Back in 1938, physicist Hans Bethe figured out that the Sun and other stars generate energy by fusing hydrogen into helium. With that mystery solved, solar scientists thought they had a pretty good understanding of what was going on at the heart of the sun.

But an experiment that started in 1967 made astronomers just a tad uneasy.

While it takes sunlight just eight minutes to travel to Earth, the energy generated in our star’s core needs tens or hundreds of thousands of years to me