Heat Explains Pioneer Drift, Not New Physics

New analysis shows the decades-long Pioneer anomaly—the small sunward drift of Pioneer 10 and 11—was caused by asymmetric thermal radiation from the spacecraft’s plutonium-238 RTGs and electronics, not a breakdown of gravity; detailed archival data and thermal modeling by Turyshev and colleagues demonstrated that the recoil from emitted infrared photons pushed the probes backward, a tiny, decaying force that disappeared as the fuel decayed, leaving general relativity intact while the probes continue to drift outward.