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Lensing putting universe out of focus
A new study has found the optical effect called gravitational lensing is causing some distant galaxies to appear brighter than they really are.

The report in the journal Nature may have implications for our understanding of how the early cosmos developed into the universe we see today.

Lead author, Professor Stuart Wyithe from the University of Melbourne's School of Physics, says the most distant galaxies were being viewed through a kind of cosmic hall of mirrors.

"When light from these galaxies passes other galaxies or supermassive black holes on its way to the Earth, the mass of the nearer objects causes the light to bend," says Wyithe.

This process is called gravitational lensing. First theorised by Albert Einstein, it happens because mass distorts space time.
Impacting the numbers

Wyithe says it's not a problem on small scales.

"But on cosmic scales it magnifies and distorts the light, changing both the shape of and numbers of images that appear to be coming from the more distant galaxies. It also makes them appear brighter than they really are," he says.

Because gravitational lensing is one of the best ways of detecting these ancient galaxies in the very early universe, it means a higher number of distant bright galaxy targets are being counted.

Acording to Wyithe that changes the number of bright early galaxies that are actually there.

Future surveys will need to be designed to account for this gravitational lensing bias, especially in these very young early galaxies when the universe was less than 500 million years old.

"We want to understand the history of the universe, how the first galaxies grew and how they interacted with their environment. So one of the most basic things to do is to count how many galaxies there are," says Wyithe.

"And one of the best ways to do this is through the observations of the Hubble [Space Telescope]. So the information needs to be accurate to reach the right conclusions."

Wyithe says the James Webb Space Telescope, scheduled for launch in 2014, may help make sense out of this gravitationally biased view of the distant universe.

"It will have exquisite resolution and sensitivity at longer wavelengths to disentangle these very distant objects from the foreground lensing galaxies," he says.

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