Life cycle of starsLife cycle of stars

Nebulae to supernovaNebulae to supernova

Stars and radiationStars and radiation

• Stars are huge nuclear reactors that give off different forms of radiation (see below) all of which can be detected by specialist telescopes.

- Visible Light- Ultra violet- Infra red- Gamma rays- X-rays- Radio waves

A star is bornA star is born

• Gas and dust particles in space collect in dense ‘clouds’ called nebulae. Gravity causes the gas and dust to collapse in on itself.

• Surrounding gases are drawn in by the increasing mass of the huge swirling Hydrogen gas cloud (called a protostar). As the mass and gravity of the protostar increases, it begins to spin and heat up.

Nebula – cloud of gas & dustNebula – cloud of gas & dust

The The ‘‘horse headhorse head’’ nebula nebula

Birth of stars continuedBirth of stars continued

• The increasing pressure causes temperature to rise as particles are squeezed together (eg bicycle pump). Finally when the temperature and pressure become great enough Nuclear fusion begins and the new star bursts into life releasing light and heat.

• Temp required for nuclear fusion = 17 million 0C

Nuclear fusionNuclear fusion

• Nuclear fusion is the process by which the nuclei of atoms collide together at great speed and extreme temperature causing them to fuse together, releasing huge amounts of energy in the form of light, heat, and radiation

• E.g. H1 + H1 He2

Our sunOur sun

SunspotsSunspots

• Dark spots on the surface of a star indicate slightly cooler areas on the surface.

Life of a starLife of a star

• Stars will continue to burn their Hydrogen and Helium fuel source while it remains. The longevity of the star is determined by its size (amount of gaseous fuel) and the rate at which it burns this fuel.

• Our sun is a small – medium sized star and will last 10 billion years before it runs out of fuel. Larger stars don’t necessarily live longer – they burn their fuel faster.

Death of a starDeath of a star

• Stars turn Hydrogen into Helium during nuclear fusion reactions. The Helium collects at the core of the star. Eventually the Hydrogen outer shell runs out and the Helium inner shell starts to expand forming a GIANT star (colour depends on size / temperature) 200 – 300 times its normal size.

• Our sun will consume the 4 inner planets of the solar system, including Earth, when this occurs.

Red GiantRed Giant

Red GiantRed Giant

Death throes of a starDeath throes of a star• Eventually the outer layers are thrown off into

space (Nova) and the remaining core of the star collapses under weight of gravity leaving behind a very dense inner core glowing brightly with remnant heat called a White Dwarf (typically the size of Jupiter).

• Very large stars have a more violent end blowing matter and energy into space in an explosion called a Supernova. Heavy elements like iron and lead are formed during supernova

• The biggest stars are thought to collapse under their own massive gravity following the supernova event forming extremely dense neutron stars (pulsars) or Black holes.

White DwarfWhite Dwarf

A SupernovaA Supernova

Black holesBlack holes

Black holeBlack hole

The fate of different sized starsThe fate of different sized stars

Stars life cycleStars life cycle