Introduction and Key Terms 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 Plasma – gas with ionized particles (some) - Electrically conductive

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? It changed due to Eris – new discovery, larger than Pluto

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. Has “space” around it All the dwarf planets also orbit the Sun (b) there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence.

Classifying Planets Planets can be classified by: 1) Composition 2) Size 3) Proximity to the Sun 4) Position relative to Earth 5) History

1) Composition Rocky or Terrestrial planets (4) 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 Small planets (4) 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 Inner planets (4) 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 Inferior planets (2) Earth 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 Classical planets 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 is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighbourhood around its orbit, and is not a satellite. Celestial body is an astronomical body (planet, comet, etc)

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