NASA's Hubble Space Telescope has detected a distant Type Ia supernova, the farthest stellar explosion that can be used to measure the expansion rate of the universe. The supernova is the remnant of a star that exploded 9 billion years ago. The sighting is the first finding of an ambitious survey that will help astronomers place better constraints on the nature of dark energy: a mysterious repulsive force that is causing the universe to fly apart ever faster. The object, nicknamed SN Primo, belongs to a special class called Type Ia supernovae, which are bright beacons used as distance markers for studying the expansion rate of the universe.

SN Primo is the farthest Type Ia supernova whose distance has been confirmed through spectroscopic observations. The supernova was discovered as part of a three-year Hubble program to survey faraway Type Ia supernovae, enabling searches for this special class of stellar explosion at greater distances than previously possible. The remote supernovae will help astronomers determine whether the exploding stars remain dependable distance markers across vast distances of space in an epoch when the cosmos was only one-third its current age of 13.7 billion years. Called the CANDELS+CLASH Supernova Project, the census uses the sharpness and versatility of Hubble's Wide Field Camera 3 (WFC3) to look in regions targeted by two large Hubble programs: the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and the Cluster Lensing and Supernova Survey with Hubble (CLASH).