The Southern Astronomer - October 2016 edition

The Southern Astronomer No.97 – October 2016

SOUTHERN ASTRONOMER THE

MONTHLY MAGAZINE OF WORTHING ASTRONOMERS & WORTHING SKYWATCHERS

The Southern Astronomer No.97 – October 2016

WORTHING ASTRONOMERS No fees, no Committee; just enjoying the night sky together.

F

ormed in 2008 by a group of regular and practical observers, Worthing Astronomers is a free to join society now with a membership of about 450 persons, who have a common interest in Astronomy and its associated subjects – no internal politics, no fees, no committees, just astronomy!

The Southern Astronomer This Issue

Our aim is simple – to bring astronomy to the public in general and to help and assist our membership in observing the night sky.

With the aid of this newsletter, website, social media, regular star parties, workshops and public observing events we hope to encourage and share our interests in observing the sky with the public, our colleagues in our own group and with those of neighbouring astronomical societies.

We try and meet at least once a month (when weather conditions allow) to do some observing but we do hold every two months a Workshop evening when we get a chance to meet up, exchange ideas and tips and help each other to make the most of observing the sky above us. Occasionally a guest speaker will talk about an aspect of practical, hands on astronomical observing or photography.

Astronomy This Month

…............

p.3

Observing Planets

…............

p.4

The Sun; The Moon

…............

p.5

Meteors & Comets

…............

p.6

Variable Stars

…............

p.8

Constellation of the Month: Cepheus

………….. p.9

Monthly Sky Chart: InOMN Observing

………….. p.10

Cover Picture & Comment With the evenings drawing in, there is now more opportunity for us to get out and enjoy looking at the night sky.

These Workshop evenings are held on the first Friday of every other month (February, April, June, August, October and, December) at Goring Methodist Church Hall, Bury Drive (off of Aldsworth Avenue), Worthing, BN12 4XB. The admission charge of £3 helps pay for the room and free refreshments and goes towards supporting our membership. Doors open at 7.00 pm with the meeting starting at 7.30.

We kick off with the first weekend of the month being a busy one for us, the Workshop on Friday followed on the Saturday and Sunday by public outreach events associated with the International Observe The Moon Night.

There are some meteor showers to observe this month – moonlight may interfere with one or two but, something to see if the sky is clear.

We can be found at: worthingastronomers.org.uk

The cover picture is by John Slinn and appropriately for October it is the Witches Broom Nebula NGC 6960 in Cygnus.

Hope the weather is good for flying on the 31st!

You will notice also that there are some advertising features in this issue. We are blessed as a group to have three members who supply astronomical equipment to the wide world so perhaps it is a good idea for members who might be thinking buying new, upgrading or looking for additions to what they might have to look in and see what our trading members can give.

There are several astronomical groups in the coastal area of Sussex - several WA members are also members of the Adur Astronomical Society, who meet every first Monday of the month for a lecture regarding an astronomical subject. Details for AAS can be found at Adur Astronomical Society

David, Paul and Zoltan will, I know, be only too happy to help any one with their equipment inquiries.

CONTRIBUTIONS AND UNSUBSCRIBING Contributions – written articles (word processed in .txt, .doc or .odt format), photographs, letters, advertising copy to the editor for the November issue should be in by October 15 and sent to the editor at the contact address: editor@worthingastronomers.org.uk

Contact addresses: info@worthingastronomers.org.uk – general society details Brian Halls

If you no longer wish to subscribe to the group and cancel newsletters and other information, please send an email to: info@worthingastronomers.org.uk with 'Unsubscribe' in the subject line; we do not want our stuff to end up like spam littering your inbox.

treasurer@worthingastronomers.org.uk – donations contact Janet Halls

Volunteers are always welcome: if you want to find out more, call 01903 521205 or drop us a line at the e-mail address above.

website@worthingastronomers.org.uk – contact for website Perry Wilkins

If you like the newsletter or its content please feel free to distribute it to anyone you know who might be interested. Content is subject to copyright to the group and/or the individuals whose images or articles are used.

editor@worthingastronomers.org.uk – newsletter content detail Brian Halls

outreach@worthingastronomers.org.uk – events contact Steve Bassett, Mike Williams

2

The Southern Astronomer No.97 – October 2016 Earth (perigee) than when it is furthest in its orbit (apogee). *

ASTRONOMY

THIS MONTH

The result of this produces a varying synodic period – but this is a difference measured in only a few hours.

October 2016

Another term one will come across is the lunar sidereal period. This is the time taken for the Moon to move from one point in the sky and return to it a lunar month later. This period is 27 days 7 hours 43minutes. However, as the Earth is moving through space in its orbit around the Sun, this period is ‘dragged’ out to become the synodic mentioned previously.

All times are expressed as Universal Time (UTC – Co-ordinated Universal Time) and can be considered the same as GMT (i.e. BST minus one hour.)

The clocks ‘fall’ back from Summer Time to GMT on the early morning of October 30.

*To be absolutely accurate, the Earth and Moon orbit each other around their common centre of gravity – which does lay below our planets crust, so the term ‘..orbiting the Earth..’ is not all that misleading.

Now we are well past the Equinox, we start to see darker mornings and evenings. The new observing season has begun.

DEEP SKY OBJECTS

QUICK VIEW DIARY 1 3 4 7 8 9 15 16 17 22 27 30 31

Sunrise 06.04h : Sunset 17.43h New Moon (00.13h) Moonrise (06.18h) Venus 4.9S of Moon (20h) Moon at apogee – furthest in its orbit from Earth (10h) WA: Workshop Evening International Moon Observing Night (see page 5/11) Moon: First Quarter (04.35h) Moonrise (13.49h) Public Moon Observing Night (see page 5/11) Uranus at opposition (10h) Full Moon: (04.25h) English trad. Harvest Moon Moonrise (17.41h) Moon at perigee – closest to Earth in its orbit (0h) Moon: Last Quarter (19.16h) Moonrise (22.42h) Mercury at superior conjunction (16h) BST ends; GMT begins (UK only) Moonrise (06.15h) New Moon (17.39h) Sunrise 06.53h : Sunset 16.41h Moon at apogee (19h) OCTOBER MOON PHASES

As with September, the calendar month and the phases of the Moon synchronise closely with a New Moon occurring just after midnight on October 1.

SUBJECT TYPE

Constellation

MAG

RA (h m)

DEC (° ' )

NGC7662

Planetary Neb

Andromeda

8.6

23 25.9

+42 32

NGC7686

Open Cluster

Andromeda

5.6

23 30.1

+49 08

NGC7585

Galaxy

Aquarius

11.4

23 18.0

-04 39

NGC7606

Galaxy

Aquarius

10.8

23 19.1

-08 29

NGC7721

Galaxy

Aquarius

11.6

23 38.8

-06 31

NGC7723

Galaxy

Aquarius

11.2

23 39.0

-12 58

NGC7727

Galaxy

Aquarius

10.6

23 39.9

-12 18

NGC7654

Open Cluster

Cassiopeia

6.9

23 24.2

+61 35

NGC7635

Bright Neb

Cassiopeia

11

23 20.2

+61 11

NGC7788

Open Cluster

Cassiopeia

9.4

23 56.7

+61 24

NGC7789

Open Cluster

Cassiopeia

6.7

23 57.4

+56 43

NGC7790

Open Cluster

Cassiopeia

8.5

23 58.4

+61 13

Mrk50

Open Cluster

Cepheus

8.5

23 15.3

+60 28

NGC7235

Open Cluster

Cepheus

7.7

22 12.6

+57 17

NGC7261

Open Cluster

Cepheus

8.4

22 20.4

+58 05

NGC7380

Open Cluster

Cepheus

7.2

22 47.3

+58 08

NGC7510

Open Cluster

Cepheus

7.9

23 11.5

+60 34

IC1434

Open Cluster

Lacerta

9

22 10.5

+52 50

NGC7209

Open Cluster

Lacerta

7.7

22 05.1

+46 29

NGC7243

Open Cluster

Lacerta

6.4

22 15.1

+49 54

NGC7245

Open Cluster

Lacerta

9.2

22 15.3

+54 20

NGC7177

Galaxy

Pegasus

11.2

22 00.7

+17 44

NGC7217

Galaxy

Pegasus

10.1

22 07.9

+31 22

NGC7331

Galaxy

Pegasus

9.5

22 37.1

+34 25

NGC7332

Galaxy

Pegasus

11.1

22 37.4

+23 48

NGC7448

Galaxy

Pegasus

11.7

23 00.1

+15 59

NGC7454

Galaxy

Pegasus

11.8

23 01.1

+16 23

NGC7479

Galaxy

Pegasus

10.9

23 04.9

+12 19

NGC7619

Galaxy

Pegasus

11.1

23 20.2

+08 12

NGC7626

Galaxy

Pegasus

11.1

23 20.7

+08 13

NGC7678

Galaxy

Pegasus

11.8

23 28.5

+22 25

NGC7742

Galaxy

Pegasus

11.6

23 44.3

+10 46

NGC7769

Galaxy

Pegasus

12

23 51.1

+20 09

NGC7541

Galaxy

Pisces

11.7

23 14.7

+04 32

NGC7562

Galaxy

Pisces

11.6

23 16.0

+06 41

PATRICK’S ASTRONOMICAL PEARLS OF WISDOM “This feature on the Moon is called The Straight Wall. It’s called that because it’s NOT straight and it’s NOT a wall.”

It takes the Moon 29 days 12 hours 44 minutes, on average, to go from one new Moon to the next. This time frame is called a synodic month. We say average as the synodic alters a little due to the fact that the Moon’s orbit around the Earth is actually an ellipse rather than a perfect circle and the Moon moves in its orbit around the Earth a bit faster when it’s closer to

3

The Southern Astronomer No.97 – October 2016 Advertisement

OBSERVING THIS MONTH:

PLANETS S

ome of the brighter planets have vacated the evening sky – Jupiter already sets before the Sun while Mars and Saturn are low in the west after sunset and will set soon after the Sun. The two outer planets Uranus and Neptune, though not bright objects are the main planets that can be seen in the night sky – Uranus is there for the whole night! Though they are in the southern sky which is not well placed this time of year they can be seen with a small telescope or binoculars.

Visibility of the planets and Moon, mid-month

For a bright object to observe, the planet Venus which is steadily making itself apparent in the twilight sky is the object to lookout for.

observed. The view of the planets diagram on the next page shows the size of Venus compared with the rest of the planets

Mid-month, its phase will look a little like a gibbous Moon when seen through a telescope or even a powerful pair of binoculars. Shining at -3.9m it will brighten to -4 by the end of the month and brightens still further as time progresses over the autumn and early winter. The angular diameter of the planet is about 13” (arc seconds). Depending on the telescope, some phase detail might be

The best time to observe the planet is while the evening sky is still bright – the planet can dazzle in a darkened sky. If possible and one has working setting circles or an aligned telescope with a ‘goto’ facility, the planet can even be picked up in daylight – though at the moment Venus is less than 15° from the Sun so I would not recommend doing a ‘sweep’ for it unless you have some

4

experience in doing this – damage to the eyesight of the unwary may occur even if the Sun is only momentarily caught in the eyepiece! Wait until early evening when the Sun has either set or is low in the sky and blocked from view by roof tops.

If you have some coloured eyepiece filters these can be used as well. The light blue 80B filter is good, as is the yellow 15; these can enhance views of any cloud detail that might appear on Venus. I try and use the 80B when conditions allow as I find this appears to steady the image of the planet

The Southern Astronomer No.97 – October 2016

The planets mid-month (comparative angular diameters) – timed at 21.30UT when viewed in atmospherically wobbly conditions.

SUN OBSERVING

The planet of course makes a good object for anyone using a planetary camera to capture views of it especially as its angular diameter is enlarging.

I

t is sometimes easy to overlook the fact that ‘stargazing’ also includes the Sun – it is the nearest star in the sky to us after all.

Last month we observed a pair of groups crossing the Sun and wondered if they would return. They did – the were just peaking over the eastern solar limb on August 31 and crossed the face of the Sun during the first two weeks or so of September.

The weather overall has not been kind to astronomers and Brian States who had a 92 day solar observing run had the weather break that during the first week of September.

As usual, combining our data for the month and averaging it, the WA sunspot number for August was 42.5 (AAVSO 42.3; WDC 50.7).

Venus in March 2012

© Brian Halls

MOON OBSERVING

INTERNATIONAL OBSERVE THE MOON NIGHT his popular annual event is once more upon us and occurs during the evening of October 8 (the night after our Workshop).

T

Because the Workshop evening precedes the event (we normally observe on the Friday) we shall be out on the evening of October 9 as well.

Information on what to look at and see is on page 11.

HYADES OCCULTATION During the late night of October 18 and the morning of October 19, the Moon passes through the Hyades open cluster in Taurus, occulting some of the stars in the group as it does so.

Some of the stars are close doubles so as the Moon passes in front of the brighter of the binary pair, it will fade slightly showing that the star is not a single pin point of light.

Sunspot activity was very much northern solar hemisphere this month. Brian States observed on 31 days in August. He recorded five days as being spotless and the ‘spottiest’ day was August 9 when The Hyades is quite an open cluster, the waxing he recorded a daily sunspot number of 65.

Moon will be bright (-87%) so proving a problem for As usual sunspot activity is low due to the recent photography. An interesting event, none the less. unusual minimum in sunspot activity.

5

The Southern Astronomer No.97 – October 2016

METEORS & COMETS T

Delta

his month we are lucky to have several meteor showers to contend with.

The Draconids are a short lived shower – starting on October 6, maximum on the morning of the October 8 and dying out on the 10th. Moonlight is not likely to be a problem with the first quarter moon. The average rate (ZHR) is variable but they do produce slow meteors.

The Delta Aurigids seem to follow on from the Draconids. They start about October 9 come to a rapid maximum on the late evening of October 10 finally petering out on the 17th. A bright waning Moon may cause problems for the descending phase of this shower. The ZHR is two!

The Piscids are a shower that has three maximum that occur during the late summer. The tertiary portion of the Piscids reaches maximum early on the morning of the 13th. The ZHR is low.

The Epsilon Geminids start around October 14, reach a maximum on the 17th – ZHR 3 – and come to a finish about the 27th. Moonlight makes this difficult meteor shower even more of a problem this year.

Later in the month we have the Orionids. They begin to appear from mid month until about October 30 with a maximum between the 21st and 24th. Moonlight is waning about this time so the chances of witnessing a ZHR of 25 is good with the BAA putting this shower down as ‘quite favourable.’

Aurigids, epsilon Geminids and Orionids

FOR SALE

Celestron NexStar 4SE - brought new, used maybe 12 times. Comes with 10mm, wide eye relief 25mm and a Barlow lens and. More of an astrophotographer with a DSLR. Shame to sell but not needed, was very much loved.

Offers in the region of £300

Draconids

Contact Sophie Watts 07456 874072 or sophiedwatts@gmail.com

6

The Southern Astronomer No.97 – October 2016

7

The Southern Astronomer No.97 – October 2016

I

OBSERVING : VARIABLE STARS

t was probably the Egyptians who first noted that a certain star – we call it Algol – dimmed and brightened with a certain regularity.

But in modern astronomy, the first official variable star is considered to be ο-Ceti (the star Mira) identified in 1638.

The observation and measurement of variable stars is an area of astronomy where amateurs can make an important scientific contribution to their hobby.

This is because a star will look the same in a pair of binoculars as it does in a small 75mm telescope; the same in a moderate 150mm telescope and the same in a large amateur 600mm telescope – a twinkling point of light!

The study of variable stars is made by visually comparing the star with other stars within the same telescopic field of view (FOV) of which the magnitudes are known and constant. By estimating the variable's magnitude and noting the time/date of observation a visual light curve can be constructed.

The Variable Star Section of the British Astronomical Association and the American Association of Variable Star Observers collect and share such observations from back garden astronomers around the world with the scientific community.

From the light curve certain data is derived: • is the brightness variation periodical, semi-periodical, irregular, or unique?

• what is the period of the brightness fluctuations?

• what is the shape of the light curve (symmetrical or not, angular or smoothly varying, does each cycle have only one or more than one minima, and so on?

There are many classifications of variable stars – too many to list here but some have long periods of many months or even years, while others brighten and dim every few days, such as Algol mentioned previously.

How do you measure the brightness? Well, humans are blessed with light sensitive devices called ‘eyes’.

The human eye has been used to measure the brightness of variable stars when comparing them with close by stars of known magnitudes. This is the oldest method and has been used by Leslie Peltier in the US and our own Patrick Moore here in the UK who between them produced many thousands of variable star estimates over their individual observing careers.

A series of charts is produced for comparing the variable star with nearby stars – some of those will equal the variable when it is bright and, other stars that are fainter and equal to the variable when it is dim and some will be in between.

Take for example the chart for variable star T Crb in the image above right. The variable star is at the centre of the chart with the comparison stars around it. The star numbers (99 and 79 for example) are the magnitudes of the comparison stars without the decimal place, so star 99 is actually 9.9m and star 79 is 7.9m and so on.

What the observer has to do is to compare the brightness of the variable star (V) with one of the comparison stars. Is V fainter than 79 but brighter than 99; is it the same as 84 or somewhere in between? With practise our human eye is capable of

The variable star T Crb in Corona Borealis noting these slight variations. This might seem tiresome but several estimates of different stars can be made in a good evening. Not every variable star has to be measured every night especially those with long periods where an estimate every few nights or even weeks can be made.

Photography can increase the number of variables observed. Some lucky observers have inadvertently captured nova, comets or even a supernova during their searches.

A free program that can do a lot of this is called IRIS and is available from here. Though designed When astronomers took up photography of the for CCD cameras which produce images in the night sky and celestial objects in the nineteenthFITS format, digital camera users of Canon and century, they were able to produce plates of the Nikon equipment are catered for with a RAW night sky which could be analysed and this method converter. IRIS can be used to capture images of was used to determine the comparative brightness solar system objects using a planetary camera or of variable stars with their neighbours. webcam.

Astronomers like Annie Jump Cannon and Henrietta Swan Leavitt would study these plates C-Munipak is another free download and can do and data of differing sorts could be gleaned from much the same as IRIS, again allowing users of them, including the variation of light of variables. digital cameras a chance to use hi-res images for photometry uses. It allows the user to create their This same method using up to date digital imaging own light curves of stars. Depending on the size of and computer tools to determine stellar brightness telescope used, it can even monitor exoplanets is a method used by amateur astronomers today. orbiting other stars as they pass in front of their primary and measure the minute variation in The usual method is to image an area of sky with a brightness. similar FOV as that of a comparison chart and take a photograph or sequence of photographs.

If you want to dip your toes into this fascinating aspect of astronomy try out the bright star Algol The best image of the run is then put through a and measure its brightness using binoculars, a piece of software that compares the brightness of small ‘scope or even, the unaided eye. It rapidly the variable star (the target) and comparison stars. changes brightness from 2.1m to 3.4m over a 9.6 The software will then produce a list of magnitudes hour period, and it has two minima observable this of stars that have been analysed. month; 17th at 2h.1 and 19th at 23h.0 (decimal of hour shown).

8

The Southern Astronomer No.97 – October 2016

CONSTELLATION OF THE MONTH:

CEPHEUS

T

he constellation of Cepheus is a one of the circumpolar groups of stars that never set from our latitude in the UK. The brightest star α-Cephei (Alderamin) is 2.4m and has a faint optical companion at 10m. In about 5500 years time, Alderamin will be the brightest star near to the north celestial point, and thus will be the Pole Star. The star γ-Cephei also takes its turn at being the pole star in about the year 4000 CE. The star μ-Cephei is known as Herschel’s Garnet Star due to the intense red colour of the star which is a red giant – if it sat at the centre of our solar system where our Sun is, it would extend out to the orbit of Saturn, engulfing many of the planets of the solar system! It is a variable star with a two year period when its magnitude can change from 3.4m to 5.1m.

The yellow star δ-Cephei is also a variable and was discovered as such by the British astronomer John Goodricke in 1784. The star is the name sake of a family of pulsating variables known as Cepheid variables that have been used to measure the distance and size of the universe. Its period is just under five and half days and differs from 3.5m to 4.4m. It is also a double star with a 6.3m blue companion.

The 4.9m double star ο-Cephei is about 200 light years away; this orange coloured star has a fainter 7m companion.

At the centre of the ‘square’ of Cepheus, between α-Cephei and ι-Cephei is ξ-Cephei, a 4.4m bluewhite star with a yellow 6.5m companion star.

The open cluster NGC 188 lays about five degrees away from the north polar point. This faint cluster of stars is believed to be quite ancient – in the region of 7 billion years. It is faint (10m) but visible in a good pair of binoculars or even a small telescope.

NGC 6946 (Caldwell 12) on the borders of Cepheus and Cygnus is an 11m spiral galaxy, discovered by William Herschel in 1798. This spiral is believed to be about the third the size of our own Milky Way galaxy. It lays 18 million light years away and is about 40 000 light years across. It is sometimes referred to as the Fireworks Galaxy.

Visually only the dense core of the galaxy can be seen – it requires photographic techniques to reveal the spiral arms.

MYTHOLOGY

A chart of the Cepheus area

The present depiction on star maps is presented above in the official International Astronomical Union star map.

The cartoonish kings head is topped by a conical ‘crown’, with Alderamin the base of the ‘neck’ with δ, ζ and, ε making up the mouth.

This was not always the way the constellation was pictorially portrayed. Urania’s Mirror showed him as a seated and turbaned potentate (below).

Cepheus was king of Aethiopia – geographically the Upper Nile/southern Sahara region. His queen was the vain Cassiopeia and they had a daughter, Andromeda.

MONTHLY STAR MAP On the next page is our regular star map for midOctober at about 21.30UT (10.30 p.m. BST).

The Milky Way stretches across the sky from south-west to north-east and a large number of deep sky objects appear.

The Summer Triangle is still present in the western sky but over to the east are the constellations that are the sign posts for cold winter nights – Orion (just rising at this time) and Taurus with the open cluster of the Pleiades.

I am sure the Pleiades (or Seven Sisters) will be the focus of attention for astroimagers whose images capture a distinctive blue-nebulosity about the group. If you are embarking or even dipping your toes into the subject of astrophotography, this open cluster is a good place to try out and experiment in the subject.

As you are probably aware, it was the queen who boasted that she and her daughter were more beautiful than the Nymphs which aroused the anger of Posiedon, the sea god, who sent Cetus the seamonster to attack the kingdom. Cepheus had no choice but to consult an oracle who told him that he needed to sacrifice Andromeda to the sea-monster to save the kingdom. Of course as the story goes, Perseus on the winged horse, Pegasus swooped in, saved Andromeda and destroyed Cetus, and they all lived happily ever after(!)

Low down and just past the due south point is the bright southern star Fomalhaut in Pisces Australis. It is one of the brightest stars that can be seen from our planet at 1.16m. There is also an exoplanet here, Dagon. The stellar system is also much younger than our solar system

9

The Southern Astronomer No.97 – October 2016

Graphic: Stellarium

O

OBSERVING THE MOON NIGHTS th

ctober the 8 is designated as International Observe the Moon Night (InOMN) when astronomers – professional and amateur – open up their observatories or take their telescopes into the public domain and share the views of nearest neighbour in the sky.

Worthing Astronomers is no different and as usual, the plan is for us as a group to go down to the seafront promenade along West Parade (near to the south end of Grand Avenue) from about 19.00 BST (7 p.m) on both Saturday and Sunday evenings – weather permitting of course.

As is usual, the InOMN group who sponsor

the event have highlighted certain areas of the Moon for astronomer and public alike to observe: the eastern lunar hemisphere ‘seas’ (mare), plus Alps Mountains and the Alpine Valley, the nearby Caucasus Mountains and Archimedes Crater plus the Apennines and the Hadley Rille area.

On the opposite page is a chart and list of the objects that we should be able to see on the Saturday evening.

The Moon will not be quite first quarter but during the evening we shall see, almost imperceptibly, the terminator cross the visible face of the Moon as objects on the

10

lunar surface are revealed.

Mid-evening, the Moon will be low in the southwest but our seafront position will, hopefully show off Mars which will be below it.

Of course there will be other sights to see in the night sky for us to enjoy and share with our colleagues and public alike.

A briefing for InOMN night will be one of the presentations on the next Workshop, October 7.

The Southern Astronomer No.97 – October 2016 INTERNATIONAL OBSERVE THE MOON NIGHT October 8 2016 This is a print out and keep feature for use on the 8th and 9th of October.

The picture left shows the Moon as it will be at about 8 p.m. BST on the night of the 8th.

Many notable and interesting features are placed near the terminator to take advantage of the mix of light and shadow.

The Alpine Valley (3) will be in shadow – a cleft cutting through the Alps mountain range. As the sunrises across the lunar landscape larger instruments may just make out a thin line passing through the valley – a rille – created by a collapsed lava flow billions of years ago.

Another rille is at (5). Larger instruments may show the Hadley rille close to the north part of the Apennine range.

It was here that the manned spacecraft Apollo 15 landed in 1971.

More rilles may be found at (4) crossing the Mare Vaporum – a lava plain just north of the centre of the Moon’s face. Some of these may be caused by lava or collapse of the lunar terrain.

At (1) is the small crater Torricelli B which is known for its changes in brightness. At one time it was thought this might be due to out gassing from beneath the lunar crust but it is now believed to be due to sunlight catching surface materials at various angles. Always worth a look at anytime.

The apparent crater chain of Theophilus, Cyrillus and Catherina (6) is prominent. At first glance they look like a crater chain but on closer inspection this is just a chance alignment caused by various asteroid bombardment over billions of years.

The crater region of Descartes (9) was visited by the astronauts of Apollo 16 in 1972.

A Moon with a view

KEY FEATURES:

Craters and features

Mare (Lunar Seas)

1 Torricelli B 2 Atlas and Hercules 3 Alpine Valley 4 Hyginus Rille 5 Hadley Rille (Apollo 15) 6 Theophilus ‘chain’ 7 Messier craters 8 Fracastorius 9 Descartes (Apollo 16) 10 Maurolycus

A Imbrium B Serenitatis C Tranquilitatis D Foecunditatis E Crisium F Nectaris Mountain ranges a Alps b Caucuses c Apennines

11

At (7) are two small craters, the Messier twins, which have a distinctive ‘comet’ like tail coming from them. This ‘tail’ is a ray of bright debris scattered across the darker lava material by the single impact that created these two craters.

Crater (10) is Maurolycus. This one of the more prominent craters in the southern highlands of the Moon.

It has distinctive terraced walls that can be seen in a small telescope. Since it was formed a ‘rain’ of small asteroids and large meteors has fallen across the crater forming craters of all shapes and sizes.

The Mountain ranges of the Alps, Caucasus and Apennines (a,b,c) are not mountains like we have on Earth. These mountains were created by an impact of a massive asteroid that created the Mare Imbrium billions of years ago. They are actually the remains of the wall of the this giant crater that has been partly eroded over many aeons.

The Southern Astronomer No.97 – October 2016

MARE

The large asteroids that roamed around the inner solar system billions of years ago have The dark ‘seas’ or mare have never had a long gone but when Earth passes through a drop of water flowing on them. They were meteor stream and we get a meteor shower once liquid – lava; not the slow oozing stuff – such as the Perseids or Geminids – the we see coming out of volcano’s in Iceland or same particles hit the lunar surface and Hawaii but a lava with the viscosity of engine these impacts of some of the larger particles oil. have been captured by light sensitive video cameras attached to telescopes close to the Unlike the Earth, the Moon has had no time of the meteor shower maximums. internal heat source so the lava that poured across the lunar surface was triggered by MOUNTAINS the bombardment that created the craters.

Once, long ago, astronomers believed that Many of the mare on display during the two the mountains of the Moon comprised of evenings have circular appearances – the jagged peaks where the effects of rain, wind most obvious is the Mare Crisium – The Sea and frost would not effect them. of Crises. Most of the other mare visible have original circular structures which give The mountains of the Moon were far different us a clue to the origins – impacts from large from what astronomers originally believed. asteroids that battered the young Moon soon There are no jagged ranges – there is no after its birth 4 billion years ago. lunar equivalent of the Himalayas or the Swiss Alps.

Further bombardment by smaller space debris has eroded the original ‘shore-lines’ The lunar mountains, like the ones on view of the lunar seas over billions of years to give around the shore of the Mare Imbrium are us the view we see today. the walls of giant craters caused by the impact of their creator asteroid.

Bombardment of the lunar surface still goes on today.

The lunar mountains reach far higher than

12

any equivalent here on earth but they are rounded in shape – very much like our own South Downs but very much larger and higher.

Lunar mountain climbing would be a more leisurely affair than the risky climbs here on Earth.

CRATERS Once believed by some to by the result of collapsed volcano’s, the lunar craters are the result of impacts by asteroid and meteor material in the distant past.

In living memory, no new lunar craters of a size to be visible from Earthbound telescopes have been formed. We shall not likely see a new craters that are visible being formed in our lifetimes – though nothing is of course impossible.

The Moon is a quite fascinating object to observe through a telescope or even a good pair of binoculars. As lunar night turns to lunar day before Full Moon and day turns to night after, we get to see so many new aspects of our nearest neighbour in space.