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STARS CHANGED OVER THEIR LIFE CYCLES
Space Science:Chapter 4: Section 4.2
Let’s Begin
Why do stars look like small points of light?
Why don’t they look like in the sky?
Stars are very far away. We only see a few thousand of stars that exist.
What unit of measurement do we use to measure the distance between stars?
Light-years The distance light travels in one year
Approximately 6 trillion miles
The closest star to Earth is our Sun
The next closest star is 4 light years away
How do we measure how far stars are away from Earth?
Using parallax The apparent shift in the position of an object when viewed from different locations
Parallax Demonstrations
Size: the Sun’s diameter is 100x greater than Earth’s
Some stars are much larger than the Sun. Giant and Super giants are 10-100’s of times larger.
Betelgeuse: 600 times greater than the Sun
There are stars much smaller than the Sun as well. These are called white dwarfs.
What color are the stars we see?
Most stars are white Some appear red Some appear blue
Why is that? Differences in color are due to differences in temperature
Think of:
The metal coils inside of a toaster
Start off as a dull red Later turn a bright orange
Temperature affects color by heating up the metal
Stars have life cycles:Length of the cycle and the way a star changes depends on the mass of the star
Nebula:
All stars form inside a cloud of gas and dust called a nebula
Gravity pulls the dust closer together
The matter contracts and forms a hot dense sphere
Main Sequence:
Fusion begins if the matter gains enough temperature and density
The birth of main sequence stars
Low-Mass Stars:
Once fusion begins the star is then classified as a main sequence star Low-mass stars use their fuel slowly Remain in this stage for billions of years
As low-mass stars run out of fuel it expands into a giant star
Once the giant sheds it outer layer it leaves behind a dead core called a white dwarf
High-Mass Stars:
Once fusion begins the star is then classified as a main sequence star High-mass stars use their fuel quickly Remain in this stage for millions of years
As high- mass stars run out of fuel it expands into a super giant
The super giant explodes when no more fusion can occur- called a supernova
High-Mass Stars: After supernova May form a dense
body called a neutron star Star squeezes itself
smaller Very DENSE- Example:
pea size sample weighs 100 million tons
Gravitational force collapses atoms
Electrons combined with protons to produce neutrons
May form a black hole More dense than
neutron star Intense surface
gravity lets no light escape
As matter is pulled into the black hole it becomes very hot and emits x-rays
The Sun is what type of star? Low-Mass Main Sequence Star
What is going to happen to the Sun? Eventually expand into a Red Giant Cool down into a white dwarf Scientist predict that in 4.5 billions years
the Sun will run out of fuel and will form a Red Giant