Artist impression of the Pioneer 10 probe (NASA)

The Pioneer Anomaly: A Deviation from Einstein Gravity?

Article Updated: 24 Dec , 2015

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Both Pioneer probes are approximately 240,000 miles (386,000 km) closer to the Sun than predicted by calculation. Scientists have been arguing over the cause of this mysterious force for a decade and reasons for the Pioneer anomaly range from the bizarre to the sublime. Is it a simple fuel leak, pushing the probes of course? Is it phantom dark matter dragging them down? Or do the gravity textbooks need to be re-written? Unfortunately there’s still no one answer, but some researchers believe there might be a small deviation in the large-scale space-time Einstein described in his famous theory of general relativity. See, I knew there would be a simple explanation…

The Pioneer 10 and 11 deep space probes were launched in 1972 and 1973, visiting Jupiter and Saturn before pushing on toward interplanetary space, into the unknown. The Pioneer program really lived up to its name, pioneering deep space exploration. But a few years on, as the probes passed the through the 20-70 AU mark, something strange happened… not suddenly, but gradually. Ten years ago Pioneer scientists noticed that something was wrong; the probes were slightly off course. Not by much, but both were experiencing a slight but constant sunward acceleration. The Pioneer probes had been measured some 240,000 miles (386,000 km) closer to the Sun than predicted. This might sound like a long way, but in astronomical terms it’s miniscule. 240,000 miles is a tiny deviation after 6.5 billion miles (10.5 billion km) of travel (it would take light 10 hours to cover this distance), but it’s a deviation all the same and physicists are having a very hard time trying to work out what the problem is.

That is until NASA physicist Slava Turyshev, co-discoverer of the anomaly, rescued a number of Pioneer magnetic data storage disks from being thrown out in 2006. These disks contain telemetric data, temperature and power readings that both Pioneer probes had transmitted back to mission control up to 2003 (when Pioneer 10 lost contact with Earth). From this, Turyshev and his colleagues teamed up with Viktor Toth, a computer programmer in Ottawa, Ontario, to design a new code designed to extract the vast quantity of raw binary code (1s and 0s), revealing the temperature and power readings from the crafts instruments. It sounds as if the search for the culprit of the Pioneer anomaly required a bit of forensic science.

Now the researchers have a valuable tool at their disposal. Turyshev and 50 other scientists are trying to match this raw data with modelled data in an effort to reconstruct the heat and electricity flow around the craft’s instrumentation. Electricity was supplied by the on-board plutonium generator, but this is only a small portion of the energy generated; the rest was converted to heat, lost to space and warmed up the probe’s bodywork. Heat lost to space and warming of the probe’s instruments are both thought to have a part to play in altering spacecraft momentum. So could this be the answer?

Tests are ongoing, and only a select few simulations have been run. However, early results indicate that around 30% of the Pioneer anomaly is down to the on-board heat distribution. The rest, it seems, still cannot be explained by probe dynamics alone. The team are currently processing a total of 50 years of telemetry data (from both Pioneer 10 and 11), so more simulations on the rich supply of transmissions from the probes may still uncover some surprises.

But on the back of everyone’s mind, and it keeps cropping up in every Pioneer anomaly article I find, that the fundamental physics of our universe may need to be brought into question. Sending long-distance deep space probes gives us a huge opportunity to see if what we observe locally is the same for other parts of the Solar System. Could Einstein’s general theory of relativity need to be “tweaked” when considering interplanetary (or interstellar) travel?

The researchers are excited if a mundane solution does not present itself (i.e. probe heat distribution effects), therefore indicating some other cosmic reason is behind this anomaly:

If we actually had a means in the solar system here to measure deviations from Einstein’s gravity, that would be phenomenal.” – Viktor Toth

In the mean time, Pioneer 10 is drifting silently toward the red star of Aldebarran and (barring any more anomalous behaviour) will arrive there in 2 million years time…

Sources: Scientific American, Symmetry Breaking News


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Haplo
Guest
Haplo
April 16, 2008 7:43 PM

Deep-space probes… lol.

A little presumptuous if you ask me.

RL
Member
RL
April 16, 2008 5:14 PM

Could someone explain how heating the spacecraft slows its momentum? Any help understanding this is greatly appreciated.

Jorge
Guest
April 16, 2008 5:59 PM

Ian, could you please add to those distances their values in km? Those of us from outside Imperialmeasureland would surely appreciate. Thanks.

Silver Thread
Member
Silver Thread
April 16, 2008 6:40 PM

Is the deviation increasing with distance from the sun or has it remained constant? I am sure it’s been considered but I wonder if interstellar wind could cause such an anomaly. It would be akin to shooting a bullet into the wind, the effects are minimal, but present.

Stephen Farrugia
Guest
Stephen Farrugia
April 17, 2008 4:24 AM

I wonder if the connecting signal itself [Earth to Pioneer] is the unknown culprit to this anomaly. Just like gravity, that pulls masses together, there may be a miniscule miniscule pull effect between a sender-receiver electromagnetic system, as yet never detected on Earth, that is causing this slow down. In the distances on EARTH the effect is negligible but over the long distances and the time span we are talking about the affect becomes noticeable.

Transmission is a recent phenomenon in Science and I’m sure there’s a lot more we need to learn about it.

Stephen, your man from Kibish

Fabio Knopf
Guest
Fabio Knopf
April 16, 2008 9:48 PM

Certainly!!

# Haplo Says:
April 16th, 2008 at 7:43 pm

Deep-space probes… lol.

A little presumptuous if you ask me.

Brad
Guest
Brad
April 16, 2008 10:49 PM

So objects in the rear view mirror may actually be FURTHER than they appear. Great.

GBendt
Guest
GBendt
April 17, 2008 12:19 AM

I think, the Pioneer anomaly isn´t an anomaly at all: It is caused by the drag of the mass in the outer solar system. The space outside the Pluto orbit is not empty. Since Pioneer has been crossing that space during the lst decades, the mass of the dust and the comets and the kuyper belt objects conzained within that space adds to the mass of the solar system, increasing it by one millionth and creating a slight additional gravity pull.

Regards

Günther

David
Member
April 17, 2008 1:03 AM

>So objects in the rear view mirror may actually be FURTHER than they appear.

AND, they happened a long time ago. wink

@ Günther, I was thinking the same thing..

Wolfgang Keil
Guest
Wolfgang Keil
April 17, 2008 1:33 AM

Certainly all internal and external energetic effects, which may lead to an imbalance of perturbation have to be considered. The probe is not undisturbed by particle radiation (GCR, solar particles) and the according absorption/transmission/reflection factors are not homogeneous for the probe. Sun depending parameters change, Sun has lost mass. etc. etc. There are a lot of fine studies triggered to get the problem solved…

john
Guest
john
April 17, 2008 1:53 AM

A nice little Mystery. Enjoy!

sail4evr
Member
sail4evr
April 17, 2008 2:45 AM

Does this influence occur on asteroids and comets? That would determine whether it is a spacecraft issue or external influence.

Dilip G Banhatti
Member
April 17, 2008 3:18 AM
To really test any gravity theory applicable, a ballistic or free fall object must be tracked, not a complex spacecraft like the Pioneers, which is affected by its internal, and initially Earth-controlled, dynamical forces. Of course, even such a ballistic object is subject to nongravitational effects, which include photon drag near Sun (Poynting-Robertson drag), solar wind, cosmic rays, possible effects of an asymmetry in Kuiper belt, Oort Cloud (which is of course rather far away at 10**5 astronomical units or so, but an asymmetry in it can have an effect, if the cloud is massive enough). I’m sure the experts (are expected to) take account of all possible effects of sufficient magnitude. However, one can sometimes lose sight… Read more »
Max
Guest
April 17, 2008 4:36 AM
Higher powered photons have more of an acceleration than lowered powered (i.e. heat) so that the net effect of any radiation should be an acceleration away from the sun (seeing as that is where the principle external warming force will be coming from) whereas the observed acceleration is towards the sun. My personal pet theory is all about observation points, in other words it looks to us as though it is being slowed down from our observation point, however if you were aboard this probe I reckon you would observe an acceleration away from the sun, the clocks run at different speeds. Does anyone know if there is an internal clock on this probe and if it can… Read more »
PHWilson
Guest
PHWilson
April 17, 2008 5:09 AM

Why not astral weather? There’s a solar wind -where there is wind, there are patterns formed by forces larger than the wind itself. Jet Streams? Turbulence? Cyclones? All totally imperceptible except by the results of a long probe.

alphonso richardson
Guest
alphonso richardson
April 17, 2008 7:51 AM

That should keep the guys busy for a LOONG time…………………..

skyweek
Member
April 17, 2008 8:34 AM

Have a look at this paper from 7 years ago that came to the conclusion that non-isotropic heat radiation is the answer and that “by accounting for the bulk of the acceleration, the proposed mechanism makes it much more likely that the entire effect can be explained without the need for new physics.”

Could it be that the “anomaly” has been kept on life-support by eager physicists when it was dead in the water already in 2001, thanks to a sound engineering study …? Anyone remember the “N-rays” of 100 years earlier? Go google for them and be astounded …

wpDiscuz