When he first published his Theory of General Relativity a century ago, Albert Einstein mentioned the possibility that some supermassive space objects could act like gravitational lenses through which more distant cosmic bodies would become visible.
But only recently, a team of astronomers from the University of California’s department of astrophysics saw with their own eyes that Einstein was right. Over the course of a few weeks Hubble Space Telescope beamed back to Earth four images of a supernova explosion, which had occurred several billion years ago.
Surprisingly, the four images captured the same event as if there was three re-runs of the same stellar explosion. Astronomers said that they were able to immortalize the moment due to the gravitational lensing effect of a nearby galaxy. This means that the galaxy, which is closer to Earth than the supernova, acted like a cosmic magnifying glass of the unique event by bending and making brighter the light emitted by the supernova.
The four images of the stellar burst taken by Hubble were later overlapped by astronomers resulting in a pattern called the “Einstein cross.” Scientists argued that the four images that formed the cross were a result of the galaxy splitting in four the light coming from the supernova.
However, Hubble didn’t take the shots at once. Instead it needed a few weeks to catch each separate image. According to the researchers the phenomenon has an explanation – since light travels long distances through space to reach our telescopes, it gets bended many times by the gravitational pull of the space objects it encounters. As a result, it usually reaches Earth at different times, although the light beams have a unique source – the supernova.
So, that’s how the astronomers were able to witness the same supernova explosion four separate times over the course of a few weeks.
“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, […], as well as about the gravitational lenses. That will be neat,”
explained Patrick Kelly, postdoctoral researcher at UC Berkeley who found the supernova on November 11, 2014, while he was looking through the infrared images taken by Hubble.
Alex Filippenko, another researcher involved in the latest discovery and professor at U.C. Berkeley, was over-thrilled with the discovery. He said that his department along with other astronomers had been looking for a “strongly lensed supernova for more than half of century. Also, Prof. Filippenko described the discovery as “wonderful” and “really cool,” as well as prone to provide astrophysicists with a lot of important data.
Image Source: Ethanhein