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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