Astronomers Discover Most Distant Gravitational Lens Yet: Starbursting Dwarf Galaxy

Astronomers have discovered the most distant gravitational lens yet, a galaxy that deflects and intensifies the light of an even more distant object. The finding has now provided the scientists with a rare opportunity to directly measure the mass of a distant galaxy and reveals that these lenses may not be as uncommon as once believed.

Light is affected by gravity. This means that light passing through a distant galaxy will be deflected. Called gravitational lenses, these distant galaxies can provide tests of Einstein's theory of general relativity and act as valuable tools. Gravitational lenses actually consist of two objects: one that is further away and supplies the light, and another that sits between us and the distant light source and whose gravity deflects the light.  Astronomers can use these gravitational lenses to determine the mass of the matter that is bending the light, including the mass of dark matter.

The latest find was actually made by chance. The astronomers were reviewing observations from an earlier project when they noticed a galaxy that was decidedly odd. In the end, it turned out to be a gravitational lens. In fact, the lensing mass is so distant that the light, after deflection, has travelled 9.4 billion years to reach us. This, in and of itself, is a record. Yet the lens also allows the astronomers to calculate the mass of the object.

"This has been a weird and interesting discovery," said Arjen van der Wel, one of the researchers, in a news release. "It was a completely serendipitous find, but it has the potential to start a new chapter in our description of galaxy evolution in the early Universe."

While the discovery is certainly interesting, it also presents astronomers with a new puzzle. Gravitational lenses are the result of a chance alignment, and the likelihood of spotting this particular gravitational lens was even slimmer, so how did astronomers find it in the first place? It's very possible that starbursting dwarf galaxies, the one that was discovered in this case, are far more common than previously thought.

The findings reveal a little bit more about distant galaxies. In addition, they may make astronomers rethink their models of galaxy evolution as they consider the possibility that these objects may be far less rare than once believed.