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| A supernova (Image credit: NASA) |
Carl Sagan famously said we are all made of stardust, and he was right on the money. Everything around us began in the death of a star. Supernovas create giant clouds of matter which provide the building blocks for new stars, planets, and the matter that makes up living and inorganic substances.
The Death of a Star
Stars produce energy by nuclear fusion. Each star contains vast reserves of hydrogen, which fuses into helium. Toward the end of its life, a star runs out of hydrogen. Without hydrogen, the star starts fusing helium into heavier elements. The core of the star shrinks, but the outer layers expand to create a red giant star, which often destroys surrounding planets.
Eventually the star runs out of helium as well. If it’s a small star, like our sun, fusion ends and the star, now a white dwarf, slowly dies. Larger stars go through violent changes when they run out of helium. The core collapses almost instantly.
Temperature within the collapsing core builds in a matter of seconds to over 100 billion degrees Fahrenheit. The outer layer collapses inwards, and then explodes outwards in a supernova. During the supernova explosion, the dying star produces enough energy to fuse heavy elements, such as uranium and gold. Any planets lucky enough to survive the star’s expansion into a red giant are obliterated by the supernova.
As for the remains of the collapse star core, if conditions are right it may become a black hole, an area where matter is crushed under gravitational forces so strong even light cannot escape.
Star Birth
The material expelled during the explosion sometimes forms massive clouds of dust and gas called nebulae that float in the interstellar void. Gravity causes nebulae material to clump together, eventually giving birth to a protostar. As millions of years pass, the protostar develops into a fully-formed star.
