A long time ago, in a galaxy far, far away a star exploded. To be more precise about 9 billion years ago, on the other side of the known universe a star turned into a supernova. The event was much too far away for even the Hubble space telescope to see. However, the Hubble telescope has seen it four times thanks to a cosmic trick of light called gravitational lensing.

Because of this effect, originally theorized by Albert Einstein but not seen for the first time until 1979, the supernova is seen as four images. This arrangement is known as an Einstein cross. Each of the four images represents a slightly time in the stars destruction.

In the coming years, as more powerful telescopes like the James Webb Space Telescope and the European Extremely Large Telescope come online, gravitational lensing is going to become more important.

Gravitational lensing happens when the gravity of an extremely dense object bends space. Think of it as the effect you get if you put a bowling ball onto a mattress. The more dense an object is, the more distortion it causes. That, at least, is the gravitational part.

The lensing half of the phrase is exactly what it sounds like. When we look into the sky, space acts as a lens in the same way that eyeglass lenses do. While all objects cause some amount of distortion, really dense objects such as black holes and galaxies cause enough of a bend in space to create some unusual effects.

They can, for example, make objects appear to be closer than they are which allows telescopes like Hubble to see things that would normally be out of range. However, they can also cause the lens to go slightly “out of focus” which can create the appearance of multiple images and other distortion effects.

In addition to the supernova, gravitational lensing recently made headlines when it allowed scientists to see an especially dusty galaxy in the early universe.

A really good and more detailed of gravitational lensing can be found in a four minute video from SciShow.

So, in this case a massive galaxy, within a cluster of other galaxies is providing the lens through which astronomers are seeing the supernova and the distortion has created four different images of the event.

“Basically, we get to see the supernova four times and measure the time delays between its arrival in the different images, hopefully learning something about the supernova and the kind of star it exploded from, as well as about the gravitational lenses. That will be neat,” said Patrick Kelly in a statement.

Kelly is the UC Berkeley postdoctoral scholar who discovered the supernova while looking through infrared images taken Nov. 10, 2014, by the Hubble Space Telescope (HST).

Astronomers are thrilled with the discovery because of the opportunity it proves to discover supernovae and the distribution of dark matter in the galaxies providing the lens. In other words, by calculating the distortion caused by the galaxies, researchers should be able to determine the amount of dark matter present.

“It’s a wonderful discovery. We’ve been searching for a strongly lensed supernova for 50 years, and now we’ve found one. Besides being really cool, it should provide a lot of astrophysically important information,” said Alex Filippenko, UC Berkeley professor of astronomy and a member of Kelly’s team.

A paper describing the discovery appears in a special issue of Science which marks the 100th anniversary of Albert Einstein’s General Theory of Relativity.