Two Supernovae in NGC 664

Two Supernovae in NGC 664
In 1997, the rareoccurrence of two supernovae in the same galaxy at the same time was observed in the spiral galaxy
NGC 664, located about 300 Mly (90 Mpc) from Earth. Supernovae observed in remote galaxies are important
standard candles used by astronomers to determine the distances to these faraway objects. The two supernovae
overlap each other, as shown. The upper, yellow-orange supernova was observed to occur 2 months before the
hotter, blue one, which was observed to occur less than 2 weeks before this image was made and had not yet achieved
maximum brightness.