Ariel Goobar & Rahman Amanullah Oskar Klein Centre at Stockholm University, Stockholm, Sweden
An international team, led by astronomers from the Stockholm University, Sweden, has discovered a distant type Ia supernova, called iPTF16geu  — it took the light 4.3 billion years to travel to Earth . The light from this particular supernova was bent and magnified by the effect of gravitational lensing so that it was split into four separate images on the sky . The four images lie on a circle with a radius of only about 3000 light-years around the lensing foreground galaxy, making it one of the smallest extragalactic gravitational lenses discovered so far. Its appearance resembles the famous Refsdal supernova, which astronomers detected in 2015 (heic1525). Refsdal, however, was a core-collapse supernova.
Type Ia supernovae always have the same intrinsic brightness, so by measuring how bright they appear astronomers can determine how far away they are. They are therefore known as standard candles. These supernovae have been used for decades to measure distances across the Universe, and were also used to discover its accelerated expansion and infer the existence of dark energy. Now the supernova iPTF16geu allows scientists to explore new territory, testing the theories of the warping of spacetime on smaller extragalactic scales than ever before.