A new theoretical model from Caltech indicates that Sun-like stars nearing the end of their lives can receive thousands of small velocity boosts from asymmetric gas eruptions. These cumulative effects may disrupt wide binary systems or, rarely, cause stellar collisions. The findings were presented at a major astronomy conference.
Jim Fuller, a theoretical astrophysicist at Caltech, developed the model based on simulations of convection in aging red giants. The calculations show that roughly 10,000 chaotic ejections of material over several hundred thousand years can impart a net speed of about 1 kilometer per second through a random-walk process.
Fuller presented the work at the 248th meeting of the American Astronomical Society in Pasadena. The study, titled "White Dwarf Kicks via Episodic Mass Ejection from Red Giant Stars," has been submitted to the Publications of the Astronomical Society of the Pacific and was funded by Caltech.
Observations by Caltech astronomer Kareem El-Badry showing fewer wide binaries after one star becomes a white dwarf provided supporting evidence. Fuller noted that each burst follows Newton's third law, giving the star an equal and opposite push. El-Badry said the model explains an observation that had puzzled him for years.
The same mechanism could, in rare cases, alter orbits enough to trigger collisions between binary companions.