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