The Next Generation of Radio Astronomy

 
 

Last year, Irish astronomy took a leap forward with the construction of the LOFAR radio telescope in Birr, Co. Offaly. Sean Mooney, who was involved in the telescope’s construction, reports on its significance for the future of astronomy.

 

Last year, Birr was thrust to the forefront of astronomy. What may seem a quaint and unassuming town, Birr, Co. Offaly, is steeped in astronomical history and it has regained its scientific prominence with the construction of a new telescope.

In 1842, William Parsons, 3rd Earl of Rosse, began construction of a telescope on his estate, Birr Castle demesne, which would colloquially come to be known as The Leviathan. Not only was it the largest telescope in the world, it held this title for a staggering 72 years. This fact can be appreciated most in the current era of rapid technological improvements where the best of anything in the world holds the title for weeks rather than years before a better model comes along.

Parsons was a brilliant man. The unprecedented size of The Leviathan meant that he had to invent many of the techniques required for its construction. His efforts were not in vain as, using The Leviathan, he discovered the spiral structure of galaxies, a key landmark in the history of astronomy, and suggested to be the inspiration behind the stars in Van Gogh’s Starry Night. Perhaps most impressively, the construction and operation of the instrument went unhindered even while the Great Famine decimated the population. First light for the telescope came as the country was on the brink of starvation.

“Using cutting-edge supercomputers and clever mathematics, all of the stations can be used in conjunction to function as a single large telescope.”

In 2017, Birr once more shot to the leading edge of astronomy with the construction of a LOFAR (low frequency array) station. Unlike The Leviathan, which is an optical telescope, LOFAR is a telescope used to detect radio waves. LOFAR is a Europe-wide project commanded from The Netherlands. The telescope is made up of stations which are scattered across the continent.

Using cutting-edge supercomputers and clever mathematics, all of the stations can be used in conjunction to function as a single large telescope. The combined stations are equivalent to a telescope as large as the separation between individual LOFAR stations, and a large telescope is important as the resolving power of a telescope depends on its size. The Irish station marks a major addition to the project: As Ireland is situated on the western fringe of the continent, it improves the overall resolution of LOFAR. Synchronising all LOFAR stations equates to having a telescope effectively the size of Europe.

“Synchronising all LOFAR stations equates to having a telescope effectively the size of Europe.”

The LOFAR station in Birr detects radio waves using antennae, and so bears little resemblance to traditional single-dish telescopes. There are two sets of antennae, each tuned to a different portion of the radio spectrum. The FM radio band lies right in the middle of what LOFAR can detect, which contaminates the signal from space, but this and other sources of interference are filtered out prior to analysis.

The build took just months to complete, but initial plans for the €2 million project were formulated over a decade ago. The funding for the telescope came from a diverse range of sources, including UCD.

Getting this project off the ground was a major achievement for all involved, especially given the challenge fundamental physics research faces in the current funding climate. LOFAR promises more than just science though. It generates over 10 TB of raw data per second (equivalent to approximately 6,000 hours of HD video), so manipulating, transporting, and storing this level of information presents the information and communications technology industry with fresh challenges. The timing also could not be better, as big data is a pertinent issue at present among technology companies, from start-ups to Google and Amazon.

“The LOFAR station in Birr detects radio waves using antennae, and so bears little resemblance to traditional single-dish telescopes.”

People from UCD were involved in the build along with a group of astrophysicists from around Ireland, which included everybody from students to professors. The first few weeks involved burying many kilometres of delicate coaxial cable. Beneath the surface, the cables are offered some protection against environmental factors such as temperature and wildlife. Building the actual telescope was relatively straightforward. The quasi-modular IKEA-esque design of the tiles, and the fact that the majority of the components are polystyrene, made assembling the 96 tiles a simple process. Despite this, the margin for error was still razor-thin.

Researchers at UCD can now observe the sky using LOFAR. The High Energy Astrophysics group use it to study jets of material being propelled from distant galaxies. Such jets are launched at near light-speed from a super-massive black hole residing at the centre of a galaxy. The jet matter cools as it collides with the matter which permeates intergalactic space, emitting radio waves. The radio waves then travel unimpeded for billions of years before being detected at LOFAR stations such as that in Birr.

The construction of the Irish LOFAR station is a captivating venture as it stands at an unexplored intersection between physics, astronomy, and engineering. The LOFAR telescope is itself just a pathfinder for a more ambitious project, the Square Kilometre Array, which is being built in the southern hemisphere and will cost several billion euro. As for Birr, LOFAR has been built so now it is time for it to start producing science. A new chapter is about to be written in astronomy.

Advertisements