Heat 'Most Likely Cause' of Pioneer Anomaly 133
astroengine writes "Everything from clouds of dark matter, weird gravitational effects, alien tampering and exotic new physics have all been blamed for the 'Pioneer Anomaly' — the tiny, inexplicable sun-ward acceleration acting on the veteran Pioneer deep space probes. However, evidence is mounting for a more mundane explanation. Yes, it's the emission of heat from the spacecrafts' onboard radioisotope thermoelectric generators (RTGs), slowly nudging the Pioneers off course, that looks like the most likely culprit. It's unlikely that this new finding will completely silence advocates of more exotic explanations, however."
It's the direction it is accelerating in (Score:4, Insightful)
Remember that any change in velocity over time is an acceleration in the proper sense, and also remember velocity has both a speed and direction component. You accelerate a car to a stop, and you accelerate around corners when you change direction.
I understand that in regular speech it just means "going faster" and the direction component is dropped. Understand that NASA is full of scientists and they may use science terms in a more precise manner.