... Supernova twins . ... Matching spectra among different supernovae can double the accuracy of distance measurements. ... The discovery was made possible by type Ia supernovae; extraordinarily bright and remarkably similar in brightness, they serve as standard candles essential for probing the universe s history. ... Using a sample of almost 50 nearby supernovae, they identified supernova twins pairs whose spectra are closely matched that reduced their brightness dispersion to a mere eight percent. ...