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Mysterious dance of dwarfs may force a cosmic rethink

THE DISCOVERY THAT many small galaxies throughout the universe do not ‘swarm’ around larger ones as bees do but ‘dance’ in orderly orbits is a challenge to our understanding of how the universe formed and evolved.

The finding, by an international team of astronomers, including Professor Geraint Lewis of the University of Sydney, was published in the prestigious science journal Nature today.

“Early in 2013 we announced our startling discovery that half of the dwarf galaxies surrounding the Andromeda Galaxy are orbiting it in an immense plane” said Professor Lewis. “This plane is more than a million light years in diameter, but is very thin, with a width of only 300,000 light years.”

The universe contains billions of galaxies. Some, such as the Milky Way, are immense, containing hundreds of billions of stars. Most galaxies, however, are dwarfs, much smaller and with only a few billion stars.

Many of the larger galaxies have dwarf galaxies circling around them. Astronomers call them satellite galaxies.

Result contradicts standard understandings

For decades astronomers have used computer models to predict how these dwarf galaxies should orbit the large galaxies, and they’d always found that the dwarfs should be scattered randomly.

“Our Andromeda discovery did not agree with expectations, and we felt compelled to explore if it was true of other galaxies throughout the universe,” said Professor Lewis.

Using the Sloan Digital Sky Survey, a remarkable resource of colour images and 3-D maps covering more than a third of the sky, the researchers dissected the properties of thousands of nearby galaxies.

An artist's impression of the orbit of dwarf galaxies about a large galaxy

An artist’s impression of the orbit of dwarf galaxies about a large galaxy. Credit Geraint Lewis. The Hubble Image Archive was used as a source of the galaxies used in this illustration.

They were surprised to find that a large proportion of pairs of satellite galaxies are travelling in opposite directions if they are on opposite sides of larger galaxy hosts, said lead author Neil Ibata of the Lycée International in Strasbourg, France. And each of the dwarfs seemed to orbiting in the same plane, or angle, around the parent galaxy.

“Everywhere we looked we saw this strangely coherent co-ordinated motion of dwarf galaxies,” said Professor Lewis. From this the astronomers have extrapolated that this phenomenon is widespread in the universe, and seen in about 50 percent of galaxies.

“This is a big problem that contradicts our standard cosmological models. It challenges our understanding of how the universe works including the nature of dark matter,” said Professor Lewis.

Keeping an open mind

The researchers think the explanation might lie in some currently unknown physical process that governs how gas flows in the universe, although, as yet, there is no obvious mechanism that can guide dwarf galaxies into narrow planes.

Some experts, however, have made more radical suggestions, including bending and twisting the laws of gravity and motion.

“Throwing out seemingly established laws of physics is unpalatable,” said Professor Lewis, “but if our observations of nature are pointing us in this direction, we have to keep an open mind. That’s what science is all about.”

Adapted from information issued by the University of Sydney.

Asteroids are pounding a pulsar

SCIENTISTS USING CSIRO’s Parkes telescope and another telescope in South Africa have found evidence that a tiny star called PSR J0738-4042 is being pounded by asteroids – large lumps of rock in space.

“One of these rocks seems to have had a mass of about a billion tons,” CSIRO astronomer and member of the research team Dr Ryan Shannon said.

PSR J0738-4042 lies 37,000 light-years from Earth in the constellation of Puppis. The environment around the star is especially harsh, full of radiation and violent winds of particles.

“If a large rocky object can form here, planets could form around any star. That’s exciting,” Dr Shannon said.

The star is a special one, a ‘pulsar’ that emits a beam of radio waves. As it spins, its radio beam flashes over Earth again and again with the regularity of a clock.

An artist's impression of an asteroid breaking up

An artist’s impression of an asteroid breaking up. Credit: NASA/JPL-Caltech

Formed from shattered remains

In 2008 Dr Shannon and a colleague predicted how an infalling asteroid would affect a pulsar. It would, they said, alter the slowing of the pulsar’s spin rate and the shape of the radio pulse that we see on Earth.

“That is exactly what we see in this case,” Dr Shannon said. “We think the pulsar’s radio beam zaps the asteroid, vaporising it. But the vaporised particles are electrically charged and they slightly alter the process that creates the pulsar’s beam.”

Asteroids circling a pulsar could have been formed by the remains of the exploding star that produced the pulsar itself, the scientists say. The material blasted out from the explosion could fall back towards the pulsar, developing into a swirling cloud of dusty debris that circles it. Astronomers call it a ‘disc’.

Not the only one

Astronomers have found a dust disc around another pulsar called J0146+61.

Parkes radio telescope

The CSIRO’s Parkes radio telescope. Photo courtesy Shaun Amy.

“This sort of dust disc could provide the ‘seeds’ that grow into larger asteroids,” said Paul Brook, a PhD student co-supervised by the University of Oxford and CSIRO who led the study of PSR J0738-4042.

In 1992 two planet-sized objects were found around a pulsar called PSR 1257+12. But these were probably formed by a different mechanism, the astronomers say.

The new study has been published in The Astrophysical Journal Letters, a leading journal of astronomical research.

Adapted from information issued by CSIRO.

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Deep freeze telescope reveals galactic carbon trail

USING A TELESCOPE INSTALLED at the driest place on earth – Ridge A in Antarctica – a UNSW-led team of researchers has identified a giant gas cloud that appears to be in an early stage of formation. Giant clouds of molecular gas – the most massive bodies in our galaxy – are the birthplaces of stars.

“This newly discovered gas cloud is shaped like a very long filament, about 200 light years in extent and ten light years across, with a mass about 50,000 times that of our Sun,” says team leader, Professor Michael Burton, an astronomer at UNSW Australia. “The evidence suggests it is in the early stages of formation, before any stars have turned on.”

Stunning new way of doing science

The team is using the High Elevation Antarctic Terahertz telescope, or HEAT, at Ridge A, along with the Mopra telescope at Coonabarabran in NSW, to map the location of gas clouds in our galaxy from the carbon they contain.

At 4,000 metres elevation, Ridge A is one of the coldest places on the planet, and the driest. The lack of water vapour in the atmosphere there allows terahertz radiation from space to reach the ground and be detected.

PLATO-R in Antarctica

The PLATO-R observatory at Ridge A. The HEAT telescope is the black object on stilts at left, the instrument module is the yellow box and the solar panel array is on the right. Image Credit: Geoff Sims.

The PLATO-R robotic observatory with the HEAT telescope was installed in 2012 by a team led by UNSW physicist, Professor Michael Ashley, and Dr Craig Kulesa of the University of Arizona.

“We now have an autonomous telescope observing our galaxy from the middle of Antarctica and getting data, which is a stunning new way of doing science. Ridge A is more than 900 kilometres from the nearest people, who are at the South Pole, and is completely unattended for most of the year,” says Professor Burton.

Following the galactic carbon trail

The HEAT telescope detects atomic carbon and the Mopra telescope detects carbon monoxide. “I call it following the galactic carbon trail,” says Professor Burton.

Mopra telescope

The Mopra telescope, near Coonabarabran in NSW.

The discovery of the new galactic cloud, which is about 15,000 light years from earth, will help determine how these mysterious objects develop in the interstellar medium.

One idea is that they are formed from the gravitational collapse of an ensemble of small clouds into a larger one. Another involves the random collision of small clouds that then agglomerate. Or it may be that the molecular gas filament is condensing out of a very large, surrounding cloud of atomic gas.

About one star per year, on average, is formed in the Milky Way. Stars that explode and die then replenish the gas clouds as well as moving the gas about and mixing it up.

The team includes researchers from Australia, Germany and the US. The results have been published in The Astrophysical Journal.

Adapted from information issued by UNSW. Image Credit: Geoff Sims.

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Oldest known star found by Australian astronomers

A TEAM LED BY ASTRONOMERS at The Australian National University has discovered the oldest known star in the Universe, which formed shortly after the Big Bang 13.7 billion years ago.

The discovery has allowed astronomers for the first time to study the chemistry of the first stars, giving scientists a clearer idea of what the Universe was like in its infancy.

“This is the first time that we’ve been able to unambiguously say that we’ve found the chemical fingerprint of a first star,” said lead researcher, Dr Stefan Keller of the ANU Research School of Astronomy and Astrophysics.

“This is one of the first steps in understanding what those first stars were like. What this star has enabled us to do is record the fingerprint of those first stars.”

The star was discovered using the ANU SkyMapper telescope at the Siding Spring Observatory, which is searching for ancient stars as it conducts a five-year project to produce the first digital map the southern sky.

Star SMSS J031300.36-670839.3

Astronomers have determined that star SMSS J031300.36-670839.3 is the oldest yet found.

A different star recipe

The ancient star is around 6,000 light years from Earth, relatively close in astronomical terms. It is one of the 60 million stars photographed by SkyMapper in its first year.

“The stars we are finding number one in a million,” says team member Professor Mike Bessell, who worked with Keller on the research.

“Finding such needles in a haystack is possible thanks to the ANU SkyMapper telescope that is unique in its ability to find stars with low iron from their colour.”

Dr Keller and Professor Bessell confirmed the discovery using the Magellan telescope in Chile.

The composition of the newly discovered star – known only as SMSS J031300.36-670839.3 – shows it formed in the wake of a primordial star, which had a mass 60 times that of our Sun.

“To make a star like our Sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron – the equivalent of about 1,000 times the Earth’s mass,” Dr Keller says.

Dr Stefan Keller with the SkyMapper telescope

Dr Stefan Keller with the SkyMapper telescope

“To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It’s a very different recipe that tells us a lot about the nature of the first stars and how they died.”

No sign of iron

Dr Keller says it was previously thought that primordial stars died in extremely violent explosions that blasted their iron into huge volumes of space. But the ancient star shows signs of pollution with lighter elements such as carbon and magnesium, and no sign of pollution with iron.

“This indicates the primordial star’s supernova explosion was of surprisingly low energy. Although sufficient to disintegrate the primordial star, almost all of the heavy elements such as iron, were consumed by a black hole that formed at the heart of the explosion,” he says.

The result may resolve a long-standing discrepancy between observations and predictions of the Big Bang.

The discovery was published in the latest edition of the journal Nature.

Adapted from information issued by ANU.

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Australian astronomer wins prestigious award

THE 2014 GROTE REBER MEDAL for innovative and significant contributions to radio astronomy has be awarded to Professor Ron Ekers of Australia. Professor Ekers was the Foundation Director of CSIRO’s Australia Telescope National Facility at Narrabri, and is a former director of the Very Large Array in New Mexico, USA, operated by the National Radio Astronomy Observatory (NRAO).

He is currently a CSIRO Fellow at the Australia Telescope National Facility (ATNF), CSIRO Division of Astronomy and Space Science in Australia, and Adjunct Professor at Curtin University in Perth and the Raman Research Institute in Bangalore, India.

Headshot of Ron Ekers

Professor Ron Ekers

The Grote Reber Medal is named after a pioneer of radio astronomy (see below).

Ekers is being recognised for his many pioneering scientific radio astronomy investigations, which extend over half a century. Working with various colleagues, Ekers studied galaxies, made precise measurements of the way the Sun’s gravity deflects radio waves, made some of the first high-resolution images of the centre of the Galaxy at radio wavelengths, and critical early observations of pulsars.

More recently he is leading a project to detect radio emission resulting from ultra high-energy neutrino interactions with the Moon.

Ekers also played a key role in developing what was probably the first interactive computer language for analysing radio astronomy images. In the mid-1990s he became the strongest force in advocating support for the international Square Kilometre Array initiative.

“Over a career lasting nearly half a century Ron Ekers has worked in almost every area of radio astronomy. As a strong believer in international collaboration, he was the earliest advocate for the Square Kilometre Array, and perhaps, more than anyone else, he was responsible for building the current level of international support for the SKA”, said Dr Ken Kellermann of the NRAO.

“Ron is the complete internationalist and has contributed significantly to the major radio astronomy instruments in Europe, the US and Australia,” said Dr David Jauncey, CSIRO Astronomy and Space Science Affiliate and ANU Visiting Fellow.

The medal will be presented to Professor Ekers during the 31st General Assembly of the International Union of Radio Science to be held in Beijing, China in August, 2014.

About Grote Reber

Grote Reber was born on 22 December 1911. Before he was 30 years of age, he became the world’s first radio astronomer. In 1937, constructed the world’s first purpose-built radio telescope, adjacent to his home in Wheaton, Illinois, just west of Chicago. Reber’s telescope was the forerunner of the classic design of the world’s famous radio telescopes (including the famous ‘dish’ at Parkes, in Australia). The same principle is used widely today in many other applications, including satellite dishes in private homes.

Reber used his telescope to make the first detailed radio map of the sky. “His work was a huge step forward for astronomy”, said Martin George, Administrator of the Grote Reber Medal. “For the first time, the Universe was being studied at wavelengths other than those visible to our eyes.”

Grote Reber using radio equipment

Grote Reber

In 1954, Reber moved to Tasmania, Australia, where he began observing at very much longer wavelengths using a quite different type of ‘telescope’: an array of dipoles, which took the form of antennas strung between the tops of poles.

Reber constructed an array that covered an area of one square kilometre. Although now dismantled, in terms of collecting area it still holds the record for the world’s largest single radio telescope ever constructed.

Although Reber’s research and ideas often fell outside the mainstream activities of other astronomers, his contributions, especially in the early days of radio astronomy, were both pioneering and critically important. He was awarded a number of prizes and an honorary Doctor of Science Degree from Ohio State University in the USA.

“Grote Reber’s achievements showed, most importantly, that one person can make a difference”, said Dr David Jauncey.

Grote Reber died in Tasmania on 20 December 2002, two days before his 91st birthday.

Adapted from information issued by Trustees of the Grote Reber Foundation. Ron Ekers and ATCA photos courtesy of CSIRO Astronomy and Space Science. Grote Reber photo courtesy NRAO.

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The ‘missing link’ pulsar

AN INTERNATIONAL TEAM of astronomers using CSIRO radio telescopes in Australia and other ground and space-based instruments, has caught a small star called a pulsar undergoing a radical transformation, described in a paper in the journal Nature.

“For the first time we see both X-rays and extremely fast radio pulses from the one pulsar. This is the first direct evidence of a pulsar changing from one kind of object into another – like a caterpillar turning into a butterfly,” said Dr Simon Johnston, Head of Astrophysics at CSIRO’s Astronomy and Space Science division.

The pulsar and its companion star

The pulsar and its companion star. The ageing pulsar rotates slower and slower, then matter from its companion spins it up again. As the pulsar is spun up, it alternates between emitting X-rays (white) and radio waves (pink). Credit: ESA

The cosmic drama is being played out 18,000 light-years away, in a small cluster of stars (called M28) in the constellation of Sagittarius.

The pulsar (called PSR J1824-2452I) has a tiny companion star, with about a fifth the mass of the Sun. Although small, the companion is fierce, pounding the pulsar with streams of matter.

Normally the pulsar shields itself from this onslaught, its magnetic field deflecting the matter stream into space.

But sometimes the stream swells to a flood, overwhelming the pulsar’s protective ‘force field.’ When the stream hits the pulsar’s surface its energy is released as blasts of X-rays.

Eventually the torrent slackens. Once again the pulsar’s magnetic field re-asserts itself and fends off the companion’s attacks.

“We’ve been fortunate enough to see all stages of this process, with a range of ground and space telescopes. We’ve been looking for such evidence for more than a decade,” said Dr Alessandro Papitto, the paper’s lead author. Dr Papitto is an astronomer of the Institute of Space Studies (ICE, CSIC-IEEC) of Barcelona, Spain.

‘Teenage’ behaviour

The pulsar and its companion form what is called a ‘low-mass X-ray binary’ system. In such a system, the matter transferred from the companion lights up the pulsar in X-rays and makes it spin faster and faster, until it becomes a ‘millisecond pulsar’ that spins at hundreds of times a second and emits radio waves. The process takes about a billion years, astronomers think.

In its current state the pulsar is exhibiting behaviour typical of both kinds of systems: millisecond X-ray pulses when the companion is flooding the pulsar with matter, and radio pulses when it is not.

“It’s like a teenager who switches between acting like a child and acting like an adult,” said Mr. John Sarkissian, who observed the system with CSIRO’s 64-m (210-ft) Parkes radio telescope in eastern Australia.

“Interestingly, the pulsar swings back and forth between its two states in just a matter of weeks.”

This video shows an artist’s impression of the pulsar and its companion star. Credit: ESA

A global effort

The pulsar was initially detected as an X-ray source with the INTEGRAL satellite. X-ray pulsations were seen with another satellite, ESA’s XMM-Newton; further observations were made with NASA’s Swift. NASA’s Chandra X-ray telescope got a precise position for the object.

Then, crucially, the object was checked against the pulsar catalogue generated by CSIRO’s Australia Telescope National Facility, and other pulsar observations. This established that it had already been identified as a radio pulsar.

The source was detected in the radio with CSIRO’s Australia Telescope Compact Array, and then re-observed with CSIRO’s Parkes radio telescope, NRAO’s Robert C. Byrd Green Bank Telescope in the USA, and the Westerbork Synthesis Radio Telescope in The Netherlands. Pulses were detected in a number of these later observations, showing that the pulsar had ‘revived’ as a normal radio pulsar only a couple of weeks after the last detection of the X-rays.

The astronomers involved in these investigations work at institutions in Australia, Canada, Germany Italy, The Netherlands, Spain, Switzerland, and the USA.

Adapted from information issued by CSIRO.

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Galactic explosion betrays black hole

TWO MILLION YEARS AGO a supermassive black hole at the heart of our galaxy erupted in an explosion so immensely powerful that it lit up a cloud 200,000 light years away, a team of researchers led by the University of Sydney has revealed.

The finding is an exciting confirmation that black holes can ‘flicker’, moving from maximum power to switching off over, in cosmic terms, short periods of time.

An artist's conception of a black hole generating a jet

An artist’s conception of a black hole generating a jet. Two million years ago the supermassive black hole at the centre of our Galaxy was 100 million times more powerful than it is today. Credit: NASA / Dana Berry / SkyWorks Digital

“For 20 years astronomers have suspected that such a significant outburst occurred, but now we know when this sleeping dragon, four million times the mass of the Sun, awoke and breathed fire with 100 million times the power it has today,” said Professor Joss Bland-Hawthorn from the University’s School of Physics, and lead author of an article on the research to be published in The Astrophysical Journal.

Professor Bland-Hawthorn unveiled the research at the international Galaxy Zoo science conference on 24 September in Sydney.

“It’s been long suspected that our Galactic Centre might have sporadically flared up in the past. These observations are a highly suggestive ‘smoking gun’,” said Martin Rees, Astronomer Royal, who was one of the first scientists to suggest that massive black holes power quasars.

Fossil record

The evidence for the findings comes from a lacy filament of hydrogen gas called the Magellanic Stream. It trails behind our galaxy’s two small companion galaxies, the Large and Small Magellanic Clouds.

“Since 1996, we’ve been aware of an odd glow from the Magellanic Stream, but didn’t understand the cause. Then this year, it finally dawned on me that it must be the mark, the fossil record, of a huge outburst of energy from the supermassive black hole at the centre of our galaxy.”

The region around the galaxy’s supermassive black hole and the black hole is called Sagittarius A* (pronounced Sagittarius A-star). It emits radio, infrared, ultraviolet, x-ray and gamma ray emissions. Flickers of radiation rise up when small clouds of gas fall onto the hot cloud of matter that swirls around the black hole.

The video below show a computer simulation of a black hole in real time showing how gas falling in forms a disc that spins around the black hole. The friction causes the gas to become so hot it produces beams of UV radiation. Credit: McKinney (UMD), Tchekhovskoy (Princeton), Blandford (KIPAC), Kaehler (KIPAC)

In stark contrast to this current inactivity, evidence is emerging that there was a cataclysmic event in the past.

“In particular, in 2010 NASA’s Fermi satellite discovered two huge bubbles of hot gas billowing out from the centre of the galaxy, covering almost a quarter of the sky,” said Professor Bland-Hawthorn.

On-and-off black holes

Earlier this year, computer simulations of the Fermi bubbles made by the University of California Santa Cruz controversially suggested that they were caused by a colossal explosion from Sagittarius A* within the last few million years.

“When I saw this research I realised that this same event would also explain the mysterious glow that we see on the Magellanic Stream,” Professor Bland-Hawthorn said.

“Together with Dr Ralph Sutherland from Mount Stromlo Observatory and Dr Phil Maloney, from the University of Colorado, I calculated that to explain the glow it must have happened two million years ago because the energy release shown by the Santa Cruz group perfectly matched, to our delight, that from the Magellanic Stream.”

“The galaxy’s stars don’t produce enough ultraviolet to account for the glow, nor could they have in the past,” said Dr Maloney. “The Galactic Centre never formed stars at a high enough rate. There had to be another explanation.”

Professor Bland-Hawthorn said, “In fact the radiation from stars is one hundred times too little to account for the radiation now or at any time. The galaxy could never have produced enough UV radiation to account for it. So the only explanation was it had to be produced from our dragon, the massive black hole.”

“The realisation that these black holes can switch on and off within a million years, which given the universe is 14 billion years old means very rapidly, is a significant discovery.”

Will such a colossal explosion ever happen again?

“Yes, absolutely! There are lots of stars and gas clouds that could fall onto the hot disk around the black hole,” says Professor Bland-Hawthorn. “There’s a gas cloud called G2 that astronomers around the world are anticipating will fall onto the black hole early next year. It’s small, but we’re looking forward to the fireworks!

Professor Bland-Hawthorn is a Fellow of the Australian Astronomical Observatory.

Adapted from information issued by the University of Sydney.

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Australian telescope to reveal early universe

SOLAR STORMS, SPACE JUNK and the formation of the Universe are about to be seen in an entirely new way with the start of operations this week of the $51 million Murchison Widefield Array (MWA) radio telescope.

The first of three international precursors facilities to the $2 billion Square Kilometre Array (SKA) telescope, the MWA is located in a remote pocket of outback Western Australia. It is the product of an international project led by Curtin University and was officially turned on this morning by Australia’s Science and Research Minister, Senator Kim Carr.

Using bleeding edge technology, the MWA will become an eye on the sky, acting as an early warning system that will potentially help to save billions of dollars as it steps up observations of the Sun to detect and monitor massive solar storms. It will also investigate a unique concept that will see stray FM radio signals used to track dangerous space debris.

Night-time photo of antennae of the MWA

Antennae of the MWA in outback Western Australia. Photo by John Goldsmith.

The MWA will also give scientists an unprecedented view into the first billion years of the Universe, enabling them to look far into the past by studying radio waves that are more than 13 billion years old. This major field of study has the potential to revolutionise the field of astrophysics.

“This collaboration between some of astronomy’s greatest minds has resulted in the creation of a groundbreaking facility,” Director of the MWA and Professor of Radio Astronomy at Curtin University, Steven Tingay said.

“Right now we are standing at the frontier of astronomical science. Each of these programs has the potential to change our understanding about the Universe.”

Nine major projects

The development and commissioning of the MWA, the most powerful low frequency radio telescope in the Southern Hemisphere, is the outcome of nearly nine years’ work by an international consortium of 13 institutions across four countries (Australia, USA, India and New Zealand).

The detailed observations will be used by scientists to hunt for explosive and variable objects in the Milky Way such as black holes and exploding stars, as well as to make the most comprehensive survey of the Southern Hemisphere sky at low radio frequencies.

From this week, regular data will be captured through the entirely static telescope, which spans a three-kilometre area at the CSIRO’s Murchison Radio-astronomy Observatory, future home to the SKA.

Close-up shot of some MWA antennae

The MWA comprises thousands of small antennae spread across a three-kilometre-wide section of the Western Australian desert.

The data will be processed 800 kilometres away at the $80 million Pawsey High Performance Computing Centre for SKA Science, in Perth, carried there on a link provided by the NBN and enabled by AARNet. The MWA will be the Pawsey Centre’s first large-scale customer.

Nine major research programs were announced at the launch, with more than 700 scientists across four continents awaiting the information the telescope has now begun to capture.

“Given the quality of the data obtained during the commissioning process and the vast areas of study that will be investigated, we are expecting to see preliminary results in as little as three months’ time,” Professor Tingay said.

“This is an exciting prospect for anyone who’s ever looked up at the sky and wondered how the Universe came to be.

“The MWA has and will continue to lift the bar even higher for the SKA.”

Forerunner to the SKA

Under Professor Tingay and fellow colleague Professor Peter Hall’s guidance, Curtin University has been awarded a $5 million grant by the Australian Government to participate in the SKA pre-construction program over the next three years, with the MWA’s unique insight being used to develop a low frequency radio telescope that is expected to be 50 times more sensitive.

The MWA has been supported by both State and Federal Government funding, with the majority of federal funding being administered by Astronomy Australia Limited.

The MWA project says it recognises the Wadjarri Yamatji people as the traditional owners of the site on which the MWA is built and thanks the Wadjarri Yamatji people for their support, as well as that of Astronomy Australia Limited.

The MWA launch event took place simultaneously at the Astronomical Society of Australia’s annual scientific meeting hosted at Monash University Melbourne and the Murchison Radio-astronomy Observatory in the Murchison, Western Australia.

More information: Murchison Widefield Array

Adapted from information issued by Curtin University.

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Astronomers spy on galaxies in the raw

A CSIRO RADIO TELESCOPE has detected the raw material for making the first stars in galaxies that formed when the Universe was just three billion years old – less than a quarter of its current age. This opens the way to studying how these early galaxies make their first stars.

The telescope is CSIRO’s Australia Telescope Compact Array telescope near Narrabri, NSW. “It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths,” says CSIRO astronomer Professor Ron Ekers.

The raw material for making stars is cold molecular hydrogen gas, called H2. It can’t be detected directly but its presence is revealed by a ‘tracer’ gas, carbon monoxide (CO), which emits radio waves.

The Spiderweb

In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space Science) and his colleagues used the Compact Array to study a massive, distant conglomerate of star-forming ‘clumps’ or ‘proto-galaxies’ that are in the process of coming together as a single massive galaxy. This structure, called the Spiderweb, lies more than ten thousand million light-years away (at a redshift of 2.16).

The Spiderweb, imaged by the Hubble Space Telescope

MAIN IMAGE: The Spiderweb, imaged by the Hubble Space Telescope – a central galaxy (MRC 1138-262) surrounded by hundreds of other star-forming ‘clumps’. (Credit: NASA, ESA, George Miley and Roderik Overzier, Leiden Observatory.) INSET: In blue, the carbon monoxide gas detected in and around the Spiderweb. (Credit: B. Emonts et al, CSIRO/ATCA)

Dr Emonts’ team found that the Spiderweb contains at least sixty thousand million  times the mass of the Sun in molecular hydrogen gas, spread over a distance of almost a quarter of a million light-years. This must be the fuel for the star-formation that has been seen across the Spiderweb. “Indeed, it is enough to keep stars forming for at least another 40 million years,” says Dr Emonts.

Magnifying lens

In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H2, in two very distant galaxies (at a redshift of 2.7).

The faint radio waves from these galaxies were amplified by the gravitational fields of other galaxies – ones that lie between us and the distant galaxies. This process, called gravitational lensing, “acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb,” says Dr Aravena.

Dr Aravena’s team was able to measure the amount of H2 in both galaxies they studied. For one of the galaxies (called SPT-S 053816-5030.8), they could also use the radio emission to make an estimate of how rapidly the galaxy is forming stars – an estimate independent of the other ways astronomers measure this rate.

Antennae of CSIRO's Compact Array telescope

Dishes of the CSIRO’s Australia Telescope Compact Array near Narrabri in New South Wales. Photo: David Smyth

Upgraded telescope

The Compact Array’s ability to detect CO is due to an upgrade that has boosted its bandwidth – the amount of radio spectrum it can see at any one time – sixteen-fold (from 256 MHz to 4 GHz), and made it far more sensitive.

“The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO,” says Ron Ekers.

Adapted from information issued by CSIRO.

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Telescope takes universe’s temperature

Australia Telescope Compact Array

CSIRO’s Australia Telescope Compact Array, used the make the temperature measurements.

ASTRONOMERS USING a CSIRO radio telescope have taken the universe’s temperature, and have found that it has cooled down just the way the Big Bang theory predicts.

Using the Australia Telescope Compact Array near Narrabri, NSW, an international team from Sweden, France, Germany and Australia has measured how warm the universe was when it was half its current age.

“This is the most precise measurement ever made of how the universe has cooled down during its 13.77 billion year history,” said Dr Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science.

Because light takes time to travel, when we look out into space we see the universe as it was in the past – as it was when light left the galaxies we are looking at. So to look back halfway into the universe’s history, we need to look halfway across the universe.

Cosmic fingerprint

How can we measure a temperature at such a great distance?

Illustration of radio waves coming from a distant quasar through a galaxy in the foreground and then on to Earth.

Radio waves from a distant quasar pass through another galaxy on their way to Earth. Changes in the radio waves indicate the temperature of the gas in that galaxy.

The astronomers studied gas in an unnamed galaxy 7.2 billion light-years away (at a redshift of 0.89).

The only thing keeping this gas warm is the cosmic background radiation – the glow left over from the Big Bang.

By chance, there is another powerful galaxy, a quasar (called PKS 1830-211), lying behind the unnamed galaxy.

Radio waves from this quasar come through the gas of the foreground galaxy. As they do so, the gas molecules absorb some of the energy of the radio waves. This leaves a distinctive ‘fingerprint’ on the radio waves.

From this ‘fingerprint’ the astronomers calculated the gas’s temperature. They found it to be 5.08 Kelvin (-267.92 degrees Celsius): extremely cold, but still warmer than today’s universe, which is at 2.73 Kelvin (-270.27 degrees Celsius).

Exactly as predicted

According to the Big Bang theory, the temperature of the cosmic background radiation drops smoothly as the universe expands.

“That’s just what we see in our measurements,” said research team leader Dr. Sebastien Muller of Onsala Space Observatory at Chalmers University of Technology in Sweden. “The universe of a few billion years ago was a few degrees warmer than it is now, exactly as the Big Bang theory predicts.”

Adapted from information issued by CSIRO. Images David Smyth and Onsala Space Observatory.

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