The standard solar model has the Sun as a fusion reactor, compressing hydrogen into deuterium and subsequently into helium in its super-dense core.
Fusion reactions are known to produce detectable neutrinos, so the detection of such neutrinos on Earth from the direction of our Sun would be a great way to confirm the standard model.
An experiment was set up in the 1960s to look for solar neutrinos. However, very few neutrinos were detected.
Sun on February 18, 2015. Taken with Canon 60d, Coronado PST, 20mm eyepiece, Vixen Polarie, 1/8 second, iso 400, HDR wavelets in Pixinsight and sharpening in GIMP.
By HalloweenNight – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44873108
This came as a great surprise to the standard solar model proponents. Something was not quite the way they had imagined.
After some deliberation, everyone agreed that the problem was not with the solar model, but with our understanding of the neutrino.
What was finally decided on was that neutrinos have the ability to change from one state to another as they move through space. By the time they reach Earth from the Sun, they are simply undetectable.
Everybody could now congratulate themselves on having used the standard model of the Sun to learn something profound about neutrinos.
Our current understanding of the neutrino is in other words based on the standard model of the Sun.
This means that if the standard model of the Sun at some point proves to be wrong, then our understanding of the neutrino will have to be revised too.
A lot of modern physics rests on the standard model of the Sun. It is therefore no big surprise that competing models of the Sun are met with skepticism and even outright hostility.