The Solar System Each galaxy is made up of thousands of solar systems – collections of celestial objects that revolve around one or more suns. It is estimated that our solar system is 5 billion years old. It is theorized that a solar system evolves as a collection of gas and dust that combined forming a sun due to gravitational attraction. Once this “new sun” forms, masses of gas/dust around the sun form celestial bodies (planets) revolving around the sun.

Components of the Solar System PLANET: Spherical objects that revolve around the Sun COMET: Small, solid masses of dust/ice that have an orbit around the Sun. ASTEROID: Irregular, solid mass that revolves around the Sun. METEOROID: Very tiny solid masses that revolve around the Sun. If these masses enter Earth’s atmosphere they are known as METEORS. METEORITES are the remnants of a meteor found on the Earth’s surface MOON: Spherical object that revolves around a planet or asteroid.

Characteristics of Planets RT = Pg. 15 The distance between a planet and the Sun has an effect on the other characteristics a planet might exhibit.

RT = Pg. 15 What patterns can you make between the planets in the Solar System using this chart?

Terrestrial Planets MERCURY VENUS EARTH MARS During the formation of the Solar System, the terrestrial planets were impacted by the high temperatures and pressure from the Sun. Less dense elements were pushed out of the inner solar system. Terrestrial Planets: 1.…are closer to the sun. 2.…have small diameters. 3.…have high densities. 4.…have solid surfaces. 5.…have few or no moons.

Jovian Planets During the formation of the Solar System, the Jovian planets were not impacted by the high temperatures and pressure from the Sun. These planets are made up of the less dense elements that were pushed out of the inner solar system. Jovian Planets: 1.…are further from the sun. 2.…have large diameters. 3.…have low densities. 4.…have gaseous surfaces. 5.…have many moons. JUPITER SATURN URANUS NEPTUNE

Planetary Motions Rotation is the movement of a planet on an imaginary axis that runs through it. The time to complete one full rotation is known as a day. The Earth rotates from west to east. Revolution is the movement of a planet on a path (orbit) around the sun. The period of time to complete one full revolution is known as a year. Planets revolve counterclockwise around the sun.

Orbital Shape A planet’s revolution around the sun is not in the form of a perfect circle, but rather an oval shape. This shape is known as an ellipse. Each planet’s “elliptical orbit” is not the same. Eccentricity is a measure of the shape of an orbit around another celestial object. Orbits that are “very eccentric” tend to be flat and oval. Orbits that are “less eccentric” tend to be more circular.

Eccentricity d = distance between foci L = length of the major axis f1f1 f2f2 Eccentricity: e = d L RT = Pg. 1 orbit Eccentricity is the measurement of the orbital shape of a celestial body. f 1 = the sun the planet revolves around. f 2 = an area in space along the major axis between the sun and the orbit. Orbits that are “nearly circular” have an eccentricity close to 0 Orbits that are “very flat and oval-like” have an eccentricity close to1

Eccentricity d = distance between foci L = length of the major axis f1f1 f2f2 Eccentricity: e = d L RT = Pg. 1 orbit Planet “X” Determine the eccentricity of Planet “X”? Eccentricity: e = e =

Orbital Velocity The revolution of one celestial object around another (Ex: planet around a sun) is a balance between the forces of inertia and gravity. Inertia is the property in which matter remains in a state or rest or motion, unless an opposing force acts upon it. Gravity is the attractive force between any two objects in the universe. The orbital velocity of a celestial body is in dynamic equilibrium – between inertia and gravity. Pathway of inertia Gravitational force between Sun and planet

Orbital Velocity Due to the eccentricity of orbits in the Solar System, the orbital velocity of a celestial body will change during its revolution. In perihelion, the planet is closest to the Sun in its orbit. The gravitational force is greatest between the planet and the Sun. The orbital velocity would be greatest at this time. In aphelion, the planet is furthest away from the Sun in its orbit. The gravitational force is at its lowest between the planet and the Sun. The orbital velocity would be the slowest at this time.

Orbital Velocity The further a planet is from the Sun in the Solar System… The weaker its gravitational attraction with the Sun… The slower its orbital velocity… The longer its period of revolution… Ex: Compare the orbital velocities of Venus and Mars. Mars is further from the Sun than Venus. Mars has a period of revolution that is 687 days. Venus has a period of revolution that is days. Venus has a shorter period of revolution and is closer to the Sun than Mars. Thus, Venus has a greater orbital velocity than Mars.