Astronomy Test Two

Front 1

What are the major patterns of motion in our solar system?

Back 1

All planets orbit the Sun in the same direction and with nearly circular orbits in nearly the same plane. The Sun and most planets rotate in the same direction that they orbit. Most large moons orbit their planets in the same direction as well.

Front 2

What are the two major types of planets?

Back 2

The two major types of planets are the small, rocky terrestrial planets and the large, hydrogen-rich jovian planets.

Front 3

Where do we find asteroids and comets in our solar system?

Back 3

Most asteroids reside in the asteroid belt between Mars and Jupiter. Comets are found in two main regions: the Kuiper belt, which begins near the orbit of Neptune, and the much more distant Oort cloud.

Front 4

Where are a few important exceptions to these general rules?

Back 4

Uranus and Pluto rotate sideways compared to their orbits. Venus rotates "backward". Triton orbits Neptune backward from what we'd expect. Earth has a surprisingly large Moon

Front 5

How does the Sun influence the planets?

Back 5

Its gravity governs planetary orbits, its heat is the primary influence on planetary surfaces temperatures, it is the source of virtually all the visible light in our solar system, and high-energy particles from the Sun influence planetary atmospheres and magnetic fields.

Front 6

What do you find particularly interesting about each planet?

Back 6

Mercury has extreme days and nights, tall steep cliffs, and large iron content.
Venus has an extreme greenhouse effect.
Mars shows evidence of a past wet era.
Jupiter has a hydrogen and helium atmosphere and many moons.
Saturn has rings and a moon, Titan, that is larger than mercury.
Uranus and its moons make up a system tipped on its side compared to toehr planets.
Neptune's largest moon, Triton, has nitrogen "geysers" and a "backward" orbit.

Front 7

What are four major categories of spacecraft missions?

Back 7

flybys, orbiters, landers, probes, sample return missions

Front 8

What four charcteristics of our solar system must be explained by any formation theory?

Back 8

patterns of motions, differences between terrestrial and jovian planets, the presence of asteroids and comets, and exceptions to the rules.

Front 9

What is the basic idea behind the nebular theory?

Back 9

Our solar system formed from a giant cloud of gas and dust, with the Sun forming at the center of the cloud and the planets forming the spinning, flattened disk of material that orbited the young Sun.

Front 10

solar nebula

Back 10

the interstellar cloud from which our solar system was born

Front 11

how did gravitational collapse affect the solar nebula?

Back 11

the nebula heated up, spun fater, and flattened into a disk

Front 12

What produced the orderly motion we observe in the solar system today?

Back 12

The orderly motion of the solar system reflects the original motion of the spinning disk of the solar nebula. The plane of this disk became the plane in which the planets now orbit the Sun, and the direction of the disk's spin became the direction of the planetary orbits.

Front 13

What key fact explains why there are two types of planets?

Back 13

Nearer to the Sun the frost line, temperature were so high that only metal and rock could condense into solid particles. Beyond the frost line, cooler temperatures allowed hydrogen compounds to condense into solid particles of ice. Thus, the solid material beyond the frost line included abundant ice in addition to rock and metal.

Front 14

How did the terrestrial planets form?

Back 14

terrestrial planets formed inside the frost line from condensation of solid grains of metal and rock that accreted into planetesimals which grew into planets.

Front 15

How did the jovian planets form?

Back 15

Jovian planets formed beyond the frost line from condensation of solid grains of metal rock and lots of ice that accreted into icy planetesimals. The capture of hydrogen and helium gas by the largest icy planetesimals made "miniature solar nebulae." The jovian planets formed at the centers of those nebulae, while moons accreted from ice in the spinning disks.

Front 16

a planet must be

Back 16

a.) in orbit around sun (star)
b.) nearly round b/c of gravity
c.) has cleared out neighborhood around orbit

Front 17

dwarf planet

Back 17

not a moon, not cleared its neighborhood

Front 18

densities of planets

Back 18

average densities of planets are determined by planet radius, orbital period, and orbital semimajor axis of moon
D=M/(4/3)piR^3

Front 19

sun

Back 19

gravity regulates orbit of planets, heat determines temp of planets, provides practically all visible light in SS, high energy particles streaming out from sun influence planetary atmosphere and magnetic fields. 99.9 % of ss mass. converts 4 million tons of mass into energy each second

Front 20

mercury

Back 20

no atmosphere that would circulate heat, no greenhouse effect: long day: very hot and cold: big difference between night and day. made of metal and rock; large iron core

Front 21

venus

Back 21

extremely hot due to greenhouse effect of atmosphere. still has active geology.

Front 22

volcanism and tectonics on venus

Back 22

impact craters are evenly spread over venusian surface, which implies planet's entire surface is same age.
lack of weather: explained by
surface of venus is very hot, so it is too hot for liquid or ice to exit
and
venus rotates slowly and backward so little wind is generated

Front 23

how are asteroids and comets related to the planetesimals that formed the planets?

Back 23

Asteroids are leftover planetesimals of the inner solar system, and comets are leftovers of the outer solar system.

Front 24

heavy bombardment

Back 24

period early in ss's history during which planets were bomborded by many left-over planetesimals

Front 25

how do we explain the exceptions to the rules?

Back 25

collisions or close encounteres with leftover planetesimals can explain the exceptions

Front 26

how do we think our moon formed?

Back 26

A mars-size leftover planetesimal slammed into earth, blasting rock from earth's outer layers into orbit, where it reaccreted to form the Moon.

Front 27

how old is SS

Back 27

4.6 billion years old, an age we determine from radiometric dating of the oldest meteorites.

Front 28

radiometric dating

Back 28

looking for radioactive isotopes and their decay products within the rock. by comparing present-day amounts of an isotope and its decay product, we can determine how much of the isotope must have been present when teh rock solidified. we can then use the half-life of the isotope to determine how long it has been undergoing decay within the rock, which tells us the rock's age

Front 29

roche limit

Back 29

close to planets there is a region where tidal forces are so strong moon will be ripped apart and become rings

Front 30

mars

Back 30

cold, low-density atmosphere that provides essentially no greenhouse effect

Front 31

jupiter's moons

Back 31

io: active volcanoes all over, yellow because of sulfur compounds
europa: possible subsurface ocean
ganymede: largest moon in ss
callisto: large cratered "ice ball"

Front 32

saturn's rings

Back 32

made of countless small chucks of ice and rock, each orbiting saturn like a tiny moon. outer rings have longer period b/c of Kepler's laws

Front 33

nebular theory again

Back 33

solar system formed from giant cold cloud of gas and dust which collapsed into a smaller rotating disk. depends on 2 principles: gravity and conservation of angular momentum.

Front 34

nebular theory trois!

Back 34

ss formed out of protostellar cloud (cloud of gas from whcih our own ss formed) which collapses under its own gravity. we have observational evidence that is we observe stars in the process of forming today, and they are always found within interstellar cloud of gas. stars form from collapse of protostellar gas clouds.

Front 35

the gravitational collapse

Back 35

solar protostellar cloud was very cold, rotating slightly.
then the shock wave from a nearby supernova, maybe, may have made the cloud collapse under own gravity.
as radius decreased, it rotated faster, forming a disk (conservation of angular momentum)
as cloud fell onto protostar and disk, gravitational p.e. was converted to heat (conservation of energy)

Front 36

flattening of solar nebula

Back 36

as cloud collapses, clumps of gas collide and merge. their random velocities average out into cloud's direction of rotation. spinning nebula assumes shape of disk.

Front 37

orderly motions in the ss

Back 37

the sun formed in the very center of the nebula. planets formed in the rest of the disk. this explains that:
all planets lie along one plane, orbit in one direction (spin direction of disk), the sun rotates same direction, planets would tend to rotate this same direction, most moons orbit in this direction, and most planetary orbits are near circular (collisions in disk)

Front 38

condensation

Back 38

rocks collided and made ga; ices (h rick gas compounds) began to condense (i.e.solidify) out of the nebula...depending on temperature.
hydrogen compounds (ices) condensed beyond the frost line

Front 39

accretion

Back 39

small grains stick to one another via electromagnetic force until they are massive enough to attract via gravity to form planetesimals which will:
combine near the sun to form rocky planets
combine beyond frostline to form icy planetesimals which
capture H/He far from sun to form gas planets

Front 40

origin of asteroids

Back 40

something cleared leftover gas, but not leftover planetesimals. leftover rocky planestimals which did not accrete into a planet: inhabit the asteroid belt btwn Mars and Jupiter (Jupiter's gravity prevented a planet from forming there)

Front 41

heavy bombardment

Back 41

heavy bombardment is the first few hundred million years after the planets formed, which is when most impact craters were formed.
it explains why some moons oribt opposite their planets rotation (capture moons like triton)
why rotation axes of some planets are tilted (impacts knock them over, like Uranus)
why some planets rotate more quickly than others (impacts 'spin them up')
why earth is only terrestrial planet w/ large moon (giant impact)

Front 42

formation of moon

Back 42

earth was struck by a mars-sized planetesimal, part of earth's mantle was ejected, with coalesced in the moon. it orbits in same direction as earth rotates, it has lower density than earth, earth was "spun up", and moon is large relative to earth, in comparison w/ other terrestrial planets

Front 43

so, recipe for planets

Back 43

gravity+angular momentum--> make rotating disk
dust settles, coagulates--> make larger bodies
gravity make many "tiny planets"
planetesimals collide w/ each other b/c multi-body system is unstable, chaotic
slower growth--> make small (terrestrial planets)
faster growth plus gas --> make giant planets
outcomes are highly variable

Front 44

sun

Back 44

its gravity governs the orbits of the planets. its heat is the primary influence on planetary temperatures, and it is the source of virtually all the visible light in our ss--the moon and planets shine only by virtue of the sunlight they reflect. high-energy particles flowing outward from the sun (solar wind) help shape the magnetic fields of the planets and can influence planetary atmospheres.

Front 45

lithosphere

Back 45

outer layer of relatively rigid rock
encompasses the crust and part of the upper mantle
earth and venus have thin ones and mars mercury and moon include most or all of mantles

Front 46

how interiors get hot

Back 46

heat of accretion: heat generated at the time the planets accreted from planetesimals.
heat from differentiaation: heat generated at the time the planets differentiated into their core-mantle-crust structures.
heat from radioactive decay: heat generated as radioactive nuclei in the planetary interior undergo natural decay.

Front 47

convection

Back 47

process in which hot material expands and rises while cooler material contracts and falls.

Front 48

conduction

Back 48

the process by which thermal energy is transferred by direct contact from warm material to cooler material.

Front 49

three requirements for global magnetic field

Back 49

an interior region of electrically conducting fluid (liquid or gas) such as molten metal.
convection in that layer of fluid.
at least moderately rapid rotation.

Front 50

4 geological processes that affect planets surfaces

Back 50

impact cratering, volcanism, tectonics, and erosion

Front 51

impact cratering

Back 51

the blasting of bowl-shaped impact craters by asteroids or comets striking a planet's surface.

Front 52

volcanism

Back 52

the eruption of molten rock, or lava, from a planet's interior onto its surface.

Front 53

tectonics

Back 53

tthe disruption of a planet's surface by internal stresses

Front 54

erosion

Back 54

the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather

Front 55

requirements for erosion

Back 55

planetary size: a terrestrial world can have an atmosphere only if it has had significant outgassing (volcanism requires internal heat and therefore bigger planets). size determines strength of gravity, and atmospheric gases are more easily lost to space on worlds with weaker gravity.
distance from sun: affects whether gas can remain in atmosphere. higher temperatures on a world closer to the sun will make it easier for atmospheric gases to escape. colder temperatures on a world farther from the sun may cause atmospheric gases to freeze out.
rotation rate: faster rotation mean stronger winds and storm.

Front 56

why is earth the only terrestrial world with a strong magnetic field?

Back 56

a planetary magnetic field requires three things: an interior layer of electrically conducting fluid, convection of that fluid, and rapid rotation.

Front 57

how are the geological processes connected to fundamental planetary properties?

Back 57

impacts affect all planets similarly, but larger planets are more likely to have their impact craters erased by other geological processes. volcanism and tectonics require interior heat, which is retained only by larger planets. erosion can occur only on planets with substantial atmospheres. this requires large size to allow outgassing to make an atmosphere, moderate distance from the sun to prevent the gas from escaping or freezing, and wind or rain. wind can occur only with moderately fast rotation.

Front 58

coriolis effect

Back 58

moving objects veer right on a surface rotating counterclockwise, moving objects veer left on a surface rotating clockwise

Front 59

four major facts which affect long-term climate

Back 59

reflectivity: cloudiness (smog, dust) will reflect light away from earth to cool us off
tilt: greater tilt makes more extreme seasons, smaller tilt keeps polar regions colder and darker
sunlight: sun is getting slowly brighter with time, brighter sunlight increases planetary surface temperatures.
greenhouse gases: an increasure in gases will warm the planet

Front 60

sources of atmospheric gas

Back 60

outgassing: release of gas trapped in interior rock by volcanism.
evaporation/sublimation: surface liquids or ices turn to gas when heated.
bombardment: micrometeorites, solar wind particles, or high-energy photons blast atoms/molecules out of surface rock.

Front 61

ways to lose atmospheric gas

Back 61

condensation: gas turns into liquids or ices on the surface when cooled. (mars used to be warmer as it got colder co2 froze, lost atmosphere.
chemical reactions: gas is bound into surface rocks or liquids
stripping: gas is knowcked out of the upper atmosphere by solar wind particles
impacts: a comet/asteroid collision with a planet can blast atmospheric gas into space.
thermal escape: lightweight gas molecules are lost to space when they achieve escape velocity.
las three permanent top two part of a cycle

Front 62

greenhouse effect

Back 62

planetary warming caused by the absorption of infrared light from a planet's surface by greenhouse gases such as carbon dioxide, methane, and water vapor