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CASS News

Bruce Slee honoured at "Slee-fest" workshop

Bruce Slee is one of the pioneers of radio astronomy and to celebrate his lifetime contribution to the field, the International Astronomical Union has named a planet after him, Minor Planet 9391 Slee.

The Minor planet naming was announced today at the "SleeFest" workshop being held to celebrate and honour Bruce's 70 year legacy to radio astronomy.

Bruce's first foray into investigations of the Solar System began in 1945, towards the end of World War II when he detected solar radio emission with a 200 MHz Royal Australian Air Force radar antennae, launching a life-long career in a field that would soon become known as radio-astronomy.

Straight after the war, Bruce joined the CSIRO Division of Radiophysics (at the time the organisation was known as CSIR) and carried out important research at Dover Heights (on the coast just south of the entrance to Sydney Harbour) which had been used by the Australian Army as a coastal defence radar station but was re-developed into a field station for radio astronomy research.

In 1946, a British radio astronomer named Hey made a surprising announcement: he detected what he described as an anomalous 'radio star' in the constellation Cygnus.

This discovery led Bruce and his colleagues, Gordon Stanley and John Bolton to continue with investigations into Cygnus-A. They began using simple 'Yagi' radio antennas and receivers and with this set-up were able to solve the mystery of the anomalous 'radio star'.

Far from being 'stars', all the radio sources they detected were discrete sources which turned out to be Taurus-A (the Crab Nebula) within our own Galaxy, while the others (Centaurus-A, Cygnus-A, and Virgo-A) were extragalactic objects, namely a pair of colliding galaxies and two individual radio galaxies.

Keen to continue their observations, but with no funding for new equipment in sight, Bruce and his colleagues decided to build a novel radio telescope themselves as a secretive lunchtime project.

Using shovels, a wheelbarrow and scrap material lying around the site, the scientists excavated a dish-shaped hole in the ground 21.9 metres across with a surface coated in ash, on top of which they laid metal strips from packing cases to provide reflectivity.

They added an adjustable antenna at the centre in order to receive the reflected radio signals, and connected this to a receiver. This instrument was the second-largest radio telescope in the world at the time, and by using the rotation of the Earth and altering the
positioning of the aerial mast it was possible to observe different regions of the sky.

After Slee, Bolton and Stanley demonstrated that the design concept worked, the 'hole-in-the ground' antenna was extended, in 1953, to a diameter of 24.4 metres and the surface was coated with concrete and lined with wire mesh to provide a reflecting surface.

At this site, Bruce and his colleagues soon established an international reputation for themselves.

Since these first discoveries, radio waves have been used to explore the entire cosmos, from the Sun and planets in our Solar System, to stars and gas in our Galaxy and beyond to other galaxies and to the most distant reaches of the Universe.

Once the Dover Heights field station was closed in 1954, Bruce moved across to the Fleurs field station (near St Marys, just west of suburban Sydney at that time) where an innovative new type of radio telescope was being trialled, known as the Mills Cross. In the mid 1950's Bruce and colleagues, Bernie Mills and Eric Hill carried out a detailed survey of the sky and recorded more than 2000 discrete radio sources. In the process, they got embroiled in a controversy with Cambridge University radio astronomers about the origin of the Universe.

By 1960 the non-stellar identity of 'radio stars' was beyond dispute, and the only genuine star known to emit radio waves was the Sun. It was time to begin searching for radio emission from other stars and the obvious first choice were the flare stars. Bruce Slee, and the distinguished British radio astronomer, Bernard Lovell, were the first to detect radio emission from flare stars.

For the last four decades, Slee and various collaborators have continued to research the radio properties of flare stars and other types of stars using a range of different instruments, including the Parkes Radio Telescope, Culgoora Circular Array (CCA), Australia Telescope Compact Array (ATCA) and the Very Large Array (VLA). Bruce has also used these radio telescopes, and others, to research many other areas of radio astronomy.

Later in his career, Bruce added the history of radio astronomy to his research portfolio, having realised that he is in the unique position as one of the last remaining scientists from the field station era and has a responsibility to document and promote Australia's remarkable early radio astronomical heritage.

Turning 92 this month, Bruce is still an active Astronomy and Space Sciences Honorary Research Associate and continues to publish papers on astrophysics (mainly on chromospherically-active stars) and on the history of radio astronomy.

On August 16th and 17th, CAASTRO (the ARC Centre for Excellence for All-Sky Astrophysics) is holding a 2-day "SleeFest" colloquium at the University of Sydney to celebrate Bruce Slee's lifetime achievements in radio astronomy and will announce the naming of minor planet 9391 Slee in his honour.

Bruce Slee is truly one of the international pioneers of radio astronomy, and over the past seventy years has made wide-ranging contributions that extend from the Solar System (the ionosphere, solar corona, interplanetary medium, Jupiter, and comets) to the Galaxy (pulsars, various types of active stars, gaseous nebulae, the interstellar medium (ISM)), and beyond to Quasi-Stellar Objects (QSOs), galaxies and clusters of galaxies.

Postscript: Bruce Slee passed away only a day after the workshop "A Celebration: Bruce Slee and 70 Years of Radio Astronomy" was held in Sydney to celebrate his long career. Our sincere condolences to Bruce's family, friends and colleagues.

Added by Fiona McFarlane on 2016-08-16

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