In a paragraph, explain the life cycle of (i) a white dwarf, (ii) a neutron star, and (iii) ablack hole. You should cover every stage.

Answer 1

White dwarfs, neutron stars and black holes are the last stage of different stars' life cycles. The different end stages are dictated by the mass that the star starts with. High mass stars have the shortest life cycle because they burn through their available fuel relatively fast. Once the prime fuel (hydrogen) is depleted in the core, the core shrinks and gets hotter, allowing the star to fuse other elements for energy. As these elements are processed the star swells up into a red giant. Heavier and heavier elements are fused to produce energy less and less efficiently until the element iron is produced, at which point no more energy can be produced from fusion. Without energy production, the weight of the star's outer layers cannot be supported and they collapse, creating an enormous explosion called a supernova. As the explosion pushes outward the core is forced in on itself creating a black hole. To create a neutron star, you start with a less massive star, but the process is the same, ending in a supernova, from which the neutron star is left behind. For a white dwarf the star must be relatively low mass (such as our sun). A similar process takes place with this star, but it can fuse fewer elements and never reaches iron. The core shrinks but never collapses and explodes. However, the outer layers of the red giant are forced outward creating an expanding planetary nebula, leaving behind the tiny super-hot core, which we see as a white dwarf.