Characteristics of Planetary Orbits and Rotations

Characteristics of the Solar System

• The orbits of the planets are nearly circular and lie in roughly the same plane.
• The direction of the planets' orbits around the Sun is the same as the Sun's rotation on its axis.
• Most planets rotate on their axes in the same direction as the Sun.

Asteroids

• Asteroids are rocks of various sizes (over 100m across), with densities similar to inner planets.
• Most asteroids remain in the Asteroid belt between Mars and Jupiter.
• Three asteroids hit the Earth every 1 million years.
• Asteroid sizes range from 100m to about 1000km.
• They are composed of carbon, iron, and other rocky materials.

Dwarf Planets

• Larger asteroids, like Ceres, are classified as dwarf planets if they have enough mass and a gravitational field strength.
• Dwarf planets have a spherical shape but lack enough mass to clear the area around them of smaller objects.

Planets

Terrestrial Planets

• Mercury, Venus, Earth, and Mars are close to the Sun, with small masses and radii.
• They have rocky, solid surfaces with a layered structure, high densities, and slow rotation.
• They have weak magnetic fields, no rings, and few moons.

Jovian Planets

• Jupiter, Saturn, Uranus, and Neptune are far from the Sun, with large masses and radii.
• They have gaseous surfaces, low densities, fast rotation, and strong magnetic fields.
• They have many rings and numerous moons.

Individual Planets

Venus

• Venus has no moons.
• Its 'spin time' is 243 Earth days.
• Its maximum surface temperature may reach 460°C.

Mars

• Mars is the Earth's nearest neighbor, with temperatures rarely above 0°C even in summer.
• It has no liquid water on the surface, but has ice caps at the poles.
• Mars appears red due to iron oxide (rust) in its soil.

Jupiter

• Jupiter is the largest and most massive planet, with a diameter 11 times bigger than Earth's.
• It is a gaseous planet, noted for its Great Red Spot.

Saturn

• Saturn is composed almost entirely of hydrogen and helium.
• It has many rings made of ice and a turbulent atmosphere.

Uranus and Neptune

• Both have rings and many moons.
• They are large, cold, and windy planets, with blue color due to methane gas in their atmospheres.
• Neptune has the fastest winds in the solar system.

Pluto

• Pluto has 5 moons.
• Part of its orbit passes inside Neptune's, making Neptune the farthest planet from the Sun at times.
• Pluto was reclassified as a dwarf planet in 2006.

The Solar System

• The Solar System consists of 1 star (the Sun), 8 planets, dwarf planets, asteroids, and moons.
• Moons orbit many of the planets.
• Comets and meteoroids make up the smaller parts of the Solar System.

Formation of the Solar System

• Any theory on the formation of the Solar System must adhere to several key facts.