Lives of Stars Section 21.3. Stephen Hawking - The Birth of Stars - YouTubeStephen Hawking - The Birth of Stars - YouTube

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


• Eclipsing Stars


• Open Cluster


• Globular Cluster


• Galaxy


• Spiral Galaxy


• Elliptical Galaxy


• Irregular Galaxy


• Quasar – an enormous, distant,bright

galaxy with a black hole at its center


• Milky Way (our galaxy)





Documents

Lives of Stars Section 21.3. Stephen Hawking - The Birth of Stars - YouTubeStephen Hawking - The Birth of Stars - YouTube