Astronomy Colloquium

SN Ia are the best astronomical objects for measuring cosmic distances.  They provide direct evidence for cosmic acceleration, as recently recognized by the 2011 Nobel Prize in Physics.  Large samples have been gathered to constrain the properties of dark energy, but they are beginning to hit the limits imposed by systematic errors.  Recent observations show that SN Ia are even better distance indicators when measured in near infrared bands from 1 to 2 microns.  They are more nearly standard candles and they are less affected by dust absorption.  I will show the evidence for the good behavior of SN IA in the IR and describe the RAISIN program being carried out now with PanSTARRS and the Hubble Space Telescope to use IR observations of SN IA to improve constraints on dark energy.