AUSTRALIAN radio astronomers have discovered the first case of a remarkable system where two galaxies are twisting our picture of a distant quasar.

Radio emissions from a quasar lying more than 10 billion light-years away are being concentrated and focussed by the gravity fields of at least two intervening galaxies, like the sun's rays through a pair of magnifying glasses.

The gravity lens system was discovered by a team from the University of Tasmania, the Australia Telescope National Facility (ATNF), and NASA's Jet Propulsion Laboratory.

"This is the strongest gravity lens effect by far that has yet been found," ATNF researcher Dr Dave Jauncey said. "It is 10 times stronger than any other known."

"We're seeing a perfect Einstein ring - the halo which Einstein predicted would occur if two objects were perfectly aligned with the Earth so the gravity of one bent and focussed light from the more distant one."

The distant quasar lies more than 10 billion light-years away - close to the edge of the known universe. Using molecular absorption to calculate redshift, radio astronomers have measured the two 'lensing' galaxies to be 2.5 billion and 10 billion light-years from Earth respectively.

"These events and Einstein rings are very beautiful as well as being astrophysically interesting. They are proving far more complex than we originally thought," says Dr Jauncey.

The team hopes that analysing the lensing system will yield an even more dramatic advance - a yardstick to measure the scale of the universe.

More information: Dr Dave Jauncey (CSIRO), tel: 06 216 7220 or Jim Lovell (Uni. of Tasmania) tel: 03 6226 2405
Graphic available: Helen Sim (CSIRO) tel: 02 9372 4251