Snapshot Distances to Type Ia Supernovae: All in “One” Night's Work

We present an empirical method that measures the distance to a Type Ia supernova (SN Ia) with a precision of similar to 10% from a single night's data. This method measures the supernova's age and luminosity/light-curve parameter from a spectrum and the extinction and distance from an apparent magnitude and color. We are able to verify the precision of this method from error propagation calculations, Monte Carlo simulations of well-sampled SNe Ia, and the Hubble diagram of sparsely observed supernovae. With the reduction in telescope time needed, this method is 3-4 times more efficient for measuring cosmological parameters than conventional light-curve-based distance estimates.