As reported in the press release “Hubble Finds Double Einstein Ring” from the Space Telescope Science Institute, the Gavazzi-Treu team found a double Einstein ring, a very rare occurrence in the universe, at least for Earth astronomers.

A double Einstein ring is the appearance of two glowing broad circles (rings) in front of a galaxy, caused by the gravitational lensing of two galaxies directly behind it.

Images of the double Einstein ring are found at "Images of 'Hubble Finds Double Einstein Ring'."

The situation is thus: A massive galaxy, in the constellation Leo, is located about three billion light-years from Earth. Directly behind it (with respect to Earth’s viewpoint), are two other galaxies—one about six billion light-years from Earth and the other about eleven billion light-years away from us.

What is unique is Earth and the three galaxies are all located on a straight line, with Earth at one end and the three galaxies all positioned on this same line at the other end.

Because of this positioning, these scientists were able to use the NASA/ESA Hubble Space Telescope to find what they are stating is a “never-before-seen” optical alignment in space called a double Einstein Ring.

That is, a pair of glowing rings, one inside the other, was formed because light from the two more distant galaxies is bending around the closest galaxy.

The results of the discovery were reported at the 211th meeting of the American Astronomical Society in Austin, Texas, United States. The team has also submitted a paper based on their discovery to The Astrophysical Journal. Now, what exactly is a gravitational lens? Please read on....