# Measuring the size of the core of the sun with multiple neutrino detectors

Back in 1998, researchers at the Super-Kamiokande neutrino detector released this image:

of the sun using their neutrino detector using approximately 500 days of data. This picture covered 90x90 degrees of the sky compared to the sun's disk angular size of about a half degree.

Is it possible that as more neutrino detectors become available, we could collect data from detectors around the world over a longer period of time to get a statistical estimate on the size of the core of the sun? Perhaps this would involve releasing data on incidental events of suspected solar neutrinos which then could be released to the public domain and pooled for statistical analysis?

All the neutrino detectors we have or might build will have course angular resolution because they detect the direction of scattered products of neutrino interactions rather than the direction of the neutrinos themselves.

Worse, the solar neutrinos are relatively low energy (a few MeV), which means the scattering angles are large.

Yes, we could accumulate data from multiple sources, but at least two things work against the results being very interesting in the foreseeable future:

• You would have to know the relative alignment off all the detectors to better than your desired resolution. This is a mixed bag. Those detectors (like super-k) that are also used in beam experiments have their alignment very well known, but those that are not (like SNO) may not be that well aligned. Is there going to be the interest in spending the money and effort? I don't see it as a slam dunk, so it would take a powerful personality to get it to happen.

• Accumulating statistical precision gets slower and slower as you ask more and more. The basic rule from counting statistics is that the uncertainty on a counted measurement (like events in a bin) goes by $\sqrt{N}$ for $N$ the number of counts. That means the fractional uncertainty goes like $1/\sqrt{N}$ meaning that getting 1% statistics is 100 times as hard as getting 10% statistics.

• I am almost certain that you can call "Nope!" on this one unless we can bring the detector very close to the sun, so close, indeed, that surviving the sun's thermal emissions would be an extreme technological challenge. May 9 '16 at 18:06
• Perhaps a 22nd century asteroid mining company could convert a mine to a neutrino detector and send it on a close orbit to the sun. May 9 '16 at 18:31

In princple yes it is possible, as detailed in this PRL article: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.211101

The main issue, as raised by other responses here, is that you need a large amount of data to be able to overcome the effect of the electrons scattering in the detector medium. No experiment has currently used their data to actually measure the solar core, however I believe the Super Kamiokande collaboration are looking into it.