We introduce a method for identifying “ twin ” Type Ia supernovae , and using them to improve distance measurements .
This novel approach to Type Ia supernova standardization is made possible by spectrophotometric time series observations from the Nearby Supernova Factory ( SNfactory ) .
We begin with a well-measured set of supernovae , find pairs whose spectra match well across the entire optical window , and then test whether this leads to a smaller dispersion in their absolute brightnesses .
This analysis is completed in a blinded fashion , ensuring that decisions made in implementing the method do not inadvertently bias the result .
We find that pairs of supernovae with more closely matched spectra indeed have reduced brightness dispersion .
We are able to standardize this initial set of SNfactory supernovae to 0.083 \pm 0.012 magnitudes , implying a dispersion of 0.072 \pm 0.010 magnitudes in the absence of peculiar velocities .
We estimate that with larger numbers of comparison SNe , e.g , using the final SNfactory spectrophotometric dataset as a reference , this method will be capable of standardizing high-redshift supernovae to within 0.06 – 0.07 magnitudes .
These results imply that at least 3/4 of the variance in Hubble residuals in current supernova cosmology analyses is due to previously unaccounted-for astrophysical differences among the supernovae .