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

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.