Double Explosion May Explain Origin of Hyper-Fast White Dwarfs
HAIFA,Israel – September 9,2025 – A newly proposed scenario involving a double detonation could solve the mystery of how some white dwarfs achieve extraordinarily high velocities,potentially reshaping our understanding of stellar evolution within the Milky Way. Researchers at the Technion-Israel Institute of Technology suggest these “hyper-velocity” dwarfs aren’t simply ejected, but propelled by a unique chain of events.
The process begins with a binary star system consisting of a larger, primary white dwarf and a smaller companion. As the stars interact, mass transfer ignites a helium detonation on the surface of the primary white dwarf. This initial explosion generates a shock wave that penetrates to the core, triggering a second, more powerful detonation within the carbon-oxygen core, ultimately resulting in a supernova explosion.
“The mass transfer triggers a helium detonation on the surface of the primary white dwarf,” explain the astronomers.This explosion spreads around the entire star and creates a shock wave that extends to the core of this white dwarf. “The shock wave then causes a secondary detonation in the carbon oxygen core,which leads to a supernova explosion,” said Glanz and her team.
Crucially, the smaller companion star is partially disrupted before the second explosion, receiving a particularly strong “kick” from the event. the resulting debris is ejected at speeds exceeding 2,000 kilometers per second,leaving behind only the core of the former companion.”This solves the puzzle about the origin of these stellar outliers,” says researcher Glanz. The dramatic destruction and double explosion explain how these hyper-velocity dwarfs maintain such high speeds and temperatures. “It is indeed the first time that we see a path of origin, accelerated through the hot white dwarfs to the hyper-speeds that we have observed in the Halo of the Milky Way,” Glanz added.
The model may also explain the existence of unusually weak Type 1A supernovae, which release less energy and eject less material then typical. “This scenario opens up a window in new types of stellar explosions,” says Glanz’s colleague, Hagai Perets.
However, the scenario remains theoretical. Astronomers emphasize that future observations are needed to confirm whether these double-detonation events actually occur. ( Nature Astronomy, 2025; DOI: 10.1038/S41550-025-02633-4)
Quelle: Technion-Israel Institute of Technology