Gravitational lenses are cosmic phenomena that radically distort light passing by, make objects behind the lens appear much brighter, and help astronomers see distant parts of the universe. And now we've seen a quasar get in on the fun.
We've seen massive objects from stars to entire galaxies act as lenses before, in which their gravitational forces are strong enough to bend the rays of light passing through them on their way to Earth. But lens aren't just great for doing wacky things to the light sources behind them - they have also proved invaluable in figuring out the precise matter distribution of the lens galaxies, which can then be used to track down everything from extrasolar planets to dark matter.
Quasars, the incredibly bright light created supermassive black holes at the center of galaxies, have been viewed through these lenses about a hundred times, but this is the first time we've observed a quasar itself creating the lens. This offers an intriguing opportunity to use the distortion created by the quasar to measure the mass of its galaxy, something we've never been able to do before.
You can see an example of a gravitational lens up top. Note some of the images that get doubled by the lens. Below is a video with its discoverers discussing what the find means.