The Star Cycle

The Star Cycle
Sun-sized Stars

	The Nebula A huge cloud of hydrogen, helium and microscopic dust.
	The Protostar The centre of the nebula gets hotter as it shrinks, finally creating a new star.
	The Life of the Star The star may last for several billions of years, reamining unchanged.
	The Red giant The star expands up to 100 times while becoming a red giant.
	Planetary Nebula In time all the helium in the core is used up, and the star again begins to shrink. The star blows off its outer layer into space. Through the telescope the matter looks much like a planet and so early astronomers called it a planetry nebula.
	The White Dwarf Eventually gravity crushes the matter in the star into a small planet-sized body of immense density.

Stars smaller than the Sun (Brown Dwarf)

	The Nebula A huge cloud of hydrogen, helium and microscopic dust.
	1/20 Solar mass star The dust and gas collapse and forms a star.
	Brown Dwarf Star The star never shines brightly.

Massive Stars (10 Solar mass stars)

	The Nebula A huge cloud of hydrogen, helium and microscopic dust.
	10 Solar mass star The nebula forms a star 10 times larger than the Sun
	Supergiant Star After burning a few million years, the star swells up into a supergiant
	Supernova The star explodes blasting itself apart spectacularly.
	Neutron Star The compressed core remains and forms a neutron star

Very Massive Stars (30 Solar Mass Stars)

	The Nebula A huge cloud of hydrogen, helium and microscopic dust.
	30 Solar mass star The nebula forms a star the size 30 times the Sun.
	Supergiant Star After burning a few million years, the star swells up into a supergiant
	Supernova The star explodes blasting itself apart spectacularly.
	The Black Hole The core of the star becomes smaller and smaller until finally it is smaller than the head of a pin. The star, however, still has gravity which is so strong that a few kilometres around the star cannot escpae. This is called a black hole.

Spot Facts:

In about 5,000 million years time the Sun will swell up into a red giant. It will certainly expand beyond the orbit of Mercury and maybe even beyond that of Venus.

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