Untitled Flashcards Set

Theories of Solar System Origins: Theories summarize how the Solar System originated and are based on current observations and facts. They may change with new discoveries.
Planet Formation Process: Planets form as natural by-products of star formation. A solar nebula (a giant cloud of gas and dust) contracts under its gravity, forming a star at the center with leftover material creating planets and moons.
Differences Between Terrestrial and Jovian Planets:
- Terrestrial Planets: High densities, few or no moons, moderate atmospheres.
- Jovian Planets: Low densities, many moons, thick atmospheres, rapid spin rates.

Models are based on current observations in space.
Our solar system may or may not be unique.
Theories are built on known facts and may evolve with new discoveries.
Planetary distances roughly double as you move outward.
Orbits lie in the same plane and travel in the same direction as the Sun's rotation.

Solar Nebula: A giant cloud of gas and dust contracts under its gravity, becoming denser and hotter.
Formation of the Sun and Planets:
- The Sun forms at the center.
- Leftover mass creates planets and moons.
- Planetesimals (small moon-like bodies) collide to form inner planets.
- Jovian planets form farther out, where lighter materials are more abundant.
End of Formation: Strong solar winds blow away remaining gas, forming the Kuiper Belt and Oort Cloud.
Collisions: Many unusual aspects of the solar system may result from late-stage planetary collisions.

Thousands of planets have been detected around other stars, most being Jupiter-sized.
Orbits range from inside Mercury’s orbit to beyond our gas giants.
Improved technology will help discover smaller Earth-like worlds.
The Kepler Spacecraft (launched in 2009) is designed to find Earth-like worlds.

Importance of Comparative Planetology: Comparing and contrasting planetary properties helps us understand their evolution and the solar system's structure.
Scale and Structure:
- One star (the Sun), 8 major planets, 6 dwarf planets, 172 moons, countless asteroids, meteoroids, and comets.
Definitions:
- Planet: Orbits the Sun, cleared its orbit of debris, and is round.
- Dwarf Planet: Orbits the Sun, is round, but hasn’t cleared its orbit.
- Moon: A natural satellite orbiting a larger body.
- Asteroid: Small rocky/metallic debris left from the Solar System's formation.
- Meteoroid: Smaller pieces of asteroids.
- Meteor: A meteoroid burning up in Earth’s atmosphere.
- Meteorite: A meteor that reaches Earth’s surface.
- Comet: A small icy body with elongated orbits.

Order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Planetary Properties:
- Jupiter is the largest; Mercury is the smallest.
- Mercury is the densest planet.
Terrestrial Planets: Mercury, Venus, Earth, Mars.
- Close to the Sun, small mass, solid surface, few/no moons, no rings.
Jovian Planets: Jupiter, Saturn, Uranus, Neptune.
- Far from the Sun, large mass, no solid surface, many moons, rings.
Other Regions:
- Asteroid Belt: Between Mars and Jupiter; likely a “failed planet.”
- Kuiper Belt: Past Neptune’s orbit, containing icy objects like Pluto and Eris.
- Oort Cloud: A spherical region extending 3 light-years from the Sun, with trillions of icy objects.

Voyager 1 and 2:
- Launched in 1977 to explore the solar system.
- Used gravity assist to gain speed.
- Voyager 1 visited Jupiter and Saturn; now the farthest man-made object.
- Voyager 2 visited all four outer planets; now the second-farthest object.
- Both are still transmitting data.