Life Cycle of a Star! Chapter 28 Section 3

All stars in the universe are at different stages of their life cycles All stars in the universe are at different stages of their life cycles. A star’s mass determine its life span – more massive the star, the shorter it lives.

Nebulae (Nebula) Cloud of gas and dust out of which stars form ~ mostly hydrogen (H) and helium (He) gas ~ Begins to contract (shrink) as gravity pulls it together

Birth of a star… Nebula

Protostar (10,000 K) As contraction continues, “clumps” start to form within the nebula, creating a protostar Begins to glow and rise in temperature

Main Sequence Fusion begins; Hydrogen atoms fuse together creating Helium within the star Stars spend most of their life in this stage. A great deal of energy is created from fusion balancing the inward pull of gravity (star will not collapse)

Main Sequence How long the star stays in the Main Sequence depends on its MASS. Larger stars, 20x our sun, burn up much faster (within millions of years) Stars like our sun (a medium yellow star) are thought to last about 10 billion years in this stage.

Red Giant Eventually the star’s fuel begins to runs out, the star expands into a RED GIANT The core contracts and the outer layers expand, over 100 times its diameter. The star then starts to cool and become less bright. As the star uses up its last remaining fuel, the outer layers wear away leaving a dense core He  C

Red Giant Super Giant Planetary Nebula

Fusion STOPS Outer layers of gas disperse (disappear) Planetary Nebula Fusion STOPS Outer layers of gas disperse (disappear) Planetary nebula NGC 2440 has an intriguing bow-tie shape in this stunning view from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase of evolution.

White Dwarf As the Red Giant continues to grow, eventually the outer layers wear away, leaving a small extremely hot core called a White Dwarf Small, white, HOT dying star Glows because of heat (like metal in a fire)

This is the life cycle our sun will take Black Dwarf White dwarf has completely cooled, does not glow Solid Carbon Ball This is the life cycle our sun will take

Other stars more MASSIVE than our Sun Red Giant Super Giant Planetary Nebula Other stars more MASSIVE than our Sun Our Sun

Super Giant Stars that are over 8x the size of our sun continue to grow from Red Giant to a Supergiant Still generates energy C  Fe (Iron)

Supernovas The star explodes, creating a great deal of space dust for new stars to be created from

Supernova

Neutron Star Black Hole

Neutron Star Very dense (heavy) HOT remains Does not glow – gives off energy 1 tsp = weight of the moon simulation

Black Hole All material contracts, creating a STRONG gravitational field – nothing can escape it simulation

H ~ R D I A G R A M

Stars are born in dark molecular clouds Stars are born in dark molecular clouds. Within these clouds, matter clumps together as it collapses under gravity. Within these clumps, even denser masses are formed, called cores. In the centre of a core, the matter becomes increasingly compressed and heats up. It begins to give off heat and light as a protostar. When the temperature of the protostar reaches 10 million°C (18 million °F) or so, nuclear fusion reactions begin, and the star begins to shine. It will shine steadily for millions or billions of years, but eventually it will start to die. Whether a star becomes a red giant or a supergiant depends on its mass.