Archive for the ‘Astronomy blog’ Category

Dave Herald answering a question on lunar eclipses_Nick Lomb

Veteran amateur astronomer Dave Herald answering a question after giving a presentation at the 2014 National Australian Convention of Amateur Astronomers. Image Nick Lomb

Attending part of the recent National Australian Convention of Amateur Astronomers I was struck by the high standard of work being done by Australian amateur astronomers. With modern equipment, dedication and expertise many are making observations and obtaining results that just a few years ago were the province of professional research astronomers.

A presentation by veteran amateur David Herald of Murrumbateman in NSW on the observation of asteroid occultations illustrates the significant results that are being obtained. Asteroids are small rocky bodies circling the Sun, generally between the paths of Mars and Jupiter. Occultations occur when an asteroid, as it circles the Sun, moves in front of a star and blocks its light for a few seconds or tens of seconds.

To observe an occultation observers spread out across its expected path and get ready to time when the light of the star blinks off and then blinks on again. For one observer each pair of times gives a chord across the shadow of the asteroid and, as the star is such a long way away, the shadow has the same dimensions as the asteroid. With a number of observers providing chords from near, but separate places useful results can be obtained.

In recent years observing such occultations has become easier. Years ago the prediction of an occultation would involve a large area, eg that it could occur somewhere in the region between Brisbane and Hobart. Now star positions are known to much greater accuracy thanks to space-based observations and the predictions of where an occultation could be seen are much more precise.

Occultation observations are now quite common with 64 observed in Australia in a recent 12 months period with 65 observed in Europe and 21 in Japan.

Recent discoveries include a satellite of about 5-km width circling the asteroid 911 Agamemnon. No Earth-bound telescope could have discovered such a small satellite. The satellite is particularly interesting as it is the second satellite discovered circling an asteroid that shares a path with the giant planet Jupiter.

Occultation timings are made with video cameras and extremely accurate timing signals. If the star being occulted is a double star the video recording will show that the star does not blink out instantaneously, but in a step-wise fashion. In this way a number of stars have been shown to be close double stars with very small separations. Seven such new double stars have been discovered since June 2012.

Asteroid occultations

A schematic diagram of the results of the observations of an asteroid occultation. Based on Figure 1 of the journal article “Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes”

From observations of the light variations of spinning asteroids at different positions in their orbits around the Sun, often by amateur astronomers, it is possible to build up models of asteroid shapes. Occultation observations allow a direct check of these models and, if there is more than one model for an asteroid, to determine which model is the better approximation. More importantly, the occultation timings also give the scale or size of an asteroid.

An example is the asteroid 9 Metis that was observed on 7 March 2014. The observations could be used to show one possible model fitted the asteroid well, while another did not.

The results described by Dave Herald make important and serious contributions to astronomical research. Many are published in professional astronomical journals under the names of the amateur observers involved together with professional astronomers.

Dave and his fellow occultation observers are looking for other people around Australia to join them in making these exciting and useful observations. Only a relatively small telescope is needed but any takers would need to invest in some necessary video and timing equipment.

Daily cosmobite: the Gum Nebula

Published by Nick Lomb on No Comments

23_Computer simulated image of Gum Nebula_Wikipedia Commons_Roberto MuraDiscovered by Australian astronomer Colin Gum in the 1950s, this is a giant bubble of gas that spreads over the constellations of Vela, Puppis and Carina. Scientists believe that it is the remains of a star that exploded over a million years ago. Its centre is about 1300 light years away.

Computer simulated image of the Gum Nebula. Courtesy Roberto Mura and Wikimedia Commons

Daily cosmobite: the Vela supernova remnant

Published by Nick Lomb on April 22, 2014 No Comments

22_Vela supernova remnant_AAOThis remnant of an exploding star is on the border of the constellations of Vela and Puppis. Inside the nebula there is a pulsar or neutron star spinning at over 100 times a second. In 1977 Australian astronomers found that this gives off brief flashes of light as it spins.

The Vela supernova remnant. Photograph from UK Schmidt plates by David Malin. Courtesy Australian Astronomical Observatory

The passing of Neville Wran is a time to reflect on how much he  contributed to the preservation of important buildings and collections in New South Wales, and to acknowledge the major investment made to our shared cultural heritage during his premiership.

Macquarie Street was transformed during the ‘Wran years’ with the Mint and Hyde Park Barracks transferred to the Museum of Applied Arts and Sciences (MAAS) in 1979. Both buildings were in a state of neglect and used as government offices. After extensive work by the NSW Public Works department, and interpretation by MAAS, The Mint was opened to the public in 1982 and then the Hyde Park Barracks in 1984.  These buildings were important in the early colony, and had varied histories which were told through MAAS collections.

I was employed as a Display Planner by the Museum of Applied Arts and Sciences in 1983 and whilst at our drawing boards in the Hyde Park Barracks, designing the exhibits on a wet and windy evening, my colleagues and I were surprised when a knock on the window turned out to be the Premier himself . Neville Wran walked in saying : ‘I saw the light on and thought I would drop in to see what was happening in here’.  Wran had a good look at our plans and the proposals for this very important convict site, now UNESCO World Heritage listed.

Sydney Observatory today. Photograph Geoff Wyatt.

Another major icon of the State, Sydney Observatory, ceased research astronomy in 1982 to become a public observatory and museum of astronomy.  Apart from its own history providing essential time, meteorology and surveying services to the State, Sydney Observatory came with a collection of clocks, telescopes and other instruments dating back to 1821. The MAAS has provided the conservation and curatorial services to build on, preserve, and continue the use of these outstanding collections. The Observatory building was in poor state when the MAAS took it over, but, guided by Government architect, Ian Sansom, and curator Nick Lomb, the government spent substantial funds on the sandstone exterior, interiors and gardens in the mid 1980s. Sydney Observatory and its collection are now State Heritage listed and on the UNESCO/IAU Portal to the Heritage of Astronomy.

Some people will remember when the Museum of Applied Arts and Sciences was located in a 20th Century Arts and Crafts building on Harris Street, adjacent to the Sydney Technical College and featured the noughts and crosses machine and a model of the Apollo Lunar Lander which stood outside. By the 1970s the MAAS had long outgrown its site and ability to care for a growing collection.

On 13 August 1979 Neville Wran announced that the derelict Ultimo Power Station and tramsheds would become a new museum for Sydney.  A few months later Jill Wran opened a fine exhibition of the Royal Doulton from the Museum of Applied Arts and Sciences collection. The exhibition was staged in Centrepoint shopping centre , because, according to the Museum’s curator Margaret Betteridge, the Museum, had insufficient space to showcase such a large collection most of which was kept in store. This exhibition showed that the Museum had significant collections and that it needed more room.  Wran also wanted to share the vision of the new Museum and in 1980 the Premier’s department, State Rail Authority and the MAAS fitted out a train to take the collection and programs to rural and regional locations across NSW.  This was rebranded as ‘Museum on the Move’ in 1984 and featured a history of NSW.

Tramsheds and Ultimo Power Station, Government Printing Office Collection, Mitchell Library, State Library of NSW.

The Power House Museum was a grand ambition and shared vision of Neville Wran, Museum Director Lindsay Sharp and Government Architect Lionel Glendenning. In 1981 Wran opened ‘Stage 1’, a vibrant, interactive exhibition space, with behind the scenes well-equipped workshops and a state-of-the-art collection store and conservation facilities. This was the staging house from which the Powerhouse Museum would emerge.

On 10 March 1988 the Powerhouse Museum was opened by the Premier, Neville Wran. He maintained his interest in the Museum and in 2003 I had the opportunity to take him through an exhibition at the Powerhouse Museum about the influence of architect and designer, Augustus Welby Pugin called ‘Creating a Gothic Paradise: Pugin at the Antipodes’.  Of course Neville Wran knew far more about Pugin’s influence on the gothic revival architecture of buildings such as The University of Sydney and the many churches in regional areas of NSW than I did.

Powerhouse Museum opened 10 March 1988

21_Vela above the Southern Cross_2013 Sydney Observatory Sky GuideThe constellation of Vela the Sails is high in the south in the early evening to the right or west of the Southern Cross. Its brightest star Gamma Velorum is the star furthest towards the west. This star is the brightest example of a group of hot massive stars called Wolf-Rayet stars.

The constellation of Vela. Sky chart from the 2014 Australasian Sky Guide

Daily cosmobite: amateur astronomers meet in Melbourne

Published by Nick Lomb on April 19, 2014 No Comments

19_NACAA logoThis Easter weekend amateur astronomers from all over Australia will gather in Melbourne at the 26th National Australian Convention of Amateur Astronomers. Topics to be discussed include collaboration with professional astronomers, observing comets by eye, photographing the Sun and the intriguing “Spotty stars”.

The NACAA logo. Courtesy NACAA

Daily cosmobite: Alpha Centauri

Published by Nick Lomb on April 18, 2014 No Comments

18_Pointer stars_Beta Cen on top_15 May 2010_Nick LombThe brightest of the two pointer stars to the Southern Cross is Alpha Centauri, also known as Rigel Kentaurus. Even a small telescope reveals it as a beautiful double star. The two components take about 80 years to circle around each other and will be at their closest for a while in November 2015.

Alpha Centauri is the lower of the two pointer stars in this image. Image Nick Lomb

Daily cosmobite: the Southern Cross

Published by Nick Lomb on April 17, 2014 No Comments

17_The Southern Cross over SO_Nick LombThis is the best-known star group or constellation in the southern sky. At this time of the year it is high in the southern sky in the evenings. It is easy to recognise as it is always accompanied by two bright stars, the pointers.

The Southern Cross appears above the Sydney Observatory time ball. Image Nick Lomb

Daily cosmobite: zodiac constellations

Published by Nick Lomb on April 16, 2014 No Comments

16_Gemini_StellariumThese are the constellations that the Sun passes through during the course of a year. Looking from west to east in the early evening the following zodiac constellations are visible: Taurus, Gemini, Cancer, Leo, Virgo and Libra.

The constellation of Gemini the Twins with the main stars shown. Courtesy Stellarium

15 April 2014 Moon eclipse from Melbourne

Published by Nick Lomb on April 15, 2014 No Comments

15 April Moon eclipse_end of totality_Nick Lomb

The Moon eclipse of 15 April 2014 soon after the end of totality. Picture Nick Lomb

The sky was gloriously clear in Melbourne and once the Moon cleared the trees it was a magnificent eclipse.

Moon eclipse_partial phase_Nick lomb

The partial phase of the Moon eclipse after the end of totality. Photo Nick Lomb

The part of the Moon still in the Earth’s shadow remained reddish well into the partial phase even as the other part already had direct sunlight.

Let’s hope for a clear sky in Sydney for the next Moon eclipse on 8 October 2014!

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