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How to Make a Black HoleWhen really massive stars burn out, they
turn into black holes. To understand how this happens – and what black holes really are, you need to remember a little bit about
atoms and gravity…
The protons and neutrons are stuck together in the center of the atom; this center is called the nucleus.
PNP
N
NP
The basic parts of an atom
E
P
N Neutron (0)
Proton (+)
Electron (-)
There is a lot of space between electrons and the nucleus.
The electrons spin around the outside of the nucleus.
Key
E
E
E
P
NP
N
N
P
In fact, there is so much empty space between an atom’s electrons and nucleus
that even this diagram is misleading
E
E
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Really far apart!
To keep things simple, let’s use this diagram for an atom
P
NP
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P
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Gravity is an attractive force (like a magnet) between 2 objects; the acceleration of an object due to gravity depends on its mass
Object 1:Many Atoms
Object 2:Few Atoms
Because Object 2 has fewer atoms than Object 1,Object 2 moves more than Object 1
P
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A simple diagram of EarthWarning: This diagram isNOT to scale!
The Earth is made of a lot more atoms than you are.
If you could jump really fast (7 miles per second), you could escape from Earth’s gravity – but you cannot jump that fast…
…however, a rocket can “jump” that fast!
US
A
As stars burn out, the electrons collapse toward the center of the nucleus of each atom
Stars are always battling 2 forces: nuclear fusion releases energy that makes the star want to expand, gravity makes the star want to collapse. After a star runs out of fuel with which to make nuclear fusion, gravity wins this battle.
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After all the star’s atoms have collapsed, it is called a “white dwarf”
A white dwarf is about the size of Earth but much more dense. Because it is so dense, it has a greater gravitational force. Our rocket must go 3000 miles per second to escape.
7 miles per second is too slow to escape
3000 miles per second is fast enough
US
A US
A
A teaspoon of a white dwarf would weigh more than a car!
A white dwarf is not made of ordinary atoms. Gravity has crushed the atoms’ electrons and nuclei together into a mixture (called “degenerate matter”).
star (such as our sun)
A white dwarf is a lot smaller than the star it comes from
white dwarf
White dwarf
A white dwarf is about the size of Earth
Hi, Mom!
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In really big white dwarfs, gravity’s enormous pressure fuses electrons with protons to
become neutrons
N
N N
Really big white dwarfs collapse into neutron stars
A neutron star is just a big bunch of neutrons stuck together. It contains no electrons or protons. It is incredibly dense – and has an enormous gravitational force.
3000 miles per second is too slow to escape
83,000 miles per second is fast enough
A simple diagram of a neutron star
US
AU
SA
A teaspoon of a neutron star would weigh more than a 100 million cars!
A neutron star is about the size of a large city
Neutron Star
Gigantic stars don’t stop collapsing after they become neutron stars – the gravitational force is so strong that neutrons collapse into each other, forming a single point – a “Black Hole”
Really big neutron stars collapse into black holes
Light moves at 186,000 miles per second (we call this “light speed”). In other words, light speed is 669,600,000 miles per hour. Even this speed is too slow to escape a black hole’s incredibly powerful gravity.
Nothing can go fast enough to escapefrom a black hole
83,000 miles per second is too slow to escape
So, imagine you are standing on a black hole with a flashlight (this would be impossible to actually do). If you pointed the flashlight up, this is what would happen to the light…
That’s why we call these objects “black holes” – “black” because light cannot escape from them; they are invisible – “holes” because anything (including the energy of light) that gets too close to a black hole falls into it because of its super strong gravity.
US
A
Don’t get too close to black holes!
US
A
Black holes really exist! Consider the evidence: scientists observe stars being
sucked into nothingness
Star being pulled into a black hole
Black hole
There’s even more evidence of black holes – scientists have seen stars orbiting nothing
Probably a black hole
here
An artist’s picture of a black hole
Star White Dwarf Neutron
Star Black Hole
Weak Gravity Strong Gravity
Summary: the family history of a black hole
PNP
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1,000,000 km
10,000 km
10 km
Smaller than 0.0000000001
cm
The End
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