Superfast white dwarfs provide clues to understanding supernovae

(ORDO NEWS) — Scientists from the Innovation Research Cluster of the RIKEN Research Institute, Japan, have shown through computer simulations how one hypothetical type of supernova evolves over thousands of years.

These results will allow researchers to search for examples of supernovae that explode according to this scenario, known as the D6 pattern.

Supernovae play an important role in cosmology: for example, type Ia supernovae are “standard candles” for measuring cosmic distances. With the help of supernovae of this type, it was possible to establish that the expansion of the Universe is accelerating.

The conventional wisdom holds that Type Ia supernovae result from the explosions of degenerate stars known as white dwarfs stars that have burned up all their hydrogen and shrunk into compact objects but the mechanism of these explosions remains largely poorly understood.

Recently, the discovery of fast-moving white dwarfs has made one of the proposed mechanisms for the explosion of these D6 supernovae more convincing.

In this scenario, one of the two white dwarfs in a binary system experiences what is called a “double detonation” – when the surface helium layer first explodes, and then a larger explosion occurs in the carbon-oxygen core of the star.

As a result, the star is destroyed, and the freed companion star is thrown out of the system with great speed.

However, the shape of such supernova remnants after a long time after the explosion has so far remained a mystery to astronomers. To clarify the issue, a team led by Gilles Ferrand of the RIKEN Institute undertook to model the long-term evolution of D6 supernova remnants.

Astronomers have found that, after thousands of years of evolution, some features remain in the system that are specific to this scenario, such as a “shadow,” or dark spot surrounded by a ring of bright material.

The authors also concluded that the type Ia supernova remnants they studied do not have to be symmetrical, as previously thought.

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