Photo/IllutrationFourth-year students involved in Kyoto University's research project on the cosmological lithium problem pose in front of a particle accelerator. (Provided by Takahiro Kawabata)

KYOTO--Kyoto University students failed in their quest for a missing piece of the Big Bang puzzle, but their research still sent shock waves through the world of scientists studying the creation of the universe.

Takahiro Kawabata, an associate professor of astrophysics at the university, led three generations of senior students on a mission to verify a hypothesis explaining a paradox in the Big Bang theory known as the cosmological lithium problem.

Instead, they ended up proving that hypothesis was likely false.

According to the Big Bang theory, lithium, along with other light elements such as hydrogen and helium, was scattered across the universe when it was created through a monumental explosion from a single point.

But studies of stars showed the universe contained only about one-third of the theorized amount of lithium.

The accepted hypothesis for this huge mystery points to beryllium, an element with the atomic No. 4 that sits next to lithium, atomic No. 3, on the periodic table.

According to the theory, beryllium-7, one of the isotopes of the element, turns into the isotope lithium-7 when an electron attaches itself to it.

Scientists speculate that the shortage of lithium in space stemmed from a higher-than-expected tendency of beryllium-7 to transform into elements other than lithium-7, namely the isotope helium-4.

But astronomers had been unable to prove this hypothesis, mainly because beryllium-7 and neutrons are highly unstable and have relatively short lifespans.

The two particles can be smashed into each other to form two helium-4 atoms, but their precarious nature made it virtually impossible to conduct experiments to accurately record how often the transformation occurred.

To tackle this conundrum, Kawabata and his team developed a method to precisely record the rate.

With the aim of letting students participate in a full-scale research project, Kawabata had his fourth-year students join the study starting in fiscal 2014.

But it was no easy task. It took three generations worth of senior students, using a neutron lab and particle accelerator, to complete the project.

The junior researchers continued to improve the experiment apparatus, and everything finally bore fruit this fiscal year.

The 20 or so students this fiscal year found that beryllium-7 rarely turns into helium-4. This led to their conclusion that the lack of lithium in the universe cannot be explained by the hypothesis that they were trying to verify.

“The mystery has further deepened,” Kawabata said. “We must consider another hypothesis to solve the cosmological lithium problem.”

Regardless, the scientific community described the disproval of a major hypothesis as a significant breakthrough in the field.

The results were published in Physical Review Letters, one of the most prestigious physics journals in the world, on Feb. 3.

“It’s rare that a graduation thesis project achieves such extraordinary results,” Kawabata said.

The students were also overjoyed.

“I kept my fingers crossed during the study, hoping the experiment apparatus we designed wouldn’t break down,” said Ami Koshikawa, 23, a student who participated in the project. “I only recently came to realize that we had accomplished something amazing. I was able to experience something really exceptional.”