It’s a well-known fact that the light we see from stars has taken hundreds, even thousands, of years to reach us. The photons made in the centers o

A Photon’s Million-Year Journey From the Center of the Sun

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2021-06-12 07:30:03

It’s a well-known fact that the light we see from stars has taken hundreds, even thousands, of years to reach us. The photons made in the centers of these distant stars have traveled across enormous expanses of space and time in order to enter our retinas. But what about the light made in our own Sun? What do those photons experience on their way to the Earth?

Our photon was produced in the core of the Sun: where the densities and temperatures—which can reach 15 million °C (27 million °F)—are high enough to sustain nuclear fusion. The hydrogen atoms that make up most of the Sun’s mass have too much energy to stay together, so they split into their component parts: protons and electrons—creating plasma.

When two protons collide inside this high-energy plasma, they bond, ultimately creating a deuterium atom, as well as releasing a neutrino and a positron. If another proton collides with a deuterium atom, they form a helium-3 nucleus and release a gamma ray. This gamma ray is our photon, albeit an extremely energized one. After the photon is created, two helium-3 nuclei can combine to create a helium-4 nucleus, and two protons.

The neutrino, being a weakly-interacting particle, will fly off into space, while the positron will interact with an electron, annihilating both of them and creating another gamma ray. In a later stage of the Sun’s life-cycle, the helium atoms produced by the fusion reaction can themselves combine, in different reactions, to make heavier and heavier elements, releasing even more energy.