phys 202 final review

cosmos

the sum total of all matter and every, everything within and between all galaxies

big bang

the events that marked the beginning of the expansion of the universe

universe expanding

average distances are increasing between galaxies

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

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

hubble’s law

the recession velocity of a galaxy is direction proportional to its distance from us

if the expansion of universe is accelerating…

it will expand forever

why can’t we see past the cosmological horizon

because we are looking back to a time before the universe had formed

dark energy

the yet unknown agent causing the universe’s expansion to accelerate

observations of white dwarf supernovae allow us to…

measure the distances of very distant galaxies

habitable zone of a star

the region around a star where liquid water can potentially exist on planetary (or moon) surfaces

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

nuclear fusion and gravitational contraction (solar thermostat)

energy sources that can help a star maintain its internal thermal pressurenu

nuclear fusion

how the sun generates energynu

nuclear fusion of hydrogen into helium

how main-sequence stars generate energy

photosphere

layer of the sun that we normally see

location where they are born

characteristic that most determines how stars differ

planetary nebula

the expanding shell of gas that is no longer gravitationally bound to the remnant of a low-mass star

stars that are at least several times the mass of the sun

end their lives with supernovae

after supernova event

neutron star or black hole left behind

sunspots appear dark in pictures of the sun because

they are actually pretty bright but appear dark against the brighter background of the sun

ultimate fate of the sun

red giant, then planetary nebula leaving behind a white dwarf that will slowly cool with time

protostar, main-sequence star, red giant, white dwarf

stages of life for a low-mass star

evidence that black holes exist

gravitational interaction with other objects

we can study how galaxies evolve because

the farther away we look, the further back in time we see

halo, bulge, spiral arms

disk components of a spiral galaxy

the stars in the spiral arms of the galactic disk

make up most of the mass of the milky way galaxy

dark matter is probably made of

exotic material

observable universe is

same size today as it was a few billion years ago

apparent brightness = luminosity / 4πr^2

luminosity-distance equation

cepheid variable importance for measuring distance b/c

their luminosity can be inferred from their period

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

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

why is dark matter “dark”

emits no or very little radiation of any wavelength

dark matter can be detected by

gravitational effects such as rotation curves and ‘lensing’

angular size of venus looks largest when

its phase is full

when electron in an atom jumps from a higher energy level to a lower energy level, it

emits a photon of a specific frequency

all planets orbit the sun at the same speed

false, a rotation curve for central mass in our star

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

convection cells in the mantle

drive the motion of the continental plates on earth

radioactivity

most important internal energy source continuing to heat the terrestrial planets today

Of the four gases CO2, H2O, N2, and O2, which are greenhouse gases?

CO2 and H2O

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.

ecliptic on the celestial sphere

the sun's apparent path during the year

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.