THERE IS GOING TO BE A TRANSIT OF VENUS ON JUNE 6TH!
IT WILL NOT HAPPEN AGAIN FOR 105 YEARS!
AND YOU WON’T BE HERE
This is a gentle reminder of a truly rare event that is on our horizon. This month’s Astro Flier will be our last
publication prior to this celestial wonder so you need to be prepared. For night- time observers, on other pages in the magazine I have reprinted – with kind permission of Geoff Smith, Observations Officer of the ASNSW, an observing list he published for the South Pacific Star Party. The list is entirely relevant to our sky for the next month or so, bearing in mind that the time advances by two hours per month (completing a full circuit in a year) and the area of sky will move 15 degrees further west than at the same time last month.
Jupiter is moving completely behind the Sun from the Earth and as such is no longer a viable target. Mars of course is easy to find near Regulus in Leo and for all its’ tiny apparent diameter is shining like a bright ruby at mag. 0.2. Saturn has also passed opposition and is in our northern sky throughout the night. It is imperative that we take advantage of the steady seeing and dustless skies to view the celestial beauty of this gas giant, we had to wait six months as we will now have to await the return of Jupiter. Venus is moving in front of the Sun next month!
The Transit of Venus on 6th June is perfectly timed for Eastern Australia and we get to see the whole event as it lasts 6½ hours. This means that even should cloud obscure our view the chances are we will see at least some part of the event. We have had a brief outline of the historical significance at an earlier meeting but it is personally significant to all of us as we will never see it again (I would have to live until I was 159 years old! Jack will be 187!) Anyone who doesn’t catch a glimpse this time will not see it ever, nor will 95% of people born this year.
Scientifically speaking this Transit commemorates one of the first real global and multilateral
scientific endeavours, one that was not primarily based on the desire for profit, but more the
advance of knowledge.
In 1619 Johannes Kepler, mathematician and astronomer, had used the meticulous observing
notes of Tycho Brahe to formulate his Three Laws of Planetary Motion. The Third law, which
concerns us here, tells us that the cube of a planet’s mean distance from the Sun is directly proportional
to the square of that planet’s orbital period. The orbital periods of the planets were easily calculated,
even by naked eye observers lacking truly accurate measuring tools. By using the Third
Law and the length of the Venus year they knew that Venus’ distance from the Sun was 72.3% of
the Earths’ distance.
If astronomers had a way of measuring one such distance accurately, the distances to all the planets could readily be calculated. Once the distances were known, the planets apparent size (angular) could be measured and the actual size could be calculated. Once the actual size of a planet was known, the orbits of that planets’ moons could give us the true mass of the planet. Astronomers were taking tentative steps on the second stage of measuring the local universe. But most importantly, if the true Earth – Sun distance could be calculated, we could begin to measure, using parallax, the distance to the nearest stars!
Parallax is the apparent shift in an objects position when viewed from different angles. In its’ simplest form our paired eyes use parallax to gauge the distance of objects we view. In astronomical terms it was seen as a means to measure the distance to the nearest stars. If an object was observed at six month intervals to move against the background of distant stars the angle could be calculated and the distance extrapolated. The baseline of the triangle would be the diameter of the orbit of Earth or twice the Earth-Sun distance.
Sir Edmund Halley, in 1677, proposed that it would be possible to calculate the Venus-Sun distance
by using the same principal if the Transit was viewed from two widely separated locations on Earth. Well
planned, well funded, well staffed, and well provisioned expeditions set off at the behest of the major European
powers to observe the Transits of 1761 and 1769. The British expedition to Tahiti, led by Lieutenant
James Cook, led to the mapping of New Zealand and the east coast of Australia. The expeditions met with
varying degrees of success, encountering issues such as cloud, local hostility, harsh conditions of travel, poor
navigation (positioning of observer) and timing issues. As well as inaccurate timepieces that were used to
calculate longitude, they also experienced “ the Black Drop”, blurring of edges due to the atmosphere and
poor optics, that affected the precise recording of the ingress and egress time that was essential to the parallax measure. Nevertheless, when all the data was collated and calculations were made, the results gave a figure within 3% of the distance known today!
The Transit begins when Venus appears to move on to the surface of the Sun and this is due at 8:16 am in
Wollongong, one second later than in Sydney. The most significant timing is ingress, interior or second contact, occurring at 8:34 am. I suggest being well set-up by 7:30 am with a clear view of the east. A comprehensive article appears on pp 8,9, 10 of Astronomy 2012 For most of us the safest way to view is by projecting the solar image . This view can be shared with many bystanders and the image can be easily
photographed by individuals. A music stand to hold your target screen would be useful.
SAFETY! Do not look at the Sun through any optical device without full aperture solar filter at the
objective end of the scope!
These are available from any astronomical supply shop and fit completely over the dew shield. SECURE IT
IN PLACE. If you project the Sun image remember that unprotected sunlight will heat the inside of any scope tube in minutes, will melt any adhesives between lenses, ruin eyepieces and burn anything in its way. If your eye gets burned, you will be blinded.
For those of you imaging, make sure the project is well planned. While the Transit lasts a long time, critical stages don’t last more than a few seconds. I suggest trying to photograph first and second contact, and/or third and fourth contact with a few shots in between. More experienced astrophotographers could take a shot every 10 or 15 minutes and create a sequence later on. One of the best things you can do is photograph
the occasion, i.e. the equipment, other viewers and friends, and the location. These will be your lasting memories. There will be thousands of photographs taken that will be better than yours so ABOVE ALL, DON’T WORRY, enjoy the occasion and the spectacle. You will be playing a small part in the history of astronomical observing.
I will be observing first and second contact from my observatory in Kangaroo Valley and then going to the KV Showground at 10 am to show interested locals. After that it’s off to a local High School so feel free to contact me if you want to join in.
Harry Roberts is to give his talk to Shoalhaven Astronomers on 18th May
The speaker began study of the sun in H-alpha on June 23, 2001. Within minutes the filter revealed prominences and surface filaments; then a small but brilliant flare erupted. It was a “revelation”!
Yet the peak of flaring for Solar Cycle 23 still lay two and a half years in the future, and flaring would be sustained well into 2007. Over that time hundreds of flares and ejection events would be logged in an extraordinary adventure of daytime astronomy.
The flaring of SC23 was probably the strongest for a century – and was followed, unexpectedly, by the deepest minimum for a century – prompting NASA to denounce the sun for “behaving unpredictably”!
Solar cycle SC24 is now well advanced, and GOES Class X flares (the strongest) erupted early in 2011; so activity is increasing. This, together with the fact that H-alpha equipment has never been cheaper, means that right now is the ideal time to enter the bizarre world of H-alpha astronomy. There is more to be seen than you’d dare imagine.
The Talk will cover:
Making a start: equipment and techniques.
Some H-alpha features and how to recognise them.
The coming maximum, what to expect.
Solar magnetism and the reversal of polar fields.
And much more.
Growing up in Adelaide during the 1950’s and 60’s, a time of intense solar activity, Harry has the sun “in his veins”.
His first sun images were projected with a small ‘scope, and then a larger reflector in the 1960’s, with regular viewing over following decades.
In 2000 he began daily recording of sunspots in white-light. In 2001 he upgraded his 8” ‘scope by fitting an H-alpha filter, taking his first steps into the bizarre world of high temperature plasmas, flares and ejections.
Observing in Sydney (often all day) he found that such events happen many times daily during solar maximum – and has since then recorded hundreds of flares and associated events.
In 2006 he adapted a freeware product to pin-point H-alpha transients on the sun– a crucial tool for serious research.
These efforts led to many articles in amateur journals as well as presentations to amateur groups and public gatherings.
His favourite astronomical moment was following an ejecting filament from the sun’s surface to a point in space more than one solar radius away; material shown to be moving at ~300 km.sec-1!
Affiliations: Sydney City Skywatchers, the Astronomical Society of NSW, the Royal Astronomical Society of NZ and the Astronomical Society of Coonabarabran.
Objective: to better communicate the dramatic and paradoxical character of our star and its high velocity transients.
Awards: ASNSW Southern Cross Award 2003, ASNSW Editor’s Award 2003, NACAA poster prize 2008 (“Anomalous Flaring in Cycle 23”), and the ASNSW Mike Kerr Medal 2009 for Observational
Astronomy (inaugural award).
Has the rain stopped? It didn’t even rain at Easter (except in Sydney somewhere, and Melbourne of course). Cool dry evenings and the end of daylight savings mean you can get out observing quite early. The lack of dust and moisture in the air make observing conditions excellent, while the lack of heat means turbulence is minimal. If you can brave the cold, the next six months are the best time of year for amateur observers.
So, what’s happening? Firstly don’t forget there is a Transit of Venus on June 6th. If anyone wants to get some advice about observing the Sun safely please contact me on firstname.lastname@example.org More immediately the best planet for us to view is beautiful Saturn. Saturn transits the meridian on April 16th (due north at local midnight) and is rising around sunset. As such, Saturn is perfectly placed for viewing throughout the night. With a modest telescope and medium magnification you should be able to see the shadow of the rings on the planet and perhaps even the dark ring dividing the two bright rings known eloquently as the A ring and B ring. Who says astronomers have no imagination? This is known as the Cassini division after its discovery in 1675 by Giovanni Domenico Cassini. The rings can even be seen in 10x binoculars if they are mounted on a tripod or held steadily. Saturn has five moons that may be seen in progressively larger telescopes but even binoculars will allow us to find Titan, which is actually the largest of all moons in the solar system, having a diameter of 5,152 klms. Saturn resides in the constellation Virgo for all of 2012 and is currently just north of the 1st magnitude star Spica, αVirginis. Spica will appear quite white and Saturn very yellow. There are few other bright stars in this area but Mars is just over the border in Leo near the bright star Regulus. Mars will appear a rusty orange colour and Regulus more yellow-white. Regulus marks the resting foreleg of Leo, the mythical Lion. Mars is actually shining brighter than Saturn but is quite small. I would be interested to hear of anyone perceiving any detail on this enigmatic planet.
For the deep sky observers, Virgo and the adjacent constellation Leo are veritable goldmines of galaxy fields. As a matter of fact a supernova was discovered on March 16th in the galaxy M95 in Leo. Currently this end of life stellar explosion is shining with the light of 500 million Suns! It is still invisible to the naked eye and actually happened 38 million years ago, its light only reaching us just now. M95 is part of a well known trio of galaxies with, M96 and M105, all visible in one low power field. Its coordinates are RA 10 44m Dec =11° 42’
M95 and the Supernova designated SN 2012aw : Image Credit: Anthony Ayiomamitis
Above we see an image of the entire galaxy field in Leo taken by my friend Bob Price from Bethanga, in Victoria. Six galaxies appear in total with one unnamed. M95 is in the bottom right of the image with the SN showing just below to the right and some glare from nearby Mars bleeding into the pixels from the right.
This SN and galaxy is easily visible in a 150mm telescope and Leo is currently in our north, about 35° up the sky.
Although they are the natural result of the end of life cycle of a massive star, supernovae are relatively rare. Only three are known to have occurred in our Milky Way in the last 1000 or so years. The first occurred in Taurus and was recorded by Chinese and Middle Eastern astronomers around 1054 A.D. It’s remnant is the famous Crab Nebula, M1. The next was discovered and observed in 1572 by the Danish Astronomer Tycho Brahe, in the constellation Cassiopeia, it became known as Tycho’s Star.
The most recent was SN 1987a in the Large Magellanic Cloud (strictly speaking not in our galaxy but in our galactic neighbourhood). It was actually discovered by radio astronomers, three hours ahead of being discovered visually, simultaneously in Chile and New Zealand.
It is now a brilliant planetary nebula with the typical hourglass shape created by the expanding rings of gas shown end on.
What is it that makes an event in nature special? Is it the rarity of its occurrence, the immensity and sheer wonder of the spectacle, or possibly the effect it has on mankind? There are arguments for all these criteria and there is also personal significance. There will be a Transit of Venus on June 6th this year and while it is
not a visual spectacle that excites the imagination of the general populace the way a Total Solar Eclipse does, it is an event that holds great significance for us all.
Firstly, it is a truly rare event. Transits of Venus occur in pairs eight years apart but then do not recur for 105.5 years and on the next cycle 121.5 years. Total Solar Eclipses occur at the rate of three every two years. Few people alive to see this transit will see another. Transits of Venus were unknown until Johannes Kepler, the great planetary mathematician, predicted an occurrence on December 6th, 1631. Venus appears as a small round black dot when crossing the face of the Sun, invisible to the naked eye. As Galileo had turned the newly invented telescope on the heavens for the first time in 1609 it had never been observed before. Due to a small error in parallax mathematics Kepler did not predict the second of the transit pair occurring eight years later but it was independently predicted and observed by English amateur Jeremiah Horrocks on 4 December 1639. As he was not well known and did not publicise his calculations it is believed he and his friend were the only two people on the planet to see this one.
Right – The Author’s photo of the Jun 8, 2004 Transit
In the eighteenth century, advances in telescope design and instrumentation continued at breakneck speed. Planetary positions and orbits were plotted more accurately and predictions could be mathematically refined. Around this time we see the great nations of Europe exploring the world by sea for trade riches and power. The Spanish, French, English, Dutch and Portuguese had been sending explorers to all corners of the globe for a hundred years. Enormous riches and influence, not to mention new territories to claim, were the spoils for the adventurous, however many of these explorers and crew perished because they became lost. Unable to accurately ascertain their longitude they could miss their target by many miles or hundreds of miles, running out of water and food or becoming becalmed in unknown waters. It was easy to find your latitude, simply measure the angle of the Sun above your horizon at local noon but to find your longitude was more difficult. The story of the search for the best method is brilliantly told by Dava Sobel in her book Longitude. If a navigator could know accurately the time at a given point on the globe, say Greenwich or Paris, he could compare it to noon at the meridian of his location.
Every hour difference was equal to 15 degrees of longitude. Many solutions were proposed but ultimately those who had accurate timepieces, unaffected by temperature, barometric pressure or the motion of a ship, would be the most astute navigators. The chronometer and its use for accurately plotting one’s position was obviously a momentous advance for mankind but what has it got to do with the Transit of Venus? As you will see both our own history and the development of astronomy are connected by this event.
After observing a transit of Mercury in 1677, the brilliant English astronomer, Sir Edmund Halley, proposed that the next transit of Venus could be used to determine the distance of Venus from the Sun, and by simple trigonometry the distance from Earth to the Sun.
Why was this important to astronomy?
Astronomers had noticed that some stars, when measured at different times of the year, appeared to move slightly against the background stars. They had known of this effect for quite some time as the superior planets (outside Earth’s orbit) would appear to move in reverse against the stellar background for a short period when Earth went past them in its own orbit. This effect was known as parallax. See the diagram below.
By checking a stars position at six monthly intervals an astronomer would be measuring the baseline of a triangle the diameter of Earth’s orbit or twice the length of the Earth – Sun distance. Knowing that distance accurately meant the parallax distance to some stars and perhaps measurement of the scale of the visible universe would be within their grasp.
Above: The transit appears differently from separate locations on Earth – (courtesy of Exploratorium TV)
Halley proposed to use a smaller measure of parallax to find this Venus-Sun/ Earth-Sun distance. He posited that two observers timing the Transit from distant locations on Earth could create a long enough baseline using parallax measures to create a heoretical angle from Earth through Venus to the Sun. Johannes Kepler, who formulated the three Laws of Planetary Motion, had also calculated, with his third Law, the ratio of a planets distance from the Sun compared to the time taken for its orbit. Kepler had proven that the ratio of Venus’ distance to the Sun compared to Earth was 0.72. By multiplying the apparent Venus /Sun angle by 0.72 we arrive at the Earth/Sun angle. Let’s not worry about the actual equation here but remember we have now worked out the angle and the length of one side of our triangle (the distance between our observers on Earth) and we can use our High School maths (remember Sine, Cos and Tan?) to calculate the distance accurately. This method is the same as used by all surveyors to determine distance with a theodolite.
Of course, unless the observers in different parts of the world knew their positions accurately they could not determine the distance between each other. Most of the advanced seafaring powers and their respective scientific societies equipped and commissioned Transit expeditions to all corners of the globe. This is where our recent history and the event of the Transit
intersect. For the Transit of 1769 the English Navy purchased a coal carrying ship called the Earl of Pembroke , and joined with the Royal Society in commissioning a Research survey to Tahiti and the South Pacific. As it was nominally a Naval vessel it could only be commanded by a ranking Naval officer so James Cook, chosen for his navigational skills and his surveying prowess,
was duly promoted to Lieutenant and commissioned to observe the Transit of Venus from Tahiti on June 3, 1769. As the Commander of the ship he was entitled to be called Captain. From Tahiti Cook was to continue to New Zealand to observe a Transit of Mercury on 9 November and map the North and South islands while there. Here he was to open his sealed orders that instructed him to continue west where he discovered and mapped the east coast of Australia. On this first tour of duty Cook navigated with the use of accurate Moon and star charts supplied by the Royal Observatory at Greenwich, using a sextant to calculate angles and lunar distance. On his second voyage of discovery in 1771 he had the benefit of a replica of Harrison’s famous
chronometer to calculate his longitude, but no Transit to time on this occasion. This chronometer cost £400 or approximately £59,000 in today’s currency.
When all the timing, positional, and angular measures were calculated the results from the earlier Transit of 1761 and those of 1769 gave a figure for the Earth/Sun distance that only varied from our modern measure by about 3%. Inaccuracies crept in because of poor seeing, poor timing, poor calculation of locations, and an anomalous effect of the Transit known as the Black Drop that made it difficult to see the exact second the planet entered or exited the disc of the Sun. Around a century later in 1874 and 1882, the research was conducted primarily with the new technique of photography but was again slightly marred by the discovery that Venus had an atmosphere which generated further inaccuracies in timings.
So, is the event rare? It certainly is! Is it an immense and wondrous spectacle? Perhaps only when you consider the implications. Does it have a profound effect on mankind? The event itself, perhaps not, but the observation generated an enormous tide of activity in the affairs of men. It pressured advances in technology, navigation, timekeeping, measurement and the science of Astronomy. Is it personally significant? To us, who will not see another, it may be. If you have an inkling of the history it must affect you. Personally, it is one of many aspects of the Universe above our Earth that astonish and compel me.
By Gerard Keyzer
As we go to press I can confidently state there has not been one clear night this year, well not clear enough to get a scope out anyway. While it hasn’t been raining every day it’s certainly been cloudy most evenings so the observing log is just about empty.
I have been doing a bit of solar observing but even that has been on hold during early February. The Sun is very active with multiple and large sunspots as well as high solar flare activity. Has this got something to do with the big wet events or the big snows in Europe? Who knows? If the weather gives a chance to observe later this month try observing Jupiter very early in the evening, in the west. The seeing will be poor for detail but as I explained at the January meeting there are quite a few Jupiter Moon events occurring at decent hours throughout February. Most of these can be seen in twilight so check the times on pp 112-113 of Astronomy 2012. The New Moon occurs on 22nd February so maybe it will coincide with better viewing conditions. Jupiter is setting around 930pm toward the end of February and by the end of March Jupiter will be only visible in twilight as it heads behind the Sun. Jupiter is not the brightest “star” in the west in the evening, that mantle belonging to Venus, shining at magnitude -4.2 ! Next month I will write a brief article on the Transit of Venus occurring in June and give a small presentation at the March Club Meeting.
Saturn, in Virgo this year, is rising at about the time Jupiter is setting (around 930pm mid February) and will become the planetary target of choice by March. As with most objects you need to wait about an hour after they rise to get decent viewing. The sky moves 15° every hour and 15° is about the minimum clearance from the horizon before the seeing becomes passable.
This is mainly due to the extra atmosphere we need to penetrate close to the horizon. The ring plane is gradually opening and will be at the greatest tilt by December but Saturn, if it is available, is the “go to” object for any observing session. At every public viewing I’ve ever attended I’ve always heard people say, “It doesn’t look real”. Hard to believe it is 1.4 billion kilometres from the Sun.
Saturn as it appears in a small telescope
As Autumn approaches the Milky Way has wheeled right over and deep sky observers begin to look out into the great void above our galaxy. Without countless billions of stars obscuring our vision we can search for all those faint galaxies in the rich constellations of Leo, Virgo and Coma Berenices, to name a few. I suggest that if you are a new observer or have a telescope with aperture around
200mm or 8- inch that you start off with the Messier objects. These are marked on any star map with a capital M followed by a number. Messier was a comet hunter who plotted these objects so that he could avoid them and not mistake them for comets in his nightly sweeps. As his equipment was of inferior quality to that which is used today he was unable to see enough detail to guess at their true nature.
His favorite telescope was a 7-1/2 inch Gregorian reflector. They are good targets because they are generally brighter than most deep sky objects. While the All Sky maps in your almanac display the M objects it would be better to use a basic star atlas like the Pocket Sky Atlas. Some of the more famous are M1 – the Crab Nebula, M42 – the Orion Nebula, M104 – the Sombrero Galaxy, M57 – the Ring Nebula. Messier has an impressive resume and there is a good biographical sketch of Messier at the following link: http://messier.seds.org/xtra/history/biograph.html
Some of you may believe that werewolves come out when there is a full moon…..and we’ve all heard about how people do crazy things during a full moon! Whatever that myth or truth is associated with full moons, to me the week of the full moon from Friday 11 November up to 19 November means that I will be busy putting in root vegetables in my garden.
Moon planting is old… I am talking, ancient! In fact, the moon planting system has been utilised by just about every early culture in the world and its popularity and relevance has not diminished over time. It is said that by planting, cultivating, harvesting, weeding and the like in the appropriate moon phase, the flavour, yield, and vigour of our edible crops can be significantly increased. This is a top outcome – for my purse, my family’s taste buds, my family’s health and the health of the planet! But what is it all about?
We know, just from sitting at the beach and watching the tide, that the moon has an impact and effect on the earth. But what has this got to do with gardening?
The moon (or lunar cycle) not only controls the tide, but is also reported to have a serious influence on the surface tension of liquids and in turn, plant growth. Scientific studies have shown that subtle changes to the biological functions of plants occur in direct correlation to the planets’ tidal changes, due to alterations to the earth’s electromagnetic fields. It is all a bit complex, but think about it this way – the moon has an impact on water movement on earth, plants take up water from the soil through their roots, while seeds require water to germinate. It makes sense then, that the phases of the moon would impact upon the way plants take up water and in turn, the way plants germinate and grow!
The moon moves through a complete cycle every 29 and a bit days, and, during that time, we have the four main moon “quarters” – the new moon, the first quarter, the full moon and the last quarter. The number of days between each change of phase can vary, but usually about 7 days.
The new moon phase – It starts from the crescent to the first quarter moon, basically when the tiniest slither of moon is visible. The moon is waxing (growing bigger) in this phase, and living things apparently feel an upsurge of energy! One thing is for sure though, sap rises during this period. Planting, grafting and transplanting leafy annuals is recommended in this phase. It’s a great time to mow the lawn, prune many plants and provide low environmental impact liquid fertiliser to the patch.
The first quarter phase – It starts from the first quarter to second quarter. The moon is still waxing (growing bigger) in this phase, and the sap is still flowing! Gardening is NOT recommended in the 12 hours before the full moon. It is still a great phase for starting things off and even better for planting, grafting and transplanting fruiting annuals (those that produce above the ground, and have their seeds inside, like tomatoes, capsicums, beans and peas).
The full moon phase – It starts from 12 hours after full moon to third quarter. All living things, be it plants, pets or people, are at the peak of their electromagnetic energy during the full moon phase (remember the werewolf, yes, it’s all about the energy!). What to do in the patch? Sap is flowing downwards during this time, so planting root crops that produce underground is perfect. Pruning and harvesting is recommended during this phase, but avoid planting most foliage and edible leaves, as their initial growth will be impressive but will wane (just like the moon during this phase).
The last quarter phase – It starts from the third quarter to the new moon. This phase is barren which, in gardening terms, can be translated as a bit boring and tedious. This phase is all about doing those annoying jobs in the garden, the ones we put off all the time like: weeding; cultivating; pest control and fertilizing. It’s also the best time to mow the lawn, especially if you want to slow down the growth of the grass. Preparing patches for impending planting is a perfect project during this phase.
Well now that I’ve explained to you what moon planting is all about, watch out! I do crazy things during the full moon! I plant potatoes!