The nation's attempt to become home to the world's biggest radio telescope was boosted last night after the field was narrowed to two countries, with Australia and South Africa shortlisted to host the $1 billion facility.

If the Australian bid succeeds thousands of antennas will be built in the Western Australian desert at Mileura Station, 100 kilometres west of Meekatharra and 350 kilometres north-east of Geraldton. Thousands more dishes will be dotted across the continent, with some possibly positioned in New Zealand.

The giant radio telescope, known as the Square Kilometre Array, will be about 50 times more sensitive than even the most powerful of today. Astronomers predict it will be able to peer back to the birth of the cosmos - a dark age, when stars and galaxies had yet to form - as well as detect any aircraft radar used by extraterrestrials, if they exist, in our galaxy.