We Are All Star Stuff

Above: A supernova scatters chemical elements throughout the universe.

By TREVOR O’DONOGHUE

One of the rarer celestial events to have been observed from Earth happened in 2017 when scientists observed two neutron stars colliding in a galaxy 130 million light years from Earth. Not only that, but the power of the collision set up gravitational ripples in space-time, which eventually made it to us here on Earth. Like many things of the cosmic variety, it is hard to wrap our brains around the power and scale of such events. A neutron star is already the result of a stellar explosion. They are formed when a large star, at the end of its lifetime, blows itself to bits in a stellar explosion known as a supernova. This is an event so powerful that the light from this explosion can outshine the rest of the stars in its galaxy, which may well be in the order of few hundred billion stars. In this instance, what remains, the neutron star, is so dense that a teaspoon of it would weigh 10 million tons. Just for context, that’s about 10 million Ford Fiestas!!! In a teaspoon!!!

These supernovae and neutron star collisions are not just bright, they also serve a useful purpose. When the universe was formed, it was predominantly hydrogen with a sprinkling of helium. Stars are powered by nuclear reactions turning this hydrogen into helium and then into gradually heavier elements, including carbon, nitrogen, and Iron. Beyond this, the heavier elements in our universe including gold, silver and so on are formed in supernova explosions and other cataclysmic events like neutron star collisions. These explosions scatter the newly formed elements such as gold far and wide, where they eventually may find a home on one planet or other. With a bit of luck, that gold will be found and end up as a watch or a ring adorning a finger. A long way indeed from the fiery cauldron of its birth in a stellar explosion billions of years ago.

Carl Sagan summed it up nicely; ”Our Sun is a second- or third generation star. All of the rocky and metallic material we stand on, the iron in our blood, the calcium in our teeth, the carbon in our genes were produced billions of years ago in the interior of a red giant star. We are made of star-stuff.”