Life Cycles of Stars

Stars Stars are a large hot balls of plasma that shine The Sun is the Star in our solar system A group of stars that form a recognizable shape are called constellations A smaller group of stars with a recognizable shape within a constellation are called asterisms

Stars Ursa Major - Constellation Big Dipper - Asterism

A Star is born...

Stars are Born From NEBULAS NEBULA – a cloud of dust and gases, that eventually collapse to form a star. The gravitational pull from a nearby star OR the shockwave from an exploding star can trigger the collapse of a nebula

A Collapsing Nebula Dust and gases are pulled in by gravity to form larger masses

A Collapsing Nebula A mass in the middle grows larger as it spins, pulls in more dust and gas, and heats up

A Collapsing Nebula A protostar has formed

Life Cycle of Stars

Size Matters Different size stars go through similar life cycles, however they are different: 1) Low Mass Stars 2) Medium Mass Stars 3) High Mass Stars All begin as nebulae that collapse to form protostars

Low Mass Star Burns slowly and lasts for 100 billion years Mature into a red dwarf (most stars in the universe are red dwarfs) When the fuel for nuclear fusion runs out, a red dwarf cools into a white dwarf

Medium Mass Star Last for about 10 billion years When a medium mass star runs out of fuel, it collapses under its own gravity The collapse heats up and pressure increases Star expands and becomes a Red Giant Eventually, burns out to form a white dwarf

High Mass Star Lasts up to 7 billion years (usually less) At least 10 times the size of our Sun When a high mass star runs out of fuel it collapses and expands to form a Supergiant Supergiants end in a massive explosion called a supernova End result: 1) cosmic debris - nebula 2) a neutron star (or pulsar) 3) a black hole

Supernova Supergiants that run out of fuel end in a massive explosion Many nuclear fusion reactions occur and new elements form and explode into space The debris from the explosion is the source for a new nebula What remains of the star depends on the original size of the star

Neutron Star Remaining core of a supergiant that was less than 40 times the size of our Sun Also called a pulsar Very dense matter made of neutrons

Black Hole Remaining core of a supergiant that was more than 40 times the size of our Sun The core of the supergiant, after a supernova, is so dense that its gravitational pull sucks in space, time, light and matter Thought to be at the centre of all galaxies

Summary All stars are born from a nebula Nebulae collapses and pulls in dust and gases to form a protostar Depending on the size of the star that forms, a different fate is met Low and medium mass stars burn out to become white dwarfs High mass stars burn out in an amazing explosion called a supernova, which gives birth to a new nebula

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