SUBSCRIPTIONS FOR 2011

 

        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 are asked for a £2 donation to any meeting to cover costs.

        Many thanks to those members who have already renewed their subscription.

 

MEETINGS

 

FEBRUARY MEETING

 

        The meeting opened was opened by our Chairman John Vale-Taylor, with an announcement that the family of Angus McDonald, a member who died recently had very kindly donated certain artefacts to the Society. which were greatly appreciated.

        Phil Berry then introduced tonight’s member-speaker, Jan Drozd who is giving his third talk to the Society.  This time he is developing on from the excellent talk he gave in March 2009 called “The Earth and its environment from an astronomer’s perspective”.  Much of his working life was spent with Shell Oil, first as a chemist and then presenting talks on the Environment.

 

Life, the Earth and the Universe

Jan Drozd

 

        To begin his talk, Jan asked the question; What is Life?  How would it start and evolve and is it elsewhere in the Universe.

        He looked first at viruses which exists without any cell structure and then at the basic cell life from such as bacteria and this led to DNA, the molecule of life that contains the genetic instruction for living things.

        Then we looked at the other extreme and at the size of the universe with its estimated 100 to 300 billion stars and was put in perspective when we were told that our nearest star would, using present methods of space travel, take us more than 20,000 years to get there.

        One image taken by the Hubble Space Telescope contained 20,000 galaxies as they were 12 billion years ago.

        To give us an idea of what our own Milky Way galaxy might look like from a distance Jan showed as an example an image of M81.  And then we were shown the most distant picture of our own planet Earth taken by Voyager 1 in February 1990 when it was 4 billion miles away and just before the spacecraft left the Solar system.  Details of this were given in a leaflet Jan handed out.

 

Planet Earth from 4 billion miles taken by Voyager 1

Collection: NASA Planetary Photo Journal Collection

        Looking at the formation of the solar system from a revolving cloud of dust, it was suggested that the Earth was probably created by a shock wave caused by some nearby huge explosion.

        It is thought that the Moon was created when an object that could have been about the size of Mars collided with the Earth.

        Jan showed a time line of the Earth from 4.65 billion years ago with the water coming from volcanic action and from meteors land on the surface.  Life started very soon after the Earth formed at about 4 billion years ago with bacteria dominating.

        About 550 million years ago something called the Cambrian Explosion occurred which resulted in the formation over several million years of higher forms of life.  Animal cells and plant cells appeared and during this period, free-living bacteria began to be absorbed into other cells.

        During the development of life on Earth there have probably been 5 or 6 mass extinctions when some cataclysmic event has wiped out certain life forms, changing the direction of evolution.  Jan said it is thought that during one event 66 million years ago called the Deccan Volcanism in India wiped out the dinosaurs, though conditions remained such that smaller mammals were able to survive.

        On a fairly scary note, Professor Martin Rees recently said that there is only a 50% chance of humans surviving the 21st century!

        Everything is finely tuned for life and certain conditions are necessary such as greenhouse gasses to keep us warm, the magnetic field which generates the earth’s internal convection, volcanism which helps with plate tectonics, the ozone layer which protects us from certain dangerous radiations and the moon which controls the tides.

        Life depends on many fortuitous events.  One of these being that the Earth is in what is called the habitable zone where conditions are just right for human life.  Also major environmental changes have great effects. 

        Jan mentioned S. J. Gould, an American evolutionary biologist and his work on evolutionary development.  Gould proposed a theory that evolution had long periods of stability punctuated with rare instances of sudden changes in direction.  There is much about S. J. Gould on the internet.

        One staggering piece of data is that at the beginning of the last century the Earth’s human population was about 2 billion, but today that stands at 6.5 billion!

        We were shown a graph of the change in the make-up of the history of the Earth’s atmosphere which showed the sudden appearance of oxygen at the same time as a fall in methane which Jan said is thought to have been brought about by photosynthesis of primitive bacteria and resulting in blue-green algae.  This developed into chloroplasts in plant cells.  The oxygen produced resulted in the reduction of oxygen-intolerant bacteria so reducing the production of methane.

        Drake’s Equation looked at the chance of extra-terrestrial civilisations within our own Milky Way galaxy and the Fermi Paradox looked at the contradiction between the number of possibilities and the lack of evidence and asking “Where are they?”  The Earth should have been visited by aliens many times.

        Finally Jan looked at some key barriers to get to technologically developed life:

¯       Non-life to life

¯       Prokaryotic cells (cells without a nucleus) to Eukaryotic cells (cells with a nucleus)

¯       Oxygen photosynthesis

¯       Intelligence

¯       The ability to communicate with life on other planets.

        And Jan’s last picture showed “intelligent life” - drinking from a bottle of beer in the street…

        The talk generated considerable interest that lasted the whole of our coffee break and beyond.

 

MARCH  MEETING

 

        Wednesday 16th March 2011 – The speaker this evening will be Robin Durant FRSA, the chairman of Adur Astronomical Society, a new society covering Hove and Brighton.  Robin’s talk is called “DSLR Astro-photography” which should be well worth hearing as we become more and more aware of the use of available digital cameras to photograph the night sky.

        Meetings begin at 1930 although members are invited to arrive any time 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 20th April 2011 – Details to follow

        Wednesday 18th May 2011 – Details to follow

 

 

OTHER NOTES AND INFORMATION

 

 

SKY NOTES FOR MARCH

 

Planets

 

Mercury reaches its greatest eastern elongation on March 23rd when it will set more than 1½ hours after the Sun, providing its best evening apparition for 2011. Its position above the western horizon is shown in the diagram which also shows the conjunction with Jupiter on the 15th. Please remember that you should never “sweep” for Mercury with optical aid until after the Sun has set - you risk permanent eye damage if you do. After this evening showing the planet suffers an inferior conjunction on April 9th after which it becomes a morning object, although for UK observers that will be an extremely poor apparition.

 

 

Venus at magnitude -3.9 is still a bright morning object in Capricornus but is becoming more difficult as it draws closer to the Sun and the eastern horizon.

 

Mars is not visible this month following its conjunction with the Sun on February 4th. It will be July before it is visible in the morning skies, and November before it becomes an evening object in the constellation of Leo.

 

Jupiter is heading towards a conjunction with the Sun on April 6th and so will probably only be visible for the first two weeks of March low down in the west. It will be visible again as a morning object by May. Interestingly Mercury, Venus, Mars and Jupiter will all lie very close together in the early morning sky around the middle of May, although due to their proximity to the Sun and the angle the ecliptic makes with the horizon they will be very difficult to see.

 

Saturn at magnitude +0.4 rises around 20.45 hrs at the beginning of the month. It is currently moving retrograde (east to west) in the constellation of Virgo, and will continue to do so until June 14th when it reaches its second stationary point. After that it resumes its direct motion (west to east) although it remains in Virgo for the rest of 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. Times are in GMT.  

 

 

Mar.

Time

Star

Mag.

Ph

PA °

11th

22.03

SAO 76588

7.0

DD

52

11th

23.08

Upsilon Tauri

4.3

DD

84

13th

21.14

XZ 85102

6.0

DD

76

13th

21.14

Eta Geminorum

3.5

DD

75

14th

16.33

Zeta Geminorum

4.0

DD

132

16th

22.47

SAO 98400

6.5

DD

144

 

The events on the 13th are for a double star with the fainter of the two components disappearing just over a second before its brighter companion. This should be an easy event to observe and time in a small telescope. The position of the star at the time of disappearance is shown in the diagram.

 

 

 

 

 

Phases of the Moon for March

 

New

First ¼

Full

Last ¼

4th

12th

19th

26th

 

ISS

Below are details of passes of the ISS as seen from Wadhurst that are magnitude -2.0 or brighter. 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 and look a few minutes before. Times are in GMT.

 

Mar.

Mag

Time

Alt°

Az.

1st

-3.6

18.20

80

N

1st

-2.2

19.54

39

W

2nd

-3.6

18.46

79

N

3rd

-3.6

19.11

78

SSW

4th

-3.6

18.01

79

N

4th

-2.8

19.37

42

SSW

5th

-3.5

18.27

75

SSW

6th

-2.6

18.52

40

SSW

8th

-2.2

18.08

38

SSW

 

Iridium Flares

The flares that I’ve listed are magnitude -3 or brighter 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 sometimes 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 apart from the last three.

 

Mar.

Time

Mag

Alt°

Az.

3rd

18.23

-3

54

S

4th

18.17

-4

54

S

11th

19.43

-3

31

N

12th

19.37

-7

33

N

13th

19.31

-3

35

N

21st

18.51

-6

48

N

28th

20.33 BST

-6

15

N

29th

20.27 BST

-6

17

N

31st

20.14 BST

-6

22

N

 

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

In the north Andromeda is setting along with Aries and Triangulum that sit beneath it. The Plough is approaching the overhead point whilst Cassiopeia, on the other side of Polaris, is doing the opposite. The bright star Vega, in Lyra, should just be visible above the north eastern horizon.

In the east Bootes, Corona Borealis and Virgo have fully risen as has the planet Saturn.

In the south Leo and Cancer are either side of the meridian whilst Hydra meanders to the south eastern horizon.

In the west, Orion and his bright retinue are still prominent although they have passed their best. Around this area there are a wealth of clusters and nebulae that are well suited for binocular viewing including the following that are shown in the map:-

 

 

 

M35 - an open cluster in Gemini at a distance of 2,800 light years. It has an apparent diameter of about half a degree which is the same as the Moon. Its magnitude is 5.1.

 

M36 - an open cluster in Auriga that measures around 14 light years across. It lies 4,100 light years distant and is thought to contain 60 members. Its magnitude is 6.3.

 

M37 - another open cluster in Auriga some 4,000 light years away that was rediscovered by Messier in 1764. It is thought to contain around 500 stars and shines at magnitude 6.2.

 

M41 - an open cluster in Canis Major thought to have 100 members. The diameter of the cluster is 25 light years and it is receding from us at more than 23 kilometres per second. Its magnitude is 4.5.

 

M42 - otherwise known as the Great Orion Nebula, it is a diffuse nebula that is a stellar nursery where star formation is taking place. It is 24 light years across and despite being some 1,300 light years away it appears visually to be magnitude 4. It is part of the much larger structure known as the Orion Molecular Cloud Complex which includes Bernard’s Loop and the Horse head Nebula.

 

M45 - is a naked eye open cluster that is much better known as the Pleiades or “Seven Sisters”. It is thought to contain 1,000 members some of which are hot blue stars that are only around 100 million years old. The nebulosity that surrounds them was originally thought to be left over gas from the formation of the stars but it is now suggested that it is part of the interstellar medium that the cluster is currently passing through. The map shows the names and positions of the brightest members.

 

 

C41 - is the other naked eye open cluster in Taurus and is more commonly known as the Hyades. The designation of C41 refers to its entry in the Caldwell catalogue, a collection of deep sky objects that was compiled by Sir Patrick Moore (or Sir Patrick Caldwell-Moore to give him his full title). The Hyades appear much more open than the Pleiades, forming a distinctive “V” shape on its side with Aldebaren at the end of one of the arms. Incidentally Aldebaren is in no way connected with the cluster, it just happens to lie in the same line of sight.

 

NGC 1647 - is an open cluster in Taurus of magnitude 6.4.

 

NGC 2281 - is an open cluster in Auriga of magnitude 5.4.

 

 

Don’t Forget

Clocks go forward by one hour at 01.00 GMT on March 27th.

They change back at 02.00 BST on October 30th.

 

Brian Mills

 

 

DEFINITIONS OF TERMS USED IN ASTRONOMY

 

Limb - This refers to the visible edge of a body, for example the Sun or Moon. In the case of the Moon we can tell that it has no atmosphere because when a star disappears behind the Moon’s limb during a lunar occultation, the light from it is extinguished instantaneously. 

 

Limb Darkening - This phrase is used when talking about stars and refers to the fact that they look less bright close to the limb than they do closer to the centre. There reason for this is that the density and temperature of a star decreases as the distance away from the centre increases.

 

Terminator - This is the line that forms the boundary between night and day and is usually used in relation to the Moon and planets.

 

 

Earthlight - This occurs in those periods in the lunar cycle between new and first quarter and then again between third quarter and new (best during crescent phases) when the unlit portion of the Moon can be seen very faintly illuminated. This is caused by sunlight falling onto the Earth and being reflected back onto the Moon.                     Brian Mills

 

NASA’S SPACE PLACE

 

Thank Goodness the Sun is Single

By Trudy E. Bell

 

It’s a good thing the Sun is single. According to new research, Sun-like stars in close double-star systems “can be okay for a few billion years—but then they go bad,” says Jeremy Drake of the Harvard-Smithsonian Astrophysical Observatory in Cambridge, Mass.

How bad? According to data from NASA’s Spitzer Space Telescope, close binary stars can destroy their planets along with any life.  Drake and four colleagues reported the results in the September 10, 2010, issue of The Astrophysical Journal Letters.

Our Sun, about 864,000 miles across, rotates on its axis once in 24.5 days. “Three billion years ago, roughly when bacteria evolved on Earth, the Sun rotated in only 5 days,” explains Drake. Its rotation rate has been gradually slowing because the solar wind gets tangled up in the solar magnetic field, and acts as a brake.

But some sun-like stars occur in close pairs only a few million miles apart. That’s only about five times the diameter of each star—so close the stars are gravitationally distorted. They are actually elongated toward each other. They also interact tidally, keeping just one face toward the other, as the Moon does toward Earth.

Such a close binary is “a built-in time bomb,” Drake declares. The continuous loss of mass from the two stars via solar wind carries away some of the double-star system’s angular momentum, causing the two stars to spiral inward toward each other, orbiting faster and faster as the distance shrinks. When each star’s rotation period on its axis is the same as its orbital period around the other, the pair effectively rotates as a single body in just 3 or 4 days.

Then, watch out! Such fast spinning intensifies the magnetic dynamo inside each star. The stars “generate bigger, stronger ‘star spots’ 5 to 10 percent the size of the star—so big they can be detected from Earth,” Drake says. “The stars also interact magnetically very violently, shooting out monster flares.”

Worst of all, the decreasing distance between the two stars “changes the gravitational resonances of the planetary system,” Drake continued, destabilizing the orbits of any planets circling the pair.  Planets may so strongly perturbed they are sent into collision paths. As they repeatedly slam into each other, they shatter into red-hot asteroid-sized bodies, killing any life. In as short as a century, the repeated collisions pulverize the planets into a ring of warm dust.

The infrared glow from this pulverized debris is what Spitzer has seen in some self-destructing star systems. Drake and his colleagues now want to examine a much bigger sample of binaries to see just how bad double star systems really are.

They’re already sure of one thing: “We’re glad the Sun is single!”

 

Read more about these findings at the NASA Spitzer site at:

www.spitzer.caltech.edu/news/1182-ssc2010-07-Pulverized-Planet-Dust-May-Lie-Around-Double-Stars

For kids, the Spitzer Concentration game shows a big collection of memorable (if you’re good at the game) images from the Spitzer Space Telescope. Visit :

spaceplace.nasa.gov/en/kids/spitzer/concentration/

 

 

Planetary collisions such as shown in this artist’s rendering could be quite common in binary star systems where the stars are very close.

 

        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 April 2011 Newsletter should be with the Editor by March 28th 2011