The Solar SystemSection 3 Section 3: Formation of the Solar System Preview Key Ideas Bellringer...

The Solar System Section 3

Section 3: Formation of the Solar System

Preview• Key Ideas • Bellringer • Early Astronomy • The Nebular Hypothesis• Rocks in Space• Comets• How the Moon Formed• Do Other Stars Have Planets?


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?


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.


Bellringer


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.


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.


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.


Visual Concept: Kepler's Law of Planetary Motion


Visual Concept: Law of Universal Gravitation


Visual Concept: Gravity and Orbit


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 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 Nebular Hypothesis


Visual Concept: Formation of the Solar System


Visual Concept: Solar System


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


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.


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.


Comets


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 mostly of iron and nickel.

• Stony-iron meteorites are a combination of the two types.


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.


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.


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.


Visual Concept: Moon Formation


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


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 SystemSection 3 Section 3: Formation of the Solar System Preview Key Ideas Bellringer...

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