The exploding stars known as Type Ia supernovae serve an important role in measuring the universe, and were used to discover the existence of dark energy. They're bright enough to see across large distances, and similar enough to act as a "standard candle" - an object of known luminosity. However, an embarrassing fact is that astronomers still don't know what star systems make Type Ia supernovae.

Source: One supernova type, two different sources