The first observed radio waves from a type Ia supernova

(Nanowerk News) For the first time, astronomers observed radio waves emitted by a Type Ia supernova, a type of explosion that originates from a white dwarf star. This provides an important clue to understanding how white dwarfs explode (Natural, “A radio-detectable Type Ia supernova with helium-rich surrounding stellar material”).

A Type Ia (One-A) supernova is a nuclear explosion from a white dwarf star. This type of supernova is well known; These supernovae are used by astronomers to measure cosmological distances and the expansion of the universe. But the explosion mechanism of a Type Ia supernova is not well understood.

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Solitary white dwarfs don’t explode, so it’s thought that mass accretion from a neighboring companion star played a role in triggering the explosion. The added mass is the outer layer of the companion star, so it is usually made up mostly of hydrogen, but it may also be possible for a white dwarf to accretion helium from a companion star that has lost its outer layer of hydrogen. .

When a white dwarf strips matter of its companion star, not all of the matter falls onto the white dwarf; some of which form clouds of circumstellar material around binary star systems. When a white dwarf explodes in a cloud of circumstellar material, the shock wave from the explosion traveling through the circumstellar material is expected to excite the atoms, causing them to emit strong radio waves.

However, although many Type Ia supernovae have been observed exploding within clouds of circumstellar material, so far astronomers have not observed the emission of radio waves associated with Type Ia supernovae.

An international team of researchers, including members from Stockholm University and the National Astronomical Observatory of Japan, made detailed observations of a Type Ia supernova that exploded in 2020. They revealed that this supernova was surrounded by stellar material consisting mostly of helium, and also succeeded in detect radio waves from supernovas.

Comparing the observed radio wave strengths with theoretical models revealed that the white dwarf star’s ancestor was accreting matter at a rate of about 1/1000 the mass of the Sun each year. It is the first confirmed Type Ia supernova to be triggered by accretion of mass from a companion star with an outer layer consisting mainly of helium.

It is hoped that radio wave observations of this helium-rich Type Ia supernova will deepen our understanding of the explosion mechanism and conditions before a Type Ia supernova. Now the team plans to look for radio emission from other Type Ia supernovae to shed light on the evolution that led to the explosion.