“Every star will someday run out of fuel in its core, bringing an end to its run as natural source of nuclear fusion in the Universe. While stars like our Sun will fuse hydrogen into helium and then – swelling into a red giant – helium into carbon, there are other, more massive stars which can achieve hot enough temperatures to further fuse carbon into even heavier elements. Under those intense conditions, the star will swell into a red supergiant, destined for an eventual supernova after around 100,000 years or so. And the brightest red supergiant in our entire night sky? That’s Betelgeuse, which could go supernova at any time.”
One of the most sobering cosmic truths is that every star in the Universe will someday run out of fuel and die. Once its core fuel is exhausted, all it can do is contract under its own gravitational pull, fusing heavier and heavier elements until it can go no further. Only the most massive stars, capable of continuing to fuse carbon (and even heavier elements) will ever create the Universe’s ultimate cataclysmic event: a Type II, or core collapse, supernova. Stars that are fusing carbon (and up) appear to us today as red supergiants, and the brightest red supergiant as seen from Earth is Betelgeuse. Sometime in the next 100,000 years or so, Betelgeuse will go supernova. When it does, it will emit incredible amounts of radiation, become intrinsically brighter than a billion suns and and be easily visible from Earth during the day. But that’s not all.
“But there’s one killer move that stars have that makes carbon a loser in the cosmic equation: when a star is massive enough to initiate carbon fusion – a requirement for generating a type II supernova – the process that turns carbon into oxygen goes almost to full completion, creating significantly more oxygen than carbon by time the star is ready to explode.”
When the Universe was first born, all we had was hydrogen and helium, with a trace amount of lithium and absolutely nothing else. 13.8 billion years later, hydrogen is still #1 in the Universe and helium is still #2, but lithium isn’t close to #3 anymore: more than two dozen elements have passed it. The key? Stars! Over billions of years, nuclear fusion in the cores of stars have built up all the naturally occurring elements we know of in the periodic table. You might think that since three heliums can fuse together to make carbon, that would be the third most common element in the Universe. And it’s close: carbon comes in at #4. But another element has it beat.