Astronomers have uncovered the origins of some of the fastest stars in the Milky Way—hypervelocity white dwarfs, which can travel at speeds exceeding 2,000 kilometers per second.
These stellar remnants, compact and faint, move so quickly that they can even escape the galaxy’s gravitational pull.
A new study published in Nature Astronomy reveals how such runaway stars are launched, linking them directly to powerful supernova explosions.
The research, led by Dr. Hila Glanz of the Technion–Israel Institute of Technology, used advanced three-dimensional simulations to model what happens when two unusual white dwarfs collide. These white dwarfs are hybrid stars, containing helium, carbon, and oxygen.
In the simulation, the lighter star is torn apart by its heavier partner.
Then, the heavier star undergoes a double-detonation explosion—two nearly simultaneous blasts that not only destroy it but also catapult the surviving fragments of the lighter star outward at staggering speeds.
“This is the first time we’ve seen such a clean pathway for creating hypervelocity white dwarfs,” explained Dr. Glanz. “Our model perfectly matches the observed properties of these faint, hot stars, solving a mystery that has puzzled astronomers for years.”
The discovery also provides new insight into a rare type of stellar explosion. Type Ia supernovae are among the most important tools in cosmology, used to measure distances across the universe.
But not all Type Ia supernovae are the same—some are fainter and stranger than expected. The new model shows that these unusual explosions can result from white dwarf mergers, explaining their puzzling behavior while also creating stellar cannonballs that shoot across the galaxy.
Two known stars, J0546 and J0927, have long stood out for their extreme speed and peculiar faintness. The new model accounts for both their velocities and their unusual appearance, something earlier theories could not fully explain.
“This discovery doesn’t just explain runaway stars,” added Professor Hagai Perets, a co-author from Technion. “It also gives us a window into new types of stellar explosions that shape galaxies and create elements essential for life.”
The study involved researchers from Technion, Universität Potsdam, and the Max Planck Institute for Astrophysics. By combining cutting-edge simulations with theoretical modeling, the team has opened a new chapter in understanding how stars live, die, and sometimes get flung across the cosmos at unimaginable speeds.
Future observations, especially from the European Space Agency’s Gaia mission and upcoming sky surveys, may reveal many more of these elusive high-speed white dwarfs.
Each new discovery will not only confirm the theory but also deepen our understanding of the violent and creative forces shaping our galaxy.
