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Transcript
The Solar System
Section 3
Section 3: Formation of the Solar System
Preview
• Key Ideas
• Bellringer
• Early Astronomy
• The Nebular Hypothesis
• Rocks in Space
• How the Moon Formed
• Do Other Stars Have Planets?
The Solar System
Section 3
Key Ideas
〉 How did early astronomers understand and describe the
solar system?
〉 Why is the solar system organized like it is?
〉 What else is in the solar system besides planets?
〉 How did Earth’s moon form?
〉 How do astronomers find planets around other stars?
The Solar System
Section 3
Bellringer
Based on what you have learned, as well as previous
knowledge, answer the following questions.
Examine the various diagrams on the following slides,
and in the spaces provided indicate the order in which
you think they might have occurred in the formation of
the solar system.
The Solar System
Bellringer
Section 3
The Solar System
Section 3
Early Astronomy
〉 How did early astronomers understand and describe
the solar system?
〉 Over time, mathematical tools were used to make
more accurate models of observed astronomical
objects.
The Solar System
Section 3
Early Astronomy, continued
• The first model put Earth at the center.
– The “Earth-centered” model of the universe is
known as the geocentric model.
• Copernicus’s model put the sun at the center.
– In 1543, Nicolaus Copernicus proposed a
heliocentric, or “sun-centered,” model.
– In 1605, Johannes Kepler improved the model by
proposing that the orbits around the sun are
ellipses, or ovals, rather than circles.
The Solar System
Section 3
Visual Concept: Kepler's Law of
Planetary Motion
Click the button below to watch the Visual Concept.
The Solar System
Section 3
Early Astronomy, continued
• Newton explained it all.
– In 1687, Isaac Newton explained that the force
that keeps the planets in orbit around the sun, and
satellites in orbit around planets, is gravity.
– His theory states that every object in the universe
exerts a gravitational force on every other object.
The Solar System
Section 3
The Solar System
Section 3
Visual Concept: Law of Universal
Gravitation
Click the button below to watch the Visual Concept.
The Solar System
Section 3
Visual Concept: Gravity and Orbit
Click the button below to watch the Visual Concept.
The Solar System
Section 3
The Nebular Hypothesis
〉 Why is the solar system organized like it is?
〉 The nebular hypothesis explains why objects that form from a
disk will lie in the same plane, have almost circular orbits, and
orbit in the same direction.
• nebula: a large cloud of dust and gas in interstellar space; a
region where stars are born
• nebular hypothesis: a model for the formation of the solar
system in which the sun and planets condense from a cloud
(or nebula) of gas and dust
The Solar System
Section 3
The Nebular Hypothesis, continued
• Planets formed by the accretion of matter in the
disk.
– Accretion is the process by which small particles
collide and stick together.
• The nebular hypothesis explains small rocks in
space.
The Solar System
The Nebular Hypothesis
Section 3
The Solar System
The Nebular Hypothesis
Section 3
The Solar System
Section 3
Visual Concept: Formation of the Solar
System
Click the button below to watch the Visual Concept.
The Solar System
Section 3
Visual Concept: Solar System
Click the button below to watch the Visual Concept.
The Solar System
Section 3
Rocks in Space
〉 What else is in the solar system besides planets?
〉 There are many types of small bodies in our solar
system, including satellites, comets, asteroids, and
meteoroids.
• comet: a small body of ice, rock, and cosmic dust that
follows an elliptical orbit and that gives off gas and
dust in the form of a tail as it passes close to the sun
The Solar System
Section 3
Rocks in Space, continued
• Comets may give clues to the origin of the solar
system.
– Comets are composed of dust and of ice made
from methane, ammonia, carbon dioxide, and
water.
– Because of their composition, comets are
sometimes called dirty snowballs.
• Comets have long tails and icy centers.
– Some comets have two tails— an ion tail made of
charged particles that is blown by the solar wind
and a dust tail that follows the comet’s orbit.
The Solar System
Section 3
Rocks in Space, continued
• Where do comets come from?
• The far-flung pieces leftover from the formation of
our solar system make up the Oort cloud of
comets, which may be up to 100,000 AU wide and
extend in all directions.
• Planetesimals that remained in the nebular disk
formed the Kuiper belt beyond the orbit of
Neptune.
The Solar System
Comets
Section 3
The Solar System
Section 3
Rocks in Space, continued
• Meteorites can be made of many elements.
– There are three major types of meteorites.
• Stony meteorites include carbon-rich
specimens that contain organic materials and
water.
• Iron meteorites are made of iron and nickel.
• Stony-iron meteorites are a combination of the
two types.
The Solar System
Section 3
Rocks in Space, continued
• Meteoroids sometimes strike Earth.
– Objects less than 10 m across usually burn up in
Earth’s atmosphere.
– Meteoroids that strike Earth may leave craters.
– Over time, natural and manmade forces may
erode craters on Earth.
– Some past climate events and extinctions are
thought by scientists to have been caused by
large meteor or comet strikes.
The Solar System
Section 3
How the Moon Formed
〉 How did Earth’s moon form?
〉 The current theory is that the moon resulted from a collision
between Earth and another large body.
• Earth collided with a large body.
– The body that struck Earth may have been as large as Mars.
– At impact, a large part of Earth’s mantle was blasted into
space.
The Solar System
Section 3
How the Moon Formed, continued
• The ejected material clumped together.
– The debris consisted of the iron core of the body,
mantle material from Earth, and other material
from the impacting body.
• The moon began to orbit Earth.
– The moon is the only large satellite around a
terrestrial planet and it is the largest moon with
respect to its planet.
The Solar System
Section 3
Visual Concept: Moon Formation
Click the button below to watch the Visual Concept.
The Solar System
Section 3
Do Other Stars Have Planets? continued
〉 How do astronomers find planets around other stars?
〉 Astronomers have discovered more than 200
exoplanets by measuring the small gravitational
effects that they have on their parent star.
• exoplanet: a planet-like body that orbits a star other
than the sun
The Solar System
Section 3
Do Other Stars Have Planets?
– As an exoplanet orbits its star, it causes the star to
wobble back and forth.
– Most of the newly discovered exoplanets have
masses close to or larger than the masses of
Jupiter or Saturn.
– Only a few exoplanets are in systems that have
more than one discovered exoplanet.
– Modern detection methods favor the finding of
large exoplanets, although scientists are working
on ways to detect smaller exoplanets.
The Solar System
Concept Mapping
Section 3