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Star Birth: The Formation of Stars
Jonathan Rowles
Star Birth: The Formation of Stars
Background: What are stars?
Where are they found?
Where are stars born?
How are they formed?
Star Birth: The Formation of Stars
Background: What are stars?
A star is a luminous ball of gas.
They produce energy by the nuclear fusion of hydrogen to form helium.
They range in size from 0.08 times the mass
of the Sun to up to 120 Solar masses.
They can have lifetimes ranging from a few
million years to the age of the universe.
Star Birth: The Formation of Stars
Background: What are stars?
Stars are found either individually, in binary
systems, larger groups and clusters.
Star Birth: The Formation of Stars
Background: What are stars?
They range in size as shown on the image
below. Note that the colour of each star is
specific to to it’s size.
Our Sun is a type G star.
Star Birth: The Formation of Stars
Where are stars found?
Star Birth: The Formation of Stars
Where are stars born?
Stars are born in dark clouds of gas and dust, at temperatures around 10­40
degrees above absolute zero.
These dark clouds can be seen against a
glowing backdrop of stars. They contain
between 5 to 500 solar masses of material.
The dark clouds are disturbed by an
outside influence and the centre begins
to contract to form a proto­star.
Star Birth: The Formation of Stars
Where are stars born?
Star Birth: The Formation of Stars
Where are stars born?
If we could look inside the the dark cloud,
we would see stars in the very process of
being born. Normally this view is shielded
from us by the density of the cloud.
Star Birth: The Formation of Stars
Where are stars born?
Star Birth: The Formation of Stars
How are stars formed?
After the dark clouds are disturbed by an
outside influence and the centre begins
to contract to form a proto­star.
Once a proto­star begins to form, it progresses through various stages of growth.
These can be seen on the following slide.
At around stage 6 the proto­star will throw
off the outer layers and can be seen for the
first time.
Star Birth: The Formation of Stars
How are stars formed?
Star Birth: The Formation of Stars
Where are stars born?
As the material falls in towards the centre
of the proto­star, a disk forms and begins to
rotate.
Some of the material in the disk will fall into
the proto­star and be added to its mass.
The remaining material in the disk will eventually coalesce through collisions and form the objects that we find in our Solar System today, for example.
Star Birth: The Formation of Stars
Where are stars born?
The accretion disk may look like:
Star Birth: The Formation of Stars
How are stars formed?
By­products of the formation process are
jets and outflows of gas. These can be the
first sign of the new star as they punch out
of the cloud.
Star Birth: The Formation of Stars
How are stars formed?
The lifetime of stars can be represented
on a “Hertzsprung­Russell diagram”:
Star Birth: The Formation of Stars
Acknowledgements:
Michael Smith and Dirk Froebrich.
“The Birth of Stars and Planets” by
John Bally and Bo Reipurth.
“The Origin of Stars” by Michael Smith.
“Oxford Dictionary of Astronomy”.
Star Birth: The Formation of Stars
Acknowledgements:
Thank you for your attention!
Any Questions?
Jonathan Rowles