Deeper Dive: The Lifecycle Of A Star
BBC (2019). The life cycle of a star - AQA - Revision 1 - GCSE Physics (Single Science) - BBC Bitesize. [online] BBC Bitesize. Available at: https://www.bbc.co.uk/bitesize/guides/zpxv97h/revision/1.
All stars begin life in the same way. A cloud of dust and gas, also known as a nebula, becomes a protostar, which goes on to become a main sequence star. Following this, stars develop in different ways depending on their size.
Stars that are a similar size to the Sun follow the left-hand path:
red giant star white dwarf black dwarf
Stars that are far greater in mass than the Sun follow the right-hand path:
red supergiant star supernova neutron star, or a black hole (depending on size)
Nebula to Protostar
Socratic.org. (n.d.). What is a nebula? How does it form a protostar? | Socratic. [online] Available at: https://socratic.org/questions/what-is-a-nebula-how-does-it-form-a-protostar#:~:text=Protostars%20are%20formed%20when%20the%20gas%20and%20dust
Protostars are formed when the gas and dust in a nebula start condensing. Its gravitational force increases as its mass increase causing more and more condensation. This leads to the formation of a pre-main sequence star in which nuclear fusion starts.
Main Sequence Star
Tillman, N.T., and Biggs, B. (2022). Main sequence stars: definition & life cycle. [online] Space.com. Available at: https://www.space.com/22437-main-sequence-star.html.
Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main-sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
How long a main sequence star lives depends on how massive it is. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces.
Stars about the same size as our sun
BBC (2019). The life cycle of a star - AQA - Revision 1 - GCSE Physics (Single Science) - BBC Bitesize. [online] BBC Bitesize. Available at: https://www.bbc.co.uk/bitesize/guides/zpxv97h/revision/1.
Stars that are about the same size as our sun Will contact under the pull of there gravity and shrink in size:
When all the hydrogen has been used up in the fusion process, larger nuclei begin to form and the star may expand to become a red giant.
When all the nuclear reactions are over, a small star like the Sun may begin to contract under the pull of gravity. In this instance, the star becomes a white dwarf which fades and changes colour as it cools.
Stars with greater mass than our sun
Stars that have greater mass than our sun will also become Red giants but A larger star with more mass will go on making nuclear reactions, getting hotter and expanding until it explodes as a supernova.
An exploding supernova throws hot gas into space.
Depending on the mass at the start of its life, a supernova will leave behind either a neutron star or a black hole.
Neutron star
Briggs, A. (2020). What is a neutron star? | Astronomy Essentials | EarthSky. [online] earthsky.org. Available at: https://earthsky.org/astronomy-essentials/definition-what-is-a-neutron-star/.
After a massive star explodes as a supernova, its core can collapse to end up as a tiny and super-dense object with not much more than our sun’s mass. These small, incredibly dense cores of exploded stars are neutron stars.
A typical neutron star has about about 1.4 times our sun’s mass, but they range up to about two solar masses. Now consider that our sun has about 100 times Earth’s diameter. In a neutron star, all its large mass – up to about twice as much as our sun’s – is squeezed into a star that’s only about 10 miles (15 km) across, or about the size of an earthly city.
Black Dwarf
Guide, U. (2018). What is a Black Dwarf Star? [online] Universe Guide. Available at: https://www.universeguide.com/fact/blackdwarfstar
Black Dwarf Stars are the result of a white dwarf star having cool down.
A Black Dwarf star would probably be solid and comprise of carbon like a diamond.
Given the length of time that a White Dwarf star will take to cool down, the universe is too young for any of those to exist. Over time, the Black Dwarf will eventually break down and disperse into space.
Black Dwarf Stars are hypothetical stars that don't yet exist but are predicted to in a far off future. When a star dies and turns into a White Dwarf Star, it will emit light for an unimaginable length of time but once it has run out of all energy, it will no longer produce light. When it has stopped producing light, it becomes black and no longer emits light.
