1. The Solar System

2. Models of the Solar System Important people in astronomy Aristotle (384-322 BC)- promoted an Earth-centered, or geocentric, model of our solar system. Everything revolved around the Earth? WRONG!

3. Copernicus- a Polish astonomer, challenged geocentric belief and proposed a heliocentric, or Sun- centered, model of the solar system in which the planets were in orbit around the Sun Galileo Galilei- confirmed Copernicus’ beliefs by observing the planets through his newly invented telescope

9. Tycho Brahe- a Danish astronomer, devoted his life to making detailed observations of the positions of the stars and planets Kepler- assistant to Brahe, developed three laws that explained most aspects of planetary motion

10. Kepler’s Three Laws I. Law of Ellipses- Each planet orbits the Sun in a path called an ellipse II. Law of Equal Areas- Describes the speed at which the different planets travel at different points in their orbits. –Example: The Earth travels fastest when closest to the Sun

11. III. Law of Periods- Describes the relationship between the average distance of a planet from the Sun and the orbit period of a planet Orbit period- time required for a planet to make one revolution around the Sun

12. The Inner Planets

13. The four planets closest to the Sun are called the inner planets, or the terrestrial planets They are called the terrestrial planets because they are similar to Earth

14. These planets consist of mostly solid rock with a metal core They do not have rings They number of moons of these planets vary from 0-2 The inner planets also impact craters on their surface

15. Mercury Planet closest to the Sun Shorter orbit period rthan any other planet- 88 days Named by Romans, after Mercurius, a swift messenger of the gods One rotation of Mercury = 59 Earth days

16. Mercury has no moons In 1974 and 1975 Mariner 10 (NASA spacecraft) visited Mercury Mercury was once volcanic Temperature: during the day  427*C and during the night – 137*C Weak magnetic field

18. Venus Second planet from the Sun Orbit period of Venus is 225 days One rotation of Venus = 243 Earth days The direction of rotation is opposite that of other planets Meaning that the Sun rises in the west and sets in the east

19. Has no moons Venus is often called the Earth’s twin due to being about the same size and having the same mass and density Much hotter than the Earth because of closeness to the Sun and thick atmosphere that provides insulating effect

20. Average surface temperature is approximately 453*C Atmospheric pressure is about 100 times that of Earth. What does that mean? May have had oceans and volcanic activity at one time Clouds on Venus are composed of sulfuric acid

21. In the 1970’s, the Soviet Union sent six Venera probes to Venus Between 1990-94, the Magellan (NASA spacecraft) orbiter produced radar images of most of the Venusian surface

25. Earth Orbit period is 365.24 days Completes one rotation in about 23 hours and 56 minutes Is the fifth largest planet in our solar system Has one moon

26. At this point in the solar system’s history, the Earth is like no other planet. What does this mean? Life on Earth is possible because of it’s distance from the Sun, meaning the temperature is warm enough for water to exist as liquid while Venus and Mercury are too hot to retain liquid water

27. Water on other planets- (Mars and outer planets) do not have liquid water due to the coldness of these planets and water exists on these planets in the form of ice Liquid water is the key to life existing on Earth

35. Mars Fourth planet from the Sun Orbit period is 687 days One rotation = 24 hours and 37 minutes Length of day on Mars and Earth are very close Also has seasons much like the Earth due to tilt of it’s axis

36. Has 2 moons Geologically active planet Volcanoes on Mars are the largest in the solar system Example: Olympus Mons, which is 3 times higher than Mt. Everest and it’s base is about the size of Nebraska Deep canyons cover the surface: the largest is Valles Marineris, which is as long as the United States

37. Atmospheric temperature and pressure are presently to low for water to exist in liquid form Viking I and Viking II (NASA spacecraft) found evidence of erosion by water on the surface of Mars; from this astronomers can infer that Mars once had a warmer and wetter climate

38. The little water that is left on Mars is frozen in polar ice caps and possibly beneath the surface Mars Pathfinder (NASA spacecraft) took wonderful pictures of Mars and studied the surface extensively You will see humans walk on Mars in your lifetime To reach other planets is the only way to ensure human existence in the future

52. The Outer Planets

53. The outer planets are composed of the five planets farthest from the Sun and are called the Jovian planets Although Jovian planets are far larger than the terrestrial planets (except Pluto) they are far less dense than terrestrial planets

54. Jupiter First of the outer planets Fifth planet from the Sun Largest planet in the solar system It’s mass is twice that of the other 8 planets combined Orbit period is almost 12 years

55. Rotation is faster than any other planet at 9 hours and 50 minutes Has at least 16 moons One ring made up of millions of particles Seems to have a liquid metallic core surrounded by lighter elements Temperature in the interior of Jupiter can rise as high as 30,000*C

56. Intense pressure has changed most of the interior of the planet into a sea of liquid hydrogen Has an enormous magnetic field Jupiter is mostly made up of gases 92% of the planet is made up of hydrogen and helium No evidence for possibility of life on Jupiter

57. Extensive atmosphere The Great Red Spot is a giant rotating storm, somewhat like a hurricane on Earth Galileo (NASA spacecraft) reached Jupiter in 1995 and dropped an entry probe into it’s atmosphere and observed wind speeds of 600 km/hour

61. Io

63. Ganymede

64. Callisto

65. Europa

70. Saturn The sixth planet from the Sun A half a billion kilometers farther from the Sun than Jupiter Second largest planet in the solar system Average temperature is –176*C Has 22 moons

71. Has several rings Orbit period is 29.5 years Rotates on it’s axis every 10 hours and 40 minutes Small rocky core with interior of liquid metallic hydrogen

72. Dense atmosphere composed of hydrogen and helium gas Much less dense than Jupiter (least dense in the solar system) Very complex system of rings

77. Uranus The seventh planet from the Sun Third largest planet in the solar system Discovered in 1781, first to be discovered since ancient times Great difficulty seeing since it is nearly 3 billion kilometers from the Sun. Has 15 moons

78. Has 11 small rings Orbit period is 84 years Rotates once every 17 hours Voyager 2 (NASA spacecraft) in 1986 discovered exact rotation rate of Uranus Atmosphere contains methane (gives greenish color) Atmosphere is mainly made up of the gases hydrogen and helium

82. Neptune The eighth planet from the Sun Similar to Uranus in size and mass Orbit period is 165 years Rotates around every 16 hours Has 8 moons Possibly 4 rings

83. Named after Neptune, the Roman god of the sea 4.5 billion kilometers from the Sun Voyager (NASA spacecraft) indicated from it’s voyage that Neptune’s atmosphere is made up largely of hydrogen, helium, and methane Very active weather system

84. Solar system’s strongest winds, exceeding 1000 km/hour Average temperature is –225*C An Earth-sized storm noted named The Great Dark Spot

88. Asteroids, Comets, and Meteoroids

89. Asteroids Largest of smaller bodies in the solar system are called asteroids Fragments of rock that orbit the Sun Astronomers have observed more than 50,000 asteroids

90. Millions may exist in the solar system Most have elliptical orbits Largest known asteroid is Ceres, is about 1000 km. In diameter Most asteroids exist in an area between Mars and Jupiter known as the asteroid belt

93. Comets Orbit the Sun in long ellipses A comet is a body of rock, dust, methane, ammonia, and ice The nucleus of a comet are usually made up of rocks, metals, and ice and are usualy between 1 to 100 km in diameter

94. A spherical cloud of gas and dust,a coma, surrounds the nucleus Bright appearance of a comet is due to sunlight reflecting off the coma Nucleus and coma combine to form the head of a comet Most spectacular part of a comet is it’s tail Tail is made up of gas and dust that streams out of the head

95. Formed by solar winds pushing gas and dust away from the head of a comet Tail always points away fro the Sun Oort Cloud- a spherical cloud of dust and ice that contains the nuclei of as many as a trillion comets This cloud surrounds our solar system

96. Long-period comets- have orbit periods of several thousand or several million years Short-period comets- have orbit periods of up to 100 years

101. Meteoroids Smaller bits of rock or metal that move throughout the solar system Most are less than 1 mm in diameter Most are small pieces of matter that come detached from comets

102. Larger meteoroids are more than 1 cm in diameter and are produced by collisions between asteroids. When a meteoroid enters the Earth’s atmosphere it is called a meteor. Most burn up when entering the atmosphere and never reach the Earth’s surface

103. Meteor shower- when a large number of small meteoroids enter the Earth’s atmosphere in a short period of time Astronomers estimate that about one million kilograms of matter from meteors falls to the Earth each day If a meteor actually reaches the Earth’s surface it is called a meteorite

104. Can possibly leave large craters: one of the best known is Meteor Crater in Arizona, struck the Earth about 20,000 years ago The meteor as it entered the Earth’s atmosphere was 50 meters in diameter weighed approximately 500,00 tons Crater is 1.3 km in diameter and 180 meters deep

105. 3 types of meteorites 1. Stony meteorites- look very similar to Earth rocks 2. Iron meteorites- have a distinctive metallic appearance 3. Stony-Iron meteorites- contain both iron and stone and are very rare

118. Various

123. The End A 923 Production