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• Stars & our Sun
•A star is a huge ball of hot glowing gases, called plasma.
•Stars twinkle because the light is distorted by Earth’s atmosphere.
•All stars have one thing in common, the way they produce energy.
•The energy comes from nuclear reactions that change hydrogen into helium.
It is as if millions of atomic bombs were going off every second inside the star.
•Unlike bombs, where it explodes and flies apart, the enormous gravity of the
star keeps the material held together.
•All of this energy that is produced gives off all types of electromagnetic
radiation, including visible light.
Mr. Schultz,
everything with
you is about
gas!
Electromagnetic Radiation
Name the seven types of
Electromagnetic Radiation
1.Gamma Rays
2. X-Rays
3.Ultraviolet
4.Visible
5.Infrared
6.Microwaves
7.Radiowaves
Our Star, the Sun
•11,000 degrees Fahrenheit
•Brighter and hotter than many of stars in Milky Way galaxy
•Made primarily of Hydrogen and Helium
•Provides heat energy for the Earth
•Should last about another 5 billion years, whew!
•Makes up 99.8% of our Solar System’s mass. That leaves only 0.2% for
everything else!
•It takes 500 seconds or 8.3 minutes for sunlight to reach the Earth!
The color of a star and the temperature at which it burns are closely linked.
Star Color
Temperature
Examples
Blue
11,000-50,000 Celsius
Regulus, Rigel
Blue-White
7,500-11,000 Celsius
Deneb, Sirius
White
6,000-7,500 Celsius
Canopus, Procyon
Yellow
5,000-6,000 Celsius
The Sun, Alpha Centauri
Orange-red
3,500-5,000 Celsius
Aldebaran, Arcturus
Red
2,000-3,500 Celsius
Betelgeuse, Proxima
Centauri
How long does a star “live”?
•The main factor that determines how long a
life a star will have is the star’s mass.
•A star of medium mass, like our Sun, will
shine for billions of years.
•A super-giant lives a much shorter life than
a smaller star.
•Also, based on their sizes, stars die
differently. A super-giant will die very
differently than a medium-sized star.
Nebulas are huge clouds of gases and dust
scattered through many regions in space that
provide the materials from which stars form.
The Ant Nebula, a cloud of dust and gas whose technical name is Mz3,
resembles an ant when observed using ground-based telescopes. The
nebula lies within our galaxy between 3,000 and 6,000 light years from
Earth .
When a star’s fuel starts to run out, the star swells to many times its
original size and it cools down.
The outer layers of the star begin to expand far out into space. As the
outer layers expand, they get farther away from the core and cool
down.
What color are cool stars? Yep, red! That is why, in this stage of a
star’s life, it is called a “red giant”.
This is what will happen to our Sun, though not for billions of years.
All stars come to this point, although from here, the
path that they take changes drastically, based on
their mass.
Let’s take a look at what happens to a low-mass star,
like our Sun.
After a long period as a red giant, the last of the fuel will run out. The star will
collapse and become a white dwarf.
A white dwarf is a dead star that shines very dimly as it cools down.
When our Sun turns into a white dwarf, it will shrink to about the size of Earth!
The particles are very tightly packed. They are more than a million times as
dense as water!
Finally, the star has died completely,
becoming a cool, darkened black dwarf.
After the red giant stage, Let the show begin…
A supernova is an exploding star that can
become billions of times as bright as the Sun.
As you learned before, a large-mass star lives a
much shorter life. They also end their life in a
much more spectacular fashion.
After the red-giant stage, the massive star
has two forces acting upon it. The outward
push caused by the hot core, and the inward
pull of gravity.
When the star’s fuel is finally used up, the
outward push is gone, and the inward pull of
gravity takes over. The outer layers fall into
the center of the star at tremendous speeds
and result in a gigantic explosion known as a
supernova.
The life of a massive star doesn’t stop at a
supernova. Some matter of the star may
remain after the explosion. Depending on the
mass of the star, having high mass, or very
high mass, the remains can become one of two
space features. A black hole or a neutron
star.
Very High Mass
High Mass
Neutron stars are compact objects that are
created in the cores of massive stars during
supernova explosions.
The collapse of a massive star is so
powerful, it crushes the star’s remaining
matter into the most dense objects in the
universe.
A typical neutron star is less than 12 miles in
diameter, but can weigh more than the sun!
A spoonful of matter from a neutron star
would weigh as much as a billion tons on
earth!
The collapse of the core of a massive star may be so
powerful that it does not stop at a neutron star.
A black hole is a tiny region, or point, with a very
strong gravitational pull.
The gravitational pull is so strong that not even
light can escape!
Here you see a photograph of a black hole pulling in
matter from a nearby neutron star. You cannot
normally see a black hole, but you can see the x-rays
given off of it with a special camera.
All Stars
Low-mass Stars
Nebula
Massive Stars
High Mass Stars
Star
Very High Mass Stars
Red-Giant
White dwarf
Black dwarf
Supernova
Neutron star
Black Hole