Large stars, with a mass much greater than our Sun’s, die a very violent death. As the hydrogen in a large star is used up, nuclear reactions produce heavier and heavier elements until a large iron core develops. This core eventually collapses under its own immense gravity, and the force of this collapse creates a tremendous explosion called a supernova. Most of the star’s matter is blown into space by this explosion, leaving a tiny, dense remainder — either a neutron star or a black hole.
The most massive stars quickly exhaust their fuel supply and explode in core-collapse supernovae, some of the most energetic explosions in the universe. A supernova’s radiation can easily (if only briefly) outshine the rest of its host galaxy. The remnant stellar core will form a neutron star or a black hole, depending on how much mass remains. If the core contains between 1.44 and 3 solar masses, that mass will crush into a volume just 10 to 15 miles wide before a quantum mechanical effect known as neutron degeneracy pressure prevents total collapse. The exact upper limit on a neutron star mass isn’t known, but around 3 solar masses, not even neutron degeneracy pressure can combat gravity’s inward crush, and the core collapses to form a black hole.
Average stars with up to 1.44 solar masses, such as the Sun, face only a slightly less exotic fate. As they run out of hydrogen to fuse in their cores, they swell into red giant stars before shedding their outer layers. The remnant left behind in these planetary nebulae is a white dwarf star. Like neutron stars, white dwarfs no longer fuse hydrogen into helium, instead depending on degeneracy pressure for support — this time, the electrons are degenerate, packed together and forced into higher energy states, rather than the neutrons.
Left to their own devices, white dwarfs will eventually fade into black dwarfs. No black dwarfs have been observed yet because a white dwarf takes longer than the current age of the universe to fade away. And if the white dwarf is part of a binary system, it may avoid that fate altogether. By accreting matter from its companion star, the white dwarf can explode in a Type a supernova, leaving no remnant behind.
The smallest stars in the universe have exceedingly long lives — in fact, none have faced their end yet. Red dwarfs, stars with less than 0.4 solar masses, burn so slowly that they might live to 100 billion years old, much longer than the current age of the universe.
Picture Credit : Google
