Birth, Life and Death of a Star Learning Objective: To learn about the life cycle of a star. Learning Outcomes: All: Will be able to correctly name (C) and simply describe (B)the phases in a life cycle of a star. Most: Will be able to describe the forces in action during the main phases of a stars life cycle (B/A) Some: Will have good knowledge about each section, which will allow them to answer A/A* exam questions with full or near to full marks.

Video on life of a star

Birth of a Star All stars start life as a nebula of gas and dust. Over millions of years gravity pulls these closer together.

Gravitational force Birth of a star Nebula Pressure builds up and the core starts to heat up giving out infra red radiation.

Birth of a star Protostar Star The gravity eventually gets so big and the temperature gets so high that nuclear fusion starts, it becomes a star The dust and gas from the nebula is added to the protostar, it gains mass. As mass is gained gravity increases and the temperature within the protostar increases

Life of a star

Radiation Pressure From the energy of fusion Gravitational force From the mass of the material A Stable Star like our Sun Nuclear fusion 4 Hydrogen 1Helium + ENERGY (Grade A) Nuclear fusion 4 Hydrogen 1Helium + ENERGY (Grade A) The force of the radiation pressure from nuclear fusion is balanced with the gravitational force in a stable star. (Grade B)

Death of a Star Star like our SunA large Star

Star Red Giant White dwarf Black Dwarf Eventually a star the size of our sun becomes a Red Giant. The star keeps increasing in size until the gravitational force causes it to collapse into itself creating a White Dwarf This cools down to become a black dwarf.

Large Star Red Supergiant Supernova Neutron Star Pulsar Black Hole A larger star eventually becomes a super Red Giant. This then collapses, heats up and explodes in a supernova. The small core becomes a neutron star. This can turn into a pulsar If a star is large enough it’ll become a black hole.