MEETINGS

JUNE MEETING

        The June meeting is our open evening when members are able to listen to short talks on astronomical subjects given mainly by members of the Society and see instruments used for observing and hear how they are used.  This is also one meeting when members have the opportunity to see and hear what other members’ interests are.

        The meeting was led by our Chairman, John Vale-Taylor who outlined the evening’s programme and then introduced the first talk given by our Director of Observations.

An Introduction to Astronomy

Brian Mills

        Brian discussed questions that non-astronomers regularly asked and he attempted to answer them in simple terms.  He began by looking at the composition of the Earth and Sun and looked at the difference between a star and a planet.  He talked about how to safely observe the Sun and warned about the certainty of blindness if the correct filters were not used when observing.

        Next Brian discussed how the Sun, Moon and Earth move with respect to each other and how they interact by way of tides and eclipses.  We saw that the tilt of the Earth’s axis is solely responsible for our seasons and that the ecliptic is the path that the Sun and planets follow across the sky.

        The sizes and positions of the planets were explained as was the demotion of Pluto to “Dwarf Planet”.

        Everything thing was put into context using slides showing where our solar system sits in the galaxy and a deep-field image from Hubble Space Telescope showed literally hundreds of individual galaxies on it.

An update on John Vale-Taylor’s Telescope Project

John Vale-Taylor

        John updated us on how his telescope project was progressing.

        Following the sad death of Angus MacDonald, a former member of the Society, John had decided to develop an idea that Angus had had to try and make telescopic observation more comfortable for those who hade limited mobility.

        Angus’s idea had been to mount an optically flat mirror at an angle of 45o in front of the open end of a Newtonian reflector to give a view of the entire sky either by revolving the flat mirror or moving the telescope, which was horizontally mounted on a table, in azimuth.  The advantage of this system was that the observer could remain seated all the time since the eyepiece was always at the same height and didn’t change its angular position as it would do in an equatorially mounted instrument.

        John described his telescope which was of the “optical-bench” style whereby all the components were mounted on one small tube and could be moved along it and locked in position.  He demonstrated that the telescope moved easily in azimuth and said that the base of an old “chop-saw” had been used as a donor.

John’s innovative optical-bench style reflecting telescope showing the observing position

Details of the Newtonian flat 45o mirror, the eyepiece assembly and the large flat mirror that makes this method of viewing possible

        During the refreshment break, members were able to inspect John’s telescope and see fine quality of the parts which he had made himself using his engineering skills and in his own workshop.

Sky Notes for June

Brian Mills

        After the break, Brian gave his regular talk about constellation recognition and described what is happening in the sky this and next month.

        He began by showing us the Plough and described how it was possible to locate Boötes and Corona Borealis by first finding Arcturus.  Once Hercules has been found it is possible to use it as a signpost to Scorpio, Libra, Ophiuchus and both parts of Serpens.

        He pointed out that in comparison to the winter sky, the summer sky is comparatively rather dull.

        Brian then updated us about what was happening in the sky this month, beginning with the total lunar eclipse that was in progress as he spoke.  He explained that the Moon would not rise until 2115 BST as seen from Wadhurst and that when it did, the total phase of the eclipse would already be under way.

        The Moon would finally leave the umbral shadow by 2302 BST.

        He then showed a map to explain how to find the planet Saturn that was still on show but was slipping close to the horizon.

        Next were two maps to show the location of Jupiter.  The first showed that on the night of the meeting (technically, the following morning) Jupiter would rise at 0230 BST although on the second map we saw that by the end of July the giant planet would be rising before midnight BST, to become an evening object.

        We were then shown a map of the location of the radiant for the June Boötids meteor shower.  Brian explained that although the ZHR (Zenith Hourly Rate – the predicted hourly rate of meteors if the radiant was immediately over head and not being partly obscured by the horizon) was quite low, this particular shower had suffered outbursts in the past and so was worth a look if the sky was clear.

        Finally we heard that there were several lunar occultations that were suitable for viewing this month.

JULY  MEETING

        Wednesday 20th July 2011 – Our own Phil Berry is giving an illustrated talk about “Nebulae”.

        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

        There is no meeting in August but again Michael and Claire Harte are allowing us to use Greenman Farm to hold an Astro-barbecue on Monday 29th August 2011.  Details will follow in August edition of the Newsletter, but this is certainly a date worth putting in your diary.  It has been a great success in the past with telescopes and a bring-your-own-food-and-drink barbecue.

        Wednesday 21st September 2011 – Bob Seaney will be giving a talk about “The Multi-Universe”, a subject we may well have heard of and Bob’s talks are always worth following.

        Wednesday 19th October 2011 – Our Director of Observations gives a talk about “Registax”, the free star programme from the Internet.

OTHER NOTES AND INFORMATION

PLUTO – THE DWARF PLANET

        At the June meeting there were several short talks - one of which that I gave was entitled “An Introduction to Astronomy”. It dealt with many of the basics of what was in the solar system, what scales and sizes were involved and how things moved. One of the things I talked about was Pluto and how it had been a planet up until 2006 before it was demoted. During the time for questions at the end I was asked what motion had been put to the International Astronomical Union (IAU) that caused Pluto’s fall from grace. I was only able to say that debate and discussion had occurred but other than the three rules which I had discussed earlier in the talk, I could not say beyond that. However, I have done a little research to try and answer the question more fully and show some of the preamble that occurred before the vote was taken.

        Prior to the 2006 General Assembly of the IAU a Planetary Definition Committee had been set up to try and formulate what tests could be applied to a solar system body to determine whether it was a planet or not. The original proposal stated that a body could be classified as a planet if:-

·          Its mass is sufficient for it to be roughly spherical in shape (hydrostatic equilibrium)

·          It is in orbit around the Sun and is not a star or the satellite of a planet.

        This would have brought the count of planets to twelve as Ceres, Charon and Eris would now be included. However, there were many other objects (Vesta, Pallas, Sedna and Makemake to give but a few examples) that may well have had to be adopted at a later date once their characteristics were better known.

        Due to considerable disagreement an alternative proposal was put forward by a Uruguayan delegate that said a body could be described as a planet if:-

·          It is by far the largest body in its local population

·          It’s mass were sufficient for it to be roughly spherical in shape (hydrostatic equilibrium)

·          It does not produce energy by nuclear fusion

        However, despite support for this the original proposal underwent some changes (called the revised draft proposal) that centred mostly (though not exclusively) around binary planet systems and how they were categorized depending on where their centre of gravity lay.

        Then came the final draft proposal which after slight adjustment became the final definition and said that:-

1. A celestial body is a planet if it:

·          Is in orbit around the Sun

·          Has sufficient mass to become nearly round (hydrostatic equilibrium)

·          Has cleared the neighbourhood around its orbit

2. A celestial body is a dwarf planet if it:

·          Is in orbit around the Sun

·          Has sufficient mass to become nearly round (hydrostatic equilibrium)

·          Has not cleared the neighbourhood around its orbit

·          Is not a satellite

3. All other objects orbiting the Sun will be known collectively as Small Solar System Bodies. (This includes asteroids and comets).

        All the above meant that there were now only 8 planets with Pluto becoming not only a dwarf planet but also a “Trans-Neptunian Object” (TNO). In 2008 this category of objects were officially named “Plutoids”. In order to belong to this sub-category of dwarf planets a body must:-

·          Be a celestial body in orbit around the Sun at a distance greater than that of Neptune

·          Have achieved hydrostatic equilibrium

·          Not have cleared the neighbourhood around its orbit

        Pluto, Haumea, Makemake and Eris all now fall into this category.

        The whole process drew widespread criticism partly because only a small percentage of IAU members actually took part in the vote and many did not make the trip to Prague for the general assembly. It was also seen as widely unpopular even with non-astronomers.

SKY NOTES FOR JUNE

Planets

Mercury is a evening object and reaches greatest eastern elongation on the 20th of the month. It is not a good apparition as seen from the UK because at sunset Mercury is only 8° above the horizon just north of west. Given a really good clear horizon and excellent sky clarity it may just be possible to glimpse it. However, please remember that you should never sweep for Mercury with optical aid until after the Sun has set.

Venus is heading for a superior conjunction on August 16th and is too close to the Sun for observation.

Earth reaches aphelion (it’s furthest from the Sun) on 4th of this month.

Mars is a morning object at magnitude +1.4 in Taurus, rising at 0230 BST in the middle of the month.

Jupiter is a morning object in the constellation of Aries, rising at around 0130 BST at the beginning of the month. By the end of the month it is just about an evening object rising at 2350 BST and is magnitude -2.4.

Saturn is still on view in the south west at magnitude +0.9 but by the middle of the month it sets at midnight BST. It’s location is virtually unchanged from last month, remaining close to the star Porrima in Virgo. The ring angle is increasing very slightly as seen from Earth. The diagram shows the position of Saturn close to the western horizon around the middle of the month at 22.00 hrs BST.

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 at more unsociable hours. DD = disappearance at the dark limb and RD = reappearance at the dark limb. I’ve included a diagram to show the position of the bright star CS Virginis when it is occulted on the 9thTimes are in BST.  

July

Time

Star

Mag.

Ph

PA °

8th

2143

SAO 157885

6.8

DD

94

9th

2153

CS Virginis

3.8

DD

100

12th

2144

SAO 185237

6.7

DD

92

12th

2144

39 Ophiuchi

5.2

DD

92.5

12th

2201

SAO 185239

6.6

DD

40

16th

2343

9 Aquarii

6.5

RD

286

23rd

2355

SAO 92905

6.7

RD

202

Phases of the Moon for July

New

First ¼

Full

Last ¼

1st

8th

15th

23rd

30th

 

ISS

        There are no passes of the ISS as seen from Wadhurst that occur before midnight although there are a few that are visible in the early hours.

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.  Times are in BST.

July

Time

Mag

Alt°

Az.

2nd

2255

-3

31

NE

6th

2240

-7

38

NE

7th

2234

-4

40

NE

11th

2219

-3

46

NE

12th

2213

-5

48

NE

15th

2328

-5

15

NNE

18th

2146

-5

55

NE

19th

2140

-4

57

NE

19th

2314

-7

23

NNE

20th

2308

-3

24

NNE

24th

2254

-7

31

NE

25th

2113

-3

64

ENE

29th

2233

-6

38

NE

The Night Sky in July (Written for 2300 BST mid-month)

        In the north the plough is pointing down towards the horizon whilst its smaller companion is standing on its tail. Draco is almost overhead and is ideally situated to allow its line of faint stars to be followed as it weaves between the two bears. Capella may just be seen close to the horizon whilst Perseus is now on view as is the double cluster in the sword handle.

        In the east Pegasus and Andromeda are fully risen whilst the rest of that area of sky is dominated by Deneb, Altair and Vega - the three bright stars of the Summer Triangle.

        In the south we see the comparatively faint constellations of Hercules, Ophiuchus and Serpens, but the exception is the bright star Antares in Scorpio. Antares is distinctly reddish in hue and is easy to identify because of the pattern of the other stars close by. See the attached diagram that shows Antares and the fan shape of stars that accompany it.

        Looking west Leo is just setting with Virgo not far behind and taking Saturn with it. The bright star Arcturus in Boötes is still relatively high in the sky along with Corona Borealis.

Meteor Showers

The Perseids.  This is one of the years most prolific showers although in 2011 there is some interference from moonlight as the night of maximum coincides with full Moon. The limits of the shower are from July 23rd to August 20th with maximum occurring on August 13th. I’ll say more about this shower next month.

Brian Mills

DEFINITIONS OF TERMS USED IN ASTRONOMY

Occultation

        An occultation occurs when a body that is apparently larger obstructs from view an object that is apparently smaller. This term most frequently refers to lunar occultations when the Moon passes in front of a more distant star or planet. These kinds of events occur because as well as the Moon being carried across the sky (from east to west) with everything else due to the earth’s rotation, it has a proper motion of its own when causes it to move gradually west to east. As it does so it sometimes passes in front of more distant bodies. If the object is a star it disappears instantaneously because the Moon has no atmosphere. Such events are comparatively common and number in their hundreds each year if you include (as I do) stars down to 10th magnitude. These are referred to as total occultations.

        Planets can also occult stars as happened last in 1984 but will not happen again until December 4th 2015 when Mercury occults Theta Ophiuchi. On October 1st 2044 we will see the amazing sight of Venus occulting Regulus (Alpha Leonis). Planets can also occult other planets though this is very rare occurrence indeed.

Graze Occultation

        As we’ve seen total occultations are not that uncommon but occasionally the position of the star  is such that it passes so close to the edge of the Moon that it “grazes” the dark limb and can be seen to flash on and off as the mountains and valleys on the Moon pass over it.

Transit

        A transit occurs when a (usually) smaller body passes in front of a (usually) larger body. An example of this would be the fairly recent transits of Mercury and Venus across the face of the Sun or the transits of Jupiter’s satellites in front of their parent planet. Planets can also extremely rarely transit in front of other planets. The last time this happened was in 1818 when Venus transited across the disk of Jupiter - an event that will not be repeated until 2065 when the same two planets will be involved.

        The word transit can also refer to the moment that an astronomical object crosses the meridian. Special transit telescopes exist (at Greenwich for example) that can move in altitude but not in azimuth - they are permanently aligned on the meridian to time the exact moment that an object culminates.

57 LEONIS – THE STAR THAT BLINKED

        You may remember that in the last newsletter I asked for volunteers who would like to attempt the graze occultation observation of a magnitude 6.6 star in the late evening of June 8th. I’m pleased to say that we got together a party of six WAS members who were either going to observe or who were happy to assist in some other way.

        As I said in “Definitions” above, total occultations are not that uncommon but occasionally the position of the star is such that it passes so close to the edge of the Moon that it “grazes” the dark limb and can be seen to flash on and off as the mountains and valleys on the Moon pass over it. If accurate timings of these events can be made and the results sent to the world clearing house in Japan they can be reduced to give valuable data about the exact profile of the limb at that point. In most cases the star must be reasonably bright as it is usually very close to the illuminated portion of the Moon.

        Because stars are so distant their light is considered to be parallel when it reaches us. This means that the star in question effectively casts a full size shadow of the Moon onto the surface of the Earth, so whatever height a mountain is on the Moon, that is the height the “shadow” will be on the Earth. From this you can see that strategically positioned observers on the ground will have the shadow of the lunar mountains and valleys pass over them to hide or reveal the star in turn and sometimes in quick succession. From these observations it is possible to build up a profile of that area of the Moon providing that observers are spread across the track so they are perpendicular to it. The position along the track is not nearly so important, and it would have been just as acceptable for me to observe the event from near my home in Hildenborough provided that I was the same distance from the track as was my actual observing position near Bewl Water.

        One afternoon a week before the event Phil Berry and I spent the afternoon driving and walking around an area close to the Bewl Water reservoir which I had identified from an Ordnance Survey map as possibly yielding some suitable observing sites. We had to be mindful of the azimuth and low altitude that the Moon would be at when the event occurred. I had been sent information from one of the Directors of the Lunar Section at the BAA, with a plot of the track of the mean limb across the country which fortunately passed very close to Wadhurst and occurred at a reasonable time of the night. See the map for our observing positions on the ground - the white line is the mean limb with the main body of the Moon to the south west of the line. This is called a “northern limit” graze as the northern limb of the Moon is involved. The term “mean limb” refers to the imaginary line that is the averaging out of the peaks of the mountains and the dips of the valleys.

           

Showing the 4 observing sites.  To give an idea of scale, the distance between 2 and 3 is about 100 metres.

        As no one else had experience of a graze occultation we decided that Phil using his Celestron would occupy point 1 (right on the track) with Miles Robinson there to help with setting up (there was a long walk from the nearest parking place) and also to watch the event using the Society’s “Ian Reeve” telescope. At point 2 was Ian McCartney with an equatorially mounted 5” refractor. I was at point 3 with a side by side bar fitted to an equatorial to allow me to mount my 5” refractor for visual observation and also a 4” refractor to try to record the event via a video camera. At point 4 was John Wayte with a 6” SCT. The advantage of the three observers being in relatively close proximity was that there was more chance of getting help to them should a problem arise than if we were more widely separated as would normally be the case. The disadvantage was that all three sites were accessed from the same gateway close to point 4 which meant that equipment had to be carried considerable distances. John Vale-Taylor was there to help with setting up and more importantly to be in charge of the timing equipment.

        Timing is fundamental to such observations and I had decided to use a 60 KHz receiver (with an audible output) that picked up the MSF time signals. The signals would then be fed to the other observers via walkie-talkies that had kindly been lent to me by West Kent Raynet. This was fine in theory but in practice I found that the radios would only stay in transmit for one minute before they timed out. This meant John had to juggle two radios and switch one on as the other went off. We were able to record these signals and our comments (when the star went off or on) onto either cassette tape or solid state voice recorders. The radios were also very useful for checking each observer was ok prior to the occultation. One thing that never ceases to amaze me is that time just seems to ebb away so quickly at such events and by the time we were in position and set up the occultation was upon us. I didn’t even have time to set up the video equipment even though the team left Phil’s house at 2115 (the occultation didn’t occur until at 2301). Despite that, three observers managed to get timings with Phil seeing four events and John (Wayte) and myself two each. Ian unfortunately had a drive problem at the critical time. I am currently evaluating our results before I collate them and send them to Japan for them to reduce and hopefully add to others from the same night.

        Despite Wadhurst being a small Society we have made observations of scientific value, which is something we should be proud of. It’s true that there are lessons to be learnt from this event, both about our preparation and methods of timing but that ought not to deter us from trying again. It’s important to learn from mistakes. I would like to thank everyone who took part and also thank Phil and his wife Nicky for once again making their home available to us.

Brian Mills

NASA’S SPACE PLACE

Finding Planets among the Stars

by Dr. Tony Phillips

        Strange but true: When it comes to finding new extra-solar planets, or exoplanets, stars can be an incredible nuisance.

        It’s a matter of luminosity. Stars are bright, but their planets are not. Indeed, when an astronomer peers across light years to find a distant Earth-like world, what he often finds instead is an annoying glare.  The light of the star itself makes the star's dim planetary system nearly impossible to see.

        Talk about frustration! How would you like to be an astronomer who's constantly vexed by stars?

        Fortunately, there may be a solution. It comes from NASA's Galaxy Evolution Explorer, an ultraviolet space telescope orbiting Earth since 2003.  In a new study, researchers say the Galaxy Evolution Explorer is able to pinpoint dim stars that might not badly outshine their own planets.

        “We've discovered a new technique of using ultraviolet light to search for young, low-mass stars near the Earth,” said David Rodriguez, a graduate student of astronomy at UCLA, and the study's lead author. “These M-class stars, also known as red dwarfs, make excellent targets for future direct imaging of exoplanets.”

        Young red dwarfs produce a telltale glow in the ultraviolet part of the electromagnetic spectrum that Galaxy Evolution Explorer can sense.  Because dwarf stars are so numerous—as a class, they account for more than two-thirds of the stars in the galaxy—astronomers could reap a rich bounty of targets.

In many ways, these stars represent a best-case scenario for planet hunting. They are close and in clear lines-of-sight, which generally makes viewing easier. Their low mass means they are dimmer than heavier stars, so their light is less likely to mask the feeble light of a planet. And because they are young, their planets are freshly formed, and thus warmer and brighter than older planetary bodies.

        Astronomers know of more than five hundred distant planets, but very few have actually been seen.  Many exoplanets are detected indirectly by means of their “wobbles”—the gravitational tugs they exert on their central stars.  Some are found when they transit the parent star, momentarily dimming the glare, but not dimming it enough to reveal the planet itself.

        The new Galaxy Evolution Explorer technique might eventually lead to planets that can be seen directly. That would be good because, as Rodriguez points out, “seeing is believing.”

        And it just might make astronomers feel a little better about the stars.

The Galaxy Evolution Explorer Web site at:

http://www.galex.caltech.edu

describes many of the other discoveries and accomplishments of this mission. And for kids, how do astronomers know how far away a star or galaxy is? Play “How Old do I Look” on The Space Place at:

http://spaceplace.nasa.gov/whats-older

and find out!

red-dwarf-system.jpg

Caption:

Exoplanets are easier to see directly when their star is a dim, red dwarf.

        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 August 2011 Newsletter should be with the Editor by July 28th 2011