Post on 28-Dec-2015
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