16 Stellar Evolution and Cosmology Flashcards
Why is it difficult to classifying stars by their brightness?
The brightness they appear from Earth also depends on their distance from the Earth.
The closer the star, the brighter it appears.
What is the name of the long stable period a star enters when the outward pressure caused by thermal expansion balances the force of gravity pulling everything inward.
The main sequence
Which of the following is NOT evidence that supports the Big Bang Theory
A. Variation in gravitational field strength
B. The red-shift observed in light reaching Earth from distant galaxies.
C. Cosmic microwaves background radiation.
A. Variation in gravitational field strength
Describe the absolute magnitude scale.
-10 0 +10
Stellar evolution for a small mass star is…
Nebula –> Protostar –> Main sequence star –> Red giant –> white dwarf
What evolutionary stages does a large mass star go through?
Large mass star
Nebula –> Protostar –> Main sequence star –> Red super giant –> Supernova –> Neutron star
Stellar evolution for a low mass star is…
Nebula –> Protostar –> Main sequence star –> Red giant –> white dwarf
What evolutionary stages does a very large mass star go through?
Very large mass star
Nebula –> Protostar –> Main sequence star –> Red super giant –> Supernova –> Black hole
Where are the cool and dim stars found on the HR diagram?
Bottom right
Which of the following is not formed after a supernova?
A. a neutron star
B. a black hole
C. a red super giant
C. a red super giant.
On the Hertzsprung-Russell diagram, white dwarfs group together because they have…
A ..negative absolute magnitudes and high temperatures
B .. negative absolute magnitudes and low temperatures
C .. positive absolute magnitudes and high temperature
C .. positive absolute magnitude and high temperatures
White dwarfs are dim and hot!
NOTE: Confusingly, the low absolute magnitude, the brighter the star ( -4 is brighter than +5)
The absolute magnitude of a star is..
A. how bright the star would appear if it was at a standard distance from Earth
B. the brightest the star could appear to an observer
C. how bright the star appears from Earth
A. how bright the stat would appear if it was at a standadrd distance from Earth.
This allows us to compare the brightness of stars without worrying about their relative distances from Earth.
In general, the further away a galaxy is….
A. the smaller the observed increase in the wavelength of its light.
B. the slower it is moving away from us.
C. the bigger the observed increase in wavelength of its light.
C. the bigger the observed increase in wavelength of its light.
A hot star will emit most its visible light at the _____________ frequencies of visible light.
highest (blue)
Below is a description of how the universe started…
1) initially, all the matter in the universe occupied a single point
2) This tiny space was very dense and very hot
3) This single spot then exploded
4) Space started expanding, and the expansion is still going.
What is stage 3 called?
The Big Bang
Locate the white dwarf in the HR diagram below.
D
white dwarf stars are dim and cool
What is cosmic microwave background (CMB) radiation believed to be?
A. Energy from exploding supernovae.
B. Radiation given out by man-made objects in space, such as satellites and telescopes.
C. Leftover energy from the Big Bang explosion.
C. Leftover energy from the Big Bang explosion.
Eventually a star runs out of hydrogen in it core. The force of gravity inward is larger than the pressure of thermal expansion outward.
The star is compressed, until it is dense and hot enough that the energy (and so the pressure) created makes the outer layers of the star expand.
What is the name of this stage?
red giant (small mass star)
red supergiant (large mass star)
Where are the hot and dim stars found on the HR diagram?
Bottom left
A cool star will emit most its visible light at the _____________ frequencies of visible light.
lowest (orange and red)