The Life Cycle of Stars

The Life Cycle of Stars

• Nebula: A star begins its life as a cloud of dust and gas (mainly hydrogen) known as a nebula. Gravity pulls these particles together.

• Protostar: As gravity continues to pull the particles together, the cloud shrinks and forms a hot core (a protostar). Heat and pressure increase in the protostar until nuclear fusion begins.

• Main Sequence Star: When the protostar becomes hot enough, it starts to emit energy in the form of light and heat. This is the ‘main sequence’ phase, where a star spends most of its life. In this stage, nuclear fusion converts hydrogen to helium.

• Red Giant or Red Supergiant: Once all the hydrogen has been converted to helium, the star swells into a Red Giant (or Red Supergiant for larger stars). It turns red because the surface cools. The helium is then converted into heavier elements like carbon or oxygen.

• White Dwarf or Supernova: Small stars like our sun become white dwarfs when they shed their outer layers and only the hot core remains. Larger stars explode in a supernova, expelling a lot of matter into space.

• Black Dwarf: After a long period, a white dwarf cools down, stops emitting energy and becomes a black dwarf.

• Neutron Star or Black Hole: The supernova may leave behind a very dense core, which could form a neutron star. If the star was large enough, instead of a neutron star, a black hole forms, from which nothing, not even light, can escape.