Flashcards
2022-01-18
What is the first stage in the evolution of a star??
A nebula.
What is the main element in a nebula??
Hydrogen.
What happens to a nebula after a long period of time??
It collapses under its own gravity.
As a nebula is collapsing under its own gravity, what happens to the stores of energy??
The gravitational potential potential is transfered to kinetic energy.
What happens as the gravitational energy of the dust particles in a nebula is transferred to kinetic energy??
The temperature increases.
What is a protostar (f)??
The object at the center of a nebula that is going to become a star, but doesn’t yet do fusion.
What is the tipping point for a protostar to become a main sequence star??
The temperature is sufficient.
Why is a main sequence star “stable”??
Because an equilibrium is reached by the force of gravity and radiation pressure.
What is the relationship between the mass of a star and the duration time that its in its main sequence??
The larger the mass, the shorter the duration.
Why does increasing the mass of a star shorten its main sequence duration??
Because it is hotter, so fusion is quicker and therefore burns out quicker.
2022-01-21
What is the next stage after the main sequence in a star’s evolution??
Becoming a red giant or red super giant.
What causes a main sequence star to become a red giant??
The hydrogen in the core runs out.
Why can a star suddenly go from running out of hydrogen to fusing helium??
No hydrogen in the core means there is no longer an equilibrium, so the core shrinks and temperature becomes sufficient for helium fusion.
What is fused after hydrogen in a red giant??
Helium.
What is the relationship between temperature and your ability to do fusion on heavier elements??
The heavier the element, the more energy is required.
What is fused after helium in a red giant??
Carbon.
What sort of vegetable do red giants end up looking like??
An onion.
What happens for a small star ($<1.44 M_\odot$) when it can no longer fuse carbon??
The red giant collapses to a white dwarf.
What other material is there around a white dwarf after a red giant collapses??
A planetary nebula.
What is the Pauli Exclusion Principle in very simple terms??
You can’t squish electrons together.
Why is a white dwarf stable??
Because an equilibrium is reached by the gravitational force and electron degeneracy pressure.
What is the Chandresakhar limit??
$$ 1.4 M_\odot $$
What is electron degeneracy pressure??
The force given by electrons not wanting to be close due to the Pauli Exclusion Principle.
When, in terms of solar masses, does a white dwarf form??
When the mass of the star is less than the Chandresakhar limit, $1.4_\odot$
What determines why a main sequence star becomes a red giant or a red supergiant??
The mass of the star.
Why do relatively “light” stars only become red giants opposed to red supergiants??
Because their mass is not great enough to overcome electron degeneracy pressure.
For a red supergiant, what comes after fusing carbon??
Fusing oxygen.
What is the limit for fusion in a red supergiant??
Fusing iron.
Why do red supergiants stop fusing at iron??
Because fusing iron doesn’t produce any energy.
When does a supernova happen??
When the star can’t fuse iron.
Why does a supernova make a big bang??
Because all the elements that make up the star collide with the central inert core and are bounced back off.
Between what masses is a neutron star formed from a red supergiant??
Between $1.4M_\odot$ (the Chandresakhar limit) and $3_\odot$
From what mass is a black hole formed from a red supergiant??
Over three $1M_\odot$
What is $1M_\odot$??
The mass of the sun.
What are the four important properties of a red giant or supergiant (SCBD)??
- Large __S__urface area
- __C__ooler
- __B__right
- Low __D__ensity
What are the four important properties of a white dwarf (DDSH)??
- __D__ense
- __D__im
- __S__mall
- __H__ot
What keeps a neutron star stable??
An equilibrium is reached by the force of gravity and neutron degeneracy pressure.
What is the relationship between size and brightness of a star??
$$ \text{size} \propto \frac{1}{\text{brightness}} $$
What is neutron degeneracy pressure??
The force given by neutrons not wanting to be close due to the Pauli Exclusion Principle.
Why is a larger mass required to become a black hole compared to a neutron star??
Because with a large enough mass you can overcome neutron degeneracy pressure.
2022-01-25
When are elements heavier than iron produced??
During a supernova.
What elements are produced during a supernova??
Elements heavier than iron.
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date: 2022-01-18 18:09
tags:
- '@?public'
- '@?school'
- '@?physics'
- '@?astrophysics'
title: Physics - Stellar Evolution