In the 60s

Life Cycle of Stars
Stellar Nebular

  * Stars are formed as a cloud of gas collapses under its own gravity, releasing energy into the form of radiation.
  * In its early life a star is bright but fairly cool; as it collapses it becomes hotter, igniting the nuclear fusion process.
  * The nuclear reactions between the hydrogen atoms cause the release of energy and the production of heavier elements such as helium.
  * At this stage, it contracts a little and becomes stable.

Massive Star

  * In heavier stars the core may collapse as hydrogen in the core is converted into helium by nuclear fusion.
  * When the hydrogen supply in the core begins to run out, the core becomes unstable and contracts.
  * The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and glows red.
  * The star has now reached the Red Super Giant phase.

Red Super Giant

  * Once massive stars reach the red giant phase, the core temperature increases as carbon atoms are formed from the fusion of helium atoms.
  * Gravity continues to pull carbon atoms together as the temperature increases forming oxygen, nitrogen, and eventually iron.
  * At this point, fusion stops and the iron atoms start to absorb energy.
  * This energy is eventually released in a powerful explosion called a supernova.
  * What remains after the supernova depends on the mass of the original star, bigger stars neutron stars, and the largest become black holes.


  * The core of a massive star that is 1.5 to 3 times as massive as our Sun ends up as a neutron star after the supernova.
  * The collapse of the star is thought to continue until very high densities are reached (1cm3 of material would have a mass of 10 000 tones).
  * At densities such as this, electrons collide with protons to form neutrons. Virtually all atoms become neutrons, thus forming a neutron star.


  * The core of a massive star that has 8 or...