Turning the moon into an Ultra-High-Energy (UHE) cosmic ray detector

The Square Kilometre Array (SKA) to be used to detect Ultra-High-Energy (UHE) cosmic rays.

Credit: University of Southampton

Scientists from the University of Southampton are to turn the Moon into a giant particle detector to help understand the origin of Ultra-High-Energy (UHE) cosmic rays - the most energetic particles in the Universe.

The origin of UHE cosmic rays is one of the great mysteries in astrophysics.

Nobody knows where these extremely rare cosmic rays come from or how they get their enormous energies.

Physicists detect them on Earth at a rate of less than one particle per square kilometre per century.

Dr Justin Bray, a Research Fellow in Cosmic Magnetism at the University of Southampton, is lead author of a proposal to use the Square Kilometre Array (SKA), set to become the largest and most sensitive radio telescope in the world, to detect vastly more UHE cosmic rays by using the Moon as a giant cosmic ray detector.

On Earth, physicists detect these high-energy particles when they hit the upper atmosphere triggering a cascade of secondary particles that generate a short and faint burst of radio waves only a few nanoseconds long.

It is this signal that astronomers hope to pick up from the Moon, but as these signals are so short and faint no radio telescope on Earth is currently capable of picking them up.

With its large collecting area and high sensitivity, the SKA will be able to detect these signals using the visible lunar surface, millions of square kilometres, giving the researchers access to more data about UHE cosmic rays than they have ever had before.

The current largest detector on Earth is the Pierre Auger Observatory in Argentina that covers an area of 3,000 square kilometres, about the size Luxembourg.

The SKA will be more than 10 times larger (33,0000 square kilometres) and researchers hope to detect around 165 UHE cosmic rays a year from the Moon compared to the 15-a-year currently observed.

Dr Bray announced details of the project at a major SKA conference in Italy.

He says: "Cosmic rays at these energies are so rare that you need an enormous detector to collect a significant number of them, but the moon dwarfs any particle detector that has been built so far."

"If we can make this work, it should give us our best chance yet to figure out where they're coming from."

Anna Scaife

Dr Bray is working with Professor Anna Scaife, also from Physics and Astronomy at the University of Southampton, who leads the development of the SKA's Imaging Pipeline as part of the Science Data Processor (SDP) work package consortium.

Professor Scaife says: "Defining science goals for the telescope is crucial for ensuring that the appropriate technical capabilities are considered during the design phase."

Using a network of radio antennas in the Southern hemisphere, the SKA will advance our understanding of how the Universe evolved and challenge Einstein's theory of relativity.

With receivers across Australia and Africa, its dishes and antennas will provide detailed information on the large scale 3D structure of the Universe.

When operational in the early 2020's, the SKA radio telescope will produce more than 10 times the current global traffic of the Internet in its internal telecommunications system.

To play back a single day's worth of SKA data on an MP3 player would take about two million years.

SKA and CAASTRO: Forecast Sky bubbling with exploding stars

It is hard to imagine that any astronomical phenomenon could escape our latest and most powerful telescopes, but an international research team has now forecast some of the exotic discoveries that will only be able to be studied with the forthcoming Square Kilometre Array (SKA).

Giancarlo Ghirlanda

The team, led by Dr Giancarlo Ghirlanda at the National Institute for Astrophysics (INAF) in Italy and including CAASTRO members Dr Davide Burlon and Dr Tara Murphy from the University of Sydney, has calculated that the SKA will reveal the lingering footprints of tens of thousands of enigmatic cosmic explosions known as "gamma-ray bursts".

Davide Burlon

"With current telescopes, we see a bright gamma-ray burst somewhere in the Universe around once per day, but new radio telescopes will soon be able to see an afterglow of the explosion after the initial burst has faded away," explains CAASTRO postdoctoral researcher Dr Burlon.

"This afterglow can generally take weeks to gradually decay and teaches us incredible amounts about both the initial explosion and its neighbourhood."

The catch is that a gamma-ray burst is not an explosion that we can see from all directions but is comprised of a very narrow, energetic jet, so we need to be looking down the barrel of the jet at the right time.

Otherwise it is invisible, equivalent to only seeing the beam of a laser pointer when it points directly at us.

The radio afterglow should be visible from any direction though and for long periods of time, even if we missed the burst.

Tara Murphy

These afterglows without a burst are known as "orphan" afterglows, they're a phenomenon that astronomers have until now been looking for without success.

"From the rate at which we detect gamma-ray bursts, we were able to predict that with the power of a sensitive new telescope like the SKA, orphan afterglows should be seen 700 times more often than their gamma-ray bursts." says Dr Burlon.

"The unprecedented sensitivity and wide field-of view of the SKA means that orphan afterglows should be visible for months or even years before eventually disappearing, bubbling across the sky more than ten thousand times per year."

Of course, the SKA's view of the sky will be full of all sorts of objects and events, such as supernova explosions and flaring black holes that are more common than orphan afterglows.

"In this new era of radio astronomy, one of the challenges will be to disentangle these different classes of radio sources." says Dr Tara Murphy, CAASTRO Associate Investigator and project leader of the "Variables and Slow Transients (VAST)" survey with the Australian SKA Pathfinder (ASKAP).

The SKA will join the Australian SKA precursor telescope ASKAP and the South African SKA precursor MeerKAT in painting an entirely new picture of the "radio sky".

"The SKA will not only allow us to finally see these orphan afterglows but help us understand how gamma-ray bursts (GRB) produce such powerful, narrow jets and will cast new light on the big question of just what causes gamma-ray bursts in the first place," concludes Dr Ghirlanda.

More information: G. Ghirlanda, D. Burlon, G. Ghisellini, R. Salvaterra, M. G. Bernardini, S. Campana, S. Covino, P. D'Avanzo, V. D'Elia, A. Melandri, T. Murphy, L. Nava, S. D. Vergani, G. Tagliaferri: "GRB orphan afterglows in present and future radio transient surveys" in The Publications of the Astronomical Society of Australia (PASA). arXiv:1402.6338 [astro-ph.HE] arxiv.org/abs/1402.6338

Murchison Widefield Array: Square Kilometre Array precursor debuts

Credit: mwatelescope.org

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 today by the $51 million Murchison Widefield Array (MWA) radio telescope.

The first of three international precursors to the $2 billion Square Kilometre Array (SKA) telescope, the MWA is located in a remote pocket of outback Western Australia.

It is the result 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 leading 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 which will see stray FM radio signals used to track dangerous space debris.

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.

Steven Tingay

"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."

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 create the most comprehensive survey of the Southern Hemisphere sky at low radio frequencies.

From today, 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.

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."

Peter Hall

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 project 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.
Australia.

Australia Square Kilometre Array Pathfinder (ASKAP): Fastest Radio Telescope on Earth

Australia is now home to the world's fastest radio telescope with the launch Friday of the $152 million Australia Square Kilometre Array Pathfinder (ASKAP), which experts said would allow a more expansive survey of the universe - both known and what remains for scientists to discover s.

The new scientific research site is located in the Shire of Murchison, a sparsely populated area in Western Australia that astronomers have picked out because of the virtual absence of man-made radio signals.

The location is ideal because it is 'radio quiet', or lacks man-made radio signals that would interfere with the antennas picking up astronomical radio signals.

The ASKAP telescope is projected to improve on the previous achievements of similar facilities, giving researchers and scientists more universe space to cover with less time required.

Putting into perspective the speed and efficiency that comes with the ASKAP, scientists said only five minutes will be spent to fully observe Milky Way's neighbouring galaxy, Centaurus A.

Earlier works on the Centaurus A were achieved after two years of careful observations that were aided by thousands of hours of computer analysis and the poring over of hundreds of images, the news agency added.

Now with use of phased array feeds coming from 36 antennas spread over an area of about 50,000 square kilometres, future scientific researchers and observations have become more specific and accurate, scientists said.

Australia will host both the low frequency component of the SKA – which will image the birth of the first stars in the universe - and a world leading survey facility based on CSIRO’s revolutionary Phased Array Feed technology.

Both of these components of the telescope are right at the cutting-edge of radio astronomy technology and data management and will attract some of the best technological brains in the world to Australia.

These well-coordinated radio waves will provide clear snap shots of what man aims to discover out there to better comprehend the universe, National Scientific Research Organisation (NSRO) project director Brian Boyle said in a news briefing held earlier this week.

"Radio waves tell us unique things about the cosmos, about the gas from which stars were formed, and about exotic objects, pulsars and quasars, that really push the boundaries of our knowledge of the physical laws in the universe," Mr Boyle said.

What the new facility has delivered is for astronomers to better understand our own universe and the 'others' on its outer realms, he added.

Over the next few years, the NSRO is gunning to gain more information on the force that led to the creation of Milky Way and its constant expansion, decode the mystery-laden black holes and investigate further on pulsars.

It could be that the new ASKAP telescope would eventually prove that 'man is not alone' after all, Mr Boyle suggested.