Download The Sun-Earth-Moon System

The Sun-Earth-Moon System
What is the
moon?
• The moon is a natural satellite
of Earth
• This means that the moon orbits
Earth.
How was the • Theories about the moon’s
moon
formation
formed?
• Capture theory
• During the formation of the solar
system, a large object came close
to Earth and got caught in its
gravitation.
• Simultaneous formation theory
• Earth & the moon formed at the
same time, of the same materials.
• Impact theory
• A large object hit Earth 4.5 billion
years ago.
• The resulting material was ejected
into space and merged together.
What are the • The moon is bigger than most
properties of
other moons in the solar
the moon?
system.
• It is 27% of Earth’s radius
• It has over 1% of Earth’s mass
Scale Size & Distance
• The moon reflects the sun’s
light, making it visible at night
from Earth
• Albedo is the amount of sunlight
reflected by an object
• The moon’s albedo is only
about 0.07 (7%)
• Most of the sun’s energy that
hits the moon is absorbed.
• This causes large differences in
surface temperatures.
Radiation & Reflection of
Sunlight
0.07(7%)
0.367 (36.7%)
• The moon has no atmosphere
• This also contributes to large
differences in surface
temperatures because heat is
not retained.
• The moon’s surface is solid
and rocky
• There is no erosion because
there is no air or water
• So, craters and other markings
are not “erased” over time
• Craters were caused by
collisions with meteorites.
• Meteorites, known as asteroids
when they are still in space, are
pieces of planets left over from the
formation of the solar system.
The lunar crater Daedalus,
about 93 kilometers (58 miles)
in diameter,.
What is the
sun?
• The sun is the star at the
center of our solar system.
• Earth (and everything else in
our solar system) revolves
around the sun.
What are the • Earth rotates on its axis one
daily
time per day.
motions of
• This makes it appear that the
sun rises and sets, even though
the sun,
the sun does not orbit the
Earth, &
Earth.
moon?
• This also accounts for the moon
rising and setting.
How do
eclipses
occur?
• An eclipse is when one object
in the sky blocks your view of
another object in the sky
• Types of eclipses
• Solar eclipse
• Occurs when the moon blocks our
view of the sun.
• Lunar eclipse
• Happens when the moon passes
through Earth’s shadow.
Stars, Galaxies, & Beyond
What is a
star?
• A star is a massive, luminous ball
of gas held together by gravity.
• Our sun is a star.
• A group of stars is called a
constellation.
What powers
a star?
• Stars are powered by nuclear
fusion.
• Fusion is the combining of
lightweight nuclei into heavier
nuclei.
• Ex. Hydrogen combines to form
helium.
• Surface temperature—the
temperature on a star’s surface
• Composition—what a star is
made of
• Composition can be determined
through spectral analysis.
• Different elements emit different
wavelengths of light.
• Spectral types are assigned letters (O,
B, A, F, G, K, and M).
• All stars have similar compositions.
• 73% hydrogen
• 25% helium
• 2% other elements
• Temperature can also affect a star’s
spectrum, so this must be
accounted for.
How are stars
classified?
• Stars are classified by their mass,
luminosity magnitude,
temperature, and diameter.
• A Hertzsprun-Russell (H-R)
diagram is used to show the
relationship between these
variables.
H-R Diagram
What is the
life cycle of a
star?
• Star formation
• A nebula collapses as a result of
gravity.
• The rotation of the collapsing
nebula forces it into a disk shape.
• The hot condensed object at the
center is a protostar.
• Fusion begins
• The temperature inside the proto
star becomes hot enough for
fusion to begin.
• The star becomes stable because
the pressure caused by fusion
balances out gravity.
• Red giant
• The star runs out of hydrogen to
use as fuel.
• It starts to collapse & heat up in
the core, but cools on the surface.
• Helium is then used as fuel for
fusion.
• White dwarf
• If the star has a low mass, it uses
up the helium.
• Out layers become a planetary
nebula again.
• The hot core that remains is a
white dwarf.
• Supernova
• If the star has a high mass, it
continues fusing elements until
iron is formed.
• There is a very dense iron core,
with less dense layers outside of
that.
• The iron core eventually collapses
violently.
• After the collapse outer layers fall
in, sending out shockwaves and
causing an explosion
• Neutron star
• The remaining collapsed core is a
neutron star.
• It is made of neutrons.
• It is very dense.
• It spins very fast.
• Black hole
• If a star is too massive it cannot
form a neutron star.
• It will continue collapsing forever,
compacting matter into a smaller
and smaller volume.
• It is dense enough that its gravity
even sucks in light.
• HOWEVER, the total mass of the
star remains unchanged
What is a
galaxy?
• A galaxy is a collection of stars,
gas, and dust held together by
gravity.
• Our galaxy is called the Milky
Way
The Expanding • Scientists observe that galaxies
Universe
are moving away from each
other.
• This is true anywhere in the
universe.
• Edwin Hubbel observed that most
galaxies have redshifts in their
spectra.
• When an object moves away, light
waves are stretched out, causing
longer (red) wavelengths.
• When an object moves toward you,
light waves are compressed, causing
shorter (blue) wavelengths.