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The Solar System
There are two broad categories of planets:Earthlike and Jupiter like
All of the planets orbit the Sun in the same direction and in almost the same plane
Most of the planets have nearly circular orbits
The Solar SystemDensity
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The average density of any substance depends in part on its composition An object sinks in a fluid if its average density is greater than that of the fluid, but rises if its average density is less than that of the fluid The terrestrial (inner) planets are made of rocky materials and have dense iron cores, which gives these planets high average densitiesThe Jovian (outer) planets are composed primarily of light elements such as hydrogen and helium, which gives these planets low average densities
The Solar System
The Inner Planets
- The Inner Planets
The inner planets take up only a small part of the solar system. Note that sizes and distances are not drawn to scale.
The Solar System
Earth is the third planet from the sun and the fifth largest. Earth has only one moon. The earth is 4.5 billion years old.
The Solar System
Earth’s Layers
- The Inner Planets
Earth has three main layers—a crust, a mantle, and a core.
The Solar System
• Mercury is the closest planet to the sun and the eighth largest.
• Mercury has no moons. • Mercury has extreme temperature fluctuations from 430 to -170 degrees celsius (day and night).
The Solar System
Mercury
- The Inner Planets
Mercury is the smallest terrestrial planet and the planet closest to the sun.
The Solar System
• Venus is called Earth’s twin • Venus’s surface is 460
degrees (could melt metal!). • Venus is covered with swirling
clouds (thick atmosphere of CO2 and Sulfuric Acid and always cloudy).
• It is the hottest planet (greenhouse effect).
The Solar System
Venus
- The Inner Planets
Venus’s density and internal structure are similar to Earth’s. But, in other ways, Venus and Earth are very different.
The Solar System
Venus
- The Inner Planets
This figure combines images of Venus taken from space with a camera (left) and radar (right). The camera image shows Venus’s thick atmosphere. Radar is able to penetrate Venus’s clouds to reveal the surface. Both images are false color.
The Solar System
• Mars is the seventh largest planet in the solar system.
• Thin atmosphere is ~95% CO2 (H20 gas or polar ice caps)
• Mars temperature ranges between -140 and 20 degrees C.
• Mars used to be warm with lots of water long ago.
The Solar System
Mars
- The Inner Planets
Mars is called the “red planet.” When you see it in the sky, it has a slightly reddish tinge. This reddish color is due to the breakdown of iron-rich rocks, which creates a rusty dust that covers much of Mars’s surface.
The Solar System
Mars
- The Inner Planets
Mares has ice caps at both poles. Scientists think that a large amount of liquid water flowed on Mars's surface in the distant past.
The Solar System
What You Know
What You Learned
Using Prior KnowledgeLook at the section headings and visuals to see what this section is about. Then write what you know about the inner planets in a graphic organizer like the one below. As you read, write what you learn.
1. Most of Earth is covered with water.2. Mercury is closest to the sun.3. Venus is very hot.4. Mars is called the “red planet.”
1. Earth is unique in our solar system for having liquid water at its surface.2. Mercury has a greater temperature range than any of the other planets.3. A day on Venus is longer than its year.4. The reddish tinge on Mars is caused by the breakdown of iron-rich
rocks.
- The Inner Planets
The Solar System
End of Section:The Inner Planets
The Solar SystemSeven large satellites are almost as big as
the terrestrial planets
Comparable in size to the planet Mercury
The remaining satellites of the solar system are much smaller
The Solar System
Gas Giants and Pluto
- The Outer Planets
The first four outer planets–Jupiter, Saturn, Uranus, and Neptune–are much larger and more massive than Earth, and they do not have solid surfaces. Pluto is small and rocky.
The Solar System
The Solar System
Jupiter’s Red Spot is a 350 year old hurricane!
Nighttime image showing lightning in Jupiter’s
atmosphere
The Solar System
Jupiter’s Structure (no solid surface!)
- The Outer Planets
Jupiter is composed mainly of the elements hydrogen and helium.
The Solar System
Jupiter’s Moons
- The Outer Planets
• The astronomer Galileo discovered Jupiter’s four largest moons. They are named Io, Europa, Ganymede, and Callisto.
• Dozens of additional Jupiter moons have been discovered since Galileo’s time
• Jupiter is the most massive planet by far (1,300 Earths and 2.5 times that of all other planets combined!
The Solar System - The Outer Planets
Saturn
Saturn has the most spectacular rings of any planet.
The Solar System
Saturn
• Saturn is the second largest planet in our solar system• Saturn has an atmosphere of thick clouds and is
composed of hydrogen and helium (similar to Jupiter)• Saturn’s rings are composed of ice and rock chunks
orbiting together in different layers• Saturn has many moons (the largest is Titan)
The Solar System - The Outer Planets
Uranus
Although the gas giant Uranus is about four times the diameter of Earth, it is still much smaller than Jupiter and Saturn.
The Solar System - The Outer Planets
Uranus
Uranus’s axis of rotation is tilted at an angle of about 90 degrees from the vertical.
The Solar System - The Outer Planets
Neptune
Neptune is a cold, blue planet (similar color and size to Uranus). Its atmosphere contains visible clouds.
Discovered by math equation in 1846 (orbital pattern)
*Scientists think Neptune is shrinking in size…and heating up!
The Solar System
Circumference To calculate the circumference of a circle, use this formula:
C = 2πr
In the formula, π ≈ 3.14, and r is the circle’s radius, which is the distance from the center of the circle to its edge. The same formula can be used to calculate the circumference of planets, which are nearly spherical.
Neptune’s radius at its equator is about 24,800 km. Calculate its circumference.
C = 2πr
= 2.00 X 3.14 X 24,800 km
= 156,000 km
- The Outer Planets
The Solar System
Circumference
Practice Problem
Saturn’s radius is 60,250 km. What is its circumference?
2 X 3.14 X 60,250 km = about 378,800 km
- The Outer Planets
The Solar System - The Outer Planets
Pluto
Pluto has a solid surface and is much smaller and denser than the other outer planets.
The Solar System
Pluto
Pluto is a special caseSmaller than any of the terrestrial planets
Intermediate average density of about 1900 kg/m3
Density suggests it is composed of a mixture of ice and rock
The Solar System
Identifying Main IdeasAs you read the section “Gas Giants and Pluto,” write the main idea–the biggest or most important idea–in a graphic organizer like the one below. Then write supporting details that further explain the main idea.
The four gas giants are similar in…
Structure–they do not have a solid surface.
Atmosphere–thick and made up mainly of hydrogen and helium.
Rings–each is surrounded by a set of rings.
Main Idea
Size and mass–each is very large and massive.
Detail Detail Detail Detail
- The Outer Planets
The Solar System
End of Section:The Outer
Planets
