Chapter 12:Dwarf Planets

and Small Solar System

Bodies

Pluto: distant ice world that was once a planet

Pluto was discovered by Clyde Tombaugh in 1930

Percival Lowell made calculations on the orbit of Neptune and predicted a 9th planet. His calculations were based on flawed data, there is no 9th planet.

Pluto’s moon Charon was discovered by James

Christy in 1978

Pluto and Charon are tidally locked on each

otherJust as we only see one side of our moon from Earth, Pluto only sees one side of Charon. Since Pluto is also tidally locked, Charon also only sees one side of Pluto.

Four more moons have been discovered around Pluto

Pluto, Charon, Nix and Hydra are not very large

Pluto Has An

Atmosphere!

The New Horizons mission is on its way to Pluto. It

will fly by in 2015

Eris is the reason Pluto isn’t a planet anymore

There are a number of “large” Kuiper Belt Objects

There are now 5 Dwarf Planets

Ceres has been promoted from asteroid to dwarf planet

Ceres was called a planet when it was discovered in 1801 but it was later demoted

when we started to find lots of other objects in the asteroid belt

The Debris of the Solar System

Asteroids and comets are leftover planetesimals. We don’t see the icy

planetesimals until the fall in to the inner part of the system solar

When a piece of an asteroid comes close to Earth it may

become a meteor

Meteoroids, Meteors and Meteorites

NEO 1994 XM1 Leonid Meteor Shower

Big rocks DO fall from the sky!

Fortunately for us, they don’t do it too

often

A bad day for the dinosaurs

The impact released trillions of tons of CO2 into the

atmosphere

The crater is buried several hundred meters under the surface and is over 200 km in diameter

Fortunately, most impacts are small

The Peekskill meteorite fell in 1992 and hit an 1980 Chevy Malibu. Insurance wouldn’t pay for the damage but she got $10k for the car and $69k for the meteorite from a collector.

Meteorites are classified as Stones, Irons or Stony-

irons

The most common meteorite, stones look like ordinary rocks with burnt

crust

The most common “find” is an iron meteorite

Widmanstätten Patterns are iron crystals that take millions of years to form

The iron has to cool from the molten state at no more than a few degrees every

million years to form these crystal patterns

Stony-Irons are intermediate between

stones and irons

Carbonaceous chondrites are from the earliest age of the solar

system

They show the original condensation grains from the solar nebula period when they formed

The different types of meteorites implies different

types of parent asteroids

Some asteroids have a lot of carbon materials. These are known as C-type

asteroids

S-type and M-type asteroids are from differentiated

bodies

To form S-type and M-type asteroids a larger body must

be smashed to pieces

Most (but not all)

asteroids orbit

between Mars & Jupiter

The Apollo, Aten and Amor asteroids cross Earth’s

orbit

Most asteroids are small and

irregular shaped

Asteroids tumble

Most have rotational periods of 9 to 10 hours

Some asteroids are piles of debris

253 Mathilde

We have landed on one asteroid: Eros

Comets are the debris of the Outer Solar System

Many comets come from the Kuiper Belt

The Kuiper Belt is a thick donut shaped region extending from about 30 AU out to 50 AU. Pluto

and Eris are the largest known Kuiper Belt objects

Some comets come from the Oort Cloud

The Oort Cloud may extend out to a lightyear (50,000 AU) from the Sun

When a comet approaches the inner solar system the

ice evaporates

The gas and flaked

off dust form a

coma and tail

A comets tail always

points away from the

SunThere are two tails: a dust tail that trails behind some and an ion tail that always points directly away from the Sun

Comet tails can be millions of kilometers long

The tail can break off due to “gusts” in the solar

wind

Comet orbits are tilted from the

ecliptic and very

eccentric

What happens to comets?

Comets “die” in one of three ways

1: They fall in to the Sun

They don’t have to actually fall into the Sun, just get close enough to burn up

2: They collide with a planet or moon

Shoemaker-Levy 9 had a amazing collision with Jupiter in 1994

Will a comet ever hit us?

The highest rated object is rated a little below 1

We were probably hit

by a fragment of a comet in

1908The Tunguska event flattened over 800 square miles of forest in Siberia. It was probably an object about the size of a football field that exploded about five miles above the surface

3: They break-up and fizzle out

Meteor Showers come at regular times of the year

Meteor Shows are the result of Earth passing through a debris

trail left by a comet

Usually, meteor

showers are a few dozen

to a few hundred per

hour

On rare occasions there are meteor storms

The 1833 Leonid meteor

storm

Most of the stuff floating around out there is dust sized

Most of the dust is flaked off from comets and burns up in the atmosphere before reaching the ground

There is so much dust in the ecliptic we can see its glow

It’s called the Zodiacal Light because it lies along the ecliptic which is the line of the

zodiac