Transcript Chapter 12

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 other
Just 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 XM
1
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 Sun
There 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
1908
The 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