Measuring helium in distant galaxies may give physicists insight into why the universe exists Premium

A recent study found that the Subaru telescope’s new measurement of the amount and type of helium in faraway galaxies may offer a solution to the matter-antimatter asymmetry problem

When theoretical physicists like myself say that we’re studying why the universe exists, we sound like philosophers. But new data collected by researchers using Japan’s Subaru telescope has revealed insights into that very question.

The Big Bang kick-started the universe as we know it 13.8 billion years ago. Many theories in particle physics suggest that for all the matter created at the universe’s conception, an equal amount of antimatter should have been created alongside it. Antimatter, like matter, has mass and takes up space. However, antimatter particles exhibit the opposite properties of their corresponding matter particles.

When pieces of matter and antimatter collide, they annihilate each other in a powerful explosion, leaving behind only energy. The puzzling thing about theories that predict the creation of an equal balance of matter and antimatter is that if they were true, the two would have totally annihilated each other, leaving the universe empty. So there must have been more matter than antimatter at the birth of the universe, because the universe isn’t empty – it’s full of stuff that’s made of matter like galaxies, stars and planets. A little bit of antimatter exists around us, but it is very rare.

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As a physicist working on Subaru data, I’m interested in this so-called matter-antimatter asymmetry problem. In our recent study, my collaborators and I found that the telescope’s new measurement of the amount and type of helium in faraway galaxies may offer a solution to this long-standing mystery.

In the first milliseconds after the Big Bang, the universe was hot, dense and full of elementary particles like protons, neutrons and electrons swimming around in a plasma. Also present in this pool of particles were neutrinos, which are very tiny, weakly interacting particles, and antineutrinos, their antimatter counterparts.

Physicists believe that just one second after the Big Bang, the nuclei of light elements like hydrogen and helium began to form. This process is known as Big Bang Nucleosynthesis. The nuclei formed were about 75% hydrogen nuclei and 24% helium nuclei, plus small amounts of heavier nuclei.