Astronomy Chapter 2 The Solar System

1. Astronomy Chapter 2The Solar System Observing the Solar System Section 1

2. Vocabulary • Geocentric: A description of the solar system in which all of the planets revolve around Earth • Ellipse: An elongated circle, or oval shape; the shape of the planets’ orbits • Heliocentric: A description of the solar system in which all of the planets revolve around the sun • Intertia: the tendency of a moving object to continue in a straight line or a stationary object to remain in place

3. Main Ideas • Ptolemy thought that Earth is at the center of the system of planets • Copernicus thought that the sun is at the center of the planets. Galileo’s observations supported Copernicus’s theory. • Kepler discovered that the orbits of the planets are ellipses • Newton concluded that two factors—inertia and gravity—combine to keep the planets in orbit

4. Guiding Questions • How is Copernicus’s description of the system of planets different from Ptolemy’s description? • How did Galileo’s observations of Jupiter’s moons help to show that the geocentric explanation is incorrect? • What shape are the orbits of the planets? How was the discovery of this orbit shape made? • What two factors act together to keep the planets in orbit around the sun?

5. The SunSection 2

6. Vocabulary • Nuclear fusion: the process by which hydrogen atoms join together to form helium, releasing energy • Core: the central part of the sun, where nuclear fusion occurs • Photosphere: the inner layer of he sun’s atmosphere • Chromosphere: the middle layer of the sun’s atmosphere • Corona: the outer layer of the sun’s atmosphere

7. Vocabulary • Solar wind: a stream of electrically charged particles produced by the sun’s corona • Sunspot: A dark area of gas on the sun that is cooler than surrounding gases • Prominence: a loop of gas that protrudes from the sun’s surface, linking parts of sunspot regions • Solar flare: an explosion of hydrogen gas from the sun’s surface that occurs when lops in sunspot regions suddenly connect

8. Main Ideas • The sun’s energy comes from nuclear fusion • The sun’s atmosphere has three layers: the photosphere, the chromosphere, and the corona • Features on or above the sun’s surface include sunspots, prominences, and solar flares

9. Guiding Questions • How is energy produced in the sun’s core? • Name the layers of the sun’s atmosphere. • What is the solar wind? • Describe three features found on or above the surface of the sun. • Why do sunspots look darker than the rest of the sun’s photosphere? • How does the number of sunspots change over time?

10. The Inner PlanetsSection 3

11. Vocabulary • Terrestrial planets: the name given to the four inner planets, Mercury, Venus, Earth, and Mars • Retrograde rotation: The spinning motion of a planet from east to west, opposite to the rotation of most planets and moons • Greenhouse effect: the trapping of heat by a planet’s atmosphere

12. Main Ideas • The four inner planets—Mercury, Venus, Earth, and Mars—are small and have rocky surfaces. They are often called the terrestrial planets

13. Guiding Questions • What features do all of the inner planets have in common? • What is Mercury’s atmosphere like? Explain • Why can astronomers see the surface of Mars clearly, but not the surface of Venus? • How have astronomers been able to study the surface of Venus? • What evidence do astrnomomers have that water once flowed on Mars?

14. The Outer PlanetsSection 4

15. Vocabulary • Gas Giant: the name given to the first four outer planets: Jupiter, Saturn, Uranus, and Neptune

16. Main Ideas • Four outer planets—Jupiter, Saturn, Uranus, and Neptune—are much larger than Earth • Pluto and Charon have solid surfaces and masses much less than that of Earth

17. Guiding Questions • How are the gas giants similar to each other? How are they different? • How is Pluto different from the gas giants? • What is the most prominent feature of Jupiter’s surface? What cuases this feature? • Why do astrnomoers think Uranus may have been hit by another object billions of years ago?

18. Comets, Asteroids, and MeteorsSection 5

19. Vocabulary • Comet a ball of ice and dust whose orbit is a long narrow ellipse • Asteroid: objects revolving around the sun that are too small and too numerous to be considered planets • Asteroid belt: the region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found • Meteoroid: a chunk of rock or dust in space • Meteor: a streak of light in the sky produced by the burning of a meteoroid in Earth’s atmosphere • Meteorites: a meteoroid that has hit Earth’s surface

20. Main Ideas • Comets are chunks of ice and dust that usually have long, elliptical orbits • Most asteroids revolve around the sun between the orbits of Mars and Jupiter

21. Guiding Questions • What is a comet made of? • Where are most asteroids found? • What are the main sources of meteoroids? • What is the difference between a meteor and a meteorite?

22. Is There Life Beyond Earth?Section 6

23. Vocabluarly • Extraterrestrial Life: life that arises outside of Earth

24. Main Ideas • Earth has liquid water and a suitable temperature range and atmosphere for living things to survive. • Since life as we know it requires water, scientists hypothesize that mars may have once had the conditions for life to exist

25. Guiding Questions • What conditions does life on Earth need to survive? • Why do astronomers think there could be life on Europa? • How did the Viking missions search fro life on Mars?