Pearson Prentice Hall Physical Science: Concepts in Action

Chapter 25 The Solar System

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25.1 Exploring the Solar System

Objectives: 1. Compare and contrast the geocentric and heliocentric models of the solar system 2. Describe the orbits of the planets around the sun and explain how gravity and inertia keep the planets in orbit 3. Name the components of the solar system 4. Identify different technologies used for exploring the solar system

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Geocentric vs. Heliocentric

The geocentric model is from ancient Greece • • • • In the geocentric model, Earth is stationary while objects in the sky move around it In the heliocentric model, Earth and the other planets revolve around the sun Imagine the path of Earth’s orbit traced on a table Def: the ecliptic plane is the path of Earth’s orbit

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Gravity plus Inertia & Components of the Solar System

Gravity and inertia combine with each other to keep the planets in orbit Without gravity, planetary inertia would cause them to fly off in space The components of the solar system are the sun, the planets, their moons, and a variety of smaller objects that mostly revolve in the same plane around the sun

Exploring the Solar System

• • • • • Modern technology including telescopes, piloted spacecraft, & space probes has allowed scientists to explore the solar system Def: a space probe in an unpiloted vehicle that carries scientific instruments into space and transmits information back to Earth NASA launched 2 vehicles, Spirit & Opportunity to land on Mars in 2004 for a 3 month mission They are still sending information back to Earth today The scientist who monitors them is at UNR

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25.2 The Earth-Moon System

Objectives: 1. Explain why the moon lacks atmosphere & the effect this has on the range of temperature on the moon • • 2. Describe the features of moon’s surface 3. State a theory about the formation of the moon • 4. Explain the phases of the moon, tides & eclipses & interpret diagrams of these events

No Atmosphere/Surface Features

• • • • Moon’s gravity is too weak to hold onto gas molecules The lack of atmosphere allows moon’s surface temperature to vary tremendously The major surface features are maria, highlands and craters Def: maria are low, flat plains formed by ancient lunar lava flows

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Features plus Formation

Def: highlands are rough mountainous regions that cover most of moon’s surface Lunar highlands are light-colored areas that surround the maria Def: craters are round depressions caused by the impact of high speed meteoroids Def: meteoroids are chunks of rock that move through the solar system Scientists hypothesize that the moon was formed after an enormous collision in Earth’s history The collision was probably caused by rocky debris which was plentiful & hit many planets about 4.6 billion years ago when Earth formed

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Phases of the Moon & Eclipses

Def: the different shapes of the moon visible from Earth are called phases The moon’s phases are caused by changes in the relative positions of the moon, sun & Earth as the moon revolves around the Earth Def: an eclipse occurs when the shadow of one body in space falls on another Def: a solar eclipse occurs when the moon casts a shadow on a portion of Earth’s surface Def: a lunar eclipse occurs when Earth casts a shadow on the moon

8 Phases of the moon

New Moon - The Moon's unilluminated side is facing the Earth. The Moon is not visible (except during a solar eclipse).

Waxing Crescent - The Moon appears to be partly but less than one-half illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.

First Quarter - One-half of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.

Waxing Gibbous - The Moon appears to be more than one-half but not fully illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is increasing.

Full Moon - The Moon's illuminated side is facing the Earth. The Moon appears to be completely illuminated by direct sunlight.

Waning Gibbous - The Moon appears to be more than one-half but not fully illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing.

Last Quarter - One-half of the Moon appears to be illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing .

Waning Crescent - The Moon appears to be partly but less than one-half illuminated by direct sunlight. The fraction of the Moon's disk that is illuminated is decreasing .

Lunar Eclipse

Tides

• • • • • Def: tides are the regular rise and fall of ocean waters Tide are caused mainly by differences in the moon’s gravitational pull on Earth The sun’s gravity affects tides about half as much as the moon Def: spring tide is the combined forces of the gravity of the sun and the moon Def: neap tide is the least tide possible & is due to first or third quarter moon being at right angles to the Earth (compared to sun’s position)

• • • • • • The solar system is the sun and the planets that orbit around it The four planets closest to the sun are the terrestrial planets Def: terrestrial planets are planets similar in structure to Earth The four inner planets are all small, dense and rocky All have a crust, mantle and iron core Five planets have been known for centuries: Mercury, Venus, Mars, Jupiter & Saturn

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25.3 The Inner Solar System Objectives:

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1. Compare the terrestrial planets and describe characteristics of each

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2. Define asteroids and state alternative hypotheses about how they were formed

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Compare and Describe

Mercury is the smallest and closest to the sun Venus is called the evening star or morning star Venus’s atmosphere has the greenhouse gas effect due to large amounts of CO traps heat and raise temperature 2 which The CO 2 also causes it to rain sulfuric acid when it combines with the sulfur in the atmosphere Earth’s atmosphere is suitable for water to exist as a liquid

• • • Mars is a major source of study right now, including experimentation with rovers from NASA named Spirit and Opportunity They landed on Mars in 2004 The rovers were designed to send information for 3 months, but functioned for years yielding information about Martian water and soil • Spirit was mobile on the Red Planet for over five years and then functioned as a stationary science platform for another year before getting killed off by a Martian winter it couldn’t avoid ”

• • • • • • As of January 2012, Opportunity still works & will spend the Martian winter in a sunny spot until the engineers wake it up in Martian spring In August 2012, NASA landed a much larger, very expensive rover called Curiosity Its mission is to see if Mars ever had the right conditions to support life Mars shows evidence of having had a lot of water in its past other missions to Mars, including manned missions are being considered Mars is sometimes called the “red planet”

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Asteroids

• Def: asteroids are small rocky bodies orbiting the sun The region in the solar system where they are found is called the asteroid belt The asteroid belt is between Mars and Jupiter Scientists hypothesize that asteroids are remnants of the early solar system that never came together to form a planet

The Inner Solar System

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25.4 The Outer Solar System

Objectives: 1. Compare the gas giants and describe characteristics of each • 2. Distinguish between planets and dwarf planets 3. Distinguish between comets and meteoroids and describe their characteristics 4. Locate and describe the Kuiper belt and Oort Cloud

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Gas Giants

The four outer planets (Jupiter, Saturn, Uranus and Neptune) are gas giants • Def: gas giants are planets composed mainly of hydrogen and helium • The four gas giants are thought to have small, dense cores, and dense atmospheres composed mostly of hydrogen and helium • Def: a ring is a disk make many small particles of rock and ice in orbit around a planet • All of the gas giants have rings

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Jupiter is the largest and most massive planet in our solar system

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Jupiter has at least 63 moons Saturn’s rings are the largest and most visible from Earth Saturn has at least 56 moons, but is known for its moon named Titan Titan is larger than Mercury

• • • • Uranus is believed to have a mantle of liquid water and dissolved ammonia The axis of Uranus’s rotation is tilted more than 90° Neptune’s bluish color comes from the methane in its atmosphere Its largest moon is called Triton and it has a thin atmosphere and an icy surface

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Dwarf Planets

Def: a dwarf planet, like a planet, is spherical and orbits the sun directly, but a dwarf has not cleared the neighborhood (more on that in a moment) The definition of planet is that it is a celestial body in orbit around the sun, has self-gravity, is not a satellite and clears the neighborhood around its orbit A satellite is any object orbiting a planet, whether natural or man-made

• • • • • Pluto does not “clear the neighborhood” because it is part of a sea of objects that occupy the same region of space Pluto and its moon Charon have an elliptical orbit that sometimes crosses into Jupiter’s orbit, thus lending support to those who want to reclassify it Planets must have sufficient force to get other objects out of their way Under the new definition as many a 12 planets have been proposed Officially at this time there are 8 planets in our solar system

• • • • • The astronomers in 2006 came up with the following proposals & definitions: 1. Planets: The eight worlds starting with Mercury and moving out to Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune 2. Dwarf planets: Pluto and any other round object that "has not cleared the neighborhood around its orbit, and is not a satellite." 3. Small solar system bodies: All other objects orbiting the sun The Pluto issue will continue to play out for some time & is not yet settled

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Comets, Meteoroids, Kuiper & Oort

Def: comets are dusty pieces of ice and rock that partially vaporize when they pass near the sun Def: meteoroids are pieces of rock, usually less than a few hundred meters in size, that travel through the solar system At the edge of the solar system beyond Neptune are Kuiper and beyond Kuiper is Oort

• Most of the objects in the Kuiper belt lie in a doughnut shaped region close to the ecliptic plane • Def: the ecliptic plane is the plane in space containing Earth’s orbit (the path of Earth’s orbit) • • Pluto is in the Kuiper belt Beyond the Kuiper belt is a great reservoir of comets called the Oort cloud • Occasionally objects from the Oort cloud enter the inner solar system as comets

25.5 The Origin of the Solar System

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Objectives:

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1. State the nebular theory

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2. Relate the nebular theory to the orbits, composition and size of the planets

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The Nebular Theory

Scientists believe the solar system was formed by the nebular model • The nebular theory state that the solar system formed from a rotating cloud of dust and gas • Def: a protoplanetary disk is a large disk shaped cloud of dust and gas resembling a giant fried egg rotating in space • Most of the mass is concentrated in the center

• • • • • • The planets eventually formed from the outer parts of the disk The central mass eventually became the sun Def: planetesimals were asteroid-like bodies that eventually combined to form planets Def: accretion is the process of adding mass by colliding with other planetesimals The cloud may have been flat as it collapsed, laying in one plane creating the orbits Accretion occurs when small particles collect and stick together to form large masses

• • • planetesimals attracted more and more matter leading to moon sized protoplanets with their own gravity • The terrestrial planets ended up close to the sun and are small and rocky This is because the inner solar system was too hot during formation for ice-forming compounds to condense The gas giants are large and have low densities because the outer solar system was cool enough for ice-forming compounds to condense