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Our Solar System Introduction and Key Terms Learning Outcomes (Students will…) -Explain the theories for the origin of the solar system -Distinguish between questions that can be answered by science and those that cannot, and between problems that can be solved by technology and those that cannot with regards to solar system formation. -Estimate quantities of distances in parsec. Estimate the age of the solar system. -Describe and apply classification systems and nomenclature used in the sciences. Classify planets as terrestrial vs. Jovian, inner vs. outer, etc. Classify satellites. Classify meteoroid, asteroid, dwarf planet, planet. Classify comets as long period vs. short period. etc -Formulate operational definitions of major variables. Given data such as diameter and density describe the properties that divide the planets and moons into groups. -Tools and methods used to observe and measure the inner and the outer planets and the minor members of the solar system Planetary Systems • A planetary system consists of the various non-stellar objects orbiting a star such as planets, dwarf planets, moons, asteroids, meteoroids, comets, and cosmic dust. Solar System • A specific planetary system around our star • The region of space that falls within the gravitational influence of our Sun • If you consider the edge of the Solar System to be Pluto’s orbit, the Solar System has a diameter of 79 AU • Consists of: – – – – – – an ordinary yellow star – the Sun Eight Planets Their moons Dwarf planets Asteroids, Comets, Meteors and Meteorites Cosmic dust Star • A star is a massive, luminous ball of plasma that is held together by gravity. • Our star is the Sun • The gravity on the Sun is 274 m/s2 Planets • There are now 8 planets in our Solar System • The Sun is one of the foci for each of these planets What is a Planet? • Former definition: NASA (2000): – Planet: A non-luminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves. – What is wrong with this definition? – Why did the definition change? New definition: NASA (2006): A “planet” is a celestial body that • (a) is in orbit around the Sun, • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and • (c) has cleared the neighbourhood around its orbit. Classifying Planets • Planets can be classified by: – 1) – 2) – 3) – 4) – 5) Composition Size Proximity to the Sun Position relative to Earth History 1) Composition A) Rocky or Terrestrial planets (4) B) Jovian planets (4) Terrestrial Planets - Composed primarily of rock and metal - No rings - Few satellites (moons) - High density - Slow rotation - Solid surface Jovian Planets - Composed primarily of gas (hydrogen and helium) - Rings - Many satellites (moons) - Low density - Rapid rotation - Deep atmospheres 2) Size A) Small planets (4) B) Giant planets (4) Small Planets - Diameters less than 13,000 km Giant Planets - Diameters greater than 48,000 km - Also called gas giants 3) Proximity to Sun A) Inner planets (4) B) Outer planets (4) The asteroid belt between Mars and Jupiter forms the boundary between the inner solar system and the outer solar system. 4) Position relative to Earth A) Inferior planets (2) B) Earth C) Superior planets (5) Inferior Planets - - Closer to the Sun than Earth Show phases like the Moon’s when viewed from Earth Superior Planets - - Farther from the Sun than Earth Always appear full or nearly full 5) History A) Classical planets B) Modern planets C) Earth Classical Planets • • • Known since prehistoric times Visible to the unaided eye (no telescope needed) In ancient times this term also referred to the Sun and the Moon Modern Planets • • Discovered in modern times Visible only with optical aid or telescope What is a Dwarf Planet? • NASA (2006): A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. Other Celestial Bodies in Our Solar System • All objects besides planets and dwarf planets, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”. • Some “small Solar-System bodies” include: – Asteroids – Comets