Unit 2 - Planets

Question 1

What are Kepler’s laws?

Answer 1

1) planets have elliptical orbits around suns
2) planets must travel faster when closer to the sun
3) r^3 is directly proportional to T^2

Question 2

Define escape velocity

Answer 2

the minimum velocity required to escape a gravitational field

Question 3

What is the relationship between escape velocity and a planet’s ability to retain its atmosphere?

Answer 3

hotter temperatures means gas molecules travel faster, if this is faster than the escape velocity the atmosphere will escape

Question 4

What is the nebular theory?

Answer 4

the sun and planets all had a common origin - formed from a huge cloud of interstellar gas and dust

Question 5

What does the nebular theory provide evidence for?

Answer 5

1) all planets lie one on plane
2) the sun rotates in the same direction and most moons orbit this same way
3) most planetary orbits are near circular
4) all planets orbit in one direction and rotate in this direction

Question 6

What is accretion?

Answer 6

the formation of planetesimals

Question 7

Explain accretion

Answer 7

collisions between small pieces of material results in some sticking together, snowball effect causes them to increase in size and mass, increased mass means increased gravitational forces

Question 8

Describe the composition of terrestrial planets

Answer 8

consist largely of metals and silicates since they are close to sun and only heavier elements condense here

Question 9

Describe the characteristics of terrestrial planets

Answer 9

small core, small volume and high density

Question 10

Describe the composition of jovian planets

Answer 10

planetesimals formed from collisions of ice, core becomes massive enough to exert a strong enough gravitational pull to trap H and He to form a large gas atmosphere

Question 11

Describe the characteristics of jovian planets

Answer 11

much larger than terrestrial planets since more ice available then metals/silicates, large volume, low density gaseous outer atmosphere and high density icy core

Question 12

Describe the characteristics of Mercury

Answer 12

small radius, low mass, cratered surface due to meteorites and long folds in the surface thought to be wrinkles in the crust formed as it cooled and shrank, suggests Mercury hasn’t been active for a long time

Question 13

What are the effects of Mercury low gravitational field strength?

Answer 13

1) low escape velocity so no atmosphere, heat escapes quickly
2) no moons

Question 14

Describe the characteristics of Venus

Answer 14

similar size and mass to Earth, extremely hot surface temperature, high winds, high pressure, few craters on surface and many volcanoes

Question 15

Why does Venus have such a high surface temperature?

Answer 15

extreme greenhouse effect - the high temperature due to being close to the sun meant gases in the atmosphere couldn’t condense to form oceans

Question 16

Describe the composition of the Earth

Answer 16

core (inner and outer) made up of iron and nickel, thick mantle made of silicates and the thin crust

Question 17

What are the 3 factors which protect life on Earth?

Answer 17

1) liquid water ocean
2) ozone layer

Question 18

What are the 4 main stages of evolution of the Earth?

Answer 18

1) differentiation of layers
2) bombardment of the crust by meteorites
3) flooding of lava, then liquid oceans
4) surface evolution due to air, water and plate tectonics

Question 19

What is unusual about the Moon and how is it thought to have formed?

Answer 19

it is Earth’s only natural satellite and has a large diameter (1/4 De) compared to moons of other planets
formed due to a collision on the young Earth

Question 20

Describe the characteristics of Mars

Answer 20

reddish appearance due to iron oxide dust, thin atmosphere since small gravitational strength

Question 21

What is apparent retrograde motion?

Answer 21

when the motion of a planet appears to reverse due to Earth’s orbit being inside that of the other planet and since Earth travels faster it ‘overtakes’ - happens every 2 years with Mars

Question 22

What evidence is there for water and life on Mars?

Answer 22

water - hematite has been discovered on the surface and there is still water stored under the ice
life - studies of a meteorite from Mars shows fossilised carbonate globules

Question 23

Why are Mars’ 2 moons irregularly shaped?

Answer 23

thought to be asteroids captured by the gravitational pull of Mars
due to small mass don’t have a large enough gravitational strength to squeeze them into spheres

Question 24

Describe the composition of Jupiter

Answer 24

composed of mainly hydrogen and helium
intense magnetic field thought to arise from electrical currents in the rapidly spinning metallic hydrogen interior

Question 25

Describe Jupiter's rotation

Answer 25

differential rotation - rotates faster at equator than poles rapid rotation has caused the planet to oblate (flattened perpendicular to spin)

Question 26

What are the zones and belts on Jupiters?

Answer 26

zones - rising currents of gas belts - falling currents of gas

Question 27

Explain why Jupiter is hotter than it should be according to the laws of black body radiation

Answer 27

due to gravitational contraction under its own gravitational forces atoms are accelerated to higher speeds resulting in increased temperature

Question 28

Describe Jupiter's moon Io

Answer 28

similar composition to terrestrial planets cracked and distorted surface due to strong tidal forces produced by the planet's gravitational pull causes volcanic

Question 29

Describe Jupiter's moon Europa

Answer 29

solid surface made of ice rather than silicates tidal forces produced by Jupiter crack the surface and allow liquid to escape, this freezes and forms ice ridges

Question 30

Describe the characteristics of Saturn

Answer 30

low density and shows differential rotation like Jupiter

Question 31

Describe the composition of Saturn

Answer 31

made mostly of H and He with a dense core of metals like iron and nickle

Question 32

What are Saturn's rings made of and how are thought to have formed?

Answer 32

small chunks of rock and ice remnants of a an old moon, fragments are then stretched out to form rings due to Kepler's laws

Question 33

Describe Saturn's moon Titan

Answer 33

thick atmosphere with a similar pressure to Earth and similar physical features to Earth but methane instead of water

Question 34

Describe Saturn's moon Enceladus

Answer 34

extremely cold due to high reflectivity close vicinity to Saturn means tidal forces crack the surface and water is forced through the cracks

Question 35

Describe the composition and characteristics of Uranus

Answer 35

made of H, He and methane ring structure similar to Saturn blue-green appearance due to methane

Question 36

What makes Uranus different to all the other planets?

Answer 36

spins parallel to its orbit plane thought to be a result of a collision with a large object on the early solar system

Question 37

Describe the composition and characteristics of Neptune

Answer 37

similar composition to Uranus faint ring structure

Question 38

What is unusual about Neptune's largest moon Triton?

Answer 38

rotates about Neptune in the opposite direction to the planet's rotation thought to be a Pluto like object captured from the Kuiper Belt

Question 39

Describe the composition and characteristics of Pluto

Answer 39

rocky and icy composition, more like a comet rather than a jovian planet smooth surface suggests volcanic activity demoted to a dwarf planet since hundreds of other similar bodies were discovered in the Kuiper Belt

Question 40

How did the sun form?

Answer 40

centre of the interstellar cloud (mainly H) collapses and heats up until it becomes hot enough for nuclear fusion outward thermal pressure balances inward gravitational forces

Question 41

What is plasma?

Answer 41

a 'soup' of charged particles which conducts electricity since the nuclei and electrons are free to move

Question 42

What are sunspots and how do they form?

Answer 42

dark areas on the surface of the sun due to reduced temperature differential rotation causes plasma to become twisted and so too the magnetic field, when the field is tightly wound plasma loops form

Question 43

What are coronal loops or prominances?

Answer 43

large loops of plasma looping in and out of the surface of the Sun

Question 44

What are coronal mass ejections?

Answer 44

violent events which eject large amounts of material (plasma) into the outer solar atmosphere and beyond

Question 45

What are the negative effects of a CME that erupts in the direction of the Earth?

Answer 45

damage to satellites, danger to astronauts and causes electrical interference / blackouts over large areas on Earth

Question 46

What natural phenomenon is produced by solar wind?

Answer 46

aurora, the charged particles in the wind pass through the atmosphere and collide with O and N molecules, releasing light energy

Question 47

What are exoplanets?

Answer 47

planets outwith our solar system orbiting other stars

Question 48

What is the radial velocity method of detecting exoplanets?

Answer 48

monitoring the oscillating wavelength of light emitted by a star due to the Dopler Effect useful for finding large planets with short orbital periods

Question 49

What is the planetary transits method of detecting exoplanets?

Answer 49

observing the oscillating brightness of the light emitted by a star as a planet orbits around it also allows the study of the planet’s atmosphere using spectroscopy