1. Guided Notes on Our Solar System Chapter 29, Section 1 and Chapter 29, Section 4

2. In 1543, Copernicus suggested that the Sun was the center of the Solar System. This is known as the heliocentric model of the solar system.

3. 2. In a heliocentric model, the inner planets move faster in their orbits than the outer planets do.

4. 3. Kepler’s first law states that each planet orbits the Sun in an ellipse, rather than a circle. An ellipse is an oval shape that is centered on 2 points, instead of a single point, as in a circle.

5. 4. Each planet’s elliptical orbit is a different size and shape, and the Sun is always at one focus.

6. 5. The length of time it takes for a planet to travel a complete elliptical orbit around the Sun is called the orbital period.

7. 6. Kepler’s second law found that an imaginary line between the Sun and a planet sweeps out equal amounts of area in equal amounts of time.

8. 7. Issac Newton’s law of universal gravitation states that every pair of bodies in the universe attract each other with a force that is proportional to the product of their masses and inversely proportional to the distance between them.

9. 8. Stars and planets form from clouds of gas and dust, called interstellar clouds, which exist in space between the stars.

10. 9. Hydrogen and Helium make up most of the interstellar cloud.

11. 10. An interstellar cloud can start to condense as a result of gravity and become concentrated enough to form a star and planets. Astronomers believe our solar system formed this way.

12. 11. A solar nebula is the disk of dust and gas that formed the Sun and planets.

13. 12. The growth of planets occurs because of continued collisions and mergers of planetesimals.

14. 13. The inner planets are rocky and dense because the Sun’s gravitational force swept up much of the gas in the area of the inner planets.

15. 14. Jupiter’s gravitational force prevented the planetesimals in the asteroid belt from merging to form a planet.

16. 15. Asteroids range in size from a few kilometers to about 1000 km in diameter and have pitted, irregular surfaces.

17. 16. When interplanetary material enters Earth’s atmosphere, it is called a meteoroid. If it burns up in Earth’s atmosphere, it will produce a streak of light called a meteor. Pieces that do not completely burn up and collide with the ground are called meteorites.

18. 17. Comets are small, icy bodies that have highly eccentric orbits around the Sun. They are made of ice and rock.