Posted by on May 16, 2022 in Main |

Society secretary Dominic Curran delivered the presentation at May’s society meeting

Society secretary Dominic Curran delivered a presentation of the contribution from Australia in the fields of Astronomy and space exploration, at the April monthly meeting of the society.

The starting point was how the first nation peoples in Australia viewed and understood the night sky. He explained that their culture was rich in legends about the world around them and the skies above them. They saw patterns in the night sky that represented animals and plants that were familiar to them.

Peoples in the North of Australia saw the start pattern know to us as the Southern Cross as a Stingray being chased by a shark. Other tribal groups identified the Southern Cross as an Emu.

The first nation peoples learned when to look for seasonal food sources, such as eggs and fish, by watching for the first appearance of particular bright stars. They created rock art based on their understanding of the night sky.

He explained that there are few sights as beautiful as the skies of the southern hemisphere. Bright stars and exotic constellations. The mysterious glow of the Magellanic clouds, and the graceful arc of the Milky Way overhead, flecked with dozens of silver white star clusters. Some of the most spectacular sights in the southern night sky, include…

The colourful stars,
star clusters,
and dark nebulae in and around Crux
The Southern Cross, the most famed of all southern constellations

The large and small Magellanic Clouds

The skies are rich with star fields towards the centre of our galaxy in the constellation Sagittarius. Home to dozens of nebulae and star clusters within easy reach of a beginning star gazer with binoculars.

The next chapter in the presentation concerned a man from Yorkshire. Captain James Cook. The main reason for the voyage of 1769 to the South Pacific – including New Zealand and Eastern Australia, Was an astronomical observation of Venus.

Captain Cooks voyage to observe the transit if Venus depicted on a British postage stamp

Cook lead the voyage to the otherside of the world on the island of Tahiti Astronomer Charles Green carried out the detailed observations. A transit is a crossing of a planet in front of the Sun’s disc. It was known that accurate timing of this event from many different parts of the Earth could be used to make an accurate calculation of the distance from Earth to the Sun. It was a great success for science.

In the 19th Century, many observatories were built in Australia. Astronomy enjoyed great popularity. The observatories provided the astronomical data for accurate measurement of time, longitude and tides, Used to study the southern skies that could not be seen from Europe.

The Sydney observatory photographed in 1874

During World War II, research concentrated on the technology called radar. Mount Stromlo Observatory near Canberra was used to build precision optical instruments.

Mount stromlo observatory

After 1945, radio scientists turned the radar receivers towards space.
The impressive research that followed at the CSIRO made Australia one of the world leaders in the new science of radio astronomy.

The Parkes Radio Telescope, was completed in 1961. It was involved in many projects such as a catalogue of the southern sky at a number of radio wavelengths.
Used in pinpointing the star responsible for the radio source known as 3C273. The operators accurately timed the cut-off and recommencement of its radio signals as the Moon occulted the source.

Working in co operation with Nasa, as a network of radio dishes, the Parkes telescope received the pictures that showed man’s first steps on the Moon in 1969.
It received pictures and other information from Voyager at Uranus and Neptune in 1986.

The Mount Stromlo observatory, expanded its research projects and continued as an important centre for the training of new astronomers.
In 1957 it became part of the Australian National University (ANU).

The Anglo-Australian Observatory, located at Siding Spring mountain, in the Warrumbungle Range of New South Wales. It is a Computer controlled 3.9 m telescope. It has ‘IRIS’ an inferred camera with 16,000 detectors working together, with an optical fibre network to record the individual spectra of many objects simultaneously.

The Sydney University Stellar Interferometer ‘SUSI’ Has 12 small mirrors are set out at fixed positions along a line 640 m long. The mirrors are used two at a time and can mimic the resolution of a huge mirror up to 640 m in diameter. It can measure the apparent angular sizes of stars down to 0.00015 sec of arc. Equivalent to the diameter of a human hair viewed from a distance of 100 km.

The Sydney University Stellar Interferometer SUSI

The Australia Telescope was completed in 1988. It is a system of eight radio telescopes which can work together to act like one giant telescope 320 km across. Five of these can move along a 3 km long track. The 7th dish is a 22 m, 100 km in the South, near Coonabarabran. The 8th dish is the 64 m Parkes telescope. For some projects these telescopes have been linked to other near Hobart and in Perth, to simulate a radio telescope stretching across Australia.

After the second world war Australia and Britain developed the Rocket launch site at Woomera, in the state of South Australia. The name is aboriginal and means ‘ Spear throwing device’.

The Woomera rocket site in the 1950’s

Prospero satellite also know as the X-3 project. was launched by the UK on 28th October 1971, from Woomera. Using a British developed Black Arrow rocket.It was designed to undertake a series of experiments to study the effects of space environment on communication satellites. It was the first and sadly the last such satellite launch made by Britain.

Dominic explained the story, a particularly exciting aspect of astronomy is ‘discovery’. Sitting in front of a computer, looking at telescopic data, you suddenly realise you are the first person ever to have witnessed some astronomical event. But frustratingly there is often no one else around to share your discovery with!

Ian Shelton must have felt that surge of excitement on 24th February 1987, when developing photographic plates of the southern sky.
One of a region near the Large Magellanic Cloud, showed a bright star where no bright star should be. Stepping outside he looked up and became the first person in almost 400 years to see a supernova with his unaided eye.
A supernova as we all know is the death of a massive star, one that begins life with more than about eight times the mass of the Sun. But of course this supernova didn’t really occur in 1987.
The star, Sanuleak –69 202, was actually in the Large Magellanic Cloud and that was about 160,000 light years away. What Ian saw was just the delayed ‘movie’ of an explosion that really happened 1600,000 years ago.
That movie of the exploding star is still travelling, at the speed of light through our galaxy.

Supernova 1987a

In 1989 it passed the star Chi Draconis. That star is on the opposite side of the celestial shere from the next object we will look at SN 1978A.

In February 1987 a giant star exploded in the southern hemisphere sky.
The brightness of the star rose significantly as observers saw it brighten to shine as bright as stars visible with the naked eye.
The intensity then fell but it was noticed that it dimmed with a characteristic exponential shape.

SN1987A taught us a lot about exploding stars. We used to think only red supergiant stars (like Betelgeuse in Orion) could go supernova, but this one was a blue star. The detection of neutrinos two hours before the visible light helped us understand what really powers the explosion, and such a bright supernove in an age of radio-telescopes, digital cameras and spacecraft has provided a wealth of information that still keeps astronomers busy.

One significant change between 1987 and now is hidden in the name; SN1987A. The ‘A’ means it was the first supernova discovered that year, in a time of photographic film and eyes at telescopes. So far this year (up to 23rd February) already 33 have been reported. Many of these found by automated telescopes with digital cameras for eyes and a computer algorithm making the discovery.

This giant star became known to astronomers as Supernova 1987A
It exploded in one of the smaller galaxies in the cluster called the LMC.
The explosion was only 150000 light years away.
Making it the closest supernova explosions.
Astronomical observations from Australia began within a few hours of the explosion commencing.

Stunning features of the southern night sky were pointed out:-
The Southern Cross
Alpha Centauri
The Jewel Box
The Milky Way
The Sagittarius star clouds
The Eta Carina region
The Large and Small Magellanic Clouds

Five of the best sights from the Southern Hemisphere were listed :-
The Tarantula Nebula
47 Tucanae
Omega Cetauri
The sculptor Galaxy
Carina Constellation

NASA’s Spitzer Space Telescope has captured in stunning detail the spidery filaments and newborn stars of the Tarantula Nebula, a rich star-forming region also known as 30 Doradus. This cloud of glowing dust and gas is located in the Large Magellanic Cloud, the nearest galaxy to our own Milky Way, and is visible primarily from the Southern Hemisphere. This image of an interstellar cauldron provides a snapshot of the complex physical processes and chemistry that govern the birth — and death — of stars.
At the heart of the nebula is a compact cluster of stars, known as R136, which contains very massive and young stars. The brightest of these blue supergiant stars are up to 100 times more massive than the Sun, and are at least 100,000 times more luminous. These stars will live fast and die young, at least by astronomical standards, exhausting their nuclear fuel in a few million years.
The Spitzer Space Telescope image was obtained with an infrared array camera that is sensitive to invisible infrared light at wavelengths that are about ten times longer than visible light. In this four-color composite, emission at 3.6 microns is depicted in blue, 4.5 microns in green, 5.8 microns in orange, and 8.0 microns in red. The image covers a region that is three-quarters the size of the full moon.
The Spitzer observations penetrate the dust clouds throughout the Tarantula to reveal previously hidden sites of star formation. Within the luminescent nebula, many holes are also apparent. These voids are produced by highly energetic winds originating from the massive stars in the central star cluster. The structures at the edges of these voids are particularly interesting. Dense pillars of gas and dust, sculpted by the stellar radiation, denote the birthplace of future generations of stars.
The Spitzer image provides information about the composition of the material at the edges of the voids. The surface layers closest to the massive stars are subject to the most intense stellar

The presentation closed with the future Plans the federal government of Australia has to continue its expertise in the field of radio astronomy.

The Australian government has recently announced a multi million dollar investment for Australia’s first mega- science infrastructure project, the Square Kilometre Array, in western Australia. It will be the worlds largest radio telescope.

The Square Kilometre Array will be made up of two telescopes; one in western Australia and one in South Africa. Both telescopes will be working together collaboratively.

In Australia, over 131,000 antennas shaped like metallic Christmas trees that for the array will tune into lower frequency emissions from deep space. It will feature 197 traditional looking radio antenna dishes that will be searching for signals in the higher frequency range.

The last video to accompany this presentation was a time lapse of the night sky from the Australian outback.