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Transcript
Science 9 THE LIFE CYCLE OF A STAR GRAVITY Gravity is a force that pulls objects toward each other The more mass an object has, the more gravity it exerts The Sun has stronger gravity than Earth The force gets smaller as the distance between two objects increases https://www.youtube.com/watch?v=hoLvOvGW3Tk THE BEGINNING OF A STAR All stars begin as nebulas Huge clouds of gas and dust, composed mainly of hydrogen and helium Matter forms into clumps due to gravity Clumps combine and pack closely together Nuclear fusion begins This is the beginning of a star’s “life” NEBULAE NEBULAE II GIANTS AND DWARFS When a star nears the end of its life, it runs out of hydrogen and other fuels needed to produce energy Pressure decreases in the star so the star swells (gets bigger) and cools down (turns red) Stars equal to or smaller than the sun become red giants Stars much larger than the Sun become red supergiants RED GIANTS I RED GIANTS II DWARFS Smaller stars die when nuclear reactions decrease, the core shrinks and parts of the star float away White dwarfs are small stars with a higher temperature than red or yellow stars DWARFS II DWARFS I SUPERNOVAS An enormous explosion that occurs at the end of a large star’s life The core collapses inward to become either a neutron star or a black hole They are rare events SUPERNOVAS NEUTRON STARS When extremely large stars die, the resulting core is called a neutron star An extremely dense star made of neutrons A pulsar is a type of neutron star that emits light and radio waves – the light appears as pulses NEUTRON STARS BLACK HOLES When a star at least 30x’s the size of the Sun dies, the result is a black hole The core’s force is so strong, nothing can escape, not even light They can exist undetected The x-rays of a black hole can be detected and other objects orbiting it It is composed of matter only a few kilometres across – should be called dark body BLACK HOLES MORE ABOUT BLACK HOLES https://www.youtube.com/watch?v=3pAnRKD4r aY https://www.youtube.com/watch?v=cW7BvabYn n8