Researchers at Caltech have developed a theoretical model describing how stars nearing the end of their lives may receive significant momentum as they transition into white dwarfs. The model was presented at the 248th meeting of the American Astronomical Society in Pasadena and has been submitted to the Publications of the Astronomical Society of the Pacific.
As Sun-like stars age, they expand into red giants before their outer layers gradually dissipate into space, leaving behind dense white dwarf cores. According to the new calculations, this process may occur in a less orderly manner than previously understood. Rather than material escaping uniformly, chaotic bursts of matter are ejected asymmetrically from the star’s surface, with each eruption imparting a small directional push to the star itself. Over several hundred thousand years, a dying star may experience approximately 10,000 such kicks, each providing motion at just a few meters per second.
While individual kicks are modest, they accumulate through a mathematical process similar to a random walk. Although material is ejected in random directions that do not perfectly cancel out, the combined effect produces an overall velocity shift of roughly 1 kilometer per second. This cumulative acceleration differs significantly from the more violent kicks experienced by neutron stars following supernovae explosions. The model builds on observations by an assistant professor of astronomy at Caltech who noted that wide binary star pairs become less common after one member becomes a white dwarf, suggesting the dying stars acquire sufficient momentum to escape their orbital bonds.
The research also generates testable predictions. In some binary systems, accumulated kicks could alter orbits enough to cause the dying star to collide with its companion, potentially producing observable explosions. Future observations of such stellar mergers may provide evidence supporting whether the proposed mechanism accurately describes the final evolutionary stages of Sun-like stars.