EVOLUTION OF STARS

All stars have a _____________ _______________

Life cycle- (They are born and AFTER MILLIONS OR BILLIONS OF YEARS they DIE)

making a a star stage 1- STARS FORM INSIDE A ________________ CLOUD OF GAS AND DUST

NEUBLA

making a star stage 2-GRAVITY CAUSES THE DENSEST PARTS OF A STAR-FORMING NEBULA TO COLLAPSE FORMING A REGION CALLED A ______________

protostar

making a star stage 3- When a protostar contracts it pulls in surrounding gas until it becomes hot and dense therefore ____________ _______________ begins producing enormous amounts of ______________

nuclear fusion, energy

making a star stage 4- The heated gas and dust get blown away and the protostars become a visible ________

star

making the star stage 5- later, the gas and dust that was blown away off the protostar might become planets or other objects that _____________ the star

orbit

when a star starts fusing hydrogen into helium , it becomes a _____________ ______________ star

main sequence

a massive star goes through a cycle near the end of its life in whichh it becomes a ____________ ____________ several times, getting bigger and bigger

red giant

nebula

cloud of gas and dust

When a developing protostar gets increasingly hotter over many thousands of years...

it heats up the surrounding gas and dust

A star spends most of it's life cycle on the ________ ___________ of the __________________________ diagram

main sequence, Hertzsprung-Russell

The main sequence area on the Hertzsprung- Russel diagram is when _____________are in a line from top left to bottom right.

stars

For a star to become a star it must fuse __________ and ____________ in the _________

hydrogen,helium, core

Once a star becomes on the main sequence it continues fusing _____________ and _______________

hydrogen and helium

A star will leave the main sequence once it's supply of ______________is nearly all used up.

HYDROGEN

Where does hydrogen and helium fuse in a star?

in the core

an example of a star will stay on the main sequence for billions of years?

an average mass star- the Sun

_______________ mass stars will only be on the main sequence for a few million years- not billions.

High

Even though high mass stars have more hydrogen they process it it _______________ , therefore running out of it

faster

Once a star moves off the main sequence it moves to the next stage of it's life cycle and becomes a __________ ___________

red giant

Once the stars hydrogen supply is gone ____________ causes the core of the star to expand and heat up.

gravity

Once the stars has become a red giant phase the outer layer of the star _______________ and _______________

expands and cools

Once a star becomes a red giant ____________ ____________ resumes

nuclear fusion

When the red giant's outer layer contracts the star begins to fuse ____________________ nuclei and form ______________

helium, carbon

When the red giant changes to a larger red giant it is because helium is running low so the core collapses again and the outer layers expand again. It begins to fuse ______________ and form _____________ _______________

carbon, other elements

The process of a red giant continues over and over forming different elements during fusion such as...

iron, silicon, oxygen, neon

The core of a red super giant is made of _______

iron

A massive star dies by:

collapsing and exploding

A low mass star dies:

slowly

Average mass stars such as the Sun do not have enough _____ to fuse elements beyond _________________.

mass, helium

Why can't average mass stars (like the sun) fuse elements beyond helium?

They do not get hot enough

Once a star loses its helium in their core the core becomes a _______________ _______________

white dwarf

White dwarf star is...

a hot, dense, slowly cooling sphere of carbon

Stars that become white dwarf are what size?

average mass or smaller mass

Eventually the Sun will become a _____________ __________

white dwarf

High mass stars ( stars with more than 10 times the mass of the sun) will _________________

explode

Supernova

an enormous explosion that destroys the star

Will an average to smaller mass star explode or become a red giant?

red giant

In the most massive stars a supernova occurs when __________ forms in the star's ____________

iron, core

In a massive star, once the core becomes iron, it loses its internal ________________ source, the core collapses under the force of ________________, then the star ________

energy, gravity, explodes

Neutron Star

a dense core of neutrons that remain after a supernova

a neutron star has a very _______________ core

dense (heavy)

When a neutron star is formed, after the explosion of a massive star- ______________ and _____________ combine to form neutrons

protons and electrons

Black hole

an object whose gravity is so great that no light can escape.

Once a star's life cycle is over much of it's _________ escapes into space

gas

The gas from a star that has died is recycled for future ______________ and _______________

stars and planets

Once an average mass star becomes a white dwarf, it casts off _________________ and _________________ as _________________ _________________

hydrogen and helium, planetary nebulae

planetary nebulae

helium and hydrogen casts off by a white dwarf

Cast off gases from planetary nebulae can be used for....

new generations of stars

Planetary nebulae have nothing to do with ______________

planets

During a supernova explosion- there is a shock wave in space expanding a cloud of dust and gas called __________________ ___________________

supernova remnants

remnants means

left over

almost all the elements in the universe other than hydrogen and helium were created by ________________ __________ inside the core of massive stars and these elements are released in a ________________________

nuclear reactions, supernova

Elements that are released in a supernova:

oxygen in the air, silicon in rocks, carbon- in you

Gravity causes recycled gases and other matter to clump in __________________ and form new stars and planets

nebulae

planetary nebulae are the expanding outer layers of a:

white dwarf

A Nebula begins as a cold, dark and dense cloud of _______________ and ________________

gas, dust

In a nebula _____________causes the densest part to ____________________ forming a protostar

gravity, collapse

A protostar contracts until the core becomes...

hot and dense

Life cycle of a massive star:

massive star- red giant, larger red giant- red supergiant

Once a massive star becomes stage 1- a red giant two things happen:

hydrogen form heliumhelium form carbon

Once a red giant becomes a larger red giant in stage 2- 3 things happen:

hydrogen form helium, helium form carbon and carbon form other elements

Once a large red giant becomes a red supergiant other elements form:

hydrogen - helium - carbon- neon-oxygen- silicon-iron

The sun will not become a supergiant because it doesn't have enough _________________

mass

Once the sun runs out of fuel ( hydrogen and helium)

1. runs out of hydrogen and becomes a red giant2. will fuse helium and contractwill run out of helium and contract again absorbing Mercury, Venus and Earth3. Will push Mars further out and finally will become a white dwarf

In a supernova the core is ________ and it wont fuse any more.

iron

With iron at a stars core a supernova will occur because it looses its energy and then ________________________.

explodes

Neutron stars are only about ____________ wide

20km

Inside a neutron star the core is so _______________ that a teaspoon of it would weigh more than a _________________ tons

dense, billion

black hole is smaller than a _______________

star

stars are ________________ and a black hole is ______ ____________

visible, not visible

Cycle of a planetary nebula:

1.average mass star becomes a white dwarf2. cast off hydrogyn and helium3. forms a planetary nebula4. gasses form new stars