phys 202 final review

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cosmos

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i need to get a 125% on the final

45 Terms

1

cosmos

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

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2

big bang

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

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3

universe expanding

average distances are increasing between galaxies

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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

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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

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6

hubble’s law

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

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7

if the expansion of universe is accelerating…

it will expand forever

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8

why can’t we see past the cosmological horizon

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

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9

dark energy

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

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10

observations of white dwarf supernovae allow us to…

measure the distances of very distant galaxies

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11

habitable zone of a star

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

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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

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13

nuclear fusion and gravitational contraction (solar thermostat)

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

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14

nuclear fusion

how the sun generates energynu

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15

nuclear fusion of hydrogen into helium

how main-sequence stars generate energy

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16

photosphere

layer of the sun that we normally see

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17

location where they are born

characteristic that most determines how stars differ

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18

planetary nebula

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

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19

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

end their lives with supernovae

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20

after supernova event

neutron star or black hole left behind

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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

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22

ultimate fate of the sun

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

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23

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

stages of life for a low-mass star

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24

evidence that black holes exist

gravitational interaction with other objects

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25

we can study how galaxies evolve because

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

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26

halo, bulge, spiral arms

disk components of a spiral galaxy

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27

the stars in the spiral arms of the galactic disk

make up most of the mass of the milky way galaxy

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28

dark matter is probably made of

exotic material

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29

observable universe is

same size today as it was a few billion years ago

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30

apparent brightness = luminosity / 4πr^2

luminosity-distance equation

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31

cepheid variable importance for measuring distance b/c

their luminosity can be inferred from their period

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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

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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

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34

why is dark matter “dark”

emits no or very little radiation of any wavelength

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35

dark matter can be detected by

gravitational effects such as rotation curves and ‘lensing’

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36

angular size of venus looks largest when

its phase is full

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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

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38

all planets orbit the sun at the same speed

false, a rotation curve for central mass in our star

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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

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40

convection cells in the mantle

drive the motion of the continental plates on earth

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41

radioactivity

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

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42

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

CO2 and H2O

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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.

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44

ecliptic on the celestial sphere

the sun's apparent path during the year

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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.

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