P8 - Space Flashcards
What is a main sequence star?
For a star to be on the main sequence it must have enough hydrogen to fuse into helium. Once the hydrogen runs out it leaves the main sequence.
Which last longer, stars with greater mass or lesser mass?
Lesser mass. Stars with greater mass have more fuel to burn, but they have higher luminosities so they run out quicker.
Why is a main sequence star sometimes said to pulse?
The energy released by fusion, produces an outwards force, causing star expansion.
However, the stars mass means that gravity acts in the opposite direction, forcing particles towards the core.
What does it mean when a star is said to be stable?
Both outward and inward forces are equal.
The star is in the main sequence phase.
How does a star form?
A nebular starts to contract due to attraction between unstable particles.
The clumps of matter have mass and are pulled together by gravity.
Nebular collapses and forms an accretion disc, with a large gravitational pull.
High pressure in the central mass, due to gravity, produces heat.
The heat in the core became high enough for fusion. Forming a star.
Planets began to form around the protostar, from material further out in the accretion disc.
What is a cloud of dust and gas called?
A nebular.
How does a nebular become a protostar?
The gravity of the nebula pulls the dust and gas together, as the mass comes together it’s temperature increases, until it’s hot enough for hydrogen to fuse into helium. Forming a protostar.
What do nebulae mostly consist of?
Hydrogen.
How does the core remain hot in a protostar?
Nuclear fusion releases energy.
What is an accretion disc?
A rotating swirling disc, that forms from a nebular.
What is the gas model view of how temperature increases in the centre, during the birth of a star?
Gas temperature increases when it is compressed, so material at centre gets hotter and begins to glow.
What is the particle model view of how temperature increases at the centre of a star during it’s birth?
Speed of particles increase due to the gravitational force, therefore, temperature increases.
How does a red giant star form?
When all hydrogen has been used up in the fusion process, larger nuclei begin to form and star expands to form a red giant.
How does a white dwarf star form?
A small star, like the sun, may begin to contract under the pull of gravity and become a white dwarf which fades and changes colour as it cools.
How does a supernova form?
A larger star with more mass will go on making nuclear reactions, getting hotter and expanding until it explodes as a supernova.
What does an exploding supernova do?
Throws hot gas into space.
What does an exploded supernova leave behind?
A neutron star or black hole.
What is the life cycle for a star much bigger than the sun?
protostar -> main sequence star -> red super giant star -> supernova -> neutron star, or a black hole (depending on size)
What is the life cycle of a star the same size as the sun?
protostar -> main sequence star -> red giant star -> white dwarf -> black dwarf
Explain in detail the life cycle of stars much bigger than the sun.
Nebula pulled together by gravity.
High pressure, increases temperature. Starting fusion process (hydrogen fuse to helium).
Star becomes main sequence.
Hydrogen begins to run out.
Helium nuclei fuse to make heavier elements and becomes a red super giant.
Star collapses and explodes (supernova), creating elements heavier than iron.
Leaves black hole or neutron star.
Explain the first stage of the life cycle of stars.
Stars initially form from a cloud of dust and gas called a nebula. The force of gravity pulls the dust and gas together to form a protostar.
