Solar System Overview

FYI … Distance Not To Scale …

The Sun• At the Center (and we do go

around it …..)

• 99.85% mass of Solar System

• 92% H / 8% He

• Source of solar wind and space weather

Inner Planets

• “Terrestrial Planets”

• Rocky• Dense• Metal cores (iron)

Asteroids

• “Minor planets” or “planetoids” or “planetesimals” less than 1000 km across

• Asteroid Belt between Mars and Jupiter

• Occasionally run into Earth and other planets (oops)

Ida

Encountered on Aug 28th, 1993 by the Galileo Spacecraft, en route to Jupiter

Dactyl

Asteroids• Asteroids -> Meteoroid -> Meteor -> Meteorite

1000-10 km -> 10m-100 µm -> space rock trapped by gravity (burning up) -> space rock that actually hits the surface of a

planet

Meteoroid fragment discovered in Argentina; on display at the Museum of Nature, Ottawa, Canada

Barringer Crater (Canyon Diablo)

1.2 kilometers wide170 m deep

~ 50 000 years ago

Used by NASA during the 1960’s to prepare for moon landing

Winslow , Arizona

Outer Planets

• Large!

• Gases and liquids

• No solid surface

• May have a small solid core

• Tumultuous atmospheres - rapid winds, large storms

• Rotate relatively quickly

Kuiper Belt

• Disk of debris at the edge of our Solar System

• Pluto is a KB Object (sorry!)

• Source of short-period comets

Oort Cloud

• A hypothesized sphere of comets surrounding the inner solar system and the kuiper belt

• ~50 000 AU from the Sun

• Helps in explaining the regularity of comets within the Solar System

Inner Planets!

• Smallest planet (0.4 Earth diam)

• Closest to Sun, moves around fastest (88 days)

• Surface -173 to 427 ºC

• ? Ice Caps – no tilt of axis so poles are cold

• No atmosphere

• Mariner 3 fly-bys in 1974 and 1975 – 40% of surface mapped

Mercury#1, Coffee Bean

What are these?How did they form?

Venus#2, Large Blueberry

• Nearly the same size as Earth (.95)

• Slowest rotation of any planet (243 days)

• Spins backwards

• Surface temp 377 to 487 C

• Cloud covered – radar observations

• Dry!• Very thick atmosphere mostly

CO2

• Surface pressure is 100 times higher than Earth’s

• Runaway greenhouse

Can see it in the night sky without a telescope!

Why is Venus hotter than Mercury?

Earth#3, Cherry

7900 mile (12756 km) diameter

23.5 degree axis tilt (seasons!)

Surface temps –73 to 48 C

Thick atmosphere, mild greenhouse effect

Liquid water – lots! - at surface

Can see it without a telescope!

Geologically active?

Core, mantle, crust

Magnetic field?

Who Cares About a Magnetic Field?

We do!

Aurora Borealis

Aurora Austrailus

6794 km diameter (4,220 miles) – about ½ of Earth’s

25 degree axis tilt (seasons!)

Rotates once every ~24 hours and orbits the Sun once every 687 days

Very cold -83 to -33 C (-117 to -27 F)

Thin atmosphere, 95% CO2, & 3% N

Iron Oxide covers its surface (RED)

Two small moons - Phobos (Fear) and Deimos (Terror)

Hosting 5 functioning spacecrafts: Mars Odyssey, Mars Express, Mars Reconaissance Orbiter, Mars Rover: Opportunity and Curiosity

Liquid water cannot exist on the surface of Mars due to low atmospheric pressure, except at the lowest elevations for short periods

Mars#4, Pea

Can see it in the night sky without a telescope!

North

South

The Gas Giants

• 89,000 miles (143,000 km) diameter – 11x Earth• 2x mass of all other planets combined (318 x Earth);

100 pounds on Earth = 254 on Jupiter• 90% H and 10% He (75/25% by mass) • Methane, water, ammonia, rock • Rocky core – liquid metallic hydrogen – electrical

conductor, generates magnetic field• Similar to Solar Nebula

Jupiter#5, Small Cantaloupe

• Cloud-tops average = -153°C = -244°F. • 10 hour rotation / 12 year orbit• Fly-bys: Pioneer 10, 11, Voyager 1, 2, Ulysses,

Cassini• Orbiter: Galileo – 8 years (recently “visited”

the planet), Probe

JupiterCan see it in the night sky without a telescope!

Giant Red Spot – at least 300 years old

3 x size of EarthWinds up to 400 km /

hr“Jr”

Storms on Jupiter

Why Doesn’t Jupiter Blow Up?

• 9x the size of Earth• 75% hydrogen and 25% helium • Water, methane, ammonia and "rock“• Rocky core• Winds up to 500 m / second• -290 F• Rings – 185,00 miles wide / /2 mi thick• Water ice in rings• 56 moons and counting• 11 hour rotation / 29 year orbit• Pioneer / Voyager Fly-by / Cassini/Huygens!

Saturn#6, Large Orange

HST image; 1999

False Color

Rather chilly in the rings

Red: -261 F Blue -333 F

Green -298 F

Dirty Snow

Turquoise= water iceRed = “dirty”

Titan!

Clues to Early Earth?

Earth

Titan

TitanClues to Early

Earth?

Average surface temperature –179C

Atmosphere of N (>90%), CH4, Ar

Hydrocarbon-rich rivers/seas (ethane – C2H6)

Water ice

Atmosphere 1.5 x Earth

Uranus# 7, Kiwi

First planet discovered with a telescope!

Uranus• 4x the size of Earth• 15% H, little helium – mostly ices• Uniform through out; no rocky core• Blue from methane absorption of red light (atmosphere) atmosphere has mostly hydrogen and helium• 11 rings, 27 satellites• -350 F at surface• 18 hour rotation, 84 year orbit• Spins on an axis inclined almost 90 degrees• Voyager fly-by

Neptune#8, Apricot or nectarine

Neptune• Ices and rock - 15% H and little He• H, He, methane atmosphere (blue!)• Uniform through out; small rocky

core?• Had storm “Great Dark Spot” MIA

since Voyager 2• Pretty Good White Spot (Scooter)

zipped around every 16 hours….• 4 Rings – unknown composition• 13 moons• 18 hour rotation / 165 year orbit• Voyager (1989)

PlutoGrain of Rice

Pluto • Diameter - 1,413 miles (2274 km) - 2/3 size of Earth’s Moon

• Rotation: 6 1/3 days• Orbit: 248 years highly elliptical• Sometimes is inside Neptune’s orbit (20 yrs)• Light from Sun takes 5.5 hours to reach it• Surface of water and methane ice, frozen

nitrogen• When closer to the Sun, heat produces an

atmosphere

Is Pluto a Planet?

• Orbits a star• Round• Not a star or a moon• “Cleared Out”/ “Dominates” its orbit

What Makes a Planet a Planet?

Is Pluto a Planet?

Yes No

It has always been considered a planet

Very smallVery elliptical orbitOut of plane of eclipticSame material as Kuiper belt objectsFound other “non-planets” that were larger

August 24th, 2006

New Horizons:Pluto-Kuiper Belt Mission

• January 2006 Launch!• July 2015 – Pluto!• 2016-2020 – Kuiper Belt

Comets

• Dirty snowballs - small objects of ice, gas, dust, tiny traces of organic material

Comet Parts

Nucleus, ComaDust tail – white, “smoke,” reflects sun. 600,000 to 6 million miles longIon tail – Solar UV breaks down CO gas, making them glow blue. 10’s of millions of miles

Hale-Bopp Comet

First seen on July 23rd, 1995

• Read section 28.3• Q: 2, 3

• Read section 28.4• Q: 2, 3, 4, 5