Astronomers Observe Radio Waves from Type Ia Supernova for the First Time

Astronomers have made an unprecedented discovery by detecting radio waves emitted from a Type Ia supernova. This groundbreaking observation reveals new insights into the nature of white dwarf explosions and their helium-rich environments.

Type Ia supernovae are nuclear explosions that occur in white dwarf stars. They are widely used by astronomers to measure cosmological distances and study the expansion of the Universe. However, the exact mechanism behind Type Ia supernovae is not fully understood. It is believed that the explosion is triggered by mass accretion from a companion star, where the accreted material consists mainly of hydrogen. However, it was also hypothesized that white dwarfs could accrete helium from a companion star that had already lost its outer layer of hydrogen.

One of the mysteries surrounding white dwarf explosions is the behavior of the stripped matter from the companion star. Not all of the material falls onto the white dwarf; some of it forms a cloud of circumstellar material around the binary star system. It was expected that shockwaves from the explosion traveling through this circumstellar material would excite atoms and result in the emission of strong radio waves. Despite many observations of Type Ia supernovae occurring within a cloud of circumstellar material, radio wave emissions had not been detected until now.

An international team of researchers, including members from Stockholm University and the National Astronomical Observatory of Japan, observed a Type Ia supernova that exploded in 2020. They found that this supernova was surrounded by circumstellar material primarily composed of helium. Additionally, they successfully detected radio waves from the supernova. Comparing the observed radio wave strength with theoretical models, the researchers determined that the white dwarf had been accreting material at a rate of about 1/1000 the mass of the Sun per year. This is the first confirmed Type Ia supernova triggered by mass accretion from a companion star with an outer layer consisting primarily of helium.

The discovery of radio waves from this helium-rich Type Ia supernova is expected to deepen our understanding of the explosion mechanism and the conditions leading up to a Type Ia supernova. The research team plans to continue searching for radio emissions from other Type Ia supernovae to gain further insights into the evolution that leads to these explosive events.

Source: “A radio-detected type Ia supernova with helium-rich circumstellar material” by Erik C. Kool, Joel Johansson, Jesper Sollerman, Javier Moldón, Takashi J. Moriya, Seppo Mattila, Steve Schulze, Laura Chomiuk, Miguel Pérez-Torres, Chelsea Harris, Peter Lundqvist, Matthew Graham, Sheng Yang, Daniel A. Perley, Nora Linn Strotjohann, Christoffer Fremling, Avishay Gal-Yam, Jeremy Lezmy, Kate Maguire, Conor Omand, Mathew Smith, Igor Andreoni, Eric C. Bellm, Joshua S. Bloom, Kishalay De, Steven L. Groom, Mansi M. Kasliwal, Frank J. Masci, Michael S. Medford, Sungmin Park, Josiah Purdum, Thomas M. Reynolds, Reed Riddle, Estelle Robert, Stuart D. Ryder, Yashvi Sharma and Daniel Stern, Nature, 17 May 2023.