Type Ia supernovae have emerged as one of the sharpest tools in the astrophysicists kit for measuring extragalactic distances, with a precision of around 6%. These exploding stars have shown that the Universe is accelerating in its expansion, a result that indicates that the cosmos must be filled with some previously unknown form of dark energy. By studying Type Ia supernovae with GSAOI, we can accurately trace the cosmic expansion to redshifts of z=2, learning key physical properties of the dark energy.
Different types of dark energy affect the rate at which the Universe expands depending on their effective equation of state. For example, the cosmological constant has one equation of state whereas quintessence - a scalar field - has a different equation of state. Each variant of dark energy has its own evolving equation of state that produces a signature in the Hubble diagram of the Type Ia supernovae. With current instrumentation, we can find and follow supernovae to a redshift of z=1.1. To move beyond this redshift, we need an instrument with excellent image quality and near-infrared sensitivity such a GSAOI.