6th Grade Science

Chapter 10 The Solar System

Notes Section 10.1

• What early astronomers observed that the Sun was the center of the solar system?

• Galileo and Copernicus both observed that the sun is the center of the solar system.

• What keeps the solar system together?• The Sun contains 99.86% of all the mass in the

solar system. Its gravity keeps the planets in their orbits.

Key Questions 1

The Tadpole Galaxy

Earth Centered View of the Solar System

Galileo’s observations of Jupiter and Venus supported a sun center view of the solar system.

Nicholas Copernicus observations of the planets led him to conclude that the Sun is the center of the solar system. He also explained why Mars seems to travel in a loop in its orbit. This apparent loop in Mars orbit it called retrograde motion.

The Sun’s huge mass keeps the planets in orbit around itself.

• What is a theory of how the solar system formed?• The solar system formed when a large cloud of

gas, dust, and ice condensed. The center was the sun. The outer part was the planets.

• Who believed that the planets did not orbit the Sun in circles?

• Johannes Kepler discovered that the planets move in ellipses not circles.

Key Questions 2

The Sombrero Galaxy

Solar System Formation Theory (see video)

Johannes Kepler 1571-1630

• What other discoveries did Kepler make?• He discovered that planets that are closer to the

sun move faster than those farther away from the sun.

• What is Earth’s average orbital speed?• Earth’s average orbital speed is 30 km/s (67,108

miles per hour).

Key Questions 3

Kepler’s Telescope

Kepler’s Model of the Solar System

The Earth is traveling around the sun at 30 km/s, or 18 miles per second, or 67,000 miles per hour.

1. Describe the Sun-centered model of the solar system. What holds the solar system together?

2. Explain how the planets in the solar system formed.3. Why is life unlikely on the outer planets in spite of the

presence of water, methane, and ammonia- materials needed for life to develop.

4. List two reason why the outer planets take longer to orbit the Sun than the inner planets do.

5. Would a year on the planet Neptune be longer or shorter than an Earth year? Explain.

Questions Section 10.1