Astro Exam 2 (5/8/23)

Question 1

motion of the planets

Answer 1

all planets in the solar system orbit in the same direction (counterclockwise) and nearly the same plane
- pluto’s orbit is not the same plane as the major planets

Question 2

rotations

Answer 2

most planets rotate in a counterclockwise direction
- Venus rotates in the opposite direction - clockwise

Question 3

tilts

Answer 3

venus and mercury have a tilt of almost 180° compared to other planets - perpendicular
Uranus - 90°

Question 4

terrestrial planets

Answer 4

inner planets:
- rock and metal, density is roughly the same
- mercury, venus, earth and mars

Question 5

jovian planets

Answer 5

outer planets:
- much larger in scale, made up of gas
- Jupiter, Saturn, Uranus, Neptune

Question 6

asteroids

Answer 6

asteroid belt - rocky band btw mars and jupiter
kuiper belt - beyond neptune’s orbit
oort cloud - edge of solar system

Question 7

meteor

Answer 7

hard to predict, very random
meteor showers - happen on the same days every year

Question 8

comets

Answer 8

Halley’s comet comes around every 76 years

Question 9

close encounter hypothesis

Answer 9

the planets formed from debris torn off from the sun by a close encounter with another star - but this doesn’t explain motions, types of planets and why the giant planets are further from the sun

Question 10

solar nebula theory: basic description

Answer 10

our solar system formed from the gravitational collapse of a giant interstellar gas cloud - the “solar nebula”
- start with a rotating cloud of gas
- contracts and flattens to become a thin disk of cloud and dust forming the sun at the center
- planets grow from gas and dust in the disk are left behind when the disk clear

Question 11

solar nebula theory: frost line

Answer 11

energy from the baby star that is forming warms up the surrounding area that is too hot from anything but rock and metal and outside the frost line its cool enough for the outer planets

Question 12

solar nebula theory: terrestrial -planetesimals

Answer 12

rock and metals that grew as the particles collided

Question 13

solar nebula theory: terrestiral- accretion

Answer 13

gravity eventually assembled these planetesimals into the terrestrial planets

Question 14

solar nebula theory: terrestiral - protoplanets

Answer 14

starts as uniform metals and rocks that gather together in a big ball but some are radioactive and heat up the inside of the planet and denser metals sink to the center = differentiation

Question 15

solar nebula theory: jovian planets

Answer 15

large icy planetesimals and protoplanets formed and the gravity of the large protoplanets was able to draw in surrounding hydrogen and helium gas resulting in large planets

Question 16

solar nebula theory: asteroids/comets

Answer 16

leftover pieces from the assertion process, inside the frost line = asteroids, outside the frost line = comets

Question 17

solar nebula theory: asteroid belt

Answer 17

protoplanets between mars and jupiter were forced apart by jupiter’s gravity

Question 18

solar nebula theory: moons

Answer 18

leftover planetesimals bombarded other objects in the late stages of solar system formation creating craters
earth’s moon:
- collision theory: grazed the earth and the metallic center of both objects made earth’s core denser and the rocky material flung out into space and became the moon

Question 19

conservation of angular momentum

Answer 19

rotation speed of the cloud from which our solar system was formed must have increased as the cloud contracted
rotation of contracting cloud speeds up as it gets smaller

Question 20

disk flattening

Answer 20

collisions between gas particles in a cloud gradually reduce random motion - “up and down” vertical motions are reduced and they flatten into a disk shape as it shrinks

Question 21

Ussher: age of the earth

Answer 21

calculated the age of the earth by working backward through the bible and comparing it to known historically events
according to him the earth was created at 6pm on Sat, October 2, 4004 BCE

Question 22

pierre and marie curie

Answer 22

discovered radioactivity
radioactive dating gives an age of rocks on the earth of about 4 billion years
moon rocks and meteorites can be similarly dated using radioactive isotopes = age of the earth is 4.6 billion years

Question 23

radioactive decay

Answer 23

C₁₃ is unstable and overtime decays
half-life - a measure of how quickly an isotope will decay
after each and every half-life, the number of remaining radioactive nuclei is reduced by a factor of two

Question 24

cooling of planetary interiors - energy transport

Answer 24

Conduction - transfers heat from hot material to cool material
Convection - transports heat as hot material rises and cool material falls
Radiation - sends energy into space in the form of light

Question 25

planetary magnetic fields

Answer 25

molten, electrically conducing interior convection "moderately rapid motion"

Question 26

processes that shape surfaces

Answer 26

impact cratering - asteroids or comets volcanism - eruption of molten rock onto surface tectonics - disruption of a planet's surface by internal stresses (convection) erosion - surface changes made by wind, water or ice

Question 27

moon

Answer 27

lava part of the moon has fewer craters because its younger than the cratered highland part created during the heavy bombardment period

Question 28

Mercury: surface

Answer 28

surface of mercury looks like Earth's moon a little bigger than the moon “Caloris Basin” - large collision on one side of Mercury “Weird terrain” - created by the collision that made the Caloris Basin that pushed the surface of Mercury to form wrinkles Small planets are affected the most by impact cratering because they have little atmosphere and no volcanism

Question 29

Mercury: days

Answer 29

Sidereal day (one rotation) - 59 Earth days Solar day - 176 earth days Mercurial year - 88 earth days

Question 30

Mercury: magnetic field and tilt

Answer 30

Metallic core, convection, “moderate” rotation is slow - weak magnetic field Mercury doesn’t have seasons because it has a very small tilt

Question 31

Venus: surface

Answer 31

Covered in clouds A little smaller than the Earth and similar surface gravity Looks so bright in our sky because the white clouds reflect a majority of the sunlight Very similar geological features as the earth Volcanoes - more than any planets, ~85,000 some are still active The most mountainous parts of Venus have no volcanoes The “miss piggy” Corona - in the plains to the south of Aphrodite Terra Pancake domes - wider than they are high, created by very thick lava that bubbles out onto the surface

Question 32

Venus: days

Answer 32

Sidereal day - 243 earth days Solar day - 117 earth days Venusian year - 225 earth days

Question 33

Venus: magnetic field and tilt

Answer 33

Doesn’t have a magnetic field and no seasons because tilt is almost 180 degrees Hotter than Mercury despite being farther from the sun - due to thick atmosphere Tilt from ecliptic - 177 degrees

Question 34

Mars: surface

Answer 34

Mostly rock than metal Halt the size of the earth and 40% of the earth’s gravity

Question 35

Mars: tilt and magnetic field

Answer 35

Tilt of 25.2 degrees with similar seasons as the earth Morning fog - water vapor Dried-up river deltas, used to be covered in water Melted salt water No magnetic field because its core is very small, and cooled off much farther than the Earth so there is no convection

Question 36

Mars: days

Answer 36

Sidereal and solar day - 24.6 hours, 1 “sol” Martian year - 1.88 earth days

Question 37

Moons of Mars

Answer 37

Phobos and Deimos Very small, and oddly shaped because they are too small Phobos: slowly spiraling towards Mars due to tidal forces an will crash in 50 million years Deimos: slowly spiraling away from Mars

Question 38

law of conservation of energy

Answer 38

energy in = energy out

Question 39

inverse square law of light

Answer 39

intensity of light increases as proximity to the light source decreases I = P/4πr² I = intensity P = power of light

Question 40

earth's atmosphere: light rays

Answer 40

x-rays and UV rays get absorbed before reaching the surface of the Earth visible and infrared light reaches the earth unimpeded

Question 41

earth's atmosphere: troposphere

Answer 41

- lowest layer - temp drops with altitude - warmed by infrared light from the surface and convection - where weather occurs - commercial airplanes fly - temp decreases with higher altitude because the density of the air is lower

Question 42

earth's atmosphere: troposphere - greenhouse effect

Answer 42

visible light comes in --> some is reflected by clouds and the surface --> infrared light bounces and stays trapped int he layers of the atmosphere

Question 43

earth's atmosphere: sky color

Answer 43

the sky is blue because the bluelight from the sun is scattered around the atmosphere scatter effect: based on the length of the colors so the longer wavelengths (red, orange, yellow and green) reach the earth but the blue and violet ones bounce around

Question 44

earth's atmosphere: stratosphere

Answer 44

- ozone layer - temp rises with altitude - warmed by absorption of UV sunlight

Question 45

earth's atmosphere: mesosphere

Answer 45

- heated by UV light but the temp decreases with altitude - meteors typically burn up in this layer

Question 46

earth's atmosphere: thermosphere and exosphere

Answer 46

- highest layers in which atmosphere gradually fades into space - space begins are 100 km above sea level = Von Kármán line - temp rises with altitude so fast-moving atoms can escape into space - atmosphere is heated and protially ionized by x-rays and UV light

Question 47

earth's atmosphere: magnetic field

Answer 47

- extends out beyond the atmosphere - deflects the path of charged particles - protects from solar wind - gaps in the magnetic field cause the solar particles to spiarl in and get drawn towards magnetic north and south = northern/southern lights

Question 48

creating an atmosphere

Answer 48

- mostly nitrogen, 1/5 oxygen, very little argon, water, and CO₂ - outgassing: water, carbon dioxide, nitrogen and sulfur compounds i) associated with volcanoes but planets can still have outgassing without volcanoes ii) as the planet cools off it releases all the vapor that was originally in the solar nebula - evaporation - surface liquids or ices - ejection from impacts

Question 49

decreasing an atmosphere

Answer 49

- condensation - chemical reactions - solar wind: nonreversible - thermal escape: nonreversible - high temp

Question 50

decreasing an atmosphere: thermal escape

Answer 50

thermal escape: nonreversible i) gravity of a planet determines how tightly the planet can hold onto its atmosphere ii) escape velocity is the speed at which you throw something up and it won't come back (earth =11.2 km/s) iii) the higher the mass the stronger the gravity and the harder it is for the atmosphere to escape

Question 51

mercurial atmosphere

Answer 51

doesn't have much of one because the escape velocity is high, has a weak magnetic field so its not well protected from the solar wind

Question 52

Venusian atmosphere (90 bar): basic description

Answer 52

has an atmosphere because despite it having super high temp, its mass is big enough to hold onto its atmosphere

Question 53

Venusian atmosphere (90 bar): composition

Answer 53

based on the light spectrum we can tell what elements are in it - mostly CO₂, little nitrogen, very little oxygen and water

Question 54

Venusian atmosphere (90 bar): layers

Answer 54

- sulfuric acid cloud layers: rains sulfuric acid on Venus but its so hot that it never reaches the surface - troposphere: 100km vs Earth's 10km - no ozone layer because there isn't enough oxygen on Venus i) if CO₂ contained in the Earth's crust were somehow released our atmosphere would become 98% CO₂ and pressure would increase by a factor of 70

Question 55

Martian atmosphere (0.006 bar): composition

Answer 55

- mostly CO₂, some nitrogen and argon, very little oxygen and water - much thinner compared to Earth or Venus because it has less gravity - too thin to retain the heat so the surface temp drops sharply at night

Question 56

Martian atmosphere (0.006 bar): layers

Answer 56

very little magnetic field because its smaller than earth and cooled off faster - not molten and its contains less iron - North Polar Cap: dry ice, freezes at a lower temp than water

Question 57

radioactive decay

Answer 57

major source of energy now

Question 58

atmospheric convection

Answer 58

when the ground is warmed by the sun causing the air above the hot ground which is less dense than cool air so it rises making a vacuum

Question 59

planetary sizes

Answer 59

- smaller worlds cool off faster and solidify quickly - larger worlds remains warm inside, promoting volcanism and tectonics - larger worlds also have more erosion because their higher gravity can retain an atmosphere

Question 60

surface area-to-volume ratio

Answer 60

- volume = 4/3πr³ - surface area = 4πr² - cooling time: volume/ surf. area = r/3 therefore larger radius planets cool more slowly

Question 61

surface area-to-volume ratio

Answer 61

- volume = 4/3πr³ - surface area = 4πr² - cooling time: volume/ surf. area = r/3 therefore larger radius planets cool more slowly

Question 62

interior structure of earth

Answer 62

- crust: lowest density, granite, basalt etc - mantle: moderate density, silicon, oxygen etc - inner: highest density, nickel and iron - outer cores: liquid metals - not all of the center of the earth is liquid because of the pressure - we know about the inside of the earth because of earthquakes

Question 63

types of waves

Answer 63

- pressure "P" waves: compress and stretch matter, changing the density of the material i) passes through liquids - shear "S" waves: shake matter side to side, material vibrates from side to side i) doesn't travel through gasses or liquids - the speeds of both types of waves depends on the properties of the matter that transmit them

Question 64

earthquakes and waves

Answer 64

by analyzing the kind of waves from earthquakes geologists can detect what is inside the core of the earth

Question 65

tidal lock

Answer 65

earth's gravity stretches the moon causing the long axis of the moon to always face us perigee - when the moon is closer to the earth apogee - when the moon is farther away from the earth

Question 66

formation of lunar Maria

Answer 66

1) early surface is covered with craters 2) large impact crater weakens crust 3) heat build-up allows lava to well up to surface 4) cooled lava is smoother and darker than the surroundings

Question 67

interior structure of the moon

Answer 67

very small liquid part in the center