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Einstein ring gives view of early universe

Astronomers are being provided a rare glimpse back to the time when galaxies were in their infancy thanks in part to the work of an ANU astronomer.

Dr Helmut Jerjen from the Mt Stromlo Observatory in Canberra says the partial Einstein Ring in the Fornax constellation is only the fourth of its kind ever observed — and its discovery comes 100 years after Albert Einstein predicted the existence of such tricks of light.

The ring is an optical phenomenon that occurs when two galaxies are perfectly aligned along the line of sight. The gravity of the nearer galaxy acts as a lens, distorting and magnifying the light from its distant counterpart into the shape of a circle.

“It’s is a pure geometrical coincidence that you have these two galaxies perfectly aligned with one another. This can be discovered anywhere in the sky, but it is extremely rare that the alignment and distances are right — like finding needles in a haystack.”

Dr Jerjen says the closer, lensing galaxy in the new Einstein Ring is eight billion light years away and up to 10 times larger than our Milky Way.

But he says the farther galaxy is 12 billion light years distant, and would remain invisible if it weren’t for the magnifying effect of the foreground galaxy, allowing a rare insight into the early epoch of galaxy formation of the still young universe.

“We can explore the stellar composition of this distant object, which is a baby galaxy. At 12 billion light years from us, this object is really located at the time when galaxies were just forming. Thanks to these magnified images, we’re able to explore parts of the universe that really wouldn’t be accessible to us otherwise.”

The ring was first detected in Dr Jerjen’s observations two years ago, but has only just been confirmed through the collaboration with a team of international astronomers at the European Southern Observatory (ESO).

The team used ESO’s Very Large Telescope, which is located in the northern part of Chile at one of the best sites for optical astronomy in the world, to take spectra of this phenomenon.

“With the help of the spectra we could measure the distance of the two objects, and we found the ring is actually at a much greater distance than the central object.”

Dr Jerjen says the possibility of such rings was first predicted by Einstein’s general relativity theory 100 years ago, which says that light will bend under the gravitational force.

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