You’re a Star….Literally

“You’re a star!”. A common expression emphatically bestowed upon athletes, actors/actresses, or even children. When we use the word “star” in this context, seldom do we consider the sun, or the trillions of stars that occupy our night sky.

Fortunately or unfortunately, very few of us will become movie or sporting stars. Do not despair, however, as we all have one thing in common. We are all made from the corpses of ancient stars.

The death and explosion of a star: Supernova SN 2014J
Image Credit: NASA/CXC/SAO/R.Margutti et al

On Earth we find hundreds of elements. Gold, silver and einsteinium (named after Albert Einstein) are just a few that exist on our rocky planet. These elements, however, did not always exist. Even carbon, the essential ingredient for life as we know it, did not exist in the early universe. So how did all of these exotic elements come into existence? To answer this, we must go back to just after the birth of our universe.

In the beginning, the universe was quite bland. Hydrogen and Helium, the two smallest elements, occupied the vast landscapes of space. As time passed, the first stars began to form. Since the universe was composed of hydrogen and helium, so too were the first stars.

As these stars burned, hydrogen and helium fused together to form heavier elements like Carbon and Nitrogen. The end of a star’s life is usually signified by a massive explosion, or supernova. These explosions are more powerful than anything seen on Earth. The remains of these dead stars are sprayed out in all directions, fertilising the cosmos.

With time, new stars were born in these fertilised fields. Containing a more exotic mix of ingredients, this next generation of stars produced even heavier elements than the first generation. Our Sun is a third generation star and was born with a high diversity of elements. Our solar system, that is the sun and the planets orbiting it, was formed from the remains of the first and second generation stars. Without this recycling of star corpses, we and all of the wonders found on Earth would not exist.

So yes, you really are made from dead stars!

Why do we care?

Understanding the life cycle of stars has important implications for us on Earth. Nuclear fusion, the process that powers the Sun and other stars, is a source of clean renewable energy. Unlike nuclear fission where large atoms are broken down into smaller ones, fusion has no harmful by-products. It produces energy of the purest form.

Understanding how stars live also helps us understand how our Sun lives and how it will die. Thankfully, we are about 5 billion years from that happening.

Finally, it is suggested that some remnant stars are made solely of carbon, meaning that planet sized diamonds could potentially exist in the cosmos. While not particularly relevant to human survival, it is cool contemplate.

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