Transcript Life Cycle of Stars

Life Cycle of Stars
Stars are born from great
clouds of gas and dust called
Nebulae
Omega / Swan Nebula (M17)
Proto Stars
The dust and gas
comes together
under its own gravity.
As they do they heat
up, and nuclear
reactions start,
forming a proto star.
As the proto star continues
to contract the nuclear
reactions increase.
An outward ‘radiation
pressure’ is created.
When this balances the
gravitation attraction then
the star stops contracting
and the star becomes
stable.
The star will remain like
this for majority of its life.
Our Sun is in this stage
and which will last
10,000,000,000 years.
Main Sequence Stage
Nuclear Fusion
- The Source of a Star’s Power During the main sequence
Hydrogen is fused
together to form Helium in
the core. This releases a
huge amount of energy.
When the Hydrogen runs
out in the core there will
no longer be an outward
radiation pressure and the
core contracts again
under its own gravity.
Red Giant
The increase in
temperature allows
Helium to be fused
together forming heavier
elements up to Iron and
Nickel around the core.
The outer layers of the
star expand forming a
red giant.
This is Betelgeuse. Its Diameter is the same as the ORBIT of Jupiter
White Dwarf
The outer layers of the
star are shed revealing
the hot core.
The core illuminates the
layers of gas which is
called a planetary nebula.
The Cat Nebula
The white dwarf will cool
to form a red dwarf, a
brown dwarf and
eventually give out no
light as a black dwarf.
Supernova
When really massive Red
Giants collapse their core
is unstable and it
explodes as a Supernova.
It is during this intense
heat and pressure that the
heaviest elements are
formed though fusion.
These are the elements
that will make new planets
and stars.
During a supernova the core
of the star is under immense
pressure, such that the
electrons of atoms are forced
into the nucleus.
The protons join with the
electrons to form neutrons.
Each atom is 100,000 times
smaller for the same mass
and so incredibly dense. This
creates a large ‘gravity well’.
After a Supernova
This remnant of the supernova is called a neutron star.
If the neutron star is massive enough then not even
light can escape its gravity and it is known as a black
hole.
The First Stars
The first stars in the universe were massive ‘fast
burners’ which only contained Hydrogen, because
there was only Hydrogen in the Universe.
All the other element have been formed in the heart
of those and subsequent Stars. Our star, the Sun
contains trace elements of iron, oxygen, carbon and
magnesium.
This tells us that our sun and solar system is much
younger than the universe.