Supernovae are among the most spectacular phenomena in our universe, and burn so brightly once they form, that they are frequently used as "standard candles" by astrophysicists to measure distances. But while astronomers discover existing supernovae quite regularly, it is much rarer to witness the initial explosions. It happens every 50 years or so.
But what if we could create a tiny version of this initial explosion in the laboratory? A team of physicists from the University of Toronto and Rutgers University have done just that, and have published their results in the journal Physical Review E.
Take it from the pop group They Might Be Giants: "Oh the sun is a mass of incandescent gas/A nuclear furnace/Where hydrogen is fused into helium/At temperatures of billions of degrees." That constant stream of nuclear reactions is what keeps a star from collapsing. As the hydrogen runs out, fusion slows down, and gravity causes the core to contract, raising temperatures even further, sufficient to give rise to a brief, shorter phase of helium fusion.
What happens next depends on a star's mass. For example, for massive stars (greater than 8 solar masses), this collapse is so violent that it causes a huge, catastrophic explosion. It is in these explosions that all elements heavier than iron are produced. The temperatures and pressures become so high that the carbon in the star's core begins to fuse. This halts the core's collapse, at least temporarily, and this process continues, over and over, with progressively heavier atomic nuclei.
The cores of those supernovae begin to resemble an onion, with layers upon layers of elements - the outermost layer is hydrogen, which surrounds a layer of hydrogen fusing into helium, surrounding a layer of helium fusing into carbon, and so on. In fact, most of the heavy elements in the periodic table were born in the intense furnaces of exploding supernovae that were once massive stars.