Supernova Explodes Without Companion Star

This image shows that the central region of this supernova remnant, SNR 0509-67.5, is empty of stars, allowing researchers to rule out a number of possible models for the original supernova system. In this image, the stars appear as white dots on the black sky, while the red ring is gas ejected by the supernova eruption close to 400 years ago. (NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

A discovery made by researchers from Louisiana State University showed that the center of a nearby supernova remnant—the leftovers of an exploding star—named SNR 0509-67.5 lacks a companion star, perhaps providing another clue as to how supernovae originate.

The finding is important because researchers theorize supernovae form when very dense, very small stars, called white dwarfs, explode. These explosions could be triggered by the merger of two white dwarfs—the so-called double-degenerate model—or by a companion star transferring mass to the white dwarf causing it to explode—the single-degenerate path.

Scientists distinguish between double-degenerate and single-degenerate models by looking for the companion star that might have been near the exploding white dwarf. If the progenitor of the remnant—the exploding white dwarf—resulted from a single-degenerate model, then there should be a companion star still visible near the supernova remnant. If the progenitor resulted from a double-degenerate, then there will be no visible companion.

In the case of this discovery, researchers could not find a companion star.

“Our NSF proposal is to help solve the Type Ia supernova progenitor problem, named one of the top nine questions in all astronomy [by the recent decadal review of the National Academy of Sciences],” said Brad Schaefer, coauthor of the study. “With this, we prove that SNR 0509-67.5 came from a double-degenerate system, where two white dwarfs in a close binary orbit slowly in-spiral until they collide and explode as a Type Ia supernova.”

This research will be published in the January 12 issue of Nature.