Stars that go supernova – meaning they explode powerfully – are responsible for creating many of the elements of the periodic table, including those that make up the human body.
The Veil Nebula is 110 light years across. It’s the remnants of a massive star supernova that exploded about 8,000 years ago. This small section of the nebula was captured by the Hubble Space Telescope. The colours correspond to different gases – oxygen is blue, hydrogen is red and sulphur is green. © NASA/ESA/HHT
Our planetary scientist, Dr Ashley King explains how, because of this spectacular phenomenon, we might actually be made of stardust.
Most of the elements that make up the human body were formed in stars.
The first generation of stars
Elements are matter that can’t be broken down into simpler substances. On the periodic table, each element is distinguished by its atomic number, which describes the number of protons in the nuclei of its atoms.
We think that the universe began about 13.8 billion years ago with the Big Bang. At that point, only the lightest elements, such as hydrogen, helium and minuscule amounts of lithium existed.
The first generation of stars formed as lumps of gas drew together and began to combust. This caused a nuclear reaction in the centre of a star. The first stars that formed after the Big Bang were greater than 50 times the size of our Sun.
“Inside stars a process takes place called nucleosynthesis, which is basically the making of elements,” Ashley says. “The bigger the star, the faster they burn their fuel.”
The first stars burned their fuel quickly and were able to make only a few elements heavier than hydrogen and helium. When those stars went supernova, they expelled the elements they had produced and seeded the next generation of stars.
NASA’s Spitzer Space Telescope shows the infrared ‘glow’ of the gas and dust ring surrounding Nebula RCW 120 in Scorpius. © NASA
The next generation of seeded stars were then able to produce other, heavier elements such as carbon, magnesium and nearly every element in the periodic table. Any element in your body that’s heavier than iron has travelled through at least one supernova.
“It’s very likely that there are a whole bunch of different stars that have contributed the elements we see in our own solar system, our planet and those found within you", explains Ashley.
“It’s totally 100% true – nearly all the elements in the human body were made in a star and many have come through several supernovas.”
The life cycle of a star
The burning that takes place inside stars draws on a huge amount of fuel and creates an enormous amount of energy.
“Stars are immense objects – over 99% of the mass in our solar system is in our Sun – and gravity squeezes them. Meanwhile, the burning inside a star creates energy which counteracts the squeeze of gravity which is why our Sun is stable.”
Stars stay in this equilibrium with gravity until they run out of fuel. “When that happens to really big stars you can get some really, really spectacular supernovas,” Ashley says. “Our own Sun won't be anywhere near as dramatic as that.”
The Tarantula Nebula, also known as 30 Doradus, is a star-forming region in the Large Magellanic Cloud, a small galaxy close to the Milky Way. About 2,400 massive stars in the centre of the nebula produce intense radiation and powerful 'winds' of ejected material. X-rays are shown in blue, produced by superheated gases, resulting from supernova explosions and stellar winds. This multimillion-degree gas carves out giant bubbles in surrounding cooler gas and dust. © X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.
When stars die and lose their mass, all the elements that had been generated inside are swept out into space. The next generation of stars form from those elements, burn and the elements are swept out again.
Ashley says, “This constant reprocessing of everything is called galactic chemical evolution. Every element was made in a star and if you combine those elements in different ways, you can make species of gas, minerals, and bigger things like asteroids