Astronomy Chapters 14-18 – Flashcards
Unlock all answers in this set
Unlock answersquestion
states that laws of physics are the same everywhere
answer
cosmological principle
question
idea where galaxies in space are distributed similarly everywhere
answer
homogeneous
question
idea where the universe looks the same to all observers regardless of the direction in which they are looking
answer
isotropic
question
a gravitationally bound large collection of stars, gas, and dust
answer
galaxy
question
spirals, ellipticals, irregulars
answer
types of galaxies
question
___ galaxy shape: flattened and thin
answer
spiral
question
___ galaxy shape: oval or football-shaped
answer
elliptical
question
galaxy classification with bright center, tight arms
answer
Sa/SBa
question
small center, open arms
answer
Sc/SBc
question
galaxy classification: cross between S and E, disk with no arms
answer
S0
question
area of a spiral galaxy where stars orbit in all directions
answer
central bulge
question
___ galaxy features: little gas, mostly hot, no star formation, golden color
answer
elliptical
question
___ galaxy features: abundant gas, mostly cold, star formation is ongoing, blue color
answer
spiral
question
___ galaxy features: lots of gas, ongoing star formation
answer
irregular
question
___ galaxy size: dwarf or giant
answer
elliptical and irregular
question
___ galaxy size: giant
answer
spiral
question
location of young, hot, bright stars
answer
spiral arms
question
this is located in the spiral arms
answer
concentrated gas and dust
question
cannot produce all the gravity observed in a galaxy
answer
luminous matter
question
an additional source of gravity that does not make light
answer
dark matter
question
do not decrease as a function of radius
answer
rotation speeds
question
this percentage of mass is dark matter
answer
95%
question
located around the galaxy (completely surrounding it)
answer
dark matter halo
question
allows astronomers to look for mass that is not visible
answer
gravitational lensing
question
massive compact halo objects
answer
MACHOs
question
weakly interacting massive particles
answer
WIMPs
question
a compact region at the center of a galaxy that has a much higher than normal luminosity
answer
AGN (active galactic nuclei)
question
quasi-stellar radio source; center of violent activity in the hearts of large galaxies
answer
quasar
question
low-luminosity cousins of quasars
answer
Seyfert galaxies and radio galaxies
question
central supermassive black hole with an accretion disk
answer
AGN model
question
masses of thousands to tens of billions of solar masses
answer
supermassive
question
material in the accretion disk fuels ___
answer
AGN
question
provide evidence that galaxies are moving away
answer
redshifts
question
states that the recession velocity of a galaxy is proportional to the distance of that galaxy
answer
Hubble's Law
question
constant of proportionality
answer
Hubble constant (H0)
question
the Hubble constant determines ___
answer
the age of the universe
question
these are used as luminous standard candles
answer
Type 1a supernovae
question
70 km/s/Mpc
answer
H0
question
dusty gas clouds that obscure our view
answer
interstellar medium
question
result when interstellar dust blocks shorter wavelengths more efficiently
answer
interstellar reddening
question
emits radio waves =21 cm
answer
neutral hygrogen
question
example of barred spiral galaxy with elongated bulge
answer
Milky Way
question
tightly gravitationally bound collections of up to a million stars
answer
globular clusters
question
location of globular clusters
answer
spherical halo
question
___ star sizes: RR Lyrae and Cepheid variable stars
answer
globular cluster
question
___are found by looking at globular clusters
answer
distances
question
distance from Solar System to the center
answer
27,000 ly
question
distance across the whole Milky Way
answer
100,000 ly
question
Milky Way + halo
answer
300,000 ly
question
the age of globular clusters
answer
13 billion years old
question
loosely bound collections of dozens to thousands of stars in the disk of a spiral galaxy
answer
open clusters
question
younger
answer
open clusters are ___ than globular clusters
question
first
answer
stars in the halo formed
question
heavier
answer
younger stars have ___ elements
question
process where gas is ejected from the disk by hot young stars and supernovae and then falls back onto the disk
answer
galactic fountain model
question
high-energy, charged particles moving near the speed of light
answer
cosmic rays
question
extend 25,000 ly above and below the galactic plane
answer
gamma ray bubbles
question
Milky Way plus a few large and dwarf galaxies
answer
Local Group
question
takes time for light from distant object to reach us
answer
look-back time
question
the term for the time when separation between galaxies was zero
answer
Hubble time
question
hot and dense
answer
early universe was
question
energy that cooled into matter as the universe cooled
answer
beginning of the universe had
question
evidence that everything is expanding
answer
cosmological redshift
question
this explains why space glows in microwaves at 3 K
answer
CMB (cosmic microwave background) radiation
question
temperature of the universe cooled enough for H atoms to form; like a fog being lifted
answer
recombination
question
smoothness of the universe (CMB variations) has ___ over time
answer
decreased
question
ratio of the critical density
answer
Ωmass = p/pc
question
density equals the critical density; universe slows to stop at infinite time
answer
Ωmass = 1
question
formula where expansion will stop and universe will contract
answer
Ωmass > 1
question
formula where expansion will go on forever, slowing but never stopping
answer
Ωmass < 1
question
0.3
answer
Ωmass (including stars, galaxies, and dark matter)
question
energy that allows expansion to speed up
answer
dark energy
question
Λ; associated with dark energy
answer
cosmological constant
question
photons, particles, anti-particles
answer
early universe composition
question
electromagnetic force
answer
QED
question
gravity, electromagnetic, weak nuclear, strong nuclear
answer
four forces of the universe
question
QED + weak
answer
electroweak
question
combination of the ideas in QCD (strong) and electroweak
answer
standard model
question
strong force + electroweak force; predicts proton decay
answer
grand unified theory (GUT)
question
GUT + gravity
answer
theory of everything (TOE)
question
name for other universes
answer
multiverse
question
gravitationally bound collections of hundreds of thousands of galaxies
answer
galaxy clusters
question
bunches of galaxy clusters
answer
superclusters
question
clusters are bright in ___
answer
x-rays (rich in hot gas)
question
formed via gravitational lenses; able to see the distorted images of background galaxies
answer
visible arcs
question
universe is homogenous and isotropic
answer
large-scale structure
question
process where small objects formed first, then grouped together
answer
hierarchical clustering
question
process where collisions between protons (hydrogen nuclei) in the early universe formed low-mass nuclei (deuterium and isotopes of helium, lithium, beryllium, and boron)
answer
Big Bang nucleosynthesis
question
all elements more massive than ___ formed in stars
answer
boron
question
slow speeds compared to C; unknown elementary particles
answer
cold dark matter
question
moving rapidly; neutrinos from Big Bang
answer
hot dark matter
question
location of the formation of the first stars
answer
dark matter mini-halos
question
size of the first stars
answer
very massive
question
these build up to make larger galaxies
answer
protogalaxies
question
the merging of many small galaxies triggers a ___
answer
supermassive black hole
question
___ galaxy evolution: the merging of spiral galaxies
answer
elliptical
question
this event heats up gas and emits x-rays
answer
merging of galaxy clusters
question
complex biochemical process that draws energy from its environment to survive and reproduce
answer
life
question
scientists who created molecules with an experiment similar to the primordial Earth
answer
Miller and Urey
question
lightning, hydrothermal vents, UV radiation
answer
possible energy sources
question
when life began
answer
3.5 billion years ago
question
dating process where one infers that the deeper layers formed earlier
answer
relative ages
question
radiometric dating
answer
absolute ages
question
these release oxygen via photosynthesis
answer
cyanobacteria
question
540-500 million years ago; explosion of new species due to climate change and increase in genetic diversity
answer
Cambrian Explosion
question
composition of all terrestrial life
answer
carbon, hydrogen, oxygen, and nitrogen (CHON)
question
the three necessities for life
answer
nutrient source, energy, liquid water
question
region around a star that provides a range of temperatures in which liquid water can exist
answer
habitable zone
question
hotter stars have ___ habitable zones
answer
larger
question
multiply the number of stars in our galaxy, fraction of stars with planets, average number of planets per star, fraction of planets with life, fraction that develop advanced technology
answer
Drake equation
question
surveys as many as a million stars per year to search for life
answer
ATA (Allen Telescope Array)
question
states that civilizations should be common; even 1 in 1 million stars = 100,000 civilizations; but we still haven't detected them
answer
Fermi's Paradox
