Download The Solar System

Lecture 2:
The Solar System
Dr Michael Burton
GENS4001 X1
The Solar System
1
Overview
• Formation from collapse of cloud of gas and
dust 4.6 billion years ago.
• Collisions and cratering dominated for first
150 million years, leaving current planetary
system.
• Inventory: 1 star, 8+1 planets, moons,
asteroids, comets, solar wind.
• Terrestrial (rock)+ Jovian (gas) planets
GENS4001 X1
The Solar System
2
Our Star, the Sun
• Giant ball of plasma undergoing
thermonuclear fusion of hydrogen in centre!
• Photosphere (visible), chromosphere
(spicules & granules), corona (solar wind)
comprise the atmosphere.
• Sunspots, magnetic fields and convection,
causing plages, prominences & solar flares.
• Solar Model well understood (neutrinos?).
GENS4001 X1
The Solar System
3
Mercury
• Day is two years long (tidal resonance)!
• Cratered surface (impacts), covered by
some lava flows.
• Iron core and magnetic field.
• Atmosphere (Na) from outgassing of planet.
GENS4001 X1
The Solar System
4
Venus
• Dante’s Inferno: 500°C, 100 atmospheres
and sulphuric acid clouds!
• Runaway greenhouse hidden by cloud.
• Rolling hills, two continents and volcanoes.
• Crust periodically melts?!
• Slowly rotates backwards with no seasons.
GENS4001 X1
The Solar System
5
Earth / Moon
• Double planet system, tidally interacting.
• Plate Tectonics produces continents, oceans,
mountains & volcanoes.
• Iron rich core producing magnetic field.
• Supports life on land, oceans & atmosphere.
• Moon created via collision-ejection.
• Weathering erased asteroid impacts on
Earth but past history
still visible on Moon. 6
GENS4001 X1
The Solar System
Mars
• No canals, but ancient river channels!
• No plate tectonics, resulting in giant shield
volcanoes over hot spots, plus canyons.
• A few impact craters.
• Thin carbon dioxide atmosphere & red dust.
• Water must once have flowed.
• Could life have once existed?
• 2 moons are captured asteroids.
GENS4001 X1
The Solar System
7
Jupiter
•
•
•
•
•
•
•
The Giant of the planets (not a failed star).
Rapid, differential rotation.
Belts & Zones, methane & ammonia clouds.
Cyclones interface: Red Spot & white ovals.
Strong magnetic fields, huge aurorae.
Gas / Liquid Metallic H / Rocky Core.
Thin, transient dust ring - meteor impacts.
GENS4001 X1
The Solar System
8
Moons of Jupiter
•
•
•
•
•
16 Moons with 4 giants (Galilean satellites).
Io: Volcanic, molten through tidal heating.
Europa: Ice, tidal heating, life in oceans??
Ganymede: Rock & Ice, past tectonics.
Callisto: Rock, cratered terrain (impacts).
GENS4001 X1
The Solar System
9
Saturn
•
•
•
•
•
•
Lord of the Rings.
Gas giant, much like Jupiter.
Razor-thin rings of icy rocks (10 cm-10 m).
Gravitational resonance with moons.
At least 20 moons.
Titan with nitrogen & hydrocarbon
atmosphere, ethane oceans - life??
GENS4001 X1
The Solar System
10
Uranus
•
•
•
•
•
A bland gas giant.
Tipped over – exaggerated seasons!
Magnetic axis at 60° to rotation axis.
15 Moons, rings.
Miranda: almost shattered by collision.
GENS4001 X1
The Solar System
11
Neptune
• A blue gas-giant, similar to Uranus.
• Discovered through prediction from
discrepancy in motion of Uranus.
• Fastest winds in solar system (1700 km/hr)!
• 8 moons, rings.
• Triton captured - retrograde orbit. Extreme
cold (36K) but nitrogen geysers! Being
pulled into Neptune by tides!
GENS4001 X1
The Solar System
12
Pluto + Charon
•
•
•
•
Not really a planet - a double moon system.
Discovered by chance in 1930.
Now furthest from Sun (again, just!).
Rock & ice.
GENS4001 X1
The Solar System
13
Comets and Asteroids
•
•
•
•
Debris from formation of Solar System.
Asteroids: lumps of rock a few km in size.
Most in belt between Mars & Jupiter.
Comets: primordial balls of ices and rocks:
transient dirty snowballs.
• Highly elliptical orbits, from Kuiper Belt
(50-500AU) or Oort Cloud (to 50,000AU).
• Tails only when near Sun (vaporised ice),
blown out by the solar wind & sunlight.