The Southern Astronomer No.87 – December 2015
SOUTHERN ASTRONOMER THE
MONTHLY MAGAZINE OF WORTHING ASTRONOMERS & WORTHING SKYWATCHERS
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The Southern Astronomer No.87 – December 2015 Astronomy Meetings The groups listed below begin their meetings at 19.30hrs Worthing Astronomers (WA) meet on the first Friday of the month, every two months (February, April, June, August, October and December) at Goring Methodist Church Hall, Bury Drive (off of Aldsworth Avenue) Worthing, BN12 4XB. Admission £3. Adur AS (AAS) meet at Southwick Christian Community Church, 1-5 Roman Crescent, Southwick BN42 4TY, first Monday of the month. Admission: £5 for guests, £3 for members. WA and AAS venues have off road parking facilities and grounds adjacent for setting up telescopes when conditions allow. More monthly details in the Quick View Diary (right). Worthing Astronomers is a free to join society with a membership of over 400 persons, all united with an interest in Astronomy and its associated subjects. 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 neighbouring societies.
This Issue Diary, listings, December Workshop Preview, Letter to the Editor, What Was That ?– an Astronomical Ghost Story December Observing Notes
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QUICK VIEW ASTRO EVENTS DIARY December All times shown are Universal Time UT is the same as UK GMT or Winter Time
For WA and AAS details, see side bar on left
1 3 4 6 7 5 11 15 18 20 21 22 25 29 31
Sunrise 0742h : Sunset 1602h Moon: Last Quarter (07h) WA: End of Year Workshop Mars 0.1°N of Moon (02h) AAS: Christmas & New Year Social Moon at apogee (15h) New Moon (10h) UK astronaut Tim Peake scheduled to fly to the ISS Moon: First Quarter (15h) Uranus 1.1°N of Moon (01h) Moon at perigee (08h) Winter Solstice (04h) Full Moon (English trad. Oak Moon) (11h) Mercury greatest elongation east, 20° (0h) Sunrise 0805h : Sunset 1607h Jupiter 1.4°N of Moon (16h)
CONTRIBUTIONS AND UNSUBSCRIBE Contributions – written articles (preferably word processed in .txt, .doc or .odt format), photographs or letters to the editor for the January 2016 issue should be in by December 15 and sent to the editor at the contact address: editor@worthingastronomers.org.uk 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.
The Planets in December
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. 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.
Moon Calendar December
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The Southern Astronomer No.87 – December 2015 LETTER TO THE EDITOR
DECEMBER WORKSHOP December 4, 2015
We meet for the last time in 2015 at our regular venue on the above date. The idea for the pre-Holidays Workshop is to get to know each other a bit more socially (some nibbles will be there plus teas and coffee) and have a relaxed time. We hope to have some imaging work of our members for the first part and then a preview of what 2016 holds in store for us astronomically speaking. Any ideas or, if there is anything that you will like covered at a future Workshop, let us know. As is usual for the December workshop the entrance fee is waived for all members (Astronomers and Skywatchers) and family/guest; the public will still need to pay the £3 entrance fee.
Total Lunar eclipse
Anyone wishing to show any pictures they have taken over the last two or three months please drop me a line and supply the pictures on the evening via a USB stick with images held in a folder – this will allow (hopefully) for fast presentation of the pictures.
E
A festive pudding
Sir. I couldn't help notice the similarity between a Christmas pudding and a picture of the recently eclipsed moon. Could they be related? I think we should be told.
WHAT WAS THAT...? An Astronomical Ghost Story
Edna Spigot, 'Ye Olde Nutt Hatch' Charlton Heston, Devon
ver since Charles Dickens penned his seasonal ghost story, A Christmas Carol, it has become a popular pastime to tell spooky stories to while away the dark, fire lit evenings of winter. Well here is a true, spooky astronomy story - if you dare read on..... The planet Mercury zips around the Sun in a very short time – its year is about 88 of our days. There is however a strange anomaly about the planet. Over a period of a century, its predicted position in the sky is off by 43” (arc-seconds) or just over a the diameter of the Moon. What causes this? During the nineteenth century one man knew the reason why. French mathematician Urban Le Verrier, worked out that Mercury was being 'tugged' ever so slightly, of its path in the sky by another smaller body that lay between it and the Sun. In other words, a trans-Mercurial planet. Le Verrier, not a modest a man by any standard had tried to work out mathematically the error in the predictions of Mercury's position. He criticised of the work of many previous mathematicians who had tried to reason why this error occurred only to discover that his own calculations were not up to much either.
Diagram showing a similar track of Lescarbault's object – North upper left
The transit was not across the disk but was almost tangential – a sort of near grazing transit. As the 'spot' was already on the Sun when he began his first observations he calculated its probable position angle (PA) of entry on the disk; as he was able to observe its leaving the solar disk he again noted the PA of exit.
He reasoned that an inter-Mercurial world would be visible during a transit of the Sun. Just before Christmas 1859, Le Verrier got an outstanding communication – someone had observed just such a transit. The message came from Edmond Modeste Lescarbault, a doctor of medicine in Orgere-en-Beauce in the Loire. Lescarbault lived very much up to his middle name, was described as dreaming more about astronomy than medicine – though not surprising in the days before antibiotics where doctors would sit and pray with their patients for help. The doctor was fascinated by the thought of other undiscovered planets in the solar system. In 1853 he began to observe the Sun and skies after sunset and before sunrise regularly in the hope of discovering such a planet. The good doctor however was not a self deluding person – he knew that his quest was unlikely to produce fruit, especially as many other, more qualified and professional than he, were looking for the same thing. On March 26, 1859, his task appeared to pay off. After a cloudy and overcast day, the skies cleared and Lescarbault pointed his telescope – a 95mm long focus refractor - at the Sun and prepared his projection equipment. At about 4 p.m. local time he saw what he thought was a small round sunspot – about a quarter of the size of Mercury in transit across the face of the Sun several years earlier. What caught his eye was that this appeared to be no ordinary sunspot as it appeared to have motion of its own. Unfortunately he was called away to attend a patient but it was a minor call and he returned to the telescope once more. The 'spot' was still there but had moved considerably.
Urban Le Verrier
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The Southern Astronomer No.87 – December 2015 What was that? continued
another that would solve the mystery of Mercury's orbital behaviour. In 1915 Albert Einstein published his paper on General Relativity which explained away the apparent anomalous behaviour of Mercury. His equations – how the massive solar gravity could bend space locally - predicted exactly the observed amount of advance of Mercury's perihelion without any recourse to the existence of a hypothetical Vulcan.
He calculated what he had seen had been on the Sun for 1 hour 17 minutes 9 seconds. Unsure of his own abilities he kept this observation to himself for the next nine months. He wanted to see this object again before he could make an announcement and he realised it was just good luck he had seen it. Years may go by before he might see it again. Perhaps too Lescarbault was waiting to hear if anyone else had observed it.
But the question remains. What did Lescarbault observe. What did other reputable observers actually see? It may be argued that Lescarbault had truly misidentified a small sunspot during his fateful observation but that would almost certainly have been the first question Le Verrier would have asked. A circular sunspot looks circular only near the centre of the solar disk – Lescarbault's observed object was circular while close to the edge of the disk – a circular sunspot would have foreshortened into an ellipsoid. It has been argued that most of these mysterious planetary transits may have been caused by comets passing in front of the Sun. Certainly for many years this answer to the problem was quite popular but our understanding of how comets are created and the comparatively small sized nucleus they actually have (measured quite often in tens or even hundreds of metres rather than hundreds of kilometres) would not account for what has been observed.
The answer will be that we may never know. Amateur astronomers and their professional counterparts regularly observe the Sun – in fact it is under almost An old postcard showing Lescarbault's observatory – it was destroyed in the 1870 Franco- continuous observation, both by enthusiastic amateurs, professional solar Prussian war observatories or by a myriad of orbiting solar observatories launched into space over the last few years. It was only after reading about Le Verrier's work did he send that letter to the imperial mathematician whose curiosity was piqued. My own belief is that many of the observations may be sightings of small sunspots – or likely, clusters of small spots that appear and disappear On December 30, Le Verrier arrived unannounced at the home of the doctor. according to atmospheric seeing and thus give the impression of some Far from greeting the doctor with Gallic bon hommie, the mathematician was dynamic movement of their own. angry at him for keeping such an observation to himself for all this time; and he began to give Lescarbault the 'third degree' concerning the circumstances At no time has anyone reported seeing a transient object such as described of his observation. This may sound harsh by our standards but Le Verrier by Lescarbault or his contemporaries over a 150 years ago. needed to be certain that he was not being taken in by some charlatan or publicity seeker. After some robust questioning and looking at the calculations Oddly this has actually created an area of astronomy that is now being made by the doctor Le Verrier left and then proceeded to enquire from locals studied – the search for vulcanoids. regarding the character of the doctor. Sounding a little like a painful and delicate medical condition, the search for large inter-mercurial asteroids is a serious research programme.
On January 2, 1860 Le Verrier made the announcement at the Acadamie des Sciences and had full-some praise of the rural doctor. Lescarbault received favourable mention at the Royal Astronomical Society while Harvard Observatory pointedly accused professional astronomers for being lack lustre in their observational programmes by letting an amateur make the discovery.
It may not come as a surprise that no vulcanoids have as yet been observed. If any are, it could provide scientists with objects left over from the early days of planetary formation.
Using the observation made be Lescarbault, Le Verrier placed the planet just 0.147 astronomical units (AU) from the Sun or some 13 million miles with an orbital period of just under 20 days. He also worked out that transits would occur in early April or early October and only when the orbital nodes of Earth and the planet – he had it named Vulcan – were in alignment. It was agreed however that further observations of the planet were required.
They are at the moment, only theoretical objects and none if any should exist would be of the type that might be observed as previously claimed. We may never witness a strange Vulcan like body cross in front of the face of the Sun but we can get a chance to observe Mercury do just this on May 9 next year when the first transit of the planet will take place in thirteen years. May transits are rarer than the November variety and this will be the last May one for quite a few years. Its entirety, ingress and egress, occurs while the Sun is above our (UK) horizon.
One question arose – had it been seen before as both Uranus and Neptune had, prior to their discoveries? Odd and suspicious sunspot observations of the past were looked for - and they were found! Unfortunately none of the 'fast moving' sunspots recorded previously fitted into the suggested orbital values Observing a Mercury transit is interesting but it also shows how small Mercury of Vulcan. is when silhouetted against the mighty face of the sun. According to the calculations, Vulcan transits were expected on March 29 and There have been two books written about the story of the hunt for planet April 2,4, and 7,1860. They came and went with nothing being observed. Vulcan; In Search of Planet Vulcan: The Ghost in Newton's Clockwork Universe, authored by Richard Baum and William Sheehan. I reviewed this But observations were still being reported by reputable observers of planet book some years ago for Astronomy Now and have used my copy as a basis like spots on the face of the Sun but these started to dwindle and between of this small article. It is still in print and a worthwhile buy if one is interested in 1866 and 1878 no reliable (if any observations of this phantom planet could astronomical history and the host of interesting characters that play upon its be described as such) observations were reported. stage. In 1878 two reliable astronomers – the professional, James Craig Watson, and the amateur, Lewis Swift observing from different locations both reported seeing a faint magnitude star close to the Sun during the solar eclipse of that year.
More recently a new book, The Hunt for Vulcan: How Albert Einstein Destroyed a Planet and Deciphered a Universe by Thomas Levenson has been published by Head of Zeus at £14.99, telling the same story.
Sadly, Le Verrier had died in 1877 aged 66, convinced he had discovered his second planet (his mathematics had pointed Galle and D'Arrest to look in the right position for Neptune). However it was obvious to many astronomers that a trans-mercurial planet was not likely to be found. It would be the work of
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The Southern Astronomer No.87 – December 2015
OBSERVING NOTES December All times are expressed as Universal (UTC – Co-ordinated Universal Time) and can be considered the same as GMT . Information below, and all sky-map on page 8, is for the 15th of the month unless otherwise stated. The brighter planets are still in the morning sky and are joined by a visitor – comet C/2014 US10 (Catalina)
T
he pre-dawn morning sky is, during the winter with its dark mornings, a condition we get familiar with.
The brighter planets are congregating in this sky. Mid month, Jupiter rises at 23.38UT and is 37”(arc-seconds) and increasing in angular size as time passes by. This makes the planet an easy object to look at with a small to moderate telescope while binoculars will show the polar flattening of it poles and possibly its four bright moons. Jupiter is quite unmistakable, shining at a bright -1.9m.
Joining the planets in November and December is a moderately bright comet C/2013 US10 (Catalina) – so named due to its discovery by the Catalina Sky Survey programme. Predicted to be about 5m at its brightest in December and January this comet will be a fixture in our night skies for most of the winter as it passes through the northern constellations.
Mars rises just after 02UT; though nearer to us than Jupiter is so much smaller; the angular diameter is 5.1” and a respectable 1.4m. Moderate to large instruments will be needed to observe it in detail but Mars, like Jupiter is slowly increasing in angular size. It comes to opposition in early summer next year.
The evening sky also contains planets. Mercury is at eastern elongation on December 29 though its angular position relative to the Sun makes it a poor object to observe.
Venus is slowly receding in its orbit from us and though brightening (-4.1m) the angular diameter is shrinking – 17.6” at the beginning of the month to 14.5” by the end. Its phase illumination is about 75%. It rises at 04.11UT midmonth and will be visible – with good sky conditions – in daylight.
Diagram describing the position of the inner planets at an eastern (evening) elongation
Uranus and Neptune are the fainter planets visible in the evenings with Neptune being in the south-west after sunset and Uranus still visible during the mid-evening. The Moon is full at the height of the end of year holidays – but the month starts off with it in the waning (post-Full) phases, as the amount of Moon visible decreases night by night. At about 06h on the morning of December 5, Jupiter, a crescent Moon, Mars, Venus and C/2013 US 10, are almost positioned in a straight line across the sky – something perhaps for the landscape astro-photographer to have a think about.
The planetary images shown above were captured by Andy Li at the beginning of November under conditions of heavy dew – well done Andy for the perseverance in obtaining them.
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The Southern Astronomer No.87 – December 2015 Observing Notes December 2015
During the evening of the 23rd the Moon lays in the Hyades open cluster and occults (eclipses) the 1m star, Aldebaran (α-Tauri) at 18h 08m 36s (times are for Sompting) – times will be a little earlier east and a little later west. The predicted time for reappearance is 19h 10m 47s. Glare from the nearly full moon may present a problem in a misty or hazy sky. The position of Aldebaran on ingress and egress relative to the lunar limb are shown in the next column We see so little of the Sun this time of year we tend to only observe it at weekends or during the holidays, and then when the weather allows. Those with more time on their hands are better placed perhaps but are still hostages to the weather. When the seeing has been good there have been few spots around though in late October and during the first half of November a large group – AR2433 traversed the visible face of the Sun and was responsible for a coronal mass ejection (CME) that caused aurora to be seen at latitudes in areas of the world that were not blanketed in cloud! In October Brian States observed the Sun on 22 days – another good result despite the weather. Totalling up the joint monthly totals we get a mean average sunspot number of 39.8 (AAVSO = 51.1; BAA = 48.1; SILSO = 61.7) Comet C/2013 US10 (Catalina) is predicted to appear in our northern skies over the next few months. Though not a bright object (5m) it will be a sight for binoculars and small telescopes; larger instruments will show more detail in the coma and tail structure. Like many recent comets it has a greenish-hue bought about by the chemical content of the ices that it is made up of.
Aldebaran egress
As has already been noted previously, the Moon passes through the Hyades during the early evening of December 23. It occults the bright red star, Aldebaran which is close by the Hyades though it is not part of the cluster but lays 'in-line-of-sight'.
It will be closest to Earth in mid-January. During December it will be a morning object. Meteors: The Taurid meteor's gave quite a display in November but the prevailing weather put paid to decent observing of the event for many of us. Perhaps we will be luckier with the Geminids which are considered favourable this month when they reach their maximum on the 14th.
The Hyades lay at a distance of 153 light years while Aldebaran is about 65 light years distant. Astronomer have put the age of the open cluster at 625 million years old – mere stellar babies when compared to a star like the Sun at 4.5 billion years old.
The Perseids in late summer will produce 80 or so meteors per hour – called a zenith hourly rate (ZHR) but the Geminids have a rate of 100 plus and are now Aldebaran is an orange giant star – and makes are own Sun look tiny by considered to be the premier annual meteor shower. Geminids are marked by comparison. It is has burned out its hydrogen core and is burning helium and slow meteors gracefully crossing the sky as well as many bright events. some hydrogen that is in a shell around the helium core. It is a multiple star system – there is a faint 11m star; this star itself has a 14m companion. It is The Geminids are active between December 8 and 17. The Moon is only likely that some of the stars are actually related to Aldebaran while some of about three days old at meteor maximum and would have long set during the the others are 'line-of-sight' or are actually associated with the Hyades. early morning hours of the 14th. The other major open cluster is The Pleiades (The Seven Sisters) or to use its more common name, M45 (the M standing for Messier who produced a catalogue of deep sky objects).
The radiant at the time of maximum – the point in space where the meteors appear to emanate from – is located near to the star Pollux (β-Gem) below.
The Geminid radiant on the 14th
The other shower in the month is the Ursids on 22/23 which come from close to the pole star, however it is considered unfavourable as this faint shower will occur close to a full moon. Stellar & Deep Sky The constellations of Taurus and Orion are rising in the east to put on their annual show. Taurus has two distinctive open clusters – the Hyades and the Pleiades and they can be seen on the all sky map on page 8.
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The Southern Astronomer No.87 – December 2015 It was once believed that this nebulosity was actually part of this young cluster of stars but, it is now thought that this is another example of line-of-sight effect and the nebulosity actually lays in the interstellar medium between us and the cluster. From a dark[ish] site, how many stars in the cluster can you see with the unaided eye? It is called the Seven Sisters due to the seven brighter stars that make up this cluster, but the general consensus is, only six are really bright enough to be seen without optical aid. This cluster of stars is recognised by many cultures in history and today. The Subaru car company of Japan uses a stylised depiction of the cluster as their company logo. Next to Taurus is the sky is Auriga. The bright star Capella at one of its 'corners' identifies it. The Milky Way passes through much of the constellation and as one might guess, there are some interesting deep sky objects in the constellation boundaries. M38 is visible with the naked eye when away from light pollution however, it is worthwhile looking at in binoculars or a small telescope as are the companion Messier objects M36 and M37. M38 is an open cluster shaped as little like a π (pi) and is 20' (arc minutes) across. M37 is described as having a 'knot' of blue stars at its heart and contains over 500 stars. M36 is also an open cluster. All the the above Messier objects lay about 4 500 light years away. M45
© Andy Li
The nearby NGC 1893 is again an open cluster which is embedded in an emission nebula which has a reddish colour to it when imaged. The California Nebula (so called due to its apparent shape in long exposure images) is The Seven Sisters are a beautiful sight in a lower power telescope eyepiece or another object and worth imaging as well. binoculars. In a colour photograph – even a short exposure will show it - the Back in Taurus and north of the star ζ Tauri (zeta) is the 8.4m object, M1 or as stars take on a blueish colour (due to their age the stars of M45 are really it is more commonly known, The Crab Nebula. blue) and a hazy nebulosity can be seen around them (above.) M45 is a much more compact cluster of stars and lays 444 light years away. Like the Hyades, it is a young cluster at about 100 million years old.
NGC 1582 California Nebula
NGC 1664
Pleiades
M38 NGC 1893 M36
M37 NGC 1802
Hyades
NGC 1750 NGC 1647
M1 +
NGC 1817
NGC 1807
M35 K Stars
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The Southern Astronomer No.87 – December 2015 Stellar & Deep Sky cont.
Not an obvious object but worth trying to get a look at due to what it was.
This object was, many thousands of years ago a star that blew itself apart; it shone in earthly skies nearly a thousand years ago and was seen by Chinese and Korean astronomers/astrologers. It shone so bright that it was visible in the daylight sky. Today, we know this as a supernova – a rare beast to observe in our own Milky Way but seen in other galaxies.
The night sky during this time of year is always a fascinating thing to look at with its variety of objects – just remember to make sure that if you do take the opportunity dress up warm, have a hat and good warm footwear and somewhere to sit – in a dark spot and comfortably – and enjoy the looking up. N
S The sky at about 21.30 on December 15
THE SEASONS GREETINGS TO ALL OUR MEMBERS & READERS 8