* Astronomy

Astronomers have spotted the most distant Einstein ring ever seen. It gives an insight into both the gravitational lensing galaxy and the more distant magnified galaxy.
Gravitational lensing occurs because massive objects - ranging from stars to entire galaxies - distort the fabric of space-time, bending the path of light passing near them. A strong gravitational lens can form multiple images of the distant object, or spread its light into an arc.



Source and lens galaxy have received the designation FOR J0332-3557 3h32m59s, -35d57m51s and lie in the direction of the Fornax galaxy cluster.
A team of astronomers led by Rémi Cabanac of the Canada-France-Hawaii Telescope found the unusually complete ring in images recorded in visible light by the European Southern Observatory's Very Large Telescope (VLT) in Chile.

It shows about 180° of the ring. But Cabanac estimates the ring actually spans about 270°, and he expects to confirm that during planned observations with the Hubble Space Telescope.

Other teams have recorded more complete rings at radio and infrared wavelengths. However, the real importance to astronomers in this case is that both the lens and the distant background galaxy are very far away, so we see them as they were when the universe was very young.

"The source amplified by the lens is the galaxy with the brightest apparent luminosity ever discovered at such a distance. It will give us unique information on the physical conditions prevailing in the interstellar medium when the universe was only 12% of its present age. The shape of the source is also very important because it gives the amount of mass within the lens at a redshift of z=1. Only a handful of Einstein rings have been discovered at such high redshift. It will give an important measurement at how elliptical galaxy mass evolved through time" - Rémi Cabanac.

The background galaxy in this case is 12 billion light years away, revealing a time just 1.7 billion years after the big bang. Normally, too faint for astronomers to record detailed spectra.
At seven billion light years away, the gravitational lens is not quite far enough away to set a record.
But it still offers important data, because its focusing power depends on its mass, which can be calculated by analysing the ring pattern, while other techniques can only estimate mass indirectly.