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The Universe
Pictures by the Hubble Space Telescope
Notice the individual stars in the picture.
They are not part of the galaxy in the picture
but part of our own Milky Way Galaxy.
We think!
This is not
really a picture
of our galaxy –
just one that
looks like what
we think our
galaxy is like!
Top view
Side view
Every star we see in
the night sky is in
our own galaxy.
The Milky Way is
estimated to have
200 billion stars.
Current estimate of the
age of the universe is
13.7 billion years.
The solar system is 4.6 billion years old.
The solar system is not the same age
as the entire universe.
They seem to form a picture in the sky.
People use them to find their way around the sky
like someone using objects to get from place to
place.
To measure the distances in space,
astronomers use a light year.
A light year is the DISTANCE
light travels in one year. One
light year is equal to a little
under 6 trillion miles!
(6,000,000,000,000)
Proxima Centauri is the closest star to our solar
system. It is about 4 light years away. Going the
speed of light it would take us 4 years to get there.
Traveling as fast as the average spaceship, it would
take between 70,000 and 100,000 years to get there!
https://www.youtube.com/watch?v=ewGsiUPeBD4
Types of Stars
Comparison of our sun with a white dwarf and a
neutron star.
Star color
Determined
by surface
temperature.
Hottest are blue – coolest are red.
https://www.youtube.com/watch?v=IurFmd8xDe0
Protostars
Gravity pulls huge nebulas
of hydrogen gas and dust
into a single spinning cloud.
The particles crash into each
other
H H
Matter heats up to about 15
million degrees.
The mass begins to shine brightly.
Fusion begins…..
A star is born!
This is when a star forms and it begins its “life.”
https://www.youtube.com/watch?v=tnzRUYSiCnc
Medium-Sized Stars
H
Hydrogen fuel is fused into
helium at the star’s
core until the hydrogen is used
up.
H
He
The core shrinks, heats up, & releases energy.
H
The star heats, expands, reddens and
becomes a …… Red Giant
These drifting gases form a nebula ring
around the star.
The star is dying. It grows fainter and fainter.
Gravity causes its matter to collapse inward.
The star is squeezed into a……
…….a White Dwarf star.
o Are super dense stars with a carbon core.
o size of our (Our sun’s) sun has been squeezed into the size
of the earth.
When a star runs out of fuel, it dies.
So a star has a life similar to a battery that
cannot be recharged. When the battery runs out
of energy, it is finished. Our sun will run out of
energy and it will be finished too.
But this will not happen for another 5 billion
years!
Life cycle of our sun
We are now here
Massive Stars
 Has about 6 times as much mass as our
sun.
 Burn hydrogen at first.
 Redden as their helium core forms.
 Become Red supergiants.
 Start expanding.
A Supernova happens !
The entire sky lit up for weeks.
http://www.maniacworld.com/Crab-SupernovaExplosion.html
After the supernova explosion of a star, a neutron star
remains..
It’s diameter is only about 16 Km.
It’s size is only about that of a chunk of a sugar cube
The core’s gravity is so strong that even light can’t
escape.
The core has become ……a…..
A Black Hole
This diagram follows the life of both large and average
stars.
https://www.youtube.com/watch?v=hoLvOvGW3Tk