Term
Spiral Galaxies Differ from Elliptical Galaxies in:
A) Direction of motion of stars
B) Relative age of most stars
C) Both A & B |
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Definition
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Term
| What does hubble's law state? |
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Definition
| The recession velocity of faraway galaxy (clusters) is proportional to their distance |
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Term
| Define Dark Matter. Does it interact electromagnetically? |
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Definition
Mass we can not see that exists to support the increased velocities of stars in spiral galaxies.
Does not interact electromagnetically. |
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Term
| What is Baryonic Dark Matter? List examples |
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Definition
1. Regular, but cold (not emitting radiation)
2. Brown Dwarfs, Non-feeding Black Holes, Cooled White Dwarfs/Neutron Stars |
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Term
What is Hot Dark Matter?
How fast is it relative to speed of light?
What is an example of it?
Does it interact? (Electromagnetically, gravitationaly or nuclear weak force)?
Has it ever been detected?
Can they clump together on small scales? |
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Definition
Hot dark matter moves near speed of light
Example is neutrino
Does not interact electromagnetically, but it does interact gravitationally and by weak nuclear force
Hard to detect but has been done before.
They can not clump together on a small scale |
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Term
What is Cold Dark Matter?
How fast is it relative to speed of light?
What is an example of it?
Does it interact? (Electromagnetically, gravitationaly or nuclear weak force)?
Has it ever been detected?
Is the rest mass large or small? |
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Definition
Cold dark matter moves slow compared to speed of light
WIMPS (weakly interactive massive particles)
Interacts gravitationally and through weak nuclear force
Has not been detected
Large rest mass |
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Term
What is warm dark matter?
How fast does it move?
How much rest mass does it have? |
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Definition
Intermediate between Hot & Cold Matter
Moves near the speed of light
Small rest mass |
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Term
| What is OMEGA (Ω)? What does a value of 0 indicate? |
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Definition
Ω is the matter density parameter
If λ=0 (no vacuum energy), then Ω determines fate of university.
Ω=0 empty universe
Ω>1 dense universe enough to collapse
Ω=1 universe stops expanding after infinite amount of time
Ω<1 the universe keeps expanding forever |
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Term
| Is the universe expanding, slowing down, or contracting? What is Ω? |
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Definition
| Universe shows that it might continue expanding forever (Ω<1, about 0.3) |
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Term
| General Relatively: what is the formula for the universe? What is the cosmological constant? |
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Definition
Gravity + Cosmological Constant (λ) = 8Pie*Mass(or energy)
Cosmological constant causes universe to expand |
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Term
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Definition
Dark energy is unobservable force (pressure) that pushes things outward (explaining infinite expansion of the universe).
States that there is energy in a vacuum (space itself) |
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Term
| What is the breakdown between normal matter, dark matter and dark energy? |
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Definition
Normal Matter: 4%
Dark Matter: 21%
Dark Energy: 75% |
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Term
| How has the hubble constant changed over time? |
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Definition
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Term
| What is the age of the universe believed to be? |
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Definition
| 14 Gyr (gigayear, billion years) |
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Term
| What is an object's absolute magnitude? |
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Definition
| The intrinsic brightness of an object converted to a logarithmic scale where lower numbers are brighter than higher numbers |
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Term
| For what is the distance modulus used? |
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Definition
| Relates distance to a difference in absolute and apparent magnitude |
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Term
| For which measurements is the distance modulus used? |
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Definition
| Spectroscopic parallax, variable stars, tully-fisher, supernovae |
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Term
| How did Hubble figure out that our galaxy was not the universe? How did he classify galaxies? What did he find out about the expansion of the universe? |
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Definition
| Cepheid variable stars. Classified galaxies through morphology (doppler shift: relationship between distance and recession velocity) |
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Term
| What are four components of galaxies (observable) |
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Definition
| Gas, Starts, Dust and Central Black Holes |
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Term
| What is active galactic nuclei? How do they produce massive amounts of light and radiation |
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Definition
Active Black Holes: Material is heated in the accretion disks of super-massive black holes in the center of some galaxies. They can limit galaxy formation:
Powerful jets of high-energy particles emanate from the vicinity of the black hole's poles
These jets heat gas around the galaxy and stop the infall of matter into the galaxy |
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Term
| Explain elliptical galaxies |
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Definition
| No net angular momentum, few or no open clusters, many globular clusters, little interstellar gas and dust |
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Term
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Definition
| Flat and wide with net angular momentum (rotation), consists of bulge, halo and spiral arms. There is gas and dust in spiral arms, stars wander in and out of arms and galactic plane |
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Term
| What are dwarf and irregular galaxies |
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Definition
Irregular: don't fit into elliptical or spiral categories
Dwarf Galaxy: Up to 10bs of stars (instead of hundreds of billions) |
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Term
| Differentiate between groups, clusters, and superclusters |
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Definition
Groups: <50 galaxies
Clusters <1000 galaxies (gravitationally bound)
Superclusters <1000 superclusters |
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Term
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Definition
| A large scale structure that is bigger than supercluster, full of clumps and voids of galaxy superclusters |
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Term
| What is Type 1a Supernova |
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Definition
| A white dwarf that has accumulated more than 1.4 Solar Masses or material from a companion star |
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Term
| Why are standard candles important (also, what are they)? |
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Definition
Standard Candles are stars whose intrinsic brightness we know.
They are of known intrinsic brightness and so the distance can be found by the comparing to the apparent brightness |
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Term
| What is the limit of the Hubble telescope magnitude (luminosity) detection? |
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Definition
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Term
| What is a Cepheid variable? |
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Definition
| A star whose period of brightness fluctuation is related to its intrinsic brightness (changes brightness periodically) |
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Term
| What is the relationship between peak brightness and period between said peaks (time)? |
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Definition
| As the period between peaks increases, the peak (intrinsic brightness) increases |
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Term
| How far away can we measure Cepheid Variable stars? What is the nearest Cepheid Variable Star? |
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Definition
| Up to 25 million parsecs. The nearest is Polaris |
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Term
What are globular clusters?
Are they older or younger than open clusters?
Are they smaller or larger than open clusters?
Are they gravitationally bound?
Do they have 100,000s of stars or 1,000s? |
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Definition
Older than open clusters
Larger than open clusters
Gravitationally bound together
100,000s of stars |
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Term
What are open clusters?
Are they older or younger than globular clusters?
Are they smaller or larger than globular clusters?
Are they gravitationally bound?
Do they have 100,000s of stars or 1,000s? |
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Definition
Younger
Smaller
Not gravitationally bound
Thousands of stars |
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Term
| According to special relatively, is the luminous aether correct? Is the speed of light different for persons in all frames of reference? |
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Definition
| Luminous aether is disproved and speed of light is same for all observers |
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Term
| What is an interval? (think of how you measure it) |
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Definition
| The space-time separation of events |
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Term
| What is the nature of an interval of 0? Positive Interval? Imaginary Interval? |
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Definition
Zero: Light-like
Positive: Time-like
imaginary: Space-Like |
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Term
| Which interval allows for different order of events based on observer? In this interval, can one event cause the other? |
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Definition
| Space-like & no, one event can not cause the other |
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Term
| What 2 things cause objects traveling near the speed of light never exceed that speed? |
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Definition
| Time dilation and length contractions |
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Term
| What is the unit of measurement for Energy (hint: E=∆mc^2) |
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Definition
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Term
| Compared to a stationary clock, a moving clock moves: SLOWER or FASTER? |
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Definition
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Term
| What forces are balanced inside a star where fusion is occuring? |
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Definition
| Gas Pressure (outward) & Gravity (inward) |
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Term
| What is the temperature of the sun (at the center)? |
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Definition
| 10-15 million degrees Kelvin |
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Term
| How do we know the ages of stars in clusters? |
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Definition
| Age of stars based on observing how much power they radiate based on number of reactions needed. |
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Term
| What creates heavy metals (materials other than Hydrogen & Helium)? |
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Definition
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Term
| When does the core of a supernova collapse? Does temperate remain the same? |
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Definition
| Supernova collapses when there is more than 1.4 solar masses at the core (Chandrasekhar limit), producing an explosion w/ 100b degrees K. Emitts neutrinos |
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Term
| What differentiates Supernova Type 1a from others? |
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Definition
| Supernova Type 1a involves the Chandrasekhar limit (1.4 solar masses) and the light curve is reproducible. |
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Term
| Is the peak brightness and length of decay the same for Supernova Type 1a? |
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Definition
| No, peak brightness and length of decay are NOT the same |
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Term
| What does parsec stand for? |
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Definition
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Term
| Do lengths perpendicular or parallel to the direction of motion contract? |
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Definition
| Only lengths parallel to the direction of motion contract |
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Term
| what are the units for Watt? |
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Definition
Joule (Energy) / Time
kg*m^2 / s^3 |
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