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Ananova - Space probe under 'mysterious' force now travelling at 27,000mph towards stars that they will encounter several million years from now. Scientists are continuing to monitor signals from Pioneer 10, which is more than seven billion miles from Earth.
Research to be published shortly in The Physical Review will show the speed of the two probes is being changed by about 6mph per century - a barely-perceptible effect about 10 billion times weaker than gravity

The effect shows no sign of getting weaker as the spacecraft travels deeper into space and scientists are considering the possibility the probe has revealed a new force of nature