The face "lives" in a cluster of galaxies — each a huge community of stars. Astronomers have given this cluster a name that is hardly memorable:
Two glowing orange eyes seem to hover above a nose that looks like a white button. Those eyes actually are very bright galaxies, roughly 4.5 billion light-years away. The apparent smile and edge of the face don't truly exist. Their curving lines are a light distortion. They are due to an effect known as strong gravitational lensing, according to scientists with the National Aeronautics and Space Administration and the European Space Agency (ESA).
Galaxy clusters are huge. Indeed, they are the most massive things in the universe. Gravity due to that great heft exerts such a powerful pull that it can distort both nearby space and time. In a sense, gravity acts like the lenses in thick eyeglasses or a telescope. But a gravitational ones lens is so strong that it not only can magnify but also bend the light behind it. Many of Hubble's discoveries were made possible by this lensing, NASA notes.
One hundred years ago this year, Albert Einstein first proposed this light bending by gravity as part of his theory of general relativity. Twenty-one years later, Einstein wrote a paper describing an optical illusion that this bending can create. It has since been dubbed an Einstein ring. When some massive object acts like a lens, the light it bends may appear from some great distance to curve in a partial or full circle (a ring).
In this photo, such illusions create the curved lines in the smile and face. The "eyes" provide the lensing that made the grin. Its light arrived from nearly 3 billion light-years behind those eyes.
Astronomers captured these features while using two of Hubble's cameras to scout for strong lenses. Artist Judy Schmidt entered a version of this picture into ESA's Hubble's Hidden Treasures contest.
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