Pick up 2 packets. Draw on the back of your notes packet:

1. Pick up 2 packets.Draw on the back of your notes packet: • 1. Your picture of the 8 planets orbiting around the sun. • What type of solar system is this called? • 2. Your picture of how ancient people must’ve drawn the planets orbiting around Earth. Remember, they had to keep their observations of retrograde motion in mind! • What is retrograde motion? • What type of solar system is this called?

2. History of our Knowledge of the Solar System Early Ideas Geocentric Universe Early Astronomers Separated Stars from Planets Planets movements can be tracked because stars do not move. Ptolmey: Geocentric Universe Earth is the center of the universe. All the planets and the Sun revolve around the Earth

3. Geocentric Model of the Universe Problems 1). Retrograde Motion A sudden change in planetary motion Planets switch from moving East to moving West Very hard problem to solve Scientists began looking for a better model of the universe/solar system. http://www.youtube.com/watch?v=ln1fHZvRr8o

4. Retrograde Motion Solved Copernicus Retrograde Motion Explained In 1543, he suggested a heliocentric model of the universe Sun centered Earth and all other planets orbit the Sun Why do we see planets moving backwards? Inner planets move faster then outer planets around the Sun. Earth will “pass” a slower moving planet This planet appears to move backward temporarily.

5. What is Eccentricity Eccentricity Details What is eccentricity? Ratio of distance between the foci to the major axis. Change in distance from the focus points; such as distance of a planet from the Sun. Planets are not always the same distance away from the Sun. http://www.youtube.com/watch?v=BIBz_GQDga0 The point in orbit when the planet comes nearest to the Sun = Perihelion The point in orbit when the planet is farthest from the Sun = Aphelion

6. Kepler’s Laws 1st Law Astronomical Unit Most planets orbit the Sun in an elliptical shape More oval like Earth being the exception Earth believed to move between an elliptical orbit and a circular orbit every 100,000 yrs or so. Planets orbit while staying centered around 2 points. Sun is one point How we measure the average distance between the Sun and planets. Sun to Earth = 1 astronomical unit (AU)

7. Kepler’s Law • Planets sweep out equal areas in equal times.

8. Perihelion/Aphelion on Earth

9. Gravity In the late 16th century early 17th century Galileo was working with gravity. Performed experiments dropping objects off the Tower of Pisa and rolling balls down inclines • Galileo found • Gravity accelerates the fall of all objects at the same rate. • Air resistance causes lighter objects to fall more slowly.

10. Gravity Sir Isaac Newton Basics 1687 Newton published his theory of universal gravitation. Also called the inverse square law This theory helped discover Neptune. Watched Uranus’s movements Something large was affecting the movements of the planet. Two objects attract each other Depends upon their mass AND the distance between them.

11. Law G = Constant 6.6726 X 10-11 This knowledge of gravity produced the law of universal gravitation. • The larger the objects (m) the stronger the force of gravity between them. • The farther apart the objects (d) the weaker the force of gravity. • Distance squared weaker

12. 3/7/13 Astronomy: Part 2 Stars

13. Fact or Fiction • Stars twinkle in the night sky • Twinkle: Change in Brightness

14. Beginning of A Stars Lifecycle • 1). Interstellar Cloud/Nebulae • Big Cloud of Gas and Dust • Once enough gas has collected the nebulae will condense forming a…. • 2). Protostar: Pre-star • As the protostar continues to condense it will heat up until it hits Critical Mass and… • 3). Nuclear fusion begins • Now we have a real main sequence star. • Main Sequence = Stable

15. What is a Star? • Star = A cloud of gas, mainly hydrogen and helium with a core so hot and dense that that nuclear fusion can occur. • Very Common • Purpose/Jobs • 1). Provide Light • Heat Energy • Warms Planet Earth • 2). Nuclear fusion within stars converts light elements into heavier ones

16. Nuclear Fusion • Create new more complex elements • Without these life would not be able to form • Will continue in a star until no heavier element can be produced • Iron is the ultimate stopping point • Helps balance out the force of gravity trying to act on stars • When fusion stops, gravity will win and cause the star to collapse. • This is when a star begins to die.

17. Important Star Qualities • Three Main Characteristics • Brightness/Magnitude • Light releasing capacity • Color • Determines Temperature • Size • Determines means of Death

18. Stars Magnitude/Brightness Magnitude The brightest star the night sky is Sirius. magnitude of -1.46 it is almost 15 times brighter than a star with a magnitude of zero. Stars with a magnitude of 8 or more are too dim to see with the naked eye. • Tells us how luminous the star is/ How much energy is being produced in the core • Astronomers rate the magnitude of a star with a scale that gives brighter stars a low number and dim stars a higher number. • Each whole number on this scale is 10 times dimmer than the previous number.

19. Color of Stars • Stars are identified by their color, which indicates their temperature. • They are divided into what are known as spectral classes. • These classes are O, B, A, F, G, K, and M. • Class O stars are the hottest and are blue in color. • The coolest stars are identified as class M and are red in color.

20. Star Size • Determines the length of a star’s life • Large Stars = Burn Out Quickly • Small Stars = Use fuel more slowly • Around for much longer periods of time. • Star size also determines the death route a star will take.

21. The Death of an Average Size Star • Fusion of Hydrogen Stops • No longer a main sequence star • Red Giant •  Large star that is reddish or orange in color • Reaching sizes of over 100 times the star's original size. • Late phase of development in a star's life • Hydrogen has been exhausted and Heliumis being fused. • This causes the star to collapse, raising the temperature in the core. • The outer surface of the star expands and cools, giving it a reddish color. • This phase will continue until the star completely runs out of fuel • Planetary Nebulae • When nuclear fusion stops • Stars blow away their outer layer of atmosphere • White Dwarf • Remaining core of the star • Present after atmosphere has blown away • Still very hot so it glows white until it cools off • Black Dwarf • Cooled off core of a star

22. Death of A Massive Star • Fusion of Hydrogen Stops • No longer a main sequence star • Red Supergiant • Extremely large star that is reddish or orange in color • Reaching sizes of over 1000times the star's original size. • Late phase of development in a star's life • Hydrogen has been exhausted and Heliumis being fused. • This causes the star to collapse, raising the temperature in the core. • The outer surface of the star expands and cools, giving it a reddish color. • This phase will continue until the star completely runs out of fuel • Betelgeuse in Orion is an example of a red supergiant star.

23. Death of A Massive Star Continued • Supernova •  violent explosion • ejects most of its mass. • often briefly outshines an entire galaxy • fade from view over several weeks or months • Neutron Star • If the remaining mass of the star is about 1.4 times that of our Sun, the core is unable to support itself and it will collapse further to become a neutron star. • The matter inside is compressed so tightly that its atoms are compacted into a dense shell of neutrons. • Black Hole • If the remaining mass of the star is more than about three times that of the Sun, it will collapse so completely that it will literally disappear from the universe. • What is left behind is an intense region of gravity called a black hole.

24. Planet Types Terrestrial Planet Gas Planet Inner Four Planets Closest to the Sun Mercury, Venus, Earth, and Mars Close to the size of Earth Solid, Rocky Surfaces Outer four Planets Farthest from the Sun Jupiter, Saturn, Uranus, Neptune Larger More Gaseous Lack Solid Surfaces

25. How Do Scientists Know How Our Solar System Formed? • Earth Based Studies • Use of telescopes in all wavelengths of the electromagnetic spectrum. • Data From Probes • Scientists Examined • 1). Why the planets are so different. • Especially Outer and Inner Planets • 2). Asteroids, Meteorites, and Comets.

26. Formation of Our Solar System Interstellar Clouds Huge Clouds of Dust and Gas in Space Made of Hydrogen and Helium Form Stars and Planets These Interstellar Clouds usually look dark because the dust blocks light. Like Smog Stars behind this cloud can’t shine through it.

27. Formation of our Solar System Interstellar Cloud But….Sometimes the light from stars within the cloud causes these interstellar clouds to glow.

28. Formation of our Solar System Location There are many interstellar clouds found within our Milky Way Galaxy. We look for high amounts of gas and dust. When enough gas and dust is present, scientist think these interstellar clouds will condense because of gravity. Can form a star or planet

29. Formation of our Solar System Collapsing Interstellar Cloud Cloud begins collapsing slowly. The smaller it gets the faster it begins to collapse and spin This spinning motion with eventually form a rotating disk with a very dense center (core).

30. Formation of our Solar System Scientist believe that one huge interstellar cloud called the solar nebula formed the Sun and all the planets. The Sun formed first in the center of this cloud. Fits with why our Sun is the brightest most dense thing in our solar system. In the center of the cloud it was the hottest On the edges of the cloud it was the coldest

31. Formation of our Solar System So What? This difference in temperature as the solar system cooled caused materials to condense and be located in very narrow regions of the solar system This is why we see inner planets and outer planets have such different composition.

32. Development of Planets Once these materials condense out they begin to collide and stick together. Keep growing larger until they form planetesimals Objects 100’s of km in diameter To produce planets, planetesimals must collide and stick together

33. Development of Planets Outer Planet Formation 1st planet of the gas to form was Jupiter This is why Jupiter is the largest. Had the most materials to build with Then Saturn and the rest of the gas giants formed Not as large because Jupiter hogged most of the materials; gas, dust, and ice to make itself. Leftovers became Moons

34. Development of Planets Inner Planet Formation Inner planets were forming from the collision of planetesimals. Made of very different things Sun took all the gas and floating debris away from the inner planets. Why they are rocky and dense Why Moons are rare for inner planets.

35. Space Rocks 101 Asteroid Leftover pieces of Planetesimals These were never planets Asteroids can collide and break apart.

36. Space Rocks 101 Meteoroid Meteor When an asteroid or any space material falls toward Earth and enters Earth’s atmosphere. The streak of light produced when a meteoroid burns up in Earth’s atmosphere.

37. Space Rocks 101 Meteorite When a space object impacts Earth Occurs when all of the meteoroid does not burn up in Earth’s atmosphere Meteor Crater: Arizona Gosses Bluff, Australia

38. Space Rocks 101 Comets Small icy and rocky bodies with a highly eccentric orbit around the Sun. When Earth is in the way of a comet’s orbit we see a meteor shower