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Milestone as radio dishes linked

ASKAP antennae

Antennae of CSIRO's Australian SKA Pathfinder (ASKAP) telescope in Western Australia were linked with other dishes across Australasia to provide incredible detail of a distant quasar. Photo: Terrace Photographers

THE DISCOVERY POTENTIAL of the future international Square Kilometre Array (SKA) radio telescope has been glimpsed following the commissioning of a working optical fibre link between CSIRO’s Australian SKA Pathfinder (ASKAP) telescope in Western Australia, and other radio telescopes across Australia and New Zealand.

The achievement will be announced at the 2011 International SKA Forum, taking place this week in Banff, Canada.

On 29 June, six telescopes—ASKAP, three CSIRO telescopes in New South Wales, a University of Tasmania telescope and another operated by the Auckland University of Technology—were used together to observe a radio source that may be two black holes orbiting each other.

Data from all sites were streamed in real time to Curtin University in Perth  (a node of the International Centre for Radio Astronomy Research) and there processed to make an image.

This ability to successfully link antennae (dishes) over large distances will be vital for the future $2.5 billion SKA telescope, which will have several thousand antennae, up to 5,500 kilometres apart, working together as a single telescope. Linking antennae in such a manner allows astronomers to see distant galaxies in more detail.

Map of antennae across Australia and New Zealand

The network of radio telescope dishes stretched across Australia and New Zealand. Image: Carl Davies, CSIRO

“We now have an SKA-scale network in Australia and New Zealand: a combination of CSIRO and NBN-supported fibre and the existing AARNET and KAREN research and education networks,” said SKA Director for Australasia, Dr Brian Boyle.

Watching as black holes feed

The radio source the astronomers targeted was PKS 0637-752, a quasar that lies more than seven and a half billion light-years away from us.

This quasar emits a spectacular radio jet with regularly spaced bright spots in it, like a string of pearls. Some astronomers have suggested that this striking pattern is created by two black holes in orbit around each other, one black hole periodically triggering the other to ‘feed’ and emit a burst of radiation.

Radio image of a quasar

The radio dish network was used to zoom in on quasar PKS0637-752, at the heart of which is thought to be two black holes circling each other. ATCA image: L. Godfrey (Curtin Uni.) and J. Lovell (Uni. of Tasmania). Image from telescope network: S. Tingay (Curtin Uni.) et al.

‘It’s a fascinating object, and we were able to zoom right into its core, seeing details just a few millionths of a degree in scale, equivalent to looking at a 10-cent piece from a distance of 1,000 kilometres,’ said CSIRO astronomer Dr Tasso Tzioumis.

During the experiment Dr Tzioumis and fellow CSIRO astronomer Dr Chris Phillips controlled all the telescopes over the Internet from Sydney.

Curtin University’s Professor Steven Tingay and his research team built the system used to process the telescope data. “Handling the terabytes of data that will stream from ASKAP is within reach, and we are on the path to the SKA,” he said.

“For an SKA built in Australia and New Zealand, this technology will help connect the SKA to major radio telescopes in China, Japan, India and Korea.”

AARNet, which provides the data network for Australia’s research institutions, has recently shown that it can implement data rates of up to 40 Gbps on existing fibre networks. That figure is for a single wavelength, and one fibre can support up to 80 wavelengths.

Adapated from information issued by CSIRO Astronomy and Space Science.

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Aboriginal community names CSIRO telescope

One of the ASKAP dishes

One of the ASKAP dishes at the Murchison Radio-astronomy Observatory in Western Australia. The first six dishes (of an eventual 36) have been given indigenous names.

THE FIRST SIX ANTENNAE of CSIRO’s Australian SKA Pathfinder telescope in Western Australia have today received names in the local Wajarri language.

The names, chosen by the Wajarri people, were bestowed by representatives of seven Aboriginal families at a ceremony at the Murchison Radio-astronomy Observatory, about 315 km northeast of Geraldton.

Name plaques will be fixed to each antenna. Further naming will take place as more antennae are installed and eventually all 36 of ASKAP’s antennae will have a Wajarri name.

The antenna names are: Bilyarli (which means “galah”, and is also the name of a past Wajarri Elder, Mr Frank Ryan); Bundarra (stars); Wilara (the Moon); Jirdilungu (the Milky Way); Balayi (a lookout, as this antenna looks down westward to others); and Diggidumble (a nearby table-top hill).

Antony Schinckel

CSIRO ASKAP Director, Antony ("Ant") Schinckel has been named "Minga", the Wajarri name for "ant".

“These names will be a permanent reminder that this is the land of the Wajarri people,” said the Chair of Wajarri Yamatji Native Title Group, Gavin Egan.

Roads and other significant structures will also be given Wajarri names.

One of the roads will be called Ngurlubarndi, the Wajarri name for Fred Simpson, a past Wajarri Elder and father of Wajarri Elder, Ike Simpson.

CSIRO’s ASKAP Director, Antony (“Ant”) Schinckel has also been given a Wajarri name—”Minga”, which means “ant”.

In March CSIRO awarded McConnell Dowell Constructors (Aust) Pty Ltd the contract to construct support infrastructure at the Murchison Radio-astronomy Observatory.

The work involves the construction of several kilometres of access roads and tracks, power and data distribution, a central control building, and foundation pads for the rest of the 36 antennae that will be installed on the site by early 2012.

The MRO is located in the Mid West region of Western Australia. As well as being home to ASKAP, it is also the Australia–New Zealand candidate core site for the future $2.5bn Square Kilometre Array (SKA) telescope project.

Adapted from information issued by CSIRO. Images courtesy Tim Wheeler and Terrace Photographers.

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Taking the pulse of the universe

Artist's impression of a pulsar

Artist's impression of a pulsar, a rapidly spinning neutron star that emits streams of radio waves and sometimes gamma rays.

  • Pulsars are small, spinning neutron stars
  • They emit radio waves or gamma rays, and sometimes both
  • Parkes radio telescope working jointly with NASA space telescope

USING THE PARKES radio telescope, CSIRO astronomers are working closely with NASA to unlock one of astronomy’s great enigmas—the science behind pulsars.

The team are using the world-class facilities at Parkes, in combination with NASA’ s Fermi Gamma-Ray Space Telescope, to understand how these small, spinning stars make their beams of radiation.

The project has tracked down 25 ultra-fast ‘millisecond’ pulsars in just two years—the same number discovered in the previous 20 years.

“This has been a hugely productive collaboration, and it is generating unprecedented returns for physics and astronomy,” said the leader of the Parkes observations, CSIRO’s Dr Simon Johnston.

The study of pulsars demands highly advanced scientific infrastructure and expertise.

Pulsars emit beams of radio waves, gamma waves, or both. Sensitive radio telescopes such as the CSIRO facility at Parkes can detect the radio waves as they sweep across the Earth.

But gamma rays—which carry billions of times more energy than the light our eyes can see—are blocked by the Earth’s atmosphere. We can study them only by using telescopes in space.

Space and ground working together

The CSIRO-NASA collaboration shows we get the best results by combining land and space-based detectors.

First, the Fermi space telescope is finding unidentified gamma-ray sources, which the Parkes telescope can investigate for radio wave pulses.

“That’s how we were able to find those 25 millisecond pulsars, an incredible haul,” Dr Johnston said.

Simon Johnston in the control room at Parkes

Dr Simon Johnston (foreground) in the control room of CSIRO's Parkes radio telescope.

Second, Parkes is doing very precise timing of 168 radio pulsars that Fermi might be able to study.

“We work out exactly when the pulsar’s radio beam sweeps over us. That tells us how fast the pulsar is rotating,” Dr Johnston said.

“That knowledge helps us make use of the gamma-ray photons that Fermi detects. If Parkes can get the timing precisely right through the radio wave pulses, we can build up a picture of the gamma-ray pulses by collecting a few photons every time the pulsar beam sweeps past.”

Intriguing results

The collaboration has thrown up some intriguing results. Of the 60 objects Fermi has found that emit gamma-ray pulses, about twenty lack detectable radio pulses.

“The most likely explanation is that these pulsars do have radio beams, but they are just not sweeping across the Earth, so we can’t detect them,” Dr Johnston said.

“In other words, we think the beam of gamma rays is a big fat beam, which is easier to detect, and the radio beam is more tightly directed, less spread out.

“This suggests certain things about where on the pulsar the two beams come from, and how they are made. It’s only when we work together that we can crack these long-standing mysteries.”

CSIRO's Parkes radio telescope

CSIRO's Parkes radio telescope

International collaboration

Innovation Minister Senator Kim Carr said the research exemplified the sorts of international collaboration that the Australian Government was fostering across the board.

“We have a proud history of cooperation and involvement with NASA on a number of fronts, from assisting with communicating with the Apollo missions to the moon, to deep space exploration, and understanding how our universe works,” Senator Carr said.

“It’s all about exploring new frontiers and building Australian capacity as a research intensive and innovative nation.

“While this might seem remote from everyday life, experience has shown that space exploration in all its forms has unforeseen spin-offs that provide wide-reaching benefits through new technologies and new approaches to a range of challenges.”

Adapted from information issued by CSIRO. Images courtesy CSIRO and NASA.

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‘Russian doll’ galaxy shows black holes’ true power

Artist's impression of a microquasar

Artist's impression of a microquasar, a black hole that produces huge jets of particles that 'pump' energy into gas clouds in surrounding space.

  • “Microquasar” within a galaxy is “powered” by a black hole
  • Shoots out jets of particles that emit radio waves
  • Jets pour energy into the clouds of gas that form stars

Following a study of what is in effect a miniature galaxy buried inside a normal-sized one—like a Russian doll—astronomers using the CSIRO’s Compact Array radio telescope have concluded that massive black holes are more powerful than we thought.

The study was made possible by a recent upgrade to the Compact Array, which can now do work of this kind five times faster than before.

The international team of astronomers, led by Dr Manfred Pakull at the University of Strasbourg in France, discovered a ‘microquasar’—a small black hole, weighing only as much as a star—that is shooting jets of radio wave-emitting particles (‘radio jets’) into the space surrounding it.

Called S26, the black hole sits inside a regular galaxy called NGC 7793, which is 13 million light-years away in the Southern constellation Sculptor.

Earlier this year Pakull and colleagues studied S26 with optical and X-ray telescopes (the European Southern Observatory’s Very Large Telescope and NASA’s Chandra space telescope).


Some of the dishes of the Australia Telescope Compact Array.

Now they have made new observations with the Compact Array (near Narrabri, NSW). These show that S26 is a near-perfect mini-version of the much larger ‘radio galaxies’ and ‘radio quasars’.

Powerful radio galaxies and quasars are almost extinct today, but they dominated the early Universe, billions of years ago, like cosmic dinosaurs. They contain big black holes, billions of times more massive than the Sun, and shoot out huge radio jets that can stretch millions of light-years into space.

Escape from a black hole

We often hear that nothing can ever escape from a black hole, so how can these ones shoot out huge jets into space? The answer is that the material does not come from within the black hole itself, but from the region immediately surrounding it.

Because black holes have huge gravitational fields, they tend to attract or suck in lots of gas and interstellar dust. If this material passes the black hole’s ‘point of no return‘, called the event horizon, it will never come out again. But a lot of the material forms into flattened, swirling cloud—what astronomers call an ‘accretion disc’—that surrounds the black hole outside the event horizon.

In the process of falling in toward the black hole, this material gains energy and become very hot. Some of it is then shot out of the region surrounding the black hole, in directions perpendicular to the accretion disc. These are the jets.

Astronomers have been working for decades to understand the precise mechanisms by which the black holes form these giant jets, and how much energy those jets inject into the interstellar gas they travel through. That gas is the raw material for forming new stars, and the effects of the jets on star-formation have been hotly debated.

Composite image of S26 and NGC 7793

A composite image showing the position of the 'miniature galaxy' S26 within the galaxy NGC 7793. The inset of S26 is a radio image made with a CSIRO telescope; the 'hotspots' mark the ends of the jets shot out by the black hole (not visible in this picture). The main image of the galaxy is made from combined X-ray and optical data.

There is evidence that the jets help to get a galaxy’s star formation going, and there is counter evidence that jets can suppress the formation of stars. The question is far from settled, and much more work is needed to understand black hole jets.

Jets powered by black holes

“Measuring the power of black hole jets, and therefore their heating effect, is usually very difficult,” said co-author Roberto Soria (University College London), who carried out the radio observations.

“With this unusual object, a bonsai radio quasar in our own backyard, we have a unique opportunity to study the energetics of the jets.”

Using their combined optical, X-ray and radio data set of S26, the scientists were able to determine how much of the jet’s energy went into heating the gas around it, and how much went into making the jet itself visible at radio wavelengths.

They concluded that only about 1/1,000th of the energy went into creating the radio glow.

“This suggests that in bigger galaxies too the jets are about a thousand times more powerful than we’d estimate from their radio glow alone,” said Dr Tasso Tzioumis of CSIRO Astronomy and Space Science.

“That means that black hole jets can be both more powerful and more efficient than we thought, and that their heating effect on the galaxies they live in can be stronger.”

Adapted from information issued by CSIRO / Soria et al / CSIRO / ATCA; NGC 7793 – NASA, ESO and NOAO.

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“Super scope” takes shape in the Outback

  • Network of 36 radio astronomy dishes called ASKAP
  • Being built in a remote corner of Western Australia
  • Pathfinder for the international Square Kilometre Array telescope

CSIRO’s Australian Square Kilometre Array Pathfinder (or ASKAP) project continues to progress to schedule, with five new antennae constructed at the Murchison Radio-astronomy Observatory (MRO) during the months of September and October, 2010.

The five new antennae bring the total number of ASKAP antennae now standing at the MRO site to six, with the first ASKAP antenna successfully built and tested earlier in the year.

All 36 ASKAP antennae are being constructed at the MRO by their manufacturer—the 54th Research Institute of China Electronics Technology Group Corporation (known as CETC54), with CSIRO’s ASKAP team and local contractors assisting.

The antennae are built and tested in China by CETC54. The antenna sections then disassembled, shipped to Australia and then reassembled on site.

ASKAP antenna being erected

ASKAP antennae being erected at the Murchison Radio-astronomy Observatory in Western Australia.

Ant Schinckel, CSIRO ASKAP Project Director, is particularly pleased with recent antenna activity, highlighting the significant success of reflector accuracy that the CETC54 team has been able to achieve upon re-assembly of the shipped antenna.

He notes, “a surface accuracy of <0.6 mm has been achieved with no site adjustments necessary to the panel alignments which is a tremendous result—it means that antennae built in the factory can be rebuilt on site quickly and reliably.”

These first six ASKAP antennae will form BETA (the Boolardy Engineering Test Array) once they are kitted out with PAFs (Phased Array Feeds), receivers and digital backends. BETA is scheduled to be completed in the second quarter of 2011.

By the end of 2011, all 36 antennae should be built, with the full ASKAP system expected to be completed by 2013.

When operational in 2013, ASKAP will be one of the world’s best radio telescope systems. In fact, for many types of astronomy, it will be the best radio telescope. It will have electronic “fish eye” technology that enables it to see huge areas of the sky at once, which means that it will be able to conduct whole-sky surveys with impressive speed. This efficiency means astronomers will be able to achieve in a matter of months or years what would have taken decades to do before.

The Head of Astrophysics for CSIRO Astronomy and Space Science, Dr Robert Braun, said ASKAP will carry out a series of ambitious surveys that will fundamentally change our view of the Universe.

“Our new ‘radio-camera’ technology makes this possible by making the useful image field of each antenna a hundred times larger,” Dr Braun said.

“We will continue refining it both for ASKAP and for future use in the SKA—for instance, by improving how it captures dynamic range in an image.”

The ‘radio-camera’ was developed by a team that included Dr John O’Sullivan, winner of the 2009 Prime Minister’s Prize for Science for his work on wireless technologies.

Adapted from information issued by CSIRO. Images courtesy CSIRO / Ross Forsyth (CSIRO).

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CSIRO “hot rods” old telescope

SKAMP telescope

The University of Sydney's MOST radio telescope, now called SKAMP, has been boosted with new CSIRO technology that dramatically improves performance.

CSIRO has helped transform the University of Sydney’s radio telescope into a world-class instrument, and along the way has learned lessons for its own ASKAP (Australian SKA Pathfinder) telescope.

Both telescopes will help demonstrate Australia’s technological expertise in its bid to host the world’s largest and most advanced radio telescope—the Square Kilometre Array (SKA).

The University of Sydney runs what was the Molonglo Observatory Synthesis Telescope (MOST) near Canberra. It contracted CSIRO to help develop signal-processing systems—a filterbank and correlator—to dramatically boost the telescope’s performance.

The upgrade has made the telescope more flexible, three times more sensitive, with ten times more bandwidth (up from 3 MHz to 30 MHz), and able to make better-quality images of objects in space.

“This project has given our telescope a whole new capability,” says Professor Anne Green of the University of Sydney, who led the process.

“It looks the same, but under the bonnet it’s been born again.”

Artist's impression of the SKA

Artist's impression of the core of the Square Kilometre Array (SKA) radio telescope system, which Australian astronomers hope to host in Western Australia.

And the “new” telescope has a new name: SKAMP (the Square Kilometre Array Molonglo Prototype).

The formal handover of the new signal-processing systems recently took place at the University of Sydney.

The knowledge CSIRO has gained during the course of this project has been applied to the design of the digital systems for its own ASKAP telescope, which is now under construction in Western Australia. Much of the SKAMP contract was carried out by the ASKAP Digital Systems team.

“What we’ve learned over several years will now allow us to dramatically shorten our design cycle for ASKAP’s digital systems, as well as potentially feed into future development work that will be required for the SKA,” says CSIRO SKA Director, Dr Brian Boyle.

Much of the funding for the SKAMP project was provided by the Commonwealth Government under the second round of the Major National Research Facilities program. The Australian Research Council has also contributed substantial funding.

In a synergy with the SKAMP project, CSIRO has built a similar correlator for the international Murchison Widefield Array (MWA) consortium, which is building a low-frequency radio telescope at the same site as the ASKAP telescope (the Murchison Radio-astronomy Observatory in Western Australia). MWA too will demonstrate technology for the SKA project.

Adapted from information issued by CSIRO / University of Sydney.

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A new way to weigh planets

Diagram showing the Sun, Earth and Jupiter orbiting a common barycentre

Measurements of signals from pulsars (purple lines) are affected by Earth's movement in its orbit around the Solar System's centre of mass, the barycentre. The barycentre moves too, due to the gravitational influence of the other planets. By working backwards from the pulsar signals, scientists can work out the gravitational pull of the planets, and from that deduce their masses.

  • Radio waves from pulsars affected by Solar System’s gravity
  • Adjusting the pulsar wave measurements gives gravity readings
  • From the gravity readings, the planet’s masses can be found

Astronomers from Australia, Germany, the UK, Canada and the USA have come up with a new way to weigh the planets in our Solar System, using radio signals from pulsars.

“This is first time anyone has weighed entire planetary systems—planets with their moons and rings,” said team leader Dr. David Champion of the Max-Planck-Institut fuer Radioastronomie in Bonn, Germany.

“And we’ve provided an independent check on previous results, which is great for planetary science.”

Measurements of planet masses made this new way could feed into data needed for future space missions.

Until now, astronomers have weighed planets by measuring the orbits of their moons or the trajectories of spacecraft flying past them. That’s because mass produces gravity, and a planet’s gravitational pull determines the orbit of anything that goes around it—both the size of the orbit and how long it takes to complete.

The new method is based on adjustments astronomers have to make to signals from pulsars…small spinning stars that deliver regular ‘blips’ of radio waves.

The Earth is travelling around the Sun, and this movement affects exactly when pulsar signals arrive here. To remove this effect, astronomers calculate when the pulses would have arrived at the Solar System’s exact centre of mass, or barycentre, around which all the planets orbit.

Because the arrangement of the planets around the Sun changes all the time, the barycentre moves around too.

To work out its position, astronomers use both a table (called an ephemeris) of where all the planets are at a given time, and the values for their masses that have already been measured.

If these figures are slightly wrong, and the position of the barycentre is slightly wrong, then a regular, repeating pattern of timing errors appears in the pulsar data.

“For instance, if the mass of Jupiter and its moons is wrong, we see a pattern of timing errors that repeats over 12 years, the time Jupiter takes to orbit the Sun,” said Dr Dick Manchester of CSIRO Astronomy and Space Science.

The CSIRO's Parkes radio telescope

The CSIRO's Parkes radio telescope made most of the pulsar signal measurements.

But if the mass of Jupiter and its moons is corrected, the timing errors disappear. This is the feedback process that the astronomers have used to determine the planets’ masses.

Better measurements of planet masses

Data from a set of four pulsars have been used to weigh Mercury, Venus, Mars, Jupiter and Saturn with their moons and rings.

Most of these data were recorded with CSIRO’s Parkes radio telescope in eastern Australia, with some contributed by the Arecibo telescope in Puerto Rico and the Effelsberg telescope in Germany.

The masses were consistent with those measured by spacecraft. The mass of the Jovian system (Jupiter and its moons)—0.0009547921 times the mass of the Sun—is significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with, but less accurate than, the value from the Galileo spacecraft.

The new measurement technique is sensitive to a mass difference of 200,000 million million tonnes—just 0.003% of the mass of the Earth, and one ten-millionth of Jupiter’s mass.

“In the short term, spacecraft will continue to make the most accurate measurements for individual planets, but the pulsar technique will be the best for planets not being visited by spacecraft, and for measuring the combined masses of planets and their moons,” said CSIRO’s Dr George Hobbs, another member of the research team.

Repeating the measurements would improve the values even more. If astronomers observed a set of 20 pulsars over seven years they’d weigh Jupiter more accurately than spacecraft have. Doing the same for Saturn would take 13 years.

“Astronomers need this accurate timing because they’re using pulsars to hunt for gravitational waves predicted by Einstein’s general theory of relativity”, said Professor Michael Kramer, head of the ‘Fundamental Physics in Radio Astronomy’ research group at the Max-Planck-Institut fuer Radioastronomie.

“Finding these waves depends on spotting minute changes in the timing of pulsar signals, and so all other sources of timing error must be accounted for, including the [influences] of Solar System planets.”

Adapted from information issued by CSIRO / D. Champion, MPIfR.

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Pulsars aren’t perfect

Artist's impression of a pulsar

An artist's impression of a pulsar. Blue lines represent its surrounding magnetic fields, while the purple beams represent the radio waves it emits.

  • Pulsars are small, spinning, magnetised stars
  • Emit regular pulses of radio waves
  • Act like celestial clocks

CSIRO astronomer George Hobbs and colleagues in the UK, Germany and Canada report in the journal Science that they’ve taken a big step towards solving a 30-year-old puzzle—why the “cosmic clocks” called pulsars aren’t perfect.

Pulsars are small, spinning stars that emit a beam of radio waves. When the beam sweeps over the Earth we detect a highly-regular “pulse” of radio waves. The rate at which the pulses repeat, fast or slow, depends on how fast the pulsar spins and therefore how often its radio beam flashes across the Earth.

The work is based on observations of 366 pulsars collected over several decades with the 76m radio telescope at the Jodrell Bank Observatory, run by the University of Manchester, and grew out of work George Hobbs did for his PhD thesis.

Each pulsar generates a cocoon of magnetic fields around itself—its magnetosphere.

The astronomers found that a pulsar’s magnetosphere switches back and forth between two different states.

“We don’t know exactly what happens,” Dr Hobbs said.

“But one idea is that from time to time there is a surge of charged particles—electrons, for instance—whirling through the magnetosphere. Such a surge could apply the brakes a bit to the pulsar spin, and also affect the pulsar’s radio beam.”

The change in a pulsar’s magnetosphere shows up both in the shape of the radio pulses recorded on Earth and the regular pattern of the pulses’ arrival times.

“Pulsars are very stable timekeepers, but not perfect,” said Dr Andrew Lyne of the University of Manchester, lead author of the Science paper and George Hobbs’ PhD supervisor.

“They have what we call ‘pulsar timing noise’, where the spin rate appears to wander around all over the place. This had baffled people for decades.”

Jodrell Bank 76m radio telescope

The Jodrell Bank 76m radio telescope

One of the aims of Dr Hobbs’ PhD thesis was to find an effective way to filter out this ‘timing noise’.

“We worked out how to do this, and along the way we were prompted to think hard about the nature of the timing noise,” Dr Hobbs said.

Haven’t solved all the mysteries yet

The key advance was noticing that when the pulsar timing changed, so did the shape of the radio pulse. “This ran against accepted thinking,” Dr Hobbs said. “Everyone had said they were unrelated. But we’ve shown they are.”

Now astronomers can compensate for ‘timing noise’ by using the pulse shape change to spot when the pulsar magnetosphere has changed its state—this will show when the pulsar spin rate has also changed.

“We now have a more fundamental understanding of how pulsars work,” Dr Hobbs said.

“We’ve shown that many pulsar characteristics are linked, because they have one underlying cause.”

Armed with this understanding, astronomers will find it easier to compensate for errors in their pulsar “clocks” when they use them as tools—for instance, in trying to detect gravitational waves, which is something Dr Hobbs is doing with CSIRO’s Parkes radio telescope.

But Dr Hobbs adds that there is no explanation yet as to why a pulsar’s magnetosphere flips from one state to another.

“The switching seems random in some pulsars and regular in others,” he said.

“We haven’t solved all the mysteries yet.”

Adapted from information issued by CSIRO / Russell Kightley / Jodrell Bank Centre for Astrophysics.

Aussie tracking stations honoured

The Canberra Deep Space Communication Complex

The Canberra Deep Space Communication Complex at Tidbinbilla near Canberra, a part of NASA’s Deep Space Network.

  • NASA’s tracking stations in Australia
  • One current, two former
  • Made sites of Historic Aerospace Significance

The Canberra Deep Space Communication Complex (CDSCC) at Tidbinbilla and former tracking stations, Honeysuckle Creek and Orroral Valley, near Canberra, have been honoured by the American Institute of Aeronautics and Astronautics (AIAA) as sites of Historic Aerospace Significance.

Managed by CSIRO Astronomy and Space Science (CASS), the CDSCC host a plaque-unveiling ceremony at Tidbinbilla on Tuesday, May 25.

The three ACT tracking stations are being recognised as part of the AIAA’s global register of Historic Aerospace Sites which includes other important sites such as; the NASA Ames Research Centre, Moffett Field, California; Kitty Hawk, North Carolina.; and Tranquility Base on the Moon.

The former launch facility at Woomera, South Australia, is the only other AIAA Historic Aerospace Site in Australia.

This award recognises the significant role these three Australian tracking stations have played throughout the last 50 years, and the hundreds of men and women who have worked at each site in support of NASA’s manned and robotic space missions.

This recognition comes during the 50th anniversary of treaty-level cooperation between Australia and the US in space exploration.

“CSIRO is honoured to accept this designation on behalf of the dedicated alumni of the Honeysuckle Creek, Orroral Valley and Canberra Deep Space tracking stations,” said CDSCC Director Dr Miriam Baltuck.

“Australia’s role in the exploration of space has been ‘mission critical’ for over half a century, and we look forward with pleasure to continuing in that role in the decades to come.”

US Ambassador Jeffrey Bleich attended the ceremony and AIAA President David Thompson (founder and CEO of Orbital Sciences Corporation) formally designated the three ACT sites.

Adapted from information issued by CSIRO.

Bursting ‘bubbles’ give our Galaxy gas

The regions of our Galaxy the researchers studied

The regions of our Galaxy the researchers studied. More gas clouds were found in the region on the right than in the region on the left.

  • 650 Milky Way gas clouds studied
  • Each contains 700 times the mass of the Sun
  • Clouds might recycle gas in and out of the Galaxy

Like bubbles bursting on the surface of a glass of champagne, ‘bubbles’ in our Galaxy burst and leave ‘flecks’ of material in the form of clouds of hydrogen gas, researchers using CSIRO’s Parkes telescope have found.

Their study explains the origin of these clouds for the first time.

Swinburne University PhD student Alyson Ford (now at the University of Michigan) and her supervisors; Dr Naomi McClure-Griffiths (CSIRO Astronomy and Space Science) and Felix Lockman (US National Radio Astronomy Observatory), have made the first detailed observations of ‘halo’ gas clouds in our Galaxy.

Just as Earth has an atmosphere, the main starry disc of our Galaxy is surrounded by a thinner halo of stars, gas and ‘dark matter’.

The Parkes radio telescope

The Parkes radio telescope

The halo clouds skim the surface of our Galaxy, sitting 400 to 10,000 light-years outside the Galactic disc. They are big — an average-sized cloud contains hydrogen gas 700 times the mass of the Sun and is about 200 light-years across.

“We’re studying the clouds to understand what role they play in recycling material between the disc and halo,” Dr McClure-Griffiths said.

“The clouds can fall back down into the main body of the Galaxy, returning gas to it.”

Gas is “spritzing” up our Galaxy

The researchers studied about 650 clouds and found striking differences between them in different areas of the Galaxy. One part of the Galaxy had three times as many clouds as another next to it, and the clouds were twice as thick.

The region with lots of thick clouds is where lots of stars form, while the region with fewer clouds also forms fewer stars.

An image made with the Parkes radio telescope of some of the 'halo clouds' above the main body of our Galaxy.

An image made with the Parkes radio telescope of some of the 'halo clouds' above the main body of our Galaxy.

But the halo clouds aren’t found exactly where stars are forming right now. Instead, they seem to be linked to earlier star formation.

Massive stars grow old quickly. After a few million years they shed material into space as a ’wind‘ and then explode.

This violence creates bubbles in the gas in space, like the holes in a Swiss cheese.

“Stellar winds and explosions sweep up gas from the Galactic disc into the lower halo.

“We’ve found this churned-up gas is ‘spritzing’ the surface of the Galactic disc in the form of halo clouds.”

A star-forming region is active for less than a million years, but a super-bubble in the Galaxy takes 20 or 30 million years to form.

“Just as yeast takes a while to make wine bubbly, stars take a while to make the Galaxy bubbly,” Dr McClure-Griffiths said.

The halo clouds are distinct from a larger population of ‘high-velocity clouds’ that also sail outside the galaxy. The halo clouds move in tandem with the rotating Galaxy, while the high-velocity clouds scud along much faster.

This study is the first to accurately locate the halo clouds in relation to the main body of the Galaxy. Its findings were presented overnight at a news conference at a meeting of the American Astronomical Society in Miami, Florida.

Adapted from information issued by CSIRO / A Ford (U. Michigan), N. McClure-Griffiths (CSIRO Astronomy and Space Science) / NASA / JPL-Caltech / David McClenaghan.