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Chapter 4: The Solar System
Comets
Comets are described as “dirty” snowballs
They are fragile conglomeration of frozen ices and dust
When they get close to the sun the ices begin to melt and jets of
gasses escape from the nucleus caring dust with it.
Comets shine by reflected solar light
Finally comets are divided into two large classes of short-term
and long term
Chapter 4: The Solar System
While the nucleus of a comet may be only a few km in size
The coma can be over 100,000 km in size
and the tail can be up to 1 AU in size
Chapter 4: The Solar System
Comets usually form two
different tails: gas and dust
The gas tail points directly away
from the Sun while the dust tail
tends to follow along the orbit
Chapter 4: The Solar System
Halley’s comet was the first comet discovered to be periodic.
Chapter 4: The Solar System
While the Kuiper belt may be the source of short period comets,
while the Oort cloud appears to be the source of long-period
comets.
Chapter 4: The Solar System
Meteoroids
There are two basic types of meteoroids: random, shower
The random kind which can be observed on any clear night
(few per hour) are probably left over interplanetary debris.
Chapter 4: The Solar System
Comets leave a dusty trail behind them
and if their orbits intercept the Earth’s
then me get meteor showers (dozens
per hour) when the Earth slams into
them.
Meteors enter the Earth’s atmosphere
at such high speeds that friction heats
them to white-hot temperatures and
they burn up.
Most meteors are the size of gravel
and burn up in the atmosphere. It
takes a first sized object to reach the
ground.
Chapter 4: The Solar System
Chapter 4: The Solar System
Some do hit the ground
Chapter 4: The Solar System
Two basic types of meteorites a) stony, b) iron
Chapter 4: The Solar System
The formation process
The solar nebular began to contract.
Due to conservation of angular
momentum the cloud begins to
flatten.
The central condensation condenses
faster than the rest and eventually
reaches densities and temperatures
high enough to form a star.
Chapter 4: The Solar System
We can see disks of material around other stars.
Chapter 4: The Solar System
As the nebula continues to contract
smaller clumps begin to grow by
accumulation and accretion to form
the planets.
Chapter 4: The Solar System
Because the planets form at different
distances from the sun (and thus
different temperatures) the planets
are made out of different materials.
The hot temperatures of the inner
solar system prevented planets from
collecting lighter gasses. So the
inner planets are made of denser
materials (iron and rock) while the
outer planets retained mostly
hydrogen and helium gases and ices.
Chapter 4: The Solar System
Finally, when the star is “born” it develops a “wind”
that blows away most of the remaining dust to give
us a “clean” solar system.