Image: Gravitational lensing in galaxy YGKOW G1

Jan 27, 2014
Credit: ESA/NASA

(Phys.org) —In this new Hubble image two objects are clearly visible, shining brightly. When they were first discovered in 1979, they were thought to be separate objects—however, astronomers soon realized that these twins are a little too identical! They are close together, lie at the same distance from us, and have surprisingly similar properties. The reason they are so similar is not some bizarre coincidence; they are in fact the same object.

These cosmic doppelgangers make up a double quasar known as QSO 0957+561, also known as the "Twin Quasar," which lies just under 14 billion light-years from Earth. Quasars are the intensely powerful centers of distant galaxies. So, why are we seeing this quasar twice?

Some 4 billion light-years from Earth—and directly in our line of sight—is the huge galaxy YGKOW G1. This galaxy was the first ever observed , an object with a mass so great that it can bend the light from objects lying behind it. This phenomenon not only allows us to see objects that would otherwise be too remote, in cases like this it also allows us to see them twice over.

Along with the cluster of galaxies in which it resides, YGKOW G1 exerts an enormous gravitational force. This doesn't just affect the galaxy's shape, the stars that it forms, and the objects around it—it affects the very space it sits in, warping and bending the environment and producing bizarre effects, such as this quasar double image.

The first detection of gravitational lensing meant more than just the discovery of an impressive optical illusion allowing telescopes like Hubble to effectively see behind an intervening galaxy. It was evidence for Einstein's theory of general relativity. This theory had identified as one of its only observable effects, but until the observation of these quasar "twins," no such lensing had been observed since the idea was first mooted in 1936.

Explore further: Image: Hubble shoots Bright Quasar 3C 273

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antialias_physorg
5 / 5 (3) Jan 27, 2014
This theory had identified gravitational lensing as one of its only observable effects

This makes it sound as if there were only a few observable effects of relativity - but there are many such effects: From time dilation/space contraction for satellites to mass increase in particle accelerators to the color of gold (wich, if you'd leave relativistic effects out of the equations, would look silver)