final practice questions Flashcards
Theoretical upper limit for the mass of a star
150-200 solar masses
How stars orbit in our galaxy
Disk: orbit in the same direction with little vertical motion
Bulge/halo: random orientations
Neutron star limit to create a black hole?
3 Msun
Put these eras in order from least to most recent: Planck Era, Era of Atoms, Particle Era, GUT Era
Planck, GUT, Particle, Atoms
What is a flaw of the original, pre-inflation Big Bang Theory?
Fails to explain large-scale uniformity of the temperature of the universe
What evidence is used to detect potential black holes?
Gravitational waves
Motion of stars and gas nearby
Materials in the surrounding accretion disk fading from view
How would a larger Hubble constant affect our understanding of the age of the universe?
The universe would be younger
How to measure distance from the center of the Milky Way?
Use RR Lyrae variable stars to measure distance to globular clusters
The cause of the first accelerating expansion of the universe
inflation
Why are white dwarf supernovae good standard candles?
They have about the same luminosity due to the Chandrasekhar limit
Difference between a nova and a supernova
Supernovae leave nothing behind; novae leave a white dwarf behind
Where does energy come from in a black hole?
Kinetic energy comes from matter falling into the black hole
What do different colors in the Cosmic Microwave Background represent?
Temperature
What electron degeneracy pressure?
High electron density, high speed of electron movement
What supports white dwarves against the crush of gravity?
Electron degeneracy pressure
Major galaxy types
Spiral
Elliptical
Irregular
Evidence supporting the Big Bang Theory
The universe is expanding
Correctly predicts the abundance of helium and other light elements
Detected leftover thermal radiation from the Big Bang
What percentage of our universe are ordinary matter, dark matter, and dark energy?
4% ordinary matter
22% dark matter
74% dark energy
What is the geometry of our universe?
Flat; at critical density
What happens to light emitted near the event horizon of a black hole?
It is redshifted and appears to stretch out
What likely contributes to formation of elliptical galaxies in densely populated galactic clusters?
Frequent collisions and mergers with other galaxies
According to Hubble’s law, galaxies that are farther away are…
moving away faster
How do new stars form when galaxies collide?
Clouds of gas and dust combine to create star-making regions
Why might distant regions in the CMB appear similar?
They were once close together, but moved apart due to inflation
What must a star’s mass be to create a Massive Star Supernova?
> 8Msun
What must a star’s mass be to create a White Dwarf Supernova?
1.4Msun
What happens to angles on a curved surface?
On a convex surface, an angle will be more than it usually is
What color indicates ongoing star formation?
Blue
What type of sensors are best for observing earliest galaxies in the universe?
Infrared
If total density of matter and energy in the universe were to slightly exceed critical density, what would be the geometry of the universe?
spherical
Rank parts of the galaxy from youngest to oldest
Outer arms, middle arms, center, halo
Suppose the total density of matter and energy is less than the critical density. What could we conclude about the universe?
Hyperbolic geometry
How do elliptical galaxies differ from spiral galaxies in composition?
Less gas and dust than spiral galaxies
During what era in the universe’s history would you find conditions for fusion of protons and neutrons into helium nuclei
Nucleosynthesis
What significant change followed the era of nucleosynthesis?
Formation of neutral atoms as the universe cooled
Spiral galaxies’ rotation curves can be measured with…
The doppler shift of the 21cm line of atomic hydrogen
Cosmological Principle
The universe looks relatively the same no matter where you are in it
Which force is present in the GUT era of the universe?
gravity
What is the Hubble Tension
tension between seemingly incompatible measurements of the rate of expansion of the universe
What will eventually happen to a main sequence star with a mass similar to our sun’s?
It will become a red giant, then a planetary nebula, then a white dwarf
Why can’t dark matter be made of protons, neutrons, or electrons?
Protons, neutrons, and electrons affect and interact with photons
How to measure amount of dark matter in an elliptical galaxy?
measure speeds of different stars at different radii from the center of the galaxy, and determine how much mass is inferior to the orbit
Order these objects from most to least luminous: galaxy, supernova, brown dwarf, quasar, white dwarf, pulsar
Quasar, supernova, galaxy with 100 million stars, pulsar, white dwarf, brown dwarf
What is WIMP?
Weakly Interacting Massive Particle; a potential explanation for dark matter
What can cepheid variable stars be used for?
Their periods can be used to determine luminosity
