Fusing

Universe originally contained just a soup of particles. For the elements such as iron to emerge, these particles had to be squished into larger structures.

The thing is, these particles ordinarily don’t want to group together, and one of the ways this can happen is inside a star. Once sufficient number of particles are in the same vicinity, a gravitational collapse can occur. If the squishing is sufficient the increase of temperature can lead to particles fusing together, creating new elements (“nuclear burning”). The comic shows a star putting effort into such fusion, sweating from the temperature increase.

Our Sun fuses helium through a proton-proton chain, but other nuclear burning processes exist that create heavier elements. Fusing beyond iron involves a different process and is rare in Sun-sized stars. There is one option available for try-hards: explosive death releases large amounts of energy and can indeed create these heavier elements.

We don’t know everything about element creation within stars and the information I’ve given above is a popular explanation based on current scientific semi-consensus.