A pulsating star鈥檚 song could be the result of fractals at play. Pressure changes inside a star can make portions of its surface expand and contract, so observers see it appearing to 鈥渂reathe鈥� as its brightness fluctuates. The star鈥檚 oscillations form a sort of melody with harmonies on top: our sun has a simple tune, variable stars have a complex one.
William Ditto and his colleagues at the University of Hawaii, Manoa, compared the two strongest oscillations, or tones, made by the variable star KIC 5520878, using observations by NASA鈥檚 Kepler space telescope. They noticed that dividing the frequency of the secondary note by that of the primary, or lowest, note gives a value near the 鈥�golden ratio鈥� 鈥� a number that shows up often in art and nature and is close to 1.618.
They then realised that its frequencies exhibited a fractal pattern: separating the tune into its constituent parts yielded more frequencies at weaker strengths, similar to the way coastlines retain their complexity as you zoom in. Three other pulsing stars with 鈥済olden鈥� ratios also showed fractal patterns, while two non-golden stars did not. This could mean the golden songs could reveal insights into stellar physics.
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Astronomers who study pulsating stars aren鈥檛 convinced the golden ratio finding is significant, however. 鈥淭he fact that this period ratio (or its reciprocal) lies close to the golden ratio may be a coincidence,鈥� says Robert Szabo of Konkoly Observatory in Hungary, 鈥渁nd in my opinion, more evidence is needed to demonstrate that it has a privileged role in the dynamics of [these] stars.鈥�
Journal Reference: Physical Review Letters, in press (arXiv.org/abs/1501.01747)
