Written by Laura Glitsos, article courtesy of ScienceNetwork WA

Last month’s international SKA-low workshop held in Perth focused on the challenges of detecting low-frequency radio waves emitted from objects throughout the Universe.

CSIRO Astronomy and Space Science chief Dr Phil Diamond says the goal of the low-frequency SKA is essentially to understand ‘dark energy’.

Dr Diamond says this goal is directly related to the recent announcement of the Physics Nobel Prize for the discovery that the Universe is expanding faster and faster, driven by dark energy.

However, to unravel the mysteries of dark energy scientists must map hydrogen—the most common occurring element—in the very early stages of the Universe and understand how it is distributed.

To do this, astronomers must figure out a way of collecting information from very long radio waves.

“The SKA will cover a wide range of frequencies from 70 megahertz, which is down below the FM radio band, up to 25 gigahertz,” Dr Diamond says.

“That is an enormous frequency range, so in order to cover it we cannot just use one single type of technology.

“So from about 1 gigahertz to 20 gigahertz [the higher frequencies] we’ll use traditional dishes—these are the much larger version of the satellite dishes you see around. There’ll be several thousand of those.

“However, the workshop in Perth focused on the lower frequencies, which requires a different type of antenna technology.”

Several different types of antennas were discussed at the workshop, but one of the main designs consists of a pole protruding from the ground to about one metre with four metal rods coming out from the centre much like “spokes from
an umbrella without the top”.

These are called “dipole antennas” and the workshop discussed cost-effectiveness and efficiency of different designs.

Putting together several thousand of these will comprise the SKA Aperture Array Verification Program (AAVP).

These low-frequency dipoles are necessary to detect hydrogen in the very distant Universe because of ‘redshift’—objects moving away quickly due to the expansion of the Universe.

“The local Universe has a wavelength of 21 centimetres but as you go further out the wavelength gets longer and longer, to about 2 metres, so the only way to detect it is with low-frequency radio signals,” Dr Diamond says.

One of the greatest challenges with the AAVP is collecting the information, as the data rates are enormous.

Whereas traditional dishes can only detect what is in the line of sight, dipoles can see the whole sky above our heads.

Dr Diamond says the process is complicated but solvable.