A small subset of the supernovas that Subaru discovered. Each set of three images shows (left to right) the sky before the supernova exploded, after, and the difference between the two images. (Credit: N. Yasuda et al.)

Before our solar system formed or our sun even began to shine, stars halfway across the cosmos were exploding in brilliant flashes of light called supernovas. The light from their death throes traveled for 8 billion light-years and arrived at Earth sometime in the past few ye