Download Chapter 28 - Trimble County Schools

Bell Ringer 9/8
• OPINION QUESTION – How do you
believe the solar system was formed?
Chapter 28
Formation of the Solar
System
Big Bang Theory
•Theory that universe
began as a point and
has been expanding
ever since
Solar System
• Theories rely on observation
and data from probes sent
into space
• Theories explain
– Shape of solar system
– Differences between planets
– Nature of planetary surface
Stars & Planets form from
interstellar clouds, which
exist in space between the
stars
http://www.astrographics.com/GalleryPrints/Display/GP0069.jpg
Orion Cloud
http://www.daviddarling.info/images/interstellar_cloud.jpg
Triangulum.nebula
http://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Triang
ulum.nebula.full.jpg/563px-Triangulum.nebula.full.jpg
Interstellar Clouds
• Consist mostly of hydrogen
and helium gas with small
amounts of other elements
and dust
– Dust makes clouds look dark by blocking light
– Dust also reflect starlight and makes clouds
look bright
How astronomers believe
solar system formed
• Density of interstellar gas is
low
• Gravity slowly draws matter
together until the matter is
concentrated enough to form
stars and planets
Interstellar Cloud
• Collapse of cloud begins slowly
but gradually gets faster
• Cloud becomes more dense at
center
• If rotating, the cloud spins
faster as it contracts, due to
centripetal force.
•
(DEMONSTRATION)
Interstellar Cloud
• Interstellar cloud that
formed our solar system
collapsed into a rotating
disk of dust and gas
• Concentrated matter at
the center acquired
enough mass to form the
Sun
• Remaining matter
gradually condensed to
form planets
Interstellar Cloud
• Temperature varied greatly with location
• Different elements and
compounds condensing, affected
distribution of elements on the
planets
–Depending on their distance
from the Sun
Planetesimals
• Space
objects built
of solid
particles that
can form
planets
through
collisions
Large Planets
• First to develop was Jupiter
–Increased in size through the
merging of icy planetesimals that
contained mostly lighter elements
• Saturn and the other gas giants formed same
way
– Not as large because Jupiter collected so much
material
Inner Planets
• Planets that formed near the young Sun
• Composed primarily of elements
that resist vaporization
(didn’t become gassy)
• Rocky and dense
Debris
• Material that remained after the
formation of the planets and satellites
• Some became icy objects known as comets
• Others formed rocky planetesimals known as
asteroids
– Thousands of asteroids have been detected in
the asteroid belt, which lies between Mars and
Jupiter.
In-Class Assignment/Homework
Bell Ringer 9/9
• Explain in your own words how scientists
believe our sun formed
28.1 B
Models of Solar System
Aristotle
• 3rd century BC
• Geocentric: Earth-centered
solar system
–did not explain retrograde
(backward) motion of planets
Aristotle
Ptolemy
•
century AD
• Planets revolve around
Earth in circles
rd
3
–epicycles to explain
retrograde motion
Ptolemy
Retrograde motion
• The apparent
backward movement
of a planet
• The changing angles
of view from Earth
create the apparent
retrograde motion of
Mars.
Tycho Brahe
• a Danish
astronomer
• Made accurate
observations of
the planets’
positions
http://honolulu.hawaii.edu/distance/sci122/Programs/p10/Brahe.jpg
Nicolaus Copernicus
http://www.cgirb.com/images/copernicus.jpg
Copernicus
•
century
• Heliocentric: sun-centered
model
• Earth and planets orbit the
sun in the same direction, but
at diff. speeds and distances
th
16
Copernicus
• Solves problem of
retrograde motion
• 1700’s Galileo proves this
with telescope
In-Class Assignment/Homework
• Ancient Astronomers WKT
Bell Ringer 9/10
• Who said our solar system was geocentric?
• Who said it was heliocentric?
Kepler
•
century
• Used observations of his
teacher, Brahe, to explain
planetary motion.
th
17
Johannes Kepler
http://www.nasa.gov/images/content/65879main_kepler-portrait-330-427.jpg
Kepler
• Each planet orbits the
Sun in a shape called
an ellipse, rather than
a circle
– An ellipse is an oval
shape that is
centered on two
points.
http://ca.geocities.com/web_sketches/ellipse_notes/ellipse_arc_length/ellipse_eccentric_angle.gif
Kepler’s
st
1
Law
• Law of ellipses : planets orbit the
sun not in a circle, but in an
ellipse.
• Astronomical unit: average
distance between the sun and the
earth.
Kepler’s
nd
2
Law
• Law of equal areas: Earth
moves fastest when closest to
the sun
–Line from the center of a
planet sweeps through equal
areas in equal periods of time.
Kepler’s
rd
3
Law
• Law of periods: Relationship
between distance from the sun
and the orbit period.
–Orbit period: the time required
for the planet to make one
revolution around the sun.
Galileo Galilei
http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Galileo.arp.300pix.jpg/300pxGalileo.arp.300pix.jpg
Galileo
 First person to use a telescope to
observe the sky
 Discovered that four moons orbit the
planet Jupiter
Proved that not all celestial bodies
orbit Earth and Earth was not
necessarily the center of the solar
system
Isaac Newton
Isaac Newton
• Inertia: objects want to move in
a straight line at constant speed
until acted upon by an outside
force
• Gravity: force that pulls them
out of that straight line
In-Class Assignment/Homework
• WKT 87 – Kepler’s La
• #3 = Major axis – line that runs along
diameter of ellipse, Semimajor axis –
average distance between sun and the planet
• #4 = Eccentricity – shape of the planet’s
elliptical orbit