The lifecycle of a star

• Gravity and nuclear fusion reactions drive the formation and development of stars.
• Stars with different masses grow and change throughout the different stages of their lives.
• The life cycle for a particular star depends on its size.
• All stars begin life in the same way: a cloud of dust and gas, also known as a nebula.
• If massive enough, these clouds can collapse under gravity to form a protostar.
• A protostar becomes a main sequence star, which is a stable stage in the life cycle of a star where nuclear fusion occurs, fusing hydrogen nuclei into helium nuclei.
• Gravity and nuclear fusion reactions drive the formation and development of stars.
• There is a balance between the outwards radiation and the force of gravity pulling inwards.
• Stars with different masses grow and change throughout the different stages of their lives.
• Following this, stars develop in different ways depending on their size.
• A star is a main sequence star for most of its lifetime.
• During the main sequence stage, nuclear fusion occurs, fusing hydrogen nuclei into helium nuclei.
• The balance between the outwards radiation and the force of gravity pulling inwards is maintained, making the star stable.
• All the naturally occurring elements in the Universe are produced by nuclear fusion reactions in stars.
• During the majority of a star’s lifetime, hydrogen nuclei fuse together to form helium nuclei.
• As the star runs out of hydrogen, other fusion reactions take place forming the nuclei of other elements.
• Elements that are heavier than hydrogen and helium are formed in the supernova.
• The large explosion at the end of a large star’s life, which distributes much of the elements formed in the star across space, is known as a supernova.
• Explosions of high mass stars cause supernovae.
• When the supernova explodes, all the elements produced are thrown out into the Universe.
• The heavy elements found on Earth, such as gold, came from material thrown out in previous supernova explosions.
• A star is formed when the hydrogen nuclei fuse together to make helium, releasing energy
• Stars greater in mass than the Sun follow the right-hand path: red supergiant star → supernova → neutron star or black hole (depending on size)
• A star forms from massive clouds of dust and gas in space, known as a nebula
• Gravity pulls the dust and gas together, forming a protostar
• During the main sequence phase, gravity is balanced by higher pressure due to high temperatures
• A larger star will explode as a supernova, throwing hot gas into space
• Stars similar in size to the Sun follow the left-hand path: red giant star → white dwarf → black dwarf
• The protostar gets hot as the mass falls together
• A supernova can leave behind either a neutron star or a black hole, depending on its mass
• Nebulae are mostly composed of hydrogen
• A red giant star forms when all the hydrogen has been used up and larger nuclei begin to form
• A white dwarf forms when a small star like the Sun contracts under the pull of gravity after nuclear reactions are over
• Gravity and nuclear fusion reactions drive the formation and development of stars
• Stars with different masses grow and change throughout the different stages of their lives
• Main sequence stars are a stable stage in the life cycle of a star where nuclear fusion occurs and there is a balance between radiation and gravity
• In a main sequence star, hydrogen nuclei fuse together to form helium nuclei