Welcome to the Solar System
A Celestial Alignment
Why do they line up?
Image from: ganymede.nmsu.edu/tharriso/ast110/class05.html
Moons also orbit in the same plane
Jupiters equitorial bands show the eliptic (tilt = 0)
Image: http://www.jb.man.ac.uk/astronomy/nightsky/Jupiterjuly10.jpg
Orbits in the Ecliptic
This also includes ring systems!
The Solar Disk
• Seen from a 100 AU
• Solar system is a dusty disk
The Layout of the Solar System• Large bodies in the
Solar System have orderly motions– planets orbit
counterclockwise in same plane
– orbits are almost circular
– the Sun and most planets rotate counterclockwise
– most moons orbit counterclockwise
The Layout of the Solar System
• Planets fall into two main categories– Terrestrial (i.e. Earth-like)
– Jovian (i.e. Jupiter-like or gaseous)
Mars Neptune
Terrestrial Jovian
Mars and Neptune to Scale
The Layout of the Solar System
• Swarms of asteroids and comets populate the Solar System
Comets are found in two main Zones:
The Kuiper Belt
The Oort Cloud
The Oort cloud goes from 5000 to 50,000 AU or further!
When Comets are disturbed from their orbits..
• They end up in eliptical orbits..• Encounters with Jovian Planets speed them
up or slow them down…• The Oort Cloud is the “shell” of slow
moving comets at aphelion• Speeds at aphelion might be a few cm/sec! • If and when they approach the Sun, the
move much faster!
They Also Grow Tails…
Image from APOD (credit and copyright Jimmy Westlake)
Not everything fits perfectly
• The line between planet and comet is not clear!
• Pluto, Quoar, Viruna, Xenia, and Sedna are all Kuiper Belt objects (KBO’s)
• Or the Solar system has at least 13 planets…or 8 major planets and 5 + minor planets!
Check out: http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html Artists conception of Xenia and the Solar
System…100AU from Sun. Note the 44
degree tilt of orbit.
Quoar’s Orbit
Meet some new family members
How out does the solar system go?
A Few (more) Exceptions to the Rules…
• Both Uranus & Pluto are tilted on their sides.• Venus rotates “backwards” (i.e. clockwise).• Triton orbits Neptune “backwards.” • Earth is the only terrestrial planet with a
relatively large moon.• Density decreases from Mercury outward,
but Earth is more dense than any other planet!
A Brief Tour of the Solar System -- Motions
What is density?
density = mass/volume
typical units: [ g/cm3]
Density of water is defined as 1 g/cm3.
Density of typical Metal is 10 g/cm3
A Brief Tour of the Solar System – Composition
A Brief Tour of the Solar System – Summary
Spacecraft Missions--categories
1. Flyby – spacecraft “flies by” a world just once
2. Orbiter – spacecraft orbits the world it studies– longer-term study is allowed
3. Lander/Probe – spacecraft lands on the surface of the world or plunges through its atmosphere
4. Sample Return – spacecraft returns to Earth with a sample of the world it has studied
These types of mission are listed in order of increasing cost.
Missions to Other Worlds
Upcoming missions:
Deep Impact:
Crashed into comet Temple 1 July 4 2005
Mars Reconnaissance Orbiter: Low orbit..one meter surface resolution! Launched Aug
12..Arives Nov 06.
New Horizons: Orbiter to Pluto/Charon leave 2006 – arrive 2020!
Highlights of coming attractions• Mercury’s extreme days and nights, tall steep cliffs, and large
iron content
• Venus’s extreme greenhouse effect
• Earth as an oasis of life
• Evidence on Mars for a past, wet era
• Jupiter’s hydrogen and helium atmosphere and its many moons
• Saturn’s rings and its moon Titan, which is larger than Mercury
• Uranus and its moons: a system tipped on its side compared to the other planets
• Neptune’s largest moon, Triton, with nitrogen “geysers” and a “backward orbit”
• Pluto as a member of the family of Minor Planets!