Where do the hourly pips on the radio come from?

The relays that used to send the pips through telephone lines to the various commercial radio stations in Sydney. The stations are listed on the board at the back. Picture Powerhouse Museum.

Where do the hourly pips come from? Recently the topic was extensively discussed on Adam Spencer’s Breakfast program on ABC702. For many years the pips originated from Sydney Observatory. I can well remember that on a few occasions the pips were not sent (due most likely to a fault in the Telecom Australia, now Telstra, lines) and immediately the Observatory’s two phones were running hot with complaints from the radio stations.

First a few facts about the pips:
* They are also known as the six-dot signals and it is the last of the six pips that marks the hour.
* Broadcasting of the pips began in Australia in July 1940.
* The time indicated is based on UTC – Coordinated Universal Time. This time scale is based on the rotation of the Earth but it is adjusted by the occasional insertion of leap seconds to align the scale to that of atomic clocks.

The basement of Sydney Observatory in about 1982 showing part of the time signal system including the slave clock of Shortt No. 49 to the right of the old refrigerator. Picture Nick Lomb

In the late 1970s Sydney Observatory was providing the hourly signals to the commercial radio stations in Sydney. The ABC had its own separate source of time though it still received the signal from the Observatory as a comparison. The signals were generated by a Rubidium atomic clock and then separately to each station via a set of relays – one for each station – were on display together with the rest of . the time equipment in the Observatory’s basement. This was a most eerie place to go into late at night when there was no sound except that of the ticking of a whole host of clocks.

The face of the historic 1865 Frodsham astronomical regulator clock that was part of Sydney Observatory’s time signal system. Picture Nick Lomb.

The other clocks were part of two separate complex networks that provided back-ups in case of failure by the atomic clock. The two network both included Shortt pendulum clocks that were the most accurate mechanical clocks ever devised and kept time to about one hundredth of a second a day. They each consisted of a master and a slave clock. In the master clock a pendulum swung in vacuum and every 30 seconds controlled a slave clock in a separate room. It was the slave clock that had the dials and sent the electrical signals for the time.

An astronomer using Sydney Observatory’s transit circle telescope in the early 1900s. Powerhouse Museum picture.

Prior to the arrival of the atomic clock in about 1970 the Observatory astronomers regularly used the transit circle telescope to check time by the stars. Each star crosses or transits the meridian – the imaginary line passing from north to south and through the zenith – once a day. A transit telescope or a transit circle can only move along the meridian. With it an astronomer can accurately determine the time of transit of the star. For stars with known positions in the sky the time of transit indicates the correct time and any deviation from that time shown by a clock is a clock error.

The chronograph that recorded the times when astronomers observed a star crossing the meridian with the transit circle, pictured in about 1982. The drum rotated once a minute and a pen marked each second on a large piece of paper wrapped around the drum. The observed transit time was recorded as an extra mark. Picture Nick Lomb

Sydney Observatory stopped providing the time signals soon after it became part of the Powerhouse Museum in 1982. The atomic clock broke down after a lightning strike and the Museum decided not to spend the funds for its repair or replacement as the time service was felt to be inappropriate for the Observatory’s new role as a museum and a public observatory. I then contacted Telecom Australia and arranged for them to take over the role.

Let’s conclude with my favourite time signal story which took place some years ago. I was at a NYE party and the host put on the radio so that we would know the exact time of the New Year. The radio station was broadcasting not the pips but the telephone time – “On the third stroke the time will be …”. Well and good except that the station forgot to take off the usual seven second time delay mandatory when broadcasting a telephone conversation! So the New Year arrived seven seconds late for many Sydneysiders that year.

Andrew spots a massive eruptive prominence

At the February 2010 meeting of Sydney City Skywatchers the guest speaker was Associate Professor Mike Wheatland from Sydney University. Mike presented “A Sunspot’s Tale”. Sunpots are regions on the Sun’s surface with strong magnetic fields, a magnetic “storm” if you like. Around sunspots intense magnetic explosions or flares can occur. How flares are actually produced is poorly understood, but they give out intense storms of X-rays.

Typically, from each active region we expect to receive many bursts of weak X-rays and fewer and fewer bursts of more and more powerful X-rays. This sort of pattern, called a power-law distribution, is very common in nature. For example, there are many cities with a relatively small population but only one or two with truly enormous populations. But at some point we would expect the power-law to come to an end because there has to be a limit somewhere to the energy involved in a flare. Unfortunately, this limit has never been seen in the data.

After being very quiet for the last two years, with few or no sunspots for months on end, at the end of October 2009 the Sun produced ‘active region 11029′. Appearing alone it gave Mike an excellent opportunity to study it in isolation. He discovered that it produced many weak flares, as expected, but no powerful flares. Careful analysis showed that it did indeed have the expected limit – something never before observed for an active region. The combination of an isolated active region and one that was small, and therefore incapable of producing very strong flares, had allowed Mike to make his fantastic discovery.

Given that several solar experts were present in the room I took the opportunity to ask for a consensus opinion – has the Sun woken up? Has the next cycle of activity begun? Yes! was the emphatic reply. This is good news for now we can expect to see plenty of large and active prominences, flares and sunspots during the Observatory’s regular solar-telescope viewing sessions.

As if to prove the point today (3 February 2010) the Sun produced a magnificent eruptive prominence. It stretched tens of thousands of kilometres above the Sun’s surface and several hundred thousand kilometres around the limb. Incredibly, we could see it change shape as we watched, something not usually visible. The image below shows the changes over approximately ten minutes! Yes, I think the Sun has finally woken up for solar cycle number 24.

Image by Geoff Wyatt and Andrew Jacob

Harry sees the Sun wake up – a report on the mid January 2010 sunspot AR11040

Sunspot AR11040, drawn by Harry Roberts

2009 December saw the sun unleash a salvo of sunspot groups – with six in the month! As if pausing for breath, the sun has (so far) produced only one group in 2010 January: AR11040. Some observers saw a small group near 11040 mid-month but it survived less than 24 hours and did not get a region number.

AR11040 grew big quickly – and many hoped for a major activity burst – but it was not to be. When first emerging it was said to be the return of November’s earlier group AR11035 that hosted flares up to GOES class C5. This previous group had covered 10º of longitude with penumbral fields of 2500 gauss (the strongest to date), and its preceding (p) spot was sited at 27/253 with the following (f) spot at 29/243.

When AR11040 appeared its (p) spot was at 30/244, the same [coordinates for all practical purposes - Nick] as the earlier group’s following spots! AR11040’s (f) spot was further east at 32/238; the two groups were linked together like railway carriages – but separated in time. Yet the centres of the two groups were 7 to 8 degrees apart – and presumably are separate groups.

My first record of AR11040 was on Jan 8 (Fig1) when it had four elongated (p) spots followed by seven or so (f) spots 6º to the east. Large filaments attended the group and spread over much of the sun’s NE quadrant –an impressive sight – accompanied by bright faculae over a wide area. In H-alpha bright plage threaded through the (f) spot, with a surge at 23:57UT.

Long-lived filaments and faculae are a feature of many C24 spots on returning, and this suggests the new group was indeed embedded within remnants of AR11035 activity. However AR11040’s spots behaved like a new group. Clouds intervened, and when next seen on Jan 12 the group stretched across >ten degrees of longitude – an impressive sight (Fig2) with 16 or more spots in two large penumbral patches. It looked set for ”fireworks” but umbral fields were <2300G and only GOES B class flares.

Changes in sunspot AR11040, drawn by Harry Roberts

Figs 2, 3 and 4 are centrally aligned, allowing us to follow changes between the 12th to the 15th – dotted lines suggest developments “Helio” © freeware had the group’s area peaking on the 12th 22:30 at 400 units over a longitude of 11 degrees. Both (p) and (f) spots had umbral fields of 2300G (Mt Wilson data). On the 15th(Fig4) the group had shrunk a bit and grown less complex, with a large faculae patch preceding – though most of this is due to perspective with the group now 45º west of the central meridian (CM).

Sunspot AR11040 near the Sun’s limb, drawn by Harry Roberts

It seemed AR11040 was waning, but as it neared the limb (16th Fig5) new field with (f) polarity (R18) emerged near the preceding spots (arrow) – an increase in complexity – and some (p) spots aligned to the interloper – a filament, surge and bright plage developed there, but the group’s following (f) component was reduced to a chain of umbral spots (Fig5). Huge areas of faculae and long filaments could be seen, showing that the group was influencing a wide area of the sun. Whatever is needed for big flares was missing in AR11040 – it had many GOES B-class flares and a few C1 and C2 flares – but these are minor events given the its complexity and size.

Yet it was a great subject to study. Will it survive to return on Feb 2nd, crackling with flares? (And what about group AR11041, approaching fast, just behind the east limb- awaiting its turn on the stage!).

[Since Harry wrote the above AR1041 has emerged displaying considerable activity. For updates on what is happening on the Sun see the Spaceweather website - Nick.]

Harry Roberts, Sun and Moon observer and member of the Sydney City Skywatchers

February 2010 night sky guide and podcast

To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month.

This month’s audio sky guide is presented by Melissa Hulbert, an Astronomy Educator at Sydney Observatory. You can listen online, or download the audio onto your ipod or mp3 player. Links to the audio and the star map are below.

There is more information and detail in our annual book, written by Dr Nick Lomb, ‘The Australian sky guide’. If you are interested in the ‘2010 Australian sky guide’ with information and star maps for months from December 2009 until December 2010 inclusive, plus information about the Sun, twilight, the Moon and tides, and a host of other fascinating astronomical information, you can purchase it at Sydney Observatory and Powerhouse Museum shops or online through Powerhouse Publishing.

The free monthly night sky map PDF (below) shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.

February 2010 night sky map

Read the transcript.

 

 February 2010 night sky guide – 11 mins: Play Now | Play in Popup | Download

Honour to mischievous astronomer – congratulations to Professor Fred Watson AM!

Fred Watson misbehaving behind Nick Lomb’s back at an event at Sydney Observatory in December 2009, picture Geoff Wyatt

Professor Fred Watson is probably the most publicly known astronomer in Australia. With his regular astronomy segments on the ABC, his public talks, books and other activities, the Astronomer-in-Charge of the Anglo-Australian Telescope at Coonabarabran is making astronomy accessible to people around Australia.

I have long bemoaned the lack of recognition for physical scientists in the Australian honours system. There are always plenty of sports people, television personalities and medical scientists on the list, but few in the physical sciences. So I was doubly pleased to see Fred Watson’s name in the Australia Day honours list. And not just any old award! Fred became a Member (AM) in the General Division of the Order of Australia.

The citation reads:

For service to astronomy, particularly the promotion of space science through public outreach.

As can be seen in the picture above Fred Watson is known for his humour. He is alo known for his skill in making up witty mnemonics for scientific projects. There was FLAIR (Fibre Light ?) and now he is project manager for RAVE (RAdial Velocity Experiment). He once unforgettably wrote a letter to the Sydney Morning Herald explaining that his name is really a mnemonic for Forgotten Remnant of an Extraterrestrial Disaster.

Fred Watson has been a good friend of Sydney Observatory for many years and has given numerous talks there that were always highly popular. As well, he has had live radio appearances there on the ABC including for the Evening Show and recently during the celebrations of the Observatory’s 150th anniversary in June 2008.

More details on Fred Watson and the award are in the Anglo-Australian Observatory press release.

Congratulations Fred Watson AM! Well deserved recognition!

Harry sketches one of the favourite objects in the Australian summer sky – the Great Nebula in Orion

The Great Nebula in Orion, sketch by Harry Roberts

Like most amateurs perhaps, my first view of a nebula was M42 in Orion. In our summer skies the hero’s sword hangs upwards from his belt, and in 1962 a school friend showed me the “sword’s” central star with his 4” reflector. Back then Adelaide streetlights went off at midnight (truly) – and the sky was dark. The impact of seeing the “Great Nebula” for the first time is with me still, and recalls summer holidays of years ago.

For “sky sketchers” M42 is a big task – it‘s very large, with much complex detail, and has a huge brightness range. A while back a friend suggested an attempt on the nebula in pencil, with a series of images recording it in parts. Recently I made a start on the “Orion Project” from my backyard, to be augmented later from darker sites. Before starting I compiled a chart of the main background stars from astro-maps to save observing time The ten inch “dob” and the C8 were both used with the 14mm Radian eye piece – and surprisingly the static image in the C8 at 140x gave the best view. And what a view it was: the sky was surprisingly good with nearby trees enhancing the darkness.

Theta 1 Orionis, “The Trapezium”, was clearly seen as six stars, each brilliant and steady, with 10.5 mag. components E and F bright specks well clear of the four main stars. They all seemed to sit in a darker patch of the main nebula – perhaps a contrast effect. Theta 2 Orionis just to the SE with its two bright neighbours formed a line pointing almost due east. The background of the Great Nebula was peppered with small stars to <11 mag. I set to with pencil and blender to map as much of the nebula as possible over about 2½ hours, adding notes on brightness, detail sketches etc.

E. E. Barnard saw M42 as “resembling a great ghostly bat” in the Yerkes refractor, and Barnard’s “Bat” loomed over the bright nebula on the north side – being the only truly dark part of the whole field – all the rest was luminous to a greater or lesser extent, and it was soon clear that my chart covered only the brighter half of the nebula! The very nebulous star V372 marks the southern edge of my sketch – but is in fact the centre of the whole vast nebula.

Apart from the “Bat’s” wings and head (also called the “fishes mouth”), there was another smaller feature that looked truly black. This was a dark column that seemed to occult the inner bright region of the nebula about 1.5’ SW of the trapezium, with maybe a faint dust tail blowing away southwards; while I’ve viewed M42 many times I’d never seen the dusty feature! Perhaps this object is one of the cooler “trunk-like structures” sustained over light-years by magnetic fields – as some research suggests. This one in M42 is easier to see than most others in, say, the “Eagle Nebula” M16, or the Eta Carina nebula.

There was too much detail to record, and the outer parts of the nebula are only sketched in brief. Within its brightest parts the nebula contains incredible detail too that I will tackle in future sessions with the 4.8 Nagler (X400), and perhaps OIII and Hα filters as well – none were used for this first sketch.

Enjoy the summer nebula – the brightest in the sky.

Harry Roberts, Sun and Moon observer and member of the Sydney City Skywatchers

Mars at opposition late January 2010 – a good time to view the red planet

Mars oppositions 2003 to 2018, drawing Nick Lomb

Have you noticed a red object low in the eastern sky soon after dark? The planet Mars is bright at the moment (January 2010) as it at its closest to us for the last two years and the closest for the two years to come. Thus it is a good time to visit Sydney Observatory, or your nearest public observatory if you live out of Sydney, to view the planet through a telescope.

Mars is close to the Earth as it will be at opposition at the end of the month. A planet is at opposition when it is at the opposite side of the Earth to the Sun. With Mars these oppositions take place at roughly two years intervals as this is the time the Earth takes to lap Mars which, of course, moves slower in its path around the Sun than the Earth.

In the drawing above, the small yellow disc in the centre denotes the Sun, the circle with the months indicated shows the Earth’s path around the Sun and the oval shape outside the Earth’s path is that of Mars. As can be seen, that oval shape means that some oppositions are more favourable than others. The famous August 2003 opposition was exceptionally favourable with Mars only 56 million km away from Earth. It was so exceptional that a hoax email has been circulating ever since.

Mars at opposition in 1924, from ASA Factsheet 13, Australian Astronomy

In 2010 Mars is somewhat further away at opposition – 99 million km – thus will appear smaller in a telescope than in 2003. Still it is worth looking. If the conditions are right some of the dark features on the surface maybe glimpsed as in the sketch from 1924.

Mars is at opposition on the morning of Saturday 30 January 2010 in Australian time. This date coincides with the first of this year’s blue moons, making it doubly worthwhile visit an observatory. Surprisingly, Mars is marginally closer two days earlier on the night of Wednesday 27 January.

The next opposition is in March 2012 and the next favourable opposition of Mars is on 31 July 2018.

Finding chart for Mars at 9:30 pm AEDT on 27 January 2010, drawing Nick Lomb

Where do you look for Mars? As indicated on the chart above, the planet is low in the north-east sky soon after it becomes dark. Look for a bright reddish object.

Happy observing.

Harry reports on sunspot AR11036 – part of the recent upturn in the Sun’s activity

A large filament (a prominence seen edge-on) near sunspot group 11040 on the morning of Sunday 10 January 2010. Image taken in red hydrogen light by Monty Leventhal OAM

In H-alpha the sun can be amazingly active, but during solar minimum such activity has been rare. Material can be ejected from the sun in a variety of ways – and perhaps the strangest is the surge.

Surges occur near sunspots with strong umbral fields. Around such spots the chromospheric granularity is often very disturbed, and looks like long grass blown over by strong winds. Often in such regions dark (i.e. cooler) material can erupt from a point within or near the penumbra of a large stable spot, yet the material remains confined within a field structure. And what we see may at first look like more disturbed granularity – but the ejecta may then travel across a great distance (tens of Mm) often in a graceful curve. Sometimes a salvo of surges will erupt side by side as recently occurred in AR11036. Having reached a maximum distance from the “parent” spot – the surge often pauses for some time, before retracting backwards (backflow) along its original path – to disappear where it first emerged! While this sounds implausible, surges are relatively common around certain spots.

Sunspot AR11036, drawn by Harry Roberts

AR11036 emerged in the sun’s SW quadrant about Dec 20, with a few tiny preceding (p) spots and two or three larger following (f) spots, these in one penumbra (Fig). When I first saw it, alerted by Monty L, it was attended by several surges, including a trio (or salvo) over 40Mm in length. Other lesser surges or patches of disturbed granularity emerged from the group at points on the NE side. Sub flares were seen where the surges emerged – as is often the case. None of these were strong enough to cause a spike in the GOES X-ray background of GOES B1-class. A dark active region filament (arf) connected p and f spots, with bright plage throughout (Fig 1). No retraction phase was seen.

Shortly after (22:53UT) the same group appeared to host a filament ejection (Fig 2). This time very dark material emerged from points both south and north of the f spot group. This followed similar paths to the earlier surges, but was strongly tuneable in H-alpha – suggesting a Doppler shift in approach (i.e.bluewards). This suggests the ejection of one or more active region filaments (arf), as a strong shift is not usual in surges (that mostly stay near the solar surface – near vertical surge is a possibility). While this ejecta was visible on-band (central Hα) it grew very dark off-band while all other Hα detail vanished – a sign of high velocity in approach along line of sight. Strong flares usually follow filament ejections but only a sub flare was logged at 22:53 UT. A B4 at the site 40 minutes later may be associated, and the strongest C24 flare to date a GOES C7 erupted at the site six hours later together with a CME.

Clearly this small group was unusually active – having the strongest flare to date. Yet its white light appearance was that of a very minor group. It faded rapidly, and when near the limb the Mt Wilson Magnetograph recorded no detectable umbral field – Mt Wilson having been closed previously by weather conditions. We must guess at AR11036’s peak umbral fields – they were presumable strong, and recent northern group AR11035 had the strongest field yet for C24 of 2500 gauss. Are we witnessing a strengthening of C24 magnetic fields? Keep sun watching.

Harry Roberts, Sun and Moon observer and member of the Sydney City Skywatchers.

This Friday’s annular (ring-like) eclipse of the Sun is the longest for the next 1000 years!

Image courtesy of Fred Espenak, NASA’s GSFC

On January 3rd 2010 at 11am AEDT, the Earth reached its closest approach to the Sun known as perihelion. This makes the Sun look its largest for the year. Incidentally, according to the laws of planetary motion devised by the German astronomer Johannes Kepler in the early 1600s the relative closeness means that we were also travelling at our fastest in out yearly free trip around the Sun. Is this why Canberra’s Summernats car shows are held during January each year?

On January 17th at 12:41pm AEDT the Moon will reach its most distant point of its “moon-thly” orbit around the Earth known as apogee. This makes the Moon look close to its minimum size.

The result of these extremes of a big Sun and small Moon is that an eclipse close to these dates will produce a long lasting annular or ring eclipse. This Friday January 15th such an eclipse will occur but sadly it will not be visible from Australia.

The eclipse begins in Western Africa at 05:14 UT (4:14pm AEDT). The eclipse path is 331 km wide at its start as the antumbra (the circular silhouette of the Moon) quickly travels east-southeast at 10km per second.

Sun, Earth and Moon geometry means the eclipse shadow changes speed and the rapid start decreases to just 1.5km/s and increases again at the end of the eclipse. The maximum duration of just over 11 minutes at 6:59 UT to 7:10 UT will be observed from the Indian Ocean off the coast of Kenya. At over 11 minutes it will be the longest annular eclipse of the 3rd Millennium and the duration will not be exceeded until the year 3043.

The path will then pass between India and Sri Lanka, across the Bay of Bengal to Burma and lastly China’s Shandong province at 08:59UT.

However, it is vital to note that despite 91% of the Sun’s disk being covered by the Moon, it is still exceedingly dangerous to look at with the unaided eye. Permanent damage may result by attempting to look at it so please ensure that if you live under the path of the antumbra or to the sides where a partial solar eclipse will be visible than you and everyone else do not observe the Sun directly. Use appropriate filters or make a pinhole camera and project a small image of the Sun or, better still, visit your local public observatory.

For more information and the complete source of the information presented here visit the NASA web site produced by Fred Espenak, NASA’s GSFC here.