the sum total of all matter and every, everything within and between all galaxies
New cards
2
big bang
the events that marked the beginning of the expansion of the universe
New cards
3
universe expanding
average distances are increasing between galaxies
New cards
4
The Big Bang theory predicts that the cosmic microwave background should have an essentially perfect thermal radiation spectrum because it came from the heat of the universe itself.
True
New cards
5
Because the chemical composition of the universe is about ¼ helium by mass and ¾ hydrogen by mass, no matter where we look, the universe itself must once have been hot enough to fuse hydrogen into helium.
True
New cards
6
hubble’s law
the recession velocity of a galaxy is direction proportional to its distance from us
New cards
7
if the expansion of universe is accelerating…
it will expand forever
New cards
8
why can’t we see past the cosmological horizon
because we are looking back to a time before the universe had formed
New cards
9
dark energy
the yet unknown agent causing the universe’s expansion to accelerate
New cards
10
observations of white dwarf supernovae allow us to…
measure the distances of very distant galaxies
New cards
11
habitable zone of a star
the region around a star where liquid water can potentially exist on planetary (or moon) surfaces
New cards
12
if a radio message was sent out in 1974, it has gotten how far?
a very small fraction of the distance across the milky way
New cards
13
nuclear fusion and gravitational contraction (solar thermostat)
energy sources that can help a star maintain its internal thermal pressurenu
New cards
14
nuclear fusion
how the sun generates energynu
New cards
15
nuclear fusion of hydrogen into helium
how main-sequence stars generate energy
New cards
16
photosphere
layer of the sun that we normally see
New cards
17
location where they are born
characteristic that most determines how stars differ
New cards
18
planetary nebula
the expanding shell of gas that is no longer gravitationally bound to the remnant of a low-mass star
New cards
19
stars that are at least several times the mass of the sun
end their lives with supernovae
New cards
20
after supernova event
neutron star or black hole left behind
New cards
21
sunspots appear dark in pictures of the sun because
they are actually pretty bright but appear dark against the brighter background of the sun
New cards
22
ultimate fate of the sun
red giant, then planetary nebula leaving behind a white dwarf that will slowly cool with time
New cards
23
protostar, main-sequence star, red giant, white dwarf
stages of life for a low-mass star
New cards
24
evidence that black holes exist
gravitational interaction with other objects
New cards
25
we can study how galaxies evolve because
the farther away we look, the further back in time we see
New cards
26
halo, bulge, spiral arms
disk components of a spiral galaxy
New cards
27
the stars in the spiral arms of the galactic disk
make up most of the mass of the milky way galaxy
New cards
28
dark matter is probably made of
exotic material
New cards
29
observable universe is
same size today as it was a few billion years ago
New cards
30
apparent brightness = luminosity / 4πr^2
luminosity-distance equation
New cards
31
cepheid variable importance for measuring distance b/c
their luminosity can be inferred from their period
New cards
32
our solary system location within milky way galaxy
in the galactic disk roughly halfway from the galactic center to the outskirts of the galactic disk
New cards
33
milky way galaxy
a spiral galaxy with a disk about 100,000 light-years in diameter and containing between 100 billion and 1 trillion stars
New cards
34
why is dark matter “dark”
emits no or very little radiation of any wavelength
New cards
35
dark matter can be detected by
gravitational effects such as rotation curves and ‘lensing’
New cards
36
angular size of venus looks largest when
its phase is full
New cards
37
when electron in an atom jumps from a higher energy level to a lower energy level, it
emits a photon of a specific frequency
New cards
38
all planets orbit the sun at the same speed
false, a rotation curve for central mass in our star
New cards
39
inner planets made of denser materials than outer planets because
the sun’s gravity pulled denser materials toward the inner part of the solar nebula, while lighter gases escaped more easily
New cards
40
convection cells in the mantle
drive the motion of the continental plates on earth
New cards
41
radioactivity
most important internal energy source continuing to heat the terrestrial planets today
New cards
42
Of the four gases CO2, H2O, N2, and O2, which are greenhouse gases?
CO2 and H2O
New cards
43
most moons always show the same face to their planet because
its caused by tidal locking, a natural consequence of tidal forces acting on the moons.
New cards
44
ecliptic on the celestial sphere
the sun's apparent path during the year
New cards
45
asteroids (asteroid belt) and comets (kuiper belt and oort cloud)
planetesimals that never accreted to form a planet. their total mass is not as large as that of a small terrestrial planet.
Studied by 22 people
Note 
Flashcard (46)