The Sun & The Solar System

1. Chapter 26 The Sun & The Solar System

2. Chapter 26.1 The Sun’s Size, Heat, and Structure

3. The Sun’s Size • Diameter of about 1,400,000 kilometers • Could fit around 1 million Earths inside the Sun • Not a large star compared to other stars

4. The Sun’s Energy • All stars get their energy from fusion • Fusion = the combining of the nuclei of lighter elements to form heavier elements • E=mc2 (energy is equal to mass times the speed of light squared) • Means that matter can be converted into energy, which happens during fusion

5. The Sun’s Energy • Stars have such intense heat and pressure that atoms are torn apart into nuclei and electrons • Hydrogen and Helium exist as plasma • Plasma = a fourth state of matter consisting of charged particles

6. The Sun’s Energy • The nuclei are moving at such great speeds and under intense heat that they will fuse • When the nuclei fuse, it creates energy

7. Describe in your own words how the Sun generates so much energy.

8. The Sun’s Layers • The Core • Consists mostly of hydrogen and helium ions in a plasma state • 100 times as dense as water • Temperature : 15,600,000 oC

9. The Sun’s Layers • Radiative Zone • Layer of plasma that lies around the core • Temperature: cooler than the core • 8,000,000 oC near the core • 2,000,000 oC near the convection zone

10. The Sun’s Layers 3. Convection Zone • Rising and falling currents of plasma carry energy to the sun’s surface, where it is radiated out into space as sunlight • Temperature: 1,500,000 oC

11. The Sun’s Layers 4. Photosphere • The visible surface of the sun • Tops of the currents form structures called granules • 1,000 km wide and last for 20 minutes • Temperature: 6,000 oC

12. The Sun’s Layers 5. Chromosphere • Inner layer of the Sun’s atmosphere • Extends thousands of kilometers above the photosphere • Temperature : 20,000 oC • Hydrogen within emits a distinctive reddish light • Solar prominences: dense clouds of material that can erupt and extend into space

13. The Sun’s Layers 6. Corona • Thin outer atmosphere • Million times less bright than the photosphere • Temperature: 1,000,000 oC to 3,000,000 oC

14. What is plasma? How is it different from a liquid or a gas?

16. Features of the Sun

17. Sunspots • Dark spots on the photosphere • Range in size from barely visible to four time larger than Earth’s diameter • Very hot and bright • Look dark because the surrounding photosphere is so much hotter and brighter • Magnetic field is 1,000 times stronger than the surrounding photosphere

18. Sunspot Movement • Move from left to right across the sun’s surface • Indicates that the sun rotates on an axis • The sun is not a solid so the rate of rotation varies from place to place • Equator = 25 days • Poles = 34 days • 11 year cycle of peak activity

19. Solar Winds • Produced by a constant stream of electrically charged particles given off by the corona • Travel through space at speeds of about 450 km per second • Earth’s magnetic field deflects most solar winds

20. Auroras • As solar wind blows by past Earth, some particles interact with Earth’s magnetic field and upper atmosphere • Causes displays of color and light in the upper atmosphere • Called northern lights because they occur in regions near Earth’s magnetic poles

21. Mars has either no magnetic field or a very weak one. Why does this fact make it unlikely that life exists at the present time on the surface of mars?

22. Observing the Solar System: A History Chapter 26.2

23. The Movement of Planets and Stars • For thousands of years people believed that Earth stood still in the center of the universe • Geocentric Model = Earth – Centered Model

24. Star Movement? • As long as 6,000 years ago, astronomers were recording the movement of the stars • Imagined that stars were like holes in a solid celestial sphere that surrounded the Earth

25. Star Movement? • Beyond the sphere, was an intense light that shone through the holes • Concluded that the stars moved around Earth as the sphere rotated

26. Draw a picture of a geocentric model with the celestial sphere of stars

27. Constellations • Early astronomers noticed that the same constellation, or groups of stars, became visible at the same time every year. • Many cultures used the changing of constellations as a basis for a calendar

28. Planetary Movement • Early astronomers noted that not all points of light in the sky are fixed in constellations • Some wander across the sky, changing position over the course of days, weeks, and months • Inferred that these points of light were other planets that are closer to Earth than the stars are

29. Retrograde Motion • Early astronomers observed that most of the time planets moved eastward relative to the background of constellations EAST WEST

30. Retrograde Motion • Periodically the planets stopped moving eastward and moved westward for a few weeks, then resumed their eastward paths • This pattern of backward motions is called Retrograde Motion

31. What is retrograde motion? What do you think is causing this phenomenon?

32. Ptolemy’s Geocentric Model • Greek astronomer who lived in Egypt in 200 A.D • Developed a model that could be used to predict the location of the planets • Ptolemy’s model was used by astronomers until the 16th century

33. Ptolemy’s Geocentric Model • Each planet moves on small circular orbits called epicycles • The center of each small orbit moved around Earth on a larger circular orbit called a deferent

34. Ptolemy’s Geocentric Model • Retrograde motion occurred when the planet moved along the part of the epicycle that an observer on Earth could see. • However, Ptolemy’s model didn’t work perfectly. Observations did not always correlate with the models predictions

36. How did Ptolemy account for retrograde motion in his model of the solar system?

37. Copernicus’s Heliocentric Model • Polish Astronomer - 1473-1543 • Proposed a Heliocentric Model: Sun – centered solar system • Suggested that Earth was a rotating planet that revolved around the Sun

38. Copernicus’s Heliocentric Model • Retrograde Motion is a result of planets orbiting the Sun counterclockwise at different distances and speeds • Example: • Earth orbits faster than Mars • When Earth overtakes and begins to pass Mars, it make Mars appear to move backward • After Earth has fully passed, Mars’s normal motion appears to resume

40. Retrograde Motion Video • http://www.youtube.com/watch?v=72FrZz_zJFU

41. Use a Venn diagram to compare and contrast Ptolemy’s Model and Copernicus’s Model?

42. Tycho, Kepler, & Planetary Motion Tycho Brahe: Danish astronomer in the 16th Century • Studied the movement of moons and planets throughout their entire orbit • Discovered unexpected occurrences within the orbits • His record were the most precise before the invention of the telescope

43. Kepler’s Laws • Johannes Kepler - Tycho’s assistant • Discovered that the unexpected occurrences could be explained if the planets’ orbits were elliptical, rather than round • Developed 3 Laws of Celestial Mechanics

44. 1st Law of Planetary Motion • Planets travel in elliptical orbits with the sun at one focus • An ellipse has two foci on opposite side of the center • Since the Sun is located at one focus of the ellipse, a planet’s distance from the sun will change throughout its orbit

45. 2nd Law of Planetary Motion • Equal Area Law: each planet moves around the sun in such a way that an imaginary line joining the planet to the sun sweeps over equal areas of space in equal periods of time • Means that the speed at which a planet travels around the sun is not constant • Planets travel faster when they are closer to the Sun

46. 3rd Law of Planetary Motion • Harmonic Law: The period (P) of a planet squared is equal to the cube of its mean distance (D) from the Sun. P2 = D 3 • The farther the planet is from the sun, the longer its period of revolution

47. Isaac Newton and the Law of Gravitation • English scientist and mathematician 1642-1727 • Developed an explanation for what kept the planets in motion

48. Law of Gravitation • Every mass exerts a force of attraction on every other mass

49. Law of Gravitation • Every mass exerts a force of attraction on every other mass • The strength of that force is proportional to each of the masses

50. Law of Gravitation • Every mass exerts a force of attraction on every other mass • The strength of that force is proportional to each of the masses • The strength of that force is inversely proportional to the distance between them