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Lives of Stars
Section 21.3
• Stephen Hawking - The Birth of Stars - YouTube
Life Cycle of Stars
Nebula – large cloud of gas and dust spread out in an immense volume
Life Cycle of Stars
• Gravity pulls gas and dust together in the densest part of the nebula
• When there
is enough mass
for a star to form
it is called a Protostar
Life Cycle of Stars
• When the contracting gas and dust from a nebula becomes so dense and hot that nuclear fusion starts, a star is born.
• Dust Cloud Theory
Life Cycle of Stars
• How long a star lives depends on its mass
-Stars with less mass live longer
- Stars with more mass live shorter
• Small mass stars use up their fuel more slowly than larger mass stars
Small stars – 200 billion yearsMedium stars – 10 billion yearsLarger stars – 10+ millions years
Life Cycle of Stars
• When a star begins to run out of fuel, its core shrinks and its outer portion expands
• Depending on its size, the star becomes a red giant or a supergiant
• After the fuel runs out it becomes a white dwarf, a neutron star, or a black hole
Life Cycle of Stars
Life Cycle of Stars
Death of Stars
When the fuel begins to run out of medium and low mass stars, their outer layers expand to become a red giant.
The outer layer then expands out in to space (planetary nebula) and the blue-white core cools (White Dwarf)
Death of Stars
The core is very dense. A spoonful of material would weigh as much as a truck
It would cool to become a black dwarf
White dwarfBlack Dwarf
Death of Stars
• Supernovas
High mass stars evolve quickly into supergiants
The supergiant can explode suddenly when it runs out of fuel
Death of Stars
The outer portion can form partly recycled stars
We are made of recycled stars
The inner portion can
become other kinds
of stars
Supernova
Death of Stars
• Neutron star
The remains of a high mass star, smaller and denser than white dwarfs
Spinning neutron stars (pulsars) give off pulses of radio waves
Death of Stars
• Black Hole
Form from the most massive stars when they die
Gravity is so strong, light (or any kind of radiation) can not escape
Black hole
Videos
• Black Holes, Neutron Stars, White Dwarfs, Space and Time
Star Systems and Galaxies
• Binary stars
Star Systems and Galaxies
• Eclipsing Stars
Star Systems and Galaxies
• Open Cluster
Star Systems and Galaxies
• Globular Cluster
Star Systems and Galaxies
• Galaxy
Star Systems and Galaxies
• Spiral Galaxy
Star Systems and Galaxies
• Elliptical Galaxy
Star Systems and Galaxies
• Irregular Galaxy
Star Systems and Galaxies
• Quasar – an enormous, distant,bright
galaxy with a black hole at its center
Star Systems and Galaxies
• Milky Way (our galaxy)
Star Systems and Galaxies
Star Systems and Galaxies
Star Systems and Galaxies
Star Systems and Galaxies
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