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 –non-stellar objects orbiting a star –Include planets, dwarf planets, moons, asteroids, meteoroids, comets, and cosmic dust.

Solar System A specific planetary system around a star Region that falls within the gravitational influence of a Sun Our Solar System –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/s 2

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: International Astronomy Union(2006) A “planet” is a celestial body that must: 1.Orbit a Sun 2.Have a sufficient mass for its self-gravity to shape it into a nearly round shape 3.Have cleared the neighbourhood around its orbit.

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 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.

Kupier Belt Lies beyond the gas giant Neptune Filled with trillions of icy objects.

Oort Cloud Massive spherical cloud that surrounds the Solar System Size of this cloud is disputed Some believe it starts 2000 or 5000 AU ends at 50,000 AU. Others think that it may extend to over 100,000 AU

Oort Cloud Named after the astronomer Jan Oort, who hypothesized its existence in Its existence has not yet been proven it is widely accepted in the scientific community. The Oort Cloud is filled with icy objects composed of ammonia, water and methane.

Other Celestial Bodies in Our Solar System Small Solar-System Bodies –Asteroids –Comets