University of Hawaiʻi at Mānoa physicists are part of a team that reports the first evidence of fractal features in the details of stellar pulsations. The paper titled “Strange nonchaotic stars” was published this week in Physical Review Letters, the flagship journal of the American Physical Society.

If confirmed, the fractal characteristics could aid the classification and detailed modeling of these variable stars. Fractals are never-ending patterns that are self-similar no matter how large or small the scale.

The research resulted from a casual conversation between John Learned, a UH Mānoa particle physics professor, and William Ditto, physics professor and dean of the College of Natural Sciences, at the start of College of Wooster Professor John Lindner’s yearlong sabbatical.

Learned was part of a group using Kepler space telescope data to study a bluish-white star 16,000 light-years away in the constellation Lyra, which pulsates at multiple frequencies.

Ditto was intrigued that two of the frequencies were nearly in the golden ratio. “From prior work I suspected that a fractal structure known as a strange nonchaotic attractor might guide the dynamics,” he recalls. Such attractors had previously been observed in the laboratory but never before in the wild.

Fractal self-similarity can describe processes in time as well as patterns in space, and a music analogy elucidates the team’s analysis of the variable starlight. “We removed the musical backbeat to discover a subtle melody,” Lindner explains.

The Kepler telescope was collecting data on the star as one of 150,000 other stars in a small portion of space for almost four years.