Transcript Chapter 20 Notes

Chapter 20 – The Formation
of the Solar System
• Nebula – A large, interstellar cloud of gas and
dust from which many bodies in space are
formed. To hold this cloud together, gravity and
pressure must be in balance.
•Solar Nebula – The nebula from which our solar
system formed.
•Planetesimals – Pieces of matter that collide
and accrete to form planets.
Structure of the Sun
• Corona – The outer atmosphere.
• Chromosphere – Below the corona where the
color of the sun originates.
• Photosphere – the visible part we can see.
• Convection Zone – The region where gases
circulate.
• Radiative Zone – A dense region towards the
core where light and energy are scattered.
• Core – the center of the sun where energy is
produced.
• Nuclear fusion – The process where the sun
produces energy by fusing two hydrogen nuclei
together to form a helium nucleus + energy.
• Solar Activity – The photosphere is ever-changing.
The convection zone circulates gases and the
photosphere gases boil and churn along with the sun’s
rotation creates magnetic fields that reach out into
space.
• Sunspots – Cooler, dark regions of the photosphere
that change on a regular cycle of about 11 years.
Sunspots have very strong magnetic fields that can
affect the Earth’s climate & temperature.
• Solar Flares – Giant eruptions on the sun that send
electrically charged solar material into space
disrupting communications and creating the Auroras.
The Formation of the Earth
• The Earth started out as planetesimals collided and built up
heat. As more and more material collected, the temperature
continued to rise eventually melting the rocky material that
composed the early Earth. Stratification of the Earth’s layers
occurred when the denser materials sank to the core and the
lighter materials rose to form the crust. The material of
intermediate density settled in between these layers forming the
mantle. The Earth’s original atmosphere was very different than
today's being composed primarily of CO2 and H2O. Volcanoes
and comets also contributed other gases along with early life
forms adding oxygen through photosynthesis. The oceans
formed as the Earth cooled enough for water vapor to
condense and heavy rains to fall for millions of years. The
continents thickened and rose above the oceans.
Planetary Motions
•
•
•
•
•
1.
2.
3.
4.
Rotation – The spinning of the Earth on it’s axis.
Revolution – A complete trip of the Earth around the sun along it’s
orbit.
Orbit – The path a body takes around another body.
Kepler – A famous mathematician who calculated many
discoveries on planetary motion. He calculated the elliptical orbits
of planets (Fig. 2, p. 631) around a star. He also explained why a
planet closer to the sun must orbit faster.
Newton – Developed the Law of Universal Gravitation which
explains:
More mass = more gravity
Closer objects = more gravity
Planets closer to the sun have to orbit faster.
Gravity can change the path of a straight moving object to curve
into an orbit.