A research team from Louisiana State University has shown that the center of a nearby supernova remnant--the leftovers of an exploding star-called SNR 0509-67.5 lacks a companion star, perhaps providing another clue as to how supernovae originate.

This finding is important because researchers theorize that supernovae form when very dense, small stars--white dwarfs--explode. These explosions may be triggered by the merger of two white dwarfs or by a companion star transferring mass to the white dwarf. Determining the ways that supernovae explode has many implications for astrophysics and for the understanding of the evolution of the universe. 

Astronomers use supernovae to determine distances to far-off galaxies. Supernovae studies have revealed that the rate of expansion of the universe is increasing. For the last three decades, astronomers believed that most Type Ia supernovae occur when material from a companion red giant star falls onto a white dwarf and tips the white dwarf's mass over the maximum possible mass for such a star. If this were always true, one should see the red giant star near the center of the supernova remnant. 

In this study, no companion was found for remnant SNR 0509-67.5, suggesting that a newly theorized way of making supernovae through the merger of two white dwarf stars took place to make SNR 0509-67.5.