A zoomed-in section of the latest version of the Hubble Ultra Deep Field, with two candidate galaxies circled in green. About 20 - 30% of these early galaxy candidates are very close to foreground galaxies, as is the case in this image.
Credit: NASA/ESA/S Wyithe
SYDNEY: Nearby bright galaxies have been distorting the view of the earliest galaxies, which are important in understanding what happened to the universe just after the Big Bang, researchers report.
Any future studies of the universe's earliest galaxies will need to be corrected for the bias, according to the researchers.
"Our finding shows images from the earliest galaxies reach us more often via a gravitationally bent path. What you see is not exactly what is really there," astrophysicist Stuart Wyithe from the University of Melbourne, lead author of the study, said in a statement.
Cosmic 'hall of mirrors' effect
Wyithe compared the 'gravitational lensing' effect to a carnival's 'hall of mirrors': "Lensing results in a distorted view of the galaxies - just like a hall of mirrors with copies that are different sizes or shapes, stretched or magnified," he told Cosmos.
Albert Einstein first predicted how gravity would distort and bend light, however its affect on any astronomical object is usually rare.
This study, published in the British journal Nature, revealed that the phenomenon is likely to occur in at least 30% of observations of the early galaxies. "What this shows is that gravitational lensing will lead to a higher number of distant galaxies being counted in future surveys, at times when the universe was less than 500 million years old," Wyithe said.
Higher numbers of distant galaxies are counted
Using images from the Hubble Space Telescope, Wyithe and colleagues measured the separation between older, more distant galaxies and brighter foreground galaxies. They compared what they saw to a mathematical model that takes in account gravitational lensing, and concluded that the ancient galaxies were seen to be larger, brighter and more distorted than they actually are.
This effect has likely resulted in inaccurate counts for number density of ancient galaxies as seen by the recent near-IR surveys with the Hubble Space Telescope Wide Field Camera 3, according to the researchers.
But, in a twist, this effect may help astronomers find these distant, hard-to-see galaxies. "The lensing acts as a natural telescope too, so it can also help us find these distant galaxies,” said Wyithe.
