Chapter 19 and 20 - Space Flashcards
How is a protostar formed?
In a nebula, gravitational forces pull together dust and gas. As regions in the nebula get denser, gravitational energy is converted into thermal energy. This region is known as a protostar.
What needs to happen for a protostar to become a star?
Nuclear fusion needs to start in its core
Which two forces push outwards to keep the shape of a main sequence star stable?
radiation pressure from photons emitted during nuclear fusion and gas pressure.
What is a solar mass?
The mass of the Sun
Stars with low mass have a…
cooler temperature
How is a red giant formed?
The energy released from nuclear fusion inside a main sequence star is reduced to the point that it is now less then the force of gravity pulling the star together. The core of the star begins to collapse, as the core shrinks the pressure increases enough for fusion to start in a shell around the core. This causes the outside of the star to expand, as these layers expand they cool, as they cool they turn red.
What will stars of mass between 0.5M and 10M evolve into?
Red giants
What will stars of mass greater than 10M evolve into?
Red supergiants
What is the heaviest element that will form inside the core of a red supergiant?
Iron
What is electron degeneracy pressure?
Pressure created inside of a collapsing star due to the Pauli exclusion principle(Two electrons can not exist in the same energy state).
What is the Chandrasekhar limit?
1.44M, The maximum Mass of a star that electron degeneracy pressure is sufficient to prevent gravitational collapse. This is the maximum stable mass of a white dwarf star.
What are the two outcomes of a supernova?
Neutron star or a black hole
What is the Hertzsprung-Russell diagram?
A graph of the stars in our galaxy that shows the relationship between their luminosity and their average surface temperature.
What are energy levels?
Electrons bound to atoms in a gas can only exist in one of discrete set of energies, knows as energy levels.
Why are energy levels negative?
Because external energy is required to remove the electron from the atom.
An electron with zero energy is…
free from the atom
The energy level with the most negative energy is known as the…
ground state
State the three kinds of spectra
Emission line
Continuous
Absorption line
Why does each element produce a unique emission line spectra?
Each element has a unique set of energy levels
What is a continuous spectra and what will produce one?
All visible frequencies of light are produced. Produced by the atoms of a heated solid metal.
How is an absorption line spectra produced?
When a continuous spectrum passes through a gas cooler than the source of the continuous spectrum. As the light passes through the gas some of the photons are absorbed by the gas, only photons with energy exactly the energy need to raise electrons to higher energy levels are absorbed, this creates dark lines in the spectrum.
What is a black body?
An idealised object that absorbs all EM radiation that shines onto it and when in thermal equilibrium emits a characteristic distribution of wavelengths at a specific temperature.
State Wien’s displacement law
The wavelength emitted with maximum intensity from a black body is inversely proportional to its temperature.
State Stefan’s law
The luminosity of a star is directly proportional to:
its radius squared
its surface area
its surface absolute temperature ^ 4
