Type Ia supernovae (SN Ia) are explosions of white dwarfs whose distances can be measured to a precision of ~5% using luminosity information that is encoded in the light curve shape. This property has been very successfully exploited to measure the history of cosmic expansion and to infer the presence of dark energy. But to learn the properties of dark energy and determine whether it is different from the cosmological constant demands higher precision and better accuracy than optical light curves alone can provide. The largest systematic uncertainties come from light curve fitters, photometric calibration errors, and from poor knowledge of the scattering properties of dust along the line of sight. Efforts to use SN Ia spectra as luminosity indicators have had some success, but have not produced a big step forward. Fortunately, observations of SN Ia in the near infrared (NIR), from 1 to 2 microns, offer a very promising path to better knowledge of the Hubble constant, improved constraints on dark energy, and, possibly, a route to discriminating the progenitor paths for SN Ia explosions.
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