Stars and their Life Cycles Flashcards
How do stars begin?
As a cloud of dust and gas which is mostly hydrogen and helium
Describe the process carried out in which a star goes from dust and gas clouds to protostars
Gravity causes the denser regions of the cloud to contract very slowly into clumps and when they get dense enough, the cloud breaks up into protostars
Describe the process in which prostars transform into their Main Sequence
They continue to collapse under gravity and reducing in volume making the particles more squashed up which increases the pressure and temperature. Once it reachers a few hundred million degrees and the hydrogen nudlei fuse to form helium then energy is released which creates enough outward pressure to stop gravitational collapse.
Where in a star does fusion happen?
In the core
What is the outer region of the star called?
The photosphere
How is energy transported to the surface of the star?
Energy released from fusion in the core is transported by photons of radiation and convection currents to the photosphere, which is the glow that we see
When does a star stop it’s main sequence?
When it runs out of hydcrogen in the core
How does the star cool down after it’s main sequence?
The core shrinks as the rest of the star swells out to become a ‘red giant’ or a ‘supergiant’ star, causing the photosphere to cool down
What do stars fuse together once hydrogen runs out?
They fuse helium into larger nuclei like carbon, nitrogen and oxygen
What happens to a star once there is too little helium left in the core for it to fuse and make other nulei?
The core becomes unstable and is compressed by the rest of the star
What happens to red giant stars after they run out of hydrogen?
They don’t have enough mass to compress the core so no more nuclear fusion occurs. The outer layers of the star are released into space and the core shrinks to become a hot white dwarf where there is no nuclear fusion so the star gradually cools and fades
What happens to Red Supergiants once they run out of hydrogen?
Their mass is large enough that it can increase the pressure and temperature of the core to fuse larger nuclei. This happens until most of the core has been fused into iron.
What happens to Red Supergiants after the core has been fused into iron?
They can’t fuse iron so the core collapses and the star explodes as a supernova. This creates nuclei with masses greater than iron
What happens to a star after a supernova?
The core collapses to form a neutron star, or if there’s enough matter, a black hole
What does the Hertzsprung-Russell diagram show?
Shows the luminosity vs temperature of stars which ends up being a divide of differently grouped stars
