Christopher Michel · CC BY-SA 4.0

Led the International Supernova Cosmology Project at Berkeley, using distant exploding stars as reference points to measure how fast the universe is expanding — and found, against expectation, that the expansion is speeding up. The result reshaped cosmology's picture of dark energy and won Perlmutter a third of the 2011 Nobel Prize in Physics, shared with Brian Schmidt and Adam Riess.