Northwestern University researchers have found that despite their ancient ages, some stars orbiting the Milky Way’s central supermassive black hole appear deceptively youthful due to violent stellar collisions. Using a new model, astrophysicists traced the journeys of 1,000 simulated stars orbiting Sagittarius A*, the galaxy’s central black hole. Star collisions and interactions in this densely packed region can result in stars losing mass to become stripped down, low-mass stars or merging with other stars to become massive and rejuvenated in appearance.
The center of the Milky Way is a chaotic place filled with millions of stars moving at high speeds due to the gravitational pull of Sagittarius A*. In this region, closely packed stars are destined to collide, with stars located closer to the supermassive black hole having a higher likelihood of collision. The research focused on simulating the outcomes of these collisions by considering factors such as density of the stellar cluster, mass of the stars, orbit speed, gravitation, and distances from the black hole.
One key factor that determined a star’s fate in the simulation was its distance from the supermassive black hole. Stars within 0.01 parsecs from the black hole often collide with each other, losing mass through violent interactions, resulting in a population of stripped down, low-mass stars. Stars located further away move at slower speeds and may merge with other stars, becoming more massive and rejuvenated in appearance. These rejuvenated stars have a shorter life expectancy due to burning through hydrogen quickly.
The extreme environment near the galactic center provides a unique opportunity to study stellar populations under the influence of a supermassive black hole. The research not only sheds light on the violent processes occurring in this region but also contributes to understanding the history of the Milky Way. The simulations conducted by the research team offer insights into hidden processes in the central cluster, which is challenging to observe directly. This work can also provide a contrast to the more familiar stellar populations observed in other regions of the galaxy.
Sanaea C. Rose, who led the research, will present this work at the American Physical Society’s April meeting. By studying the effects of stellar collisions and interactions near the supermassive black hole, the research aims to uncover new insights into the formation and evolution of the galactic center. The research findings published in The Astrophysical Journal Letters and The Astrophysical Journal highlight the complex dynamics of stars in the extreme environment near the galactic center. This work was supported by grants from the National Science Foundation, NASA, and various fellowships and institutes.
