As recently as September scientists were perplexed about a strange, unexplained acceleration affecting the Pioneer spacecraft. Measurements didn't match up. Heads were scratched. New physics were excited hypothesized. Let's pump the brakes a moment, though, shall we?
Seems the phenomenon is on the verge of being debunked. It's not dark matter or energy or some fantastic new realm of physics that was messing with Pioneer instruments. In fact, it might be something scientists have speculated about for some time now.
In a PopSci article this month, scientists Viktor Toth and Slava Turshyev don their debunking hats:
Five years have passed. Using the telemetry data, the two scientists created an extremely elaborate "finite element" 3-D computer model of each Pioneer spacecraft, in which the thermal properties of 100,000 positions on their surfaces are independently tracked for the duration of the 30-year mission. Everything there is to know about heat conduction across the spacecraft's surfaces, as well as the way that heat flow and temperature declined over time as the power of the generators lessened, they know. The results of the telemetry analysis? "The heat recoil force accounts for part of the acceleration," said Turyshev.
For those holding out hope the strange acceleration phenomenon is still crazy new physics or something as-of-yet unexplained, there is still hope. Toth and Turshyev wouldn't say in the article how big an effect the hear conduction is having on Pioneer, which has opened the door to skeptics like researcher Johan Masreliez.
Other physicists are more combative. "Heat? That's simply not the right explanation. They are wrong," commented Johan Masreliez, an independent researcher in Washington who supports the expanding spacetime model of cosmology, for which it is crucial that the value of the Pioneer anomaly equals c times H. "But then I'm biased."