Washington, Jan 11 : Observations from the Hubble Space Telescope have revealed the presence of a pair of glowing rings, dubbed as the "Einstein ring", which are caused by the complex bending of light from two distant galaxies strung directly behind a foreground massive galaxy.
Found by an international team of astronomers led by Raphael Gavazzi and Tommaso Treu of the University of California, Santa Barbara, this never before seen optical alignment in space consists of two bright rings, which are nestled inside each other like a bull's eye pattern.
The inner ring and outer ring are comprised of multiple images of two galaxies at a distance of 6 billion and approximately 11 billion light-years.
"The twin rings were clearly visible in the Hubble image", said Tommaso.
This particular phenomenon, also known as gravitational lensing, occurs when a massive galaxy in the foreground bends the light rays from a distant galaxy behind it, in much the same way as a magnifying glass would.
When both galaxies are exactly lined up, the light forms a circle, called an "Einstein ring", around the foreground galaxy. If another more distant galaxy lies precisely on the same sightline, a second, larger ring will appear.
In this case, the massive foreground galaxy is almost perfectly aligned in the sky with two background galaxies at different distances.
According to Adam Bolton of the University of Hawaii's Institute for Astronomy in Honolulu, "The original signature that led us to this discovery was a mere 500 photons (particles of light) hidden among 500,000 other photons in the SDSS (Sloan Digital Sky Survey) spectrum of the foreground galaxy."
The discovery of this double "Einstein ring" is of great significance to astronomers.
For one, it can help in mapping the distribution of dark matter in the foreground galaxies that is warping space to create the gravitational lens.
In fact, a sample of 50 suitable double Einstein rings would be sufficient to measure the dark matter content of the Universe and the equation of state of the dark energy (a measure of its pressure) to 10 percent precision.
In addition, the geometry of the two Einstein rings has allowed the team to measure the mass of the middle galaxy precisely to be a value of 1 billion solar masses.
The comparative radius of the rings could also be used to provide an independent measure of the curvature of space by gravity.