A team of researchers led by Dr. Hila Glantz and Prof. Hagai Peretz from the Technion found that a merger between special white dwarfs leads to a dramatic double explosion, leaving behind the remnants of stars that fly at dizzying speed out of the boundaries of the Milky Way.
In a groundbreaking study published in the journal Nature Astronomy Researchers at the Technion have succeeded in revealing the origin of some of the fastest stars ever observed – hypervelocity white dwarfs, which are the remnants of stars flying through space at speeds exceeding 2,000 kilometers per second.
The study was led by Dr. Hila Glantz and Prof. Hagai Peretz from the Faculty of Physics at the Technion with an international team of researchers. The results revealed a dramatic scenario: the lighter dwarf partially disintegrates, while the companion undergoes a massive double explosion. As a result, the remains of the lighter dwarf are thrown out at a dizzying speed of more than 2,000 kilometers per second – a speed sufficient to escape the gravity of the Milky Way galaxy.
"This is the first time we see a clear trajectory where a merger of white dwarfs can produce a remnant that is ejected at enormous speed, with properties that match the hot, dim white dwarfs we see in the galactic halo," explains Dr. Glantz. "This finding solves the mystery of the origin of these runaway stars – and also reveals a new channel for a particular and unusual class of Type Ia thermonuclear supernovae."
Unlike previously proposed scenarios, the new model explains not only the extreme velocities but also the unusual temperatures and luminosities of well-known white dwarfs like J0546 and J0927. It also provides new clues about unusual, weak thermonuclear explosions—explosions that are important for measuring the expansion of the universe and understanding how elements are formed in galaxies.
"This discovery not only helps us understand hypervelocity stars – it opens a window to new types of stellar explosions," says Prof. Peretz.
The study was carried out by Technion researchers with Akash Bhatt (University of Potsdam) and Dr. Rüdiger Packmoor (Max Planck Institute for Astrophysics) and combined high-performance simulations with new theoretical models. The researchers used advanced 3D simulations of a rare merger between two special white dwarfs that contain both helium and carbon and oxygen.
The findings are of great importance for future sky surveys and data from the Gaia sky survey expected to be released in the coming years, which may reveal more elusive "stellar cannonballs" flying throughout the galaxy.
for the article in the journal Nature Astronomy
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Interesting theory. I once read that there should be more matter in the universe than you see. (Normal matter, not dark matter.) So maybe it was thrown between galaxies this way – in an explosion between a pair of stars. Which is what fights do…