A white dwarf beats a red giant

Astronomers were able, for the first time, to collect data through a unique set of observations made in a short period of time after a supernova explosion

When a white dwarf star reaches the end of its path and explodes, it leaves behind a cloud of "stardust" that spreads rapidly. This phenomenon is known as a "type Ia supernova". These are extremely bright supernovae, and there is a lot of similarity between them, which is why they arouse interest among scientists, who use them as cosmological "reference points", which allow to follow the expansion of the universe.

Despite the significant progress made recently in the study of type Ia supernovae, the exact nature of these exploding stars, and the physical laws governing their violent explosions, are only partially understood. Recently, significant progress was made in understanding the phenomenon, when astronomers were able, for the first time, to collect detailed data through a unique set of observations that were made in a relatively short period of time (four months) after the supernova explosion. These data made it possible to identify the material surrounding the white dwarfs before the explosion. The observations were made using two giant telescopes: the ESO/VLT telescope located in Chile, and the Keck telescope located in Hawaii.

The findings support the accepted model according to which the white dwarf interacts with a neighboring star, of the red giant type. The strong gravitational force of the white dwarf acts as a kind of "pump" that draws gases that are emitted from the red giant, and are swallowed by the white dwarf. In this way, the red giant gradually loses its mass, in favor of the white dwarf. When the mass of the white dwarf exceeds a certain critical level - it explodes.

Through the observations, the scientists were able to notice the existence of several expanding rings, which surround the white dwarf when it explodes. These rings are probably the remains of the red giant that was "eaten" by the white dwarf.

These findings, recently published in the scientific journal Science, were collected by two groups of researchers. Dr. Ferdinando Patat headed the group of astronomers in Chile, and Dr. Avishi Gal-Yam headed the group at the California Institute of Technology. Dr. Gal-Yam recently joined the faculty of the Condensed Matter Physics Department at the Weizmann Institute of Science as a senior researcher.