The Pioneer anomaly grows ever more fascinating.
Here’s the background: Pioneer 10 and 11 were launched in 1972 and 1973 respectively and, after sweeping past a number of the outer gas giants, have been heading out of the solar system ever since.
NASA has been accurately tracking their position and speed using Doppler tracking measurements of radio signals from the craft. But this data has thrown up a problem. Both probes appear to be decelerating faster than can be explained by the Sun’s gravity. All that has been widely discussed and numerous explanations have been put forward to explain this discrepancy.
What isn’t so well known is that there is a periodic component to the anomaly. The team at the NASA’s Jet Propulsion Lab who have been collecting the data say that it’s unlikely that this variation is a from the spacecraft. Instead, they think probably the result of something at our end such as a tiny variation in Earth’s orbit.
Now Bruno Christophe and pals from the French aerospace lab, ONERA, near Paris and various other French institutions, have carried the most detailed analysis yet on these periodic variations and raise another interesting possibility.
A number of people have suggested modifications to general relativity that would explain the Pioneer anomaly. But there has never been a way to test these modifications.
Now Christophe and co say that the periodic variations are compatible with the effects on radio signals that some of these modifications might cause.
That’s an extraordinary claim. Obviously, more analysis is needed and it always pays to be cautious with these kinds of ideas. But could it really be possible that the Pioneer anomaly is the first evidence of physics beyond Einstein’s version of general relativity?
Ref: arxiv.org/abs/0809.2682: Pioneer Doppler Data Analysis: Study of Periodic Anomalies