Pearson Prentice Hall Physical Science: Concepts in Action

Chapter 25The Solar System

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

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

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

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

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

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 moonNew 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

25.3 The Inner Solar System• Objectives:• 1. Compare the terrestrial planets

and describe characteristics of each• 2. Define asteroids and state

alternative hypotheses about how they were formed

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 CO2 which traps heat and raise temperature

• The CO2 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”

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

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

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

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

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

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• Objectives:• 1. State the nebular theory• 2. Relate the nebular theory to

the orbits, composition and size of the planets

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 The planets eventually formed from the outer parts of the diskouter parts of the disk

• The central mass eventually became the sunThe central mass eventually became the sun• Def: planetesimals were asteroid-like bodies Def: planetesimals were asteroid-like bodies

that eventually combined to form planetsthat eventually combined to form planets• Def: accretion is the process of adding mass Def: accretion is the process of adding mass

by colliding with other planetesimalsby colliding with other planetesimals• The cloud may have been flat as it collapsed, The cloud may have been flat as it collapsed,

laying in one plane creating the orbitslaying in one plane creating the orbits• Accretion occurs when small particles collect Accretion occurs when small particles collect

and stick together to form large massesand 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