it can reveal larger sunspots when the hole is pointed towards the sun.  In this way it is possible to see if it is worth getting more equipment out.

        A better way is to use a pair of binoculars on a tripod.  They can be used through a gap in curtains so that the image from the eyepiece projects an image of the sun onto a screen in a darkened room.  This is a great way to see the face of the sun and reveal quite small sunspots.  The greater the distance between the binocular and the screen obviously gives a bigger image but it will become dimmer.  Leaving the lens cap on the eyepiece that cannot be focussed can help.

        There are various filters for observing the sun.  It is always better to use a filter that fits over the object lens so that solar heat doesn’t cause damage to the inside of a telescope.  Mylar reduces the brightness of the sun by a factor of about 10,000 and is suitable for solar observation.  The filter should never be taut because this can stretch and damage it, which might result in loss of its properties.  Mylar gives the image a bluish tinge.

Another sheet filter is made by Baader and costs as little as £15 for an A4 size sheet.  Baader filter produces a much more accurate image colour but again should not be stretched tight.

There are also various ways of looking at the spectrum of the sun and resolving absorption lines.  The most accurate is to use a prism that receives rays from the sun through a narrow sharp-edged slit.  Various lenses bring the spectrum to a focus for either observing with the naked eye or for photographing.  They are expensive but can be home-made.  Details can be found on the internet.

There are two much cheaper, though inferior ways of seeing the lines using an old CD.  One method again uses a slit in a piece of card at one end of a box and then inserting a CD (if there is a label, use the shiny side) at an angle of about 60o so that by looking straight down onto the CD, the eye is directed towards the slit.  It should be possible to make out the Fraunhofer lines, care being taken to avoid looking directly at the reflection of the sun.

The second CD method is again to use a narrow slit on one end of a cardboard tube, but this time using a CD without a label (shiny both sides) on the other end of the tube.  By looking through the CD the Fraunhofer lines should be seen by looking towards the bottom of the tube and not directly at the sun.  I found that breaking a CD and using just a small piece of it makes construction easier, although the piece may need rotating to find the right position for viewing.

A great way to look at the surface of the sun is by using a PST; Personal Solar Telescope.  They can cost over £400 but enable the observer to see prominences and flares, and by using the tuning ring it is possible to retune the Hydrogen-alpha filter to see granulations on the surface and again by retuning, it is possible to see details around sunspots.

 

Geoff Rathbone

 

SKY NOTES FOR JUNE

 

Planets

 

Mercury is not observable this month and will pass through superior conjunction on the 28th. See the “definitions” section for an explanation.

 

Venus is still a brilliant object (at magnitude -3.9) in the western sky after sunset. During June its hours of visibility gradually decrease until by the end of the month it sets at around 23.45 (BST) which is a little over two hours after the Sun.

 

Mars is at magnitude +1.2 and now lies in the constellation of Leo. It is disappearing into the twilight although by the end of the month it still sets two and a half hours after the Sun. On the 7th it passes just north of Regulus, the brightest star in Leo. (See map below)

 

Jupiter is a morning object at magnitude -2.5 in the constellation of Pisces. By the end of the month it rises around forty five minutes past midnight. During July it technically becomes an evening object, rising a little before 24.00 (BST).

 

Saturn at magnitude +1.1 is still in Virgo as shown in the map below but is now moving directly (west to east) after reaching its second stationary point on May 31st.

 

 

Lunar Occultations

As usual in the table I’ve only included events for stars down to around magnitude 7.0 that occur before midnight. DD = disappearance at the dark limb.

Times are all BST.

 

June

Time

Star

Mag.

Ph

PA °

16th

22.00

SAO 117851

6.8

DD

135

19th

22.54

SAO 138716

6.8

DD

129

20th

22.46

SAO 157778

6.9

DD

63

23rd

23.42

SAO 183982

5.4

DD

92

24th

21.55

SAO 184735

6.9

DD

30

 

A partial eclipse of the Moon takes place on June 26th but it is not visible from the UK.

 

Phases of the Moon for June

 

Last ¼

New

First ¼

Full

4th

12th

19th

26th

 

ISS

There are a large number of evening passes of the ISS this month so I have only included those of magnitude -2 or above. There are many more that are fainter or occur after midnight, the details of which can be found at www.heavens-above.com Please remember that the times shown below are for when the ISS is at its maximum elevation, so you should start looking a few minutes beforehand. Times are all BST.

 

June

Mag

Time

Alt°

Az.

23rd

-3.1

23.52

43

SSE

24th

-2.1

22.40

21

SSE

25th

-3.1

23.02

42

SSE

26th

-2.0

21.50

21

SSE

26th

-3.5

23.25

76

SSE

27th

-3.0

22.12

41

SSE

27th

-3.3

23.47

79

N

28th

-3.5

22.35

75

SSE

29th

-3.3

22.57

80

N

30th

-3.4

21.44

73

SSE

30th

-3.3

23.19

78

N

 

Iridium Flares

The flares that I’ve listed are magnitude -3 or above, although some of the brighter ones are quite low down in the sky. There are a lot more flares that are fainter, occur at lower altitudes or after midnight. If you wish to see a complete list, go to www.heavens-above.com   Times are all BST.  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.

 

Jun

Time

Mag

Alt°

Az.

1st

23.42

-4

42

WSW

6th

23.21

-6

40

WSW

9th

23.12

-3

36

W

10th

23.06

-3

37

W

13th

22.58

-7

33

W

16th

22.49

-7

29

W

19th

22.40

-4

26

W

21st

22.37

-6

23

WNW

23rd

22.34

-3

20

WNW

24th

22.38

-6

17

W

25th

22.41

-6

15

WNW

26th

23.33

-5

41

WSW

30th

23.18

-4

38

WSW

 

The Night Sky in June

By 22.00 BST mid month the Plough has passed its highest position and is starting to point its nose down towards the horizon whilst the Little Bear is pointing towards the zenith. Cassiopeia is close to the northern horizon and Draco is well positioned high in the sky allowing its long tail to be identified as it  weaves its way between the Bears. Towards the east all three members of the summer triangle have risen whilst in the west Gemini and Cancer are setting. Looking south Arcturus in Boötes is close to the meridian with Corona Borealis and Hercules nearby with Spica in Virgo a little closer to the horizon. Nearer the horizon but a little to the east is the bright star Antares in Scorpio. From the map below you can see how to use the stars of Hercules to direct you towards Antares.

 

 

Meteors

There are several minor showers that could be worth a casual watch during June.

1.       June Lyrids. These are active from the 10th to the 27th with most activity occurring on the night of 15th/16th although predictions for the number of meteors is very sketchy. The position of the radiant is shown on the map above by the ® symbol close to the star Vega.

2.       June Boötids. This shower is active from June 21st to July 1st with maximum occurring on the night of 23rd/24th. Following outbursts in previous years predictions are unclear but most sources suggest the maximum will be in the order of between 5 and 20 meteors per hour. I have marked the position of the radiant with the symbol ® on the map close to the constellation of Boötes.

 

Comet McNaught

There are suggestions that Comet McNaught could reach naked eye visibility during June. Sadly it will be close to the horizon and then lost to our view by late in the month. It could attain fifth magnitude with one estimate putting it as bright as mag 3.

 

Advanced Warning for July

The Perseid meteors begin on July 23rd.

A total eclipse of the Sun takes place on July 11th and although it is not visible from the UK there are sure to be live feeds available on the internet. The track begins in the South Pacific at 18.10, crosses Easter Island and ends in South America at 22.57 BST. Totality lasts for 5m 20s.

 

Definitions

One of the things that came out of the questionnaire was that it would be useful to explain some of the astronomical terms that we use regularly. With that in mind, if space permits, I plan to add one or two to the end of the sky notes.

 

Inferior and Superior Conjunction

These are terms that we use to describe the planets Mercury and Venus (confusingly called the inferior planets) when either of them line up with the Sun and the Earth. As you can see from the diagram an inferior conjunction occurs when the Earth and either Mercury or Venus are lined up on the same side of the Sun. This is the time to see a transit of either of the inferior planets but this very rarely happens. This is because the orbits of planets don’t lie in exactly the same plane with the result that the planet in question will appear to pass either above or below the Sun. In a superior conjunction Mercury or Venus again form a line with the Earth and Sun but this time the inferior planet is on the opposite side of the Sun to us.

Conjunction

The word conjunction is also used when talking about planets that lie outside the orbit of the Earth - the superior planets. It refers to the alignment of the Earth, Sun and superior planet when the superior planet and the Earth and in line on opposite sides of the Sun. The planet is then said to be in conjunction with the Sun. However when the superior planet and Earth line up on the same side of the Sun it is called opposition and is a favourable time for that planets observation.

 

 

Brian Mills

 

NASA’S SPACE PLACE

 

Ancient Supernova Riddle, Solved

By Dr. Tony Phillips

 

      Australopithecus squinted at the blue African sky. He had never seen a star in broad daylight before, but he could see one today. Was it dangerous? He stared for a long time, puzzled, but nothing happened, and after a while he strode across the savanna unconcerned.

      Millions of years later, we know better.

That star was a supernova, one of many that exploded in our corner of the Milky Way around the Pliocene era of pre-humans.  Australopithecus left no records; we know the explosions happened because their debris is still around. The Solar System and everything else within about 300 light-years is surrounded by supernova exhaust—a haze of million-degree gas that permeates all of local space.

Supernovas are dangerous things, and when one appears in the daytime sky, it is cause for alarm.  How did Earth survive? Modern astronomers believe the blasts were too far away (albeit not by much) to zap our planet with lethal amounts of radiation. Also, the sun’s magnetic field has done a good job holding the hot gas at bay.  In other words, we lucked out.

The debris from those old explosions has the compelling power of a train wreck; astronomers have trouble tearing their eyes away. Over the years, they’ve thoroughly surveyed the wreckage and therein found a mystery--clouds of hydrogen and helium apparently too fragile to have survived the blasts.  One of them, whimsically called “the Local Fluff,” is on the doorstep of the Solar System.

“The observed temperature and density of the Fluff do not provide enough pressure to resist the crushing action of the hot supernova gas around it,” says astronomer Merav Opher of George Mason University.   “It makes us wonder, how can such a cloud exist?

NASA’s Voyager spacecraft may have found the answer.

NASA's two Voyager probes have been racing out of the solar system for more than 30 years. They are now beyond the orbit of Pluto and on the verge of entering interstellar space.  "The Voyagers are not actually inside the Local Fluff," explains Opher. "But they are getting close and can sense what the cloud is like as they approach it."

And the answer is….

“Magnetism,” says Opher. "Voyager data show that the Fluff is strongly magnetized with a field strength between 4 and 5 microgauss. This magnetic field can provide the pressure required to resist destruction."

If fluffy clouds of hydrogen can survive a supernova blast, maybe it’s not so surprising that we did, too. “Indeed, this is helping us understand how supernovas interact with their environment—and how destructive the blasts actually are,” says Opher.

Maybe Australopithecus was on to something after all.

Opher’s original research describing Voyager’s discovery of the magnetic field in the Local Fluff may be found in Nature, 462, 1036-1038 (24 December 2009). The Space Place has a new Amazing Fact page about the Voyagers’ Golden, with sample images and sounds of Earth. After all, just in case one of the Voyager’s ever meets up with ET, we will want to introduce ourselves. Visit:

http://spaceplace.nasa.gov/en/kids/voyager

 

tycho-150.jpg

 

Left-over cloud from the Tycho supernova, witnessed by Tycho Brahe and other astronomers over 400 years ago. This image combines infrared light captured by the Spitzer Space Telescope with x-rays captured by the Chandra X-ray Observatory, plus visible light from the Calar Also Observatory in Spain.

 

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

                                                      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 July 2010 Newsletter should be with the Editor by June 28th 2010