Lifetime is only a few years. As the nebula shrinks a central mass will collect towards the center. It heats up because of the collision of particles and the increase in pressure. This will become a main sequence star when it reaches temperatures above 10,000,000 C- the temp at which fusion begins.

These stars last for about 5- 10 billion years. The larger the star- the shorter the life of this stage. The energy for fusion comes from the massive amounts of gravity and pressure. This causes Hydrogen atoms to collide and fuse into helium atoms. The star is considered stable because the force of fusion causing the star to expand is equal to the force of gravity. This stage ends when it runs out of fuel (most of the hydrogen is fused into helium)

This type of star forms when the main sequence star runs out of Hydrogen to fuse in the core. This causes the star to collapse. When the star collapses- the increase in pressure causes an increase in temperatures that are high enough to fuse Helium into larger atoms up to Carbon atoms. Only Giant stars are much larger than M.S stars because they are expanding. The Giant stars expand because they not only fuse helium in their core- but they are also fusing leftover hydrogen into helium in the outer regions of the star- causing the force of fusion to be greater than the force of gravity. Giant stars come to an end when most of the Helium in the core is fused to Carbon.

This stage is very short (years). It is a small giant star that has run out of helium to fuse in the core. This causes the star to collapse. As it collapses- the outer regions of the star can be left in space- giving the star a ring of gases that are shed off into space. This stage has no fusion because it is not big enough and the collapse does not allow it to get hot enough to cause Carbon to fuse into larger elements.

A star becomes this when the star loses its outer gases and reveals its core. This stage consists primarily of Carbon and can last for 100’s of billions of years. This is the final stage of small stars. These stars still glow because they are still very hot. Black dwarfs are believed to be white dwarfs that no longer glow because they have cooled- however the universe is not old enough for this to have occurred.

This stage is the final explosion of a very massive star, in which the fusion of elements past iron can occur. These occur when a very large star (Supergiants) collapses. The collapse creates enough pressure to raise the temperatures high enough to fuse carbon into larger elements up to Iron. This stage of a star is very short (weeks). When the core is almost completely iron there is an additional collapse as fusion stops. After this final explosion – stars will typically reveal an extremely dense core of neutrons (called a neutron star). Only the very largest of these will cause the formation of a black hole.

Once one of these stars form, it should have a very long life (100’s of billions of years). It is a core of a supernova after an explosion which causes it to contract into a very small but incredibly dense ball of neutrons. A spoonful of matter from one of these would weigh up 100 million tons on earth.

A ____________________ is when the core of an extremely large supernova contracts with such great force that it collapses leaving a hole in space. They have tremendous amounts of gravity- so much that not even light can escape it. They also give off x-rays just before it pulls matter in from its companion stars. Astronomers think that these are found in the center of galaxies.

When temperatures are high enough in the core of a high-mass star, this element starts to form (after helium).

When an ______ core is reached in a high-mass star, gravity takes over.

When an iron core is reached gravity takes over and a(n) _________ occurs.

Supernovas are one of the largest _______ in the Universe.

All elements heavier than carbon were formed in supernova explosions.

Low-mass stars like our Sun will never explode.

What is the name of the cloud that a star is formed in?

When a Red Giant runs out of fuel, it become a:

A small White Dwarf has a diameter similar to:

What is a protostar?

What is fusion?

What is the source of energy for the Sun?

What type of star is the Sun?

)What is the name of the nebula left behind by a supernovae recorded by Chinese astronomers in 1054 AD

Scientists use spectra from stars to determine what?

(remember absorption/emission lines we talked about when stars create light)

Where does fusion happen in the Sun, or other star?

When hydrogen fuses to hydrogen during nuclear fusion, what is the result?

Once a star uses up all of the _________ in its core, the star will expand into a giant or supergiant

What determines if a star becomes a giant or a supergiant?

After a low mass star sheds its outer layers into a planetary nebula, it leaves behind its core, called a

Very massive stars continue to fuse elements in their cores all the way up to...

What event causes heavier elements to scatter across the universe?

What has to happen to the protostar in order for it to become a star?

Based on the ratio of 75% hydrogen and 25% helium that is currently in the Sun, how old is it?

Once the Sun has fused up all of its Helium what will happen to it?

Eventually after 35,000 years a white dwarf will begin to cool, and over billion of years it will become a ........

What is left behind after a supernova?

What keeps a star alive (main-sequence stage)?