An international team of astronomers has combined information obtained with NASA's Hubble Space Telescope and the Very Large Telescope (VLT) of the European Southern Observatory (ESO) to test Albert Einstein's general theory of relativity at the scale of the entire Milky Way, confirming that, indeed, gravity behaves as predicted by the historical scientist.

It is the most accurate severity test outside of the Solar System, and has been carried out by a research group led by Dr. Thomas Collett of the Institute of Cosmology and Gravitation at the University of Portsmouth. The corresponding report has been published in the journal Science.

Collet himself explains that "general relativity predicts that massive objects deform space-time, this means that when light passes near another galaxy, the path of light is diverted".

"If two galaxies are aligned along our line of sight," the astronomer continues, "this can lead to a phenomenon called a strong gravitational lens, where we see multiple images of the background galaxy."

Collet concludes his explanation by stating that if the mass of the galaxy is known in the foreground, then the amount of separation between the multiple images reveals whether General Relativity is the correct theory of gravity in galactic scales.

The general theory of relativity, proposed in 1915, gave an explanation to the behavior of gravity that has since resisted a series of high precision tests within the Solar System. However, never before have precise tests been carried out on this theory at a galactic or large-scale astronomical level.