Louis Lackey
Day 7 Notes
Chapter 6 is about the formation of
planetary systems.
Section 6.1 is about a tour of our
solar system.
The solar system exhibits clear
patterns of composition and motion.
The small rocky planets are the
terrestrial planets, large, hydrogen rich planets are the Jovian
planets. There are swarms of asteroids and comets in the solar
system, concentrated in three regions. Uranus has a unusual axis
tilt, Venus rotates clockwise (backwards), and the earth has a
unusually large moon. The planets are very tiny compared to the
distances between them.
The sun is over 99.8% of the solar
system's mass. It is made mostly of H/He gas. The Sun converts 4
million tons of mass into energy each second.
Mercury is made of metal and rock,
with a large iron core. It is very hot and very cold at day and
night.
Venus is nearly identical in size to
earth, with the surface hidden by clouds. Venus is extremely hot and
high pressure because of the greenhouse effect. It is even hotter
than mercury.
Earth is an oasis of life. It has the
only surface liquid water in the solar system. It has a surprisingly
large moon.
Mars looks earth-like but is
inhabitable. It has volcanoes and polar caps. Water flowed on mars in
the past and may have supported life.
Jupiter is much farther away from the
sun. It is mostly H/He and has no solid surface. It is 300 times more
massive than earth, with many moons
Jupiter's moons are notable,
especially the Galilean moons. Io has active volcanoes, Europa
possibly has an underground ocean, Ganymede is the largest moon in
the solar system, Callisto is an ice ball.
Saturn is also giant and gaseous, with
spectacular rings. The rings are made of small chunks of ice and
rocks, like millions of tiny moons. It has many moons including
titan.
Uranus is small than the previous gas
giants. It is made of H/He and additional hydrogen compounds. It has
an extreme axis tilt.
Neptune is similar to Uranus with a
normal axis
Pluto and other dwarf planets are much
smaller than other planets. They have icy comet-like compositions.
Section 6.2 is about the clues to the
formation of our solar system
There are clues that show how the
solar system was formed. All large bodies orbit in the same direction
and nearly the same plane, and most rotate in that direction. There
are two major planet types, terrestrial and Jovian. There are swarms
of small objects. And there are exceptions to the rules (Uranus, the
moon, Venus)
The theory that best explains the
solar system is the nebular theory. It says our system formed from a
giant cloud of interstellar gas.
Section 6.3 is about the birth of the
solar system.
The recycling effect of the sun
produces elements that form planets. We can see stars forming in
other interstellar gas clouds, supporting the nebula theory. The
nebula shrank, and three processes altered it-heating, spinning, and
flattening.
Section 6.4 is about the formation of
planets
There are two types of planets because
of the elements present and the temperature. As gravity contracts a
cloud, it heats up, same as with solar systems. Inner parts are
hotter than outside, and rocks can be solid at different temperatures
than ice. These particles or planetesimals collide and build up, and
gravity assembles these into planets. This is called accretion.
Jovian planets start as ice particles, and draw in surrounding gas.
Asteroids and comets are leftovers of the accretion process. Water
may have come to earth by icy planetesimals from the outer solar
system. The moon is thought to have formed when the earth was smashed
by another object.
Section 6.5 is about other systems
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