Lesson 1: The Structure of the Solar System - The Motion of the Planets: We learned that one way an object in the solar system moves is by orbiting, or revolving, around another object. The amount of time it takes an object to revolve once around the Sun is its period of revolution. Then we learned that objects in the solar system also spin or rotate. The time it takes an object to rotate once is its period of rotation. Next we learned that the shape of a planet’s orbit is an ellipse which is a stretched-out circle. The Sun is at one of the foci of the ellipse so the distance between a planet and the Sun changes as the planet moves. A planet moves faster when it is closer to the Sun than when it is farther away.
Discussion Question:
If an asteroid is a sphere, could it be a planet? Explain your answer.
The asteroid would be spherical, and it orbits the Sun. However, its mass would not be much larger than the mass of objects around it, so it could not be a planet.
Lesson 2: The Inner Planets – Mercury: We learned that the inner planets made of rock which are the closest to the Sun, are also called terrestrial planets. Then we learned that the inner planets are made of rock and metallic materials. The outer layers of the inner planets are in the solid-state. Then we looked at Mercury which is the closest planet to the Sun. Due to its small mass, Mercury’s gravity is not strong enough to hold gases close to its surface so it has no atmosphere. Mercury has no wind to move energy from place to place so the temperatures on the side facing the Sun are always extremely high. The surface is covered with impact craters, smooth planes, and high cliffs. Mercury’s core is made of iron and nickel. Its mantle is made of oxygen and silicon.