1. Lesson 5- The Lives of Stars
Stars are born in nebulas
A nebula is a large cloud of gas and dust spread out in an immense volume.
A protostar is the first stage of a star’s life.
“proto” means first
Nuclear fusion is what begins a protostar

3. Lifetime of stars
The greater the mass of a star, the shorter it lives.
Just like large car burns fuel faster than a small one, more massive stars burn out faster than less massive ones
Our sun will live for about 10 billion years. Since it has been burning for around 4.6 billion, it is around halfway through its lifespan (it’s middle-aged!)
Supergiant stars may only live for about 10 million years, which is actually a very small amount of time for a star.

4. A star’s death
After a star runs out of fuel, it becomes a white dwarf, a neutron star or a black whole.
The way a star dies depends on how massive it was to start with.
Low mass and medium mass stars take a long time to run out of fuel: they become white dwarfs.
After a few billion years they will stop glowing and become black dwarfs.
High-mass stars burn quickly and can explode suddenly!
The explosions of these stars are called supernovas. They are brighter than millions of our suns. The material from the explosion expands out into space.
Supernova explosions provide the incredible amounts of energy to create some of the heaviest elements in the universe.

5. After a supernova- Neutron Stars
Sometimes the material leftover from a supernova explosion creates a neutron star.
They are even smaller and denser than white dwarfs. They are only about the size of a city.
When neutron stars start to spin they are called pulsars. These spin extremely fast.

6. After a supernova- Black holes
The most massive stars may become black holes when they die.
A black holes an object with gravity so strong that nothing, not even light, can escape.
When the star explodes, more than 5 times the mass may be left. This energy and mass accretes and can form a black hole
Scientists can detect black holes by seeing X-rays being emitted from heated gas being sucked into them.

7. Grab a white board and a marker
Write # 1-8 on your white board
-Without using your chapter pages try to label the sun image below
Word Bank
Corona
Prominance
Photosphere
Chromoshere
Radioactive zone
Sunspot
Convection zone
core

8. Answers

9. Life cycle of a low-mass or medium-mass star (including the sun)