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Wadhurst Astronomical Society
Newsletter
August 2016
REPORT ON THIS YEAR’S SAGAS SUMMER CONVENTION
Some members attended the SAGAS (Southern Area Group of Astronomy Societies) Summer Convention held this year at
Southwick near Hove on Saturday the 16th of January in the Barn Theatre.
There were a series of five talks given by leaders in their field of astronomy. William Joyce talked about the Moon in a totally different
one to the talk he gave us in July. Professor Lucie Green brought us up to date on the physics of the Sun and other talks covered
subjects such as Dark Matter and Energy and the birthplace of stars.
SAGAS holds a convention each year and everyone is invited with a reduction in the entry fee for members of Wadhurst
Astronomical Society and is well worth going to.
Professor Lucie Green talks about the Sun
MEETINGS
THE JULY MEETING
The July meeting was opened by Phil Berry who began with the exciting news that the Dark Skies Survey he performed in 2012 and
the Street Lighting Survey he performed in 2014 have been used by the Parish Council in a bid to obtain an award. As a result
Wadhurst has been awarded the full £10,000 sum by the Sussex Community Foundation towards replacing poor quality street
lighting in the area with new a new improved less light-polluting installation. It is hoped that the Parish Council will match the award
with £10,000 to be spread over the next two years.
Phil then introduced our speaker, William Joyce who is a qualified astrophysicist and also a planetary scientist, a FRAS, and a
Chartered Physicist, currently engaged in research at a London university, studying the Moon and until recently was the in-house
astronomer at the Herstmonceux science centre.
Observing the Moon
William Joyce
We began by looking at how we see the Moon by eye relative to the landscape of the Earth. We can probably make out the ‘seas’
but we certainly can’t see the craters without the use of a good pair of binoculars or a telescope. The mass of the Moon is just over
1% that of the Earth and reaches a temperature during the lunar day of 120 o C at the hottest part but at night that temperature drops
to around -170o C. At the poles the highest temperature reaches about -30o C and falls to as low as -245o C.
William described the Moon’s orbit as being very complex with changes due to the influence of the Sun, although he did say that
overall; the Moon is increasing its distance from the Earth by 3.8 cm per year.
He described the Moon/Earth system as having the centre of gravity within the Earth itself with one lunar orbit taking 27.3 days.
Another aspect of the Moon’s orbit is that we only see one face, although due to changes in the orbital plain and positions in the orbit
we manage to see about 59% of the face. This effect is called Libration.
William also talked about the Moon’s effect on the Earth’s oceans, causing the tides and also described how the tides are affected by
the Sun’s gravity which when in line cause higher tides.
From talking about the movement of the Moon William now turned to the fascinating side of the Moon’s geology.
He described how, in the early stages of the Moon’s existence huge impacts caused lava to flow out into what we now see as the
‘marias’ or seas and this material over time has darkened. Much later, small impacts caused craters with much lighter material being
visible. It was also mentioned that there are no lava-filled impact craters on the far side of the Moon.
He described in great detail how some of the older craters have had newer impacts within them and how astronomers have been
able to say how their affect has influenced the floors and walls of the older impact craters.
Some more recent impacts have thrown material far over the surface. Tycho for example is about 100 million years old, has a crater
diameter of 86 km and is 4.8 km deep with a central peak 1.6 km high and material from its impact was thrown as far as 1,000 km,
forming rays of lighter material radiating out.
Tycho’s rays – NASA/HST
William looked at areas where there have been large lava flows such as Sinus Iridum where the very old surface has few newer
impact craters and some finer surface features reveal themselves on photographs taken with the Sun at a low angle.
Sinus Iridum – NASA image
Lunar rilles – NASA image
We were told that some lava flows created tunnels which have now partially collapsed, creating rills and caves that show up on
images as odd landscapes. Other strange features William introduced us to were Swirls of very light coloured material and appear
not to be impact craters but could be associated with them. It has also been discovered that they exhibit high local magnetic fields.
We looked back at early photography of the Moon, the first astro-photograph of the surface was taken by an English-American
scientist, John Draper in about 1840 who was born in Lancashire but worked in New York USA. We were shown several images of
the Moon taken at various phases showing how much more detail can be seen when the Sun is at a very low angle at the Terminator.
One remarkable photograph showed the International Space Station silhouetted against the Moon. William said that this was
particularly good at showing the contrast in colour between the seas.
We now turned to solar eclipses made possible because of the relative visual size of the Sun and the Moon being almost exactly the
same, resulting in it being possible to see a total solar eclipse when the Moon was nearest the Earth in its orbit and an annular
eclipse when the Moon doesn’t exactly cover the Sun’s disk. William said that much has been learnt about both the Sun and Moon
from eclipses.
In 1959, the Russian Luna 3 spacecraft imaged the far side of the Moon for the first time and William compared that with a much
more recent image taken by the Lunar Reconnaissance Orbiter in 2009. There appear to be far less large impact craters and no
seas resulting from lava flows.
Finally, William showed all the landing sights made so far by all nations and labelled with their relative positions on the nearside of
the Moon’s surface and one final slide showed the Apollo 11 landing sight taken in very high resolution by the Lunar Reconnaissance
Orbiter.
Apollo 11 landing site taken by
NASA’s Lunar Reconnaissance
Orbiter
William pointed out that tonight’s meeting is exactly 47 years to the day since the landing of Apollo 11 on the Moon!
Snippets from the World of Science
John Wayte
Rosetta
The European Space Agency’s Rosetta Mission will shortly be coming to an end, but here is one of the remarkably detailed images of
the Khonsu region which is the area between the two main parts of the comet, taken from a height of 11.7 km.
Khonsu region – ESA image
Comet 67P – ESA image
The ESA has a number of videos relating to the comet. They can be found by going to the ESA website and selecting ‘videos’. The
two shown tonight were:
ESA video of achievements
Where is Rosetta now?
The final date for the mission is scheduled for 30 th of September 2016. The main reason is that the charging cells of Rosetta are now
picking up so little sunlight that it will start to lose power.
The intention is to have enough power that the very clever people at the European Space Agency can perform as soft a landing on
the comet as they can. They will be taking masses of close up photographs as they close in on the surface.
Because of the size of the charging cells it is considered very unlikely that they will survive the landing, undamaged.
There was some consideration of putting it into deep sleep but they considered Rosetta would not have survived the intense cold of
deep space without its heaters.
Planning the soft landing is far more complex and dangerous due to the ever decreasing elliptical orbit necessary for the final descent
but the data and very detailed photographs taken during this time will be well worth the effort. Rosetta is currently on an elliptical
orbit of 27 x 9 km but this will gradually decrease over the next few weeks.
The actual landing speed will be about 50 cm/s (about 1.1 mph), about half that of Philae in November 2014.
Commands will be uploaded to automatically switch off all transmitters and instruments to fulfil spacecraft disposal requirements.
This event ends the spacecraft’s operations – now starts years of scientific analysis of the data!
NOTE!
There is no meeting in August. Our next meeting will be on Wednesday the 21 st of September
FUTURE MEETINGS
21st September 2016 – We welcome back Melanie Davies who will be talking about “The Pleiades”. This is a change from our
earlier programme of talks.
19th October 2016 – Dr David Whitehouse returns to tell us about what we might encounter on a “Journey to the Centre
of the Earth”.
16th November 2016 – Jan Drozd tells about “A History of Man’s Understanding of Our Universe”.
14th December 2016 (NB the second Wednesday of this month) – Brian Mills FRAS talks about “Local Astronomers”.
SKY NOTES FOR AUGUST 2016
Planets
Mercury is currently an evening object and will reach greatest eastern elongation (27°) on August 16 th. Unfortunately, the long twilight
at this time of the year and the proximity of the ecliptic to the horizon means that the planet will be extremely low down and difficult to
observe. Its position is shown in fig 1 on the night of elongation with the planet just 5° high at sunset. Mercury then moves back
towards the Sun reaching inferior conjunction in mid September, after which it becomes a morning object. Please note that if you
are sweeping for Mercury then you must remember not to do so until after the Sun has set. You risk blindness if you
inadvertently look at the Sun using any optical aid.
When we talk about the angle at greatest elongation, east on this occasion, we are referring to the planets greatest apparent
distance, in degrees, from the Sun. Obviously observation is easier the larger this angle becomes. In the case of Mercury the
maximum angle at elongation can vary between 18° and 28° (because of its highly elliptical orbit) but for Venus it varies between just
45° and 47°. This means that, at times, Venus is far enough from the Sun to be seen in a dark sky whereas Mercury cannot.
Venus becomes visible to naked eye observers towards the end of the month, although binocular and telescope users will have been
able to find the planet in mid July. If you have a reliable go-to mount then the task is simple and safe, but if not please note that the
warning given above for Mercury is just as relevant here. The planet’s elongation, and therefore its observability as described
above, improves by the day with this figure being 15° at the start of the month and 23° at the end although it will not reach greatest
elongation until early next year. At magnitude -3.9 Venus should be a moderately easy target, something that will be an advantage on
August 27th. On that day two planets, Jupiter and Venus, will pass just 4' (four arc minutes) apart. The closest approach occurs after
they have set, but if you look at sunset (19.55 BST) you should be able to see the brilliant Venus almost due west with the fainter
(mag. -1.7) Jupiter just to the left of it. Fig 3 shows the situation at the above time when the two bodies are 10' (ten arc minutes)
apart. Of course the other option is to observe them in close proximity in the afternoon, although the earlier warning must be heeded
if you don’t have go-to or are not proficient with setting circles.
Mars is still an evening object visible quite low down in the south to south west. Its brightness falls from -0.7 to -0.3, and its apparent
size from 13” to 10.5” (arc seconds) as the Earth pulls away from it.
The red planet is moving swiftly eastwards and spends most of August in Scorpio apart from a brief excursion into neighbouring
Ophiuchus. Fig 4 shows the position of Mars on the evening of the 24th when it lies almost directly on a line between Saturn and the
red star Antares, whose name rather appropriately means “Rival of Mars”. Don’t forget that if you look earlier in the month it will be
further west (to your right).
Jupiter may be visible to the naked eye briefly in the early part of this month but it will quickly be lost in the twilight as it moves
towards a solar conjunction at the end of September. Venus will act as a good signpost to it on the 27 th as described above. If you
haven’t observed the four Galilean moons then they are visible with binoculars provided that they can be tripod mounted or supported
in another way. Following conjunction, Jupiter becomes visible as a morning object in mid October low down in the east before
sunrise. However, it will be late January 2017 before the gas giant is visible in the evening skies once more.
Saturn currently lies in Ophiuchus and begins the month moving retrograde until it reaches its second stationary point on the 13 th.
Following this it moves slowly eastwards as it regains its direct motion once more. The ringed planet lies due south at 21.00 BST at
the beginning of the month and has set by 01.00. By the end of August the planet will be lost to view by 23.00. Saturn’s north pole
remains tilted towards us by 26° providing us with excellent views of the upper surface of the ring system. This angle will increase
slightly as the year progresses.
Lunar Occultations
In the table below I’ve listed events for stars down to magnitude 7.0 that occur before midnight although there are many others that
are either of fainter stars or occur at more unsociable hours. DD = disappearance at the dark limb whilst RD = reappearance at the
dark limb. The column headed “mm” (millimetres) shows the minimum aperture telescope required for each event. Times are in
BST.
August
Time
Star
Mag
Ph
Alt °
% illum.
mm
7th
21.22
ZC 18.49
6.1
DD
10
24
40
14th
20.46
ZC 2699
6.8
DD
18
86
100
14th
21.53
SAO 161665
7.0
DD
20
86
110
16th
00.59
ZC 2865
5.7
DD
16
93
70
Phases of the Moon for August
New
2nd
First ¼
10th
Full
18th
Last ¼
25th
ISS
Below are details for passes of the International Space Station (ISS) that occur before midnight and are magnitude -2 or brighter. The
details of all passes, including those visible after midnight, can be found at www.heavens-above.com. Please remember that the
times and directions shown below are for when the ISS is at it’s maximum elevation, so you should go out and look at least five
minutes beforehand. Times are in BST.
Aug.
1st
1st
2nd
2nd
3rd
4th
4th
Time
21:28:58
23:05:25
22:12:21
23:48:28
22:55:45
22:02:40
23:38:19
Mag.
-3.4
-3.3
-3.3
-3.3
-3.4
-3.3
-2.5
Alt°
70°
78°
79°
65°
89°
80°
40°
Az.
SSE
N
N
WSW
N
N
WSW
Aug.
5th
6th
7th
8th
9th
10th
Time
22:46:00
21:52:56
22:36:08
21:43:05
22:26:08
21:33:07
Mag.
-3.4
-3.4
-2.9
-3.2
-2.0
-2.6
Alt°
69°
88°
45°
64°
27°
40°
Az.
SSW
S
SSW
SSW
SSW
SSW
Iridium Flares
The flares that I’ve listed are magnitude -2.0 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 before and after the “flare” although, of course, it will be
much fainter at those times. Times are in BST.
Aug.
3rd
6th
7th
8th
12th
13th
17th
18th
19th
Time
23.01
21.18
22.47
22.41
22.26
20.45
22.05
21.59
21.53
Mag.
-4.6
-5.6
-3.1
-3.4
-4.2
-5.8
-3.7
-3.9
-2.0
Alt°
24°
63°
32°
32°
38°
71°
45°
45°
46°
Az.°
35° (NE)
68° (ENE)
42° (NE)
44° (NE)
50° (NE)
87° (E)
58° (ENE)
60° (ENE)
63° (ENE)
Aug.
20th
23rd
23rd
24th
26th
27th
30th
30th
Time
23.01
21.39
22.54
21.33
22.45
22.39
21.06
22.31
Mag.
-5.5
-3.5
-6.2
-4.6
-4.2
-2.5
-8.3
-7.0
Alt°
10°
52°
16°
52°
21°
21°
59°
26°
Az.°
23° (NNE)
69° (ENE)
32° (NNE)
72° (ENE)
40° (NE)
42° (NE)
85° (E)
48° (NE)
The Night Sky in August (Written for 22.00hrs BST mid month)
In the north the sixth brightest star in the night sky, Capella, is climbing away from the horizon although, from the south of
England it never sets. A little north of it lies a pair of open clusters, NGC 1528 and NGC 1545 of magnitudes 6.4 and 6.2 respectively,
that actually belong to neighbouring Perseus. North of Capella we find the small and faint group of stars that constitute
Camelopardalis and contain the magnitude 5.7 open cluster NGC 1502 into which Kemble’s Cascade seems to flow. Both Cepheus
and Cassiopeia lie to the east of the meridian whilst to the west we find the two bears and Draco the dragon. Draco has a number of
faint galaxies within its borders plus the magnitude 8.8 planetary nebula (NGC 6543) known as the “Cat’s Eye”. It has a central star of
brightness 9.5 that can be easily seen with a moderate sized telescope. It was first observed by William Herschel in 1786 and later
investigated spectroscopically by William Huggins in an attempt to prove such objects were gaseous. Now is a good time to look for
the Cat’s Eye as its altitude is just under 75°.
Looking east we find that Pegasus and Andromeda are now prominent with the great spiral already at an altitude of 30°.
Below the winged horse, Pisces is clearing the horizon bringing Uranus with it, and a little to the west is Aquarius that has Neptune
within its borders. Just beyond the horse’s outstretched neck is the globular cluster, M15, at magnitude 6.4. Its age has been
estimated at around 12 billion years, making it one of the oldest globulars known. It is a conglomeration of some 100,000 stars, many
of which are densely packed towards the centre, and is only one of a handful of globulars known to contain a planetary nebula. Just
west of Pegasus is the small constellation of Equuleus within which at this time can be found the magnitude 9.3 asteroid (2) Pallas.
The Summer Triangle sits astride the meridian, due south with Vega just 12° from the zenith. In fact the overhead point lies
within the boundary of the dragon at this moment in time. Two small groups, Sagitta and Vulpecula, lie within the Triangle, the latter
of which contains Collinder 399, alternatively known as Brocchi’s Cluster, or more appropriately the Coathanger Asterism. The Milky
Way rises from the southern horizon, where the rich star fields of Sagittarius can be found, and passes through Scutum, Aquila and
along the spine of the celestial swan providing excellent views of our own galaxy with the Sun now well out of the way at -14°.
Towards the west Arcturus in Boӧtes is still 30° in altitude, providing one of the pointers to the rather faint constellation of
Hercules. The other pointer is Alphekka, the brightest star in Corona Borealis. A line drawn through the two and continued
northwards will reach the quadrilateral of stars in the strong man known as the “Keystone”. Currently the head of the dragon lies
almost due west and points in the general direction of Hercules.
As I said above, now is an excellent time to look for the Milky Way. If you wait a little later, until 23.00 mid month, the Sun will be
more than 18° below the horizon which means that we have true darkness once more at night. If you can find a site away f rom
artificial lights then your view of our galaxy will be even better, but do allow plenty of time for your eyes to “dark adapt”. If you are
looking from less than perfect skies, the best area is around Cygnus as it is high in the sky and least likely to suffer from light
pollution. See fig 5 for an impression of the Milky Way as it passes through the Summer Triangle area.
Meteors
The Perseids are active from July 23rd until August 20th with maximum occurring on August 12th at 12.00 BST (lunchtime). In view of
this it would be wise to observe on both the night of 11 th/12th and 12th/13th. The Moon will interfere in the later stages of the shower
although on the night of maximum it sets at 01.00. At this time of night, and of the year, the ecliptic is low so that at least the altitude
of our nearest neighbour will be limited.
The position of the radiant, the point where the meteors appear to radiate from, lies not far from the double cluster in the “sword” of
Perseus (see fig 6). Due to the length of time that the shower takes place over, the radiant appears to move a little due to our
passage around the Sun. The radiant, however, is not the best place to look as the meteors that are seen close to it tend to be quite
short. I tend to look east of the radiant around the Pegasus/Cygnus area because I have had more luck there than looking west
towards Ursa Major, although generally speaking the meteors can be seen of an extremely large area of sky. Perseids are known for
their high velocity (around 60 kilometres/sec) and for the number of bright events that leave ionised trains behind them, sometimes
for a few seconds.
The best time to observe is after midnight because by then the Earth has rotated so that it is facing into the stream of material that
will hopefully meet the atmosphere and burn up. The zenithal hourly rate (ZHR) is around 80, but this assumes a perfectly dark sky
with the radiant at the zenith (overhead point). All things considered we could reasonably expect to see, on average, one meteor
every minute or so. The best way to observe is to lie on a sun lounger with the head end raised slightly, so you can look at your
selected area of sky without any neck strain, and point it roughly towards the east or north east. If your view isn’t hindered too much
by trees or buildings, you can be aware of a surprisingly large area of sky. If the Moon hasn’t set then position yourself so it is
obscured from your field of view.
Advance Warning
Annular eclipse of the Sun – September 1st.
This is not visible from the UK but will be available to watch on the web from a variety of sources if you do a search.
Penumbral eclipse of the Moon – September 16th.
Already in progress when the Moon rises at 19.15. The effects of a penumbral eclipse are very subtle and it is unlikely that you will
perceive the Moon to be noticeably darker than normal.
Brian Mills
SPACEPLACE - NASA
This article is provided by NASA Space Place.
With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages
everyone to get excited about science and technology.
Visit spaceplace.nasa.gov to explore space and Earth science!
Venus and Jupiter prepare for their close-up this August
By Ethan Siegel
As Earth speeds along in its annual journey around the Sun, it consistently overtakes the slower-orbiting outer planets, while the
inner worlds catch up to and pass Earth periodically. Sometime after an outer world—particularly a slow-moving gas giant—gets
passed by Earth, it appears to migrate closer and closer to the Sun, eventually appearing to slip behind it from our perspective. If
you've been watching Jupiter this year, it's been doing exactly that, moving consistently from east to west and closer to the Sun ever
since May 9th.
On the other hand, the inner worlds pass by Earth. They speed away from us, then slip behind the Sun from west to east, reemerging in Earth's evening skies to the east of the Sun. Of all the planets visible from Earth, the two brightest are Venus and
Jupiter, which experience a conjunction from our perspective only about once per year. Normally, Venus and Jupiter will appear
separated by approximately 0.5º to 3º at closest approach. This is due to the fact that the Solar System's planets don't all orbit in the
same perfect, two-dimensional plane.
But this summer, as Venus emerges from behind the Sun and begins catching up to Earth, Jupiter falls back toward the Sun, from
Earth's perspective, at the same time. On August 27th, all three planets—Earth, Venus and Jupiter—will make nearly a perfectly
straight line.
As a result, Venus and Jupiter, at 9:48 PM Universal time, will appear separated by only 4 arc-minutes, the closest conjunction of
naked eye planets since the Venus/Saturn conjunction in 2006. Seen right next to one another, it's startling how much brighter Venus
appears than Jupiter; at magnitude -3.80, Venus appears some eight times brighter than Jupiter, which is at magnitude -1.53.
Look to the western skies immediately after sunset on August 27th, and the two brightest planets of all—brighter than all the stars—
will make a dazzling duo in the twilight sky. As soon as the sun is below the horizon, the pair will be about two fists (at arm’s length)
to the left of the sun’s disappearance and about one fist above a flat horizon. You may need binoculars to find them initially and to
separate them. Through a telescope, a large, gibbous Venus will appear no more distant from Jupiter than Callisto, its farthest
Galilean satellite.
As a bonus, Mercury is nearby as well. At just 5º below and left of the Venus/Jupiter pair, Mercury achieved a distant conjunction with
Venus less than 24 hours prior. In 2065, Venus will actually occult Jupiter, passing in front of the planet's disk. Until then, the only
comparably close conjunctions between these two worlds occur in 2039 and 2056, meaning this one is worth some special effort—
including travelling to get clear skies and a good horizon—to see!
Image credit: E. Siegel, created with Stellarium, of a small section of the western skies as they will appear this August 27th just after
sunset from the United States, with Venus and Jupiter separated by less than 6 arc-minutes as shown. Inset shows Venus and
Jupiter as they'll appear through a very good amateur telescope, in the same field of view.
To teach kids more about Venus and Jupiter, visit the NASA Space Place web pages titled “All About Venus”
[http://spaceplace.nasa.gov/all-about-venus/en/] and “All About Jupiter” [http://spaceplace.nasa.gov/all-about-jupiter/en/].
CONTACTS
General email address to contact the Committee
[email protected]
Chairman
Brian Mills
Secretary & Events
Phil Berry
Treasurer
John Lutkin
Membership Secretary
John Wayte
Newsletter Editor
Geoff Rathbone
Director of Observations
Brian Mills
Committee Members
Jim Cooper
Eric Gibson
01892 783544
01959 524727
01732 832691 email: [email protected]
Wadhurst Astronomical Society website:
www.wadhurstastro.co.uk
SAGAS web-site:
www.sagasonline.org.uk
Any material for inclusion in the September 2016 Newsletter should be with the Editor by August 28th 2016