In the early stages of planetary system formation, young exoplanets gravitationally interact with their surrounding environments and leave observable signature on protoplanetary disks. Among these structures, a pair of nearly symmetric spiral arms can be driven by a giant protoplanet. For the double-spiraled SAO 206462 protoplanetary disk, we obtained three epochs of observations spanning 7yr using the Very Large Telescope's SPHERE instrument in near-infrared J-band polarized light. By jointly measuring the motion of the two spirals at three epochs, we obtained a rotation rate of -0.85+/-0.05 deg per year. This rate corresponds to a protoplanet at 66+/-3au on a circular orbit dynamically driving both spirals. The derived location agrees with the gap in ALMA dust-continuum observations, indicating that the spiral driver may also carve the observed gap. What is more, a dust filament at ~63 au observed by ALMA coincides with the predicted orbit of the spiral-arm-driving protoplanet. This double-spiraled system is an ideal target for protoplanet imaging.

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