Earth

Science Unit 9: Our Place in the

Universe What is your favorite planet?!?!

Lessons 6 and 7: The Solar System and the Inner Planets

Make sure to have your study guide and a pencil and be ready to go when the timer dings!

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Student Expectations… Being part of this “school” is awesome! How can YOU make this ocean even more

awesome??.

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I will BE HERE! respond when my name is called, use polling

tools , complete classwork, notes, and chat to participate!

I will choose my attitude!

I will demonstrate respect and follow directions for my

classmates and teachers to help make their day!

I will have fun learning!

What you can expect from class

Essential question: What causes the sun to burn so brightly and with such heat?

Vocabulary Geocentric System –

Heliocentric Theory -

The Universe

Throughout our galaxy, and perhaps the universe, there are other planets being warmed by their own sun. In other places in the universe, planets are orbiting central stars (our sun is a star) in solar systems. These solar systems formed in ways similar to the way our own solar system formed. In fact, some are still forming today like the Cartwheel galaxy pictured here.

Our Solar System We call the star at the center of our solar system the sun. Eight planets, three known dwarf planets, and

many asteroids and comets all orbit our sun. Moons, like earth’s own moon, are also part of the solar

system. Moons orbit their planets as the planets move around the sun. The only star of the solar system is the

sun. All other stars are merely part of our galaxy!

Quick Check! Which of the following objects is NOT a part of

our solar system?

A. The North Star

B. The dwarf planet Pluto

C. The asteroid belt

D. Jupiter’s moons

Geocentric System

- a model of the solar system with the earth as its center.

The ancient Greeks identified stars that moved in fixed patterns relative to one another and five bright objects that did not maintain fixed patterns. Early Greek astronomers named these objects planets, which means “wanderers” in Greek.

Heliocentric Theory

In the mid-1500s, the Polish mathematician and astronomer Nicolaus Copernicus proposed that the sun, and not the earth, is actually in the center of the solar system.

In the 1600s, the German astronomer Johannes Kepler determined that all the planets actually revolve around the sun in elliptical paths, and not in perfect circles

Quick Check!

In a Geocentric System, the planets revolve around the sun.

Quick Check

Early Greek astronomers named the objects they observed in the night sky planets, which means:

A. “giant star”

B. “wanderers”

C. “planet fitness”

D. “colorful orbs”

The Outer Planets…

As the planets formed, gases such as hydrogen and helium became concentrated in the large atmospheres of the planets farther from the sun. The massive outer planets (Jupiter, Saturn, Uranus, and Neptune) sucked up hydrogen and helium from nearby space and are now known as the gas giants. The gas giants are all massive, have many moons, and are each surrounded by a set of rings. A ring is a disk made of small pieces of rock and ice that surrounds these distant planets.

The Planets… The inner material in the solar nebula formed dense, rocky planets. Mercury, Venus, Earth, and Mars are known as the terrestrial planets, meaning they are rocky like Earth. Early on, leftover large rocky objects continually slammed into the planets, leaving large impact craters. These powerful collisions often broke off pieces of the planets. Scientists think that some planetary moons, including Earth’s, were created from the broken-off pieces of these planets.

Quick Check! Which planet has a thick atmosphere of mainly hydrogen and helium due to conditions during

the formation of the planets?

A. Mercury

B. Mars

C. Neptune

D. Venus

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The Inner Planets • Mercury, Venus, Mars and Earth. • Closest to the sun • Are also known as the terrestrial planets, meaning

earth-like. • Planet sizes are similar to each other and are relatively

small compared to other planets in our solar system. • They are all made of rock with metallic cores. • They rotate slowly and do not have rings. • They have few, if any, moons.

Mercury Atmosphere: Extremely thin because it is so close to the sun. Energy from the sun and Mercury’s weak gravity cause gas molecules to fly off into space. Surface characteristics: Has many craters on its surface because the thin atmosphere doesn’t protect it from objects like meteoroids. Mercury doesn’t have water or wind to cause erosion or active plate movements to recycle crust materials, so the craters last a long time. Temperature: Daytime temperatures can reach 873°F. At night, temperatures dip down to –280°F. Other characteristics: Named after the Roman god who wore winged shoes. This is appropriate because Mercury “flies” around the sun once every 88 earth days. Mercury is nearest to the sun and is the smallest planet in the solar system.

Venus Atmosphere: very dense atmosphere—about 90 times denser than Earth’s. Its atmosphere contains mostly carbon dioxide, which is a powerful greenhouse gas. Surface characteristics: Has mountains, volcanoes, and lots of lava plains. Venus has fewer craters than Mercury or Mars because it has a thick atmosphere and a tectonically active surface. Temperature: Average surface temperature is about 860°F. It’s the hottest planet in our solar system. Other characteristics: Second planet from the sun and is about the same size as Earth. Sometimes, scientists refer to Venus as Earth’s twin because they are similar in size, mass, and density. However, Venus rotates very slowly and in the opposite direction from the other planets!

Quick Check! The inner planets are all similar to Earth in size, composition, and orbit.

Earth Atmosphere: Mostly nitrogen, along with lots of oxygen that is essential for supporting most animal and plant life. Surface characteristics: About 70 percent of Earth’s surface is covered with water. It is the only known planet with oceans of liquid water. Earth’s surface is very active. Running water, ice, wind, and plate tectonics are constantly resurfacing the earth. Temperature: Temperatures do not change a lot between day and night or throughout the year. One reason for this is because the earth has a protective atmosphere that keeps it from heating up or cooling off too much. Other characteristics: The only planet we know of that can support life. It also has a relatively large moon. Earth is the third planet from the sun and is slightly larger than Venus. Earth is the largest of the inner planets.

Mars Atmosphere: Mostly carbon dioxide. It is fairly thin. Surface characteristics: Some massive volcanoes, canyons, and craters. There is evidence that Mars once had liquid water on its surface. Now, water on Mars’s surface is found only in its polar ice caps. Large amounts of water may still be frozen underground. Mars’s iron-rich surface gives it a rusty red color. Temperature: Average surface temperatures, -125°F to 23°F, are lower than those of the other inner planets. Other characteristics: Mars is the outermost inner planet. A Mars year is twice as long as Earth’s. Mars also rotates on a tilted axis and has seasons. Mars has two tiny moons.

Shooting stars aren’t actually stars, they are meteors! Meteors occur when meteorites move through space and strike Earth’s upper atmosphere. The light you are seeing is the meteoroid actually vaporizing into a fireball!

Fun Science Fact!

Vocabulary Geocentric System - the belief that the Earth is at the center of the universe

Heliocentric Theory - idea that the sun is in the center of the universe

Sun

Dwarf

Earth

Heliocentric

Closest terrestrial

slowly

gravity

thin

Smallest

Second

carbon dioxide

Hottest

Third

Fourth carbon dioxide

Iron rich

liquid water

REMEMBER!!!

• Unit 9 bundle and

• USA TEST PREP BENCHMARK by FRIDAY!!!

Exit Ticket

Homework

Want to learn more?

Complete Unit 9 Lesson 6 or 7