Lecture 15: The Solar System

Question 1

different types of bodies in solar system and where they’re located

Answer 1

planets
- mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
- spherical bodies orbiting the sun that dominate their neighbourhood of other bodies

dwarf planets
- pluto, ceres, eris, haumea, makemake
- spherical bodies orbiting the sun that don’t dominate their neighbourhoods

the sun
- closest star to the earth

asteroids

comets

kuiper belt objects

oort cloud

Question 2

how to determine age of solar system

Answer 2

given potassium(K) and argon(Ar) ratio and half life:

potassium-40 slowly decays via radioactive decay to argon-40:
- half life is 1.25 billion years

current argon-40 to potassium-40 ratio is 11.5 to 1:
- fraction that remains as potassium-40 is 1/12.5=0.08
- this gives an age of ~4.6 billion years

Question 3

the planets and their moons

Answer 3

most of the solar systems moons orbit in the same plane as planets and in the same direction

moons:
earth- 1
jupiter- 79
saturn- 62

Question 4

the orbit of planets

Answer 4

all planets orbit in the same direction

orbits lie close to the ecliptic, nearly coplanar

orbits are very nearly circular

orbital distances are regularly spaced

all planets rotate in the same direction (except venus and uranus)

planets, short period comets, and asteroids have an almost coplanar orbit, unlike long period comets that have orbits coming from all directions

Question 5

the 4 jovian planets

Answer 5

jupiter, saturn, uranus, neptune

all 4 jovian planets have ring systems

made of small particles, mainly water ice

Question 6

asteroids

Answer 6

irregular rocky bodies ~ a few km

<25m will not survive the atmosphere

> 1km will have global impact

most orbit the sun in the asteroid belt (region between mars and jupiter)

Question 7

the 2 types of comets

Answer 7

long-period and short-period

Question 8

what is a meteor shower?

Answer 8

occur when the earth passes through a comets orbit and they leave behind relatively large, pebble-sized particles

appear to originate from a single point in the sky due to earths motion

Question 9

comet tails

Answer 9

the temperature of a comet increases as it approaches the sun, causing gas and dust to be blown off, forming a long tail with this material

have two tails:
- a plasma (charged particle) tail due to being swept radially by the solar wind

• a dust (neutral) tail due to being pushed slowly out by sunlight/ radiation pressure

Question 10

kuiper belt

Answer 10

ring of material 30-100 AU from the sun

short period comets

e.g. pluto, eris, haumea

Question 11

oort cloud

Answer 11

cloud of material extending to about 50,000 AU from the sun

long period comets

may contain a trillion objects/ comets

Question 12

the planets and their satellites

Answer 12

all planets except mercury and venus have satellites

galileo discovered 4 of jupiters satellites:
- io
- europa
- ganymede
- callisto