UC Berkeley, Stanford astronomers link stellar flybys with creation of planetary systems

Diagram showing impact of stellar flyby on planetary orbit
Jenn Zeng/Staff

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UC Berkeley and Stanford astronomers recently linked stellar flybys — the close contact of stars in the solar system — to the creation of planetary systems, finding a potential “smoking gun” in the structure of outer space.

UC Berkeley adjunct professor of astronomy Paul Kalas and project scientist at Stanford University Robert De Rosa studied the HD 106906 star system, located 300 light-years from Earth. The system is very young — approximately 15 million years old.

“It’s important because stellar flybys have been used to explain the evolution of our own solar system, yet we haven’t caught a flyby really happening to a planetary system,” Kalas said in an email. “HD 106906 offers a rare example where such a flyby happened recently and may have perturbed its distant giant planet.”

The astronomers theorized that after a planetary system forms within a disk of gas and dust around a star, the initial configuration of objects changes because of gravitational interactions. The “giant planet” that the study focused on may have been disturbed by another pair of stars that skated too close to the system between 2 and 3 million years ago, soon after the planet formed from a swirling disk of dust and gas.

If confirmed, the research bolsters arguments that close stellar misses can sculpt planetary systems and may determine whether or not the systems harbor planets with stable orbits.

Going forward, the researchers hope to discover what happens during the perturbations of planetary structures along with the origins of the perturbations.

“Our work provides tangible evidence that a planetary system has been influenced by two passing stars,” Kalas said in an email. “Stars need to pass very close to a planetary system to have a significant effect — our calculations show that the flyby stars gave HD 106906 a gentle gravitational tug rather than a strong one. This is definitely work in progress.”

Stanley von Ehrenstein-Smith covers research and ideas. Contact him at [email protected] and follow him on Twitter at @von_ehrenstein.