The Solar System

• The Solar System includes the Sun and all celestial objects that revolve around it
• The universal law of gravitation, explained by Sir Isaac Newton, states that the Sun's gravity holds planets in orbit
• Inertia keeps planets in their states of motion

Members of The Solar System

• The sun is a huge ball of very hot gases
• The temperature of the sun is 15,000,000 C at the center and 5,000 C at the surface
• The sun is the largest star in the solar system, but is considered a middle-sized yellow star due to its distance from Earth
• The sun rotates on its own, with a rotation period equal to 25 Earth days

The Planets

• Terrestrial Planets include Mercury, Venus, Earth, and Mars
• Terrestrial Planets have rocky compositions and are dense bodies, also called 'inner planets'
• Gas Giant Planets include Jupiter, Saturn, Uranus, and Neptune
• Gas Giant Planets are characterized by their larger sizes and gaseous composition, also called 'outer planets'

The Inner Planets

Mercury

• Mercury is the closest planet to the Sun
• Mercury is one of the hottest planets
• Mercury is the smallest planet in the solar system (less than half the size of Earth)
• Mercury's surface has many craters, similar to the Earth's moon, with cliffs as high as 3 km
• Mercury has no moon

Venus

• Venus is the second planet from the Sun
• Venus is the brightest object in the sky
• Venus is known as Earth's twin planet
• Venus is the hottest planet
• Venus has a yellow-white color due to sulfuric acid contained clouds, resulting in acid rain
• Venus is the closest neighbor of Earth
• Venus's surface has craters, fault-like cracks, and volcanoes
• Venus has no moon

Earth

• Earth is the third planet from the Sun
• Earth is called a living planet
• Earth has abundant liquid water
• Earth has an atmosphere that supports and protects life
• Earth has a moderate surface temperature
• Earth has three major layers: crust, mantle, and core
• Earth has one large moon.

Mars

• Mars is known as the 'red planet'
• Mars has a thin atmosphere
• Mars has 1/1000 the amount of water in its atmosphere compared to Earth
• The days on Mars are almost the same length as on Earth
• Mars has traces of rushing water from the past
• Mars' gravity is about two-fifths as strong as Earth's
• Mars has two irregularly shaped moons

The Outer Planets

Jupiter

• Jupiter is the largest planet in the solar system (11 times the size of Earth and 300 times the mass)
• Jupiter has 89 moons
• Jupiter's atmosphere is composed of hydrogen, helium, ammonia, methane, and water vapor
• Jupiter has very small, faint dust rings
• One of Jupiter's moons has an active volcano
• Jupiter's core is 30,500 C hot
• Jupiter has a permanent storm known as the red spot

Saturn

• Saturn is the second largest planet and has the lowest density (0.5 times the size of Earth)
• Saturn has a complex ring system
• Saturn is a gaseous planet
• A day on Saturn is just a little longer than on Jupiter: 10 hours and 39 minutes
• Saturn has 62 moons, the largest is called Titan

Uranus

• Uranus is the third largest planet with a system of 11 thin, dark rings
• Uranus has at least 27 moons, the largest is Titana
• Uranus is a gaseous planet
• Uranus's axis of rotation is tilted more than 82 degrees
• The gravity of Uranus is a little stronger than Earth's

Neptune

• Neptune is the eighth planet from the Sun
• Neptune has an elliptical orbit
• Neptune's atmosphere is made up of methane gas
• Neptune has a dark colored storm called the Great Dark
• Neptune has 14 moons and several rings

Dwarf Planets

Pluto

• Pluto was considered the ninth planet until 2006
• Pluto rotates in about 6.387 Earth days
• Many astronomers believe Pluto and Caron are members of the Kuiper Belt

Eris

• Eris is located almost 10 million miles from the Sun and beyond Neptune

Ceres

• Ceres is the largest asteroid orbiting between Mars and Jupiter

Other Members of the Solar System

• Comets are made up of dust and rock particles mixed with frozen water, methane, and ammonia
• Meteoroids are pieces of dust and rocks that break from a comet's nucleus
• Asteroids, also known as planetoids, are small pieces of rocks and metals that orbit around the Sun between Mars and Jupiter

Motions of the Earth

Rotation - Daily Motion

• Rotation is the movement of an object on its axis
• The Earth rotates from west to east, clockwise as seen above the North Pole and counterclockwise as seen above the South Pole
• One complete rotation takes 23 hours, 56 minutes, and 4.2 seconds
• Earth's rotation is tilted 23.5 degrees relative to its plane of revolution around the Sun

Results from Earth's Rotation

• Occurrence of day and night
• The daily rising and setting of the Sun, stars, and the Moon with a pattern of motion visible in the sky
• The flow of air and water on Earth
• Coriolis Effect, which is the diversion of direction

Revolution - Annual Motion

• Revolution is the movement of an object around a bigger object
• Earth's orbit around the Sun is a slightly flattened circle called an ellipse
• Perihelion is 147 million kilometers from the Sun
• Aphelion is 152 million kilometers from the Sun

Result from Earth's Revolution

• Occurrence of seasonal changes

Seasons of Earth

• June, July, August: The northern hemisphere faces the Sun, experiencing summer, while the Southern Hemisphere experiences winter
• When the North Pole tilts directly toward the Sun, it is called the Summer Solstice, around June 22, with longer days
• As Earth moves, summer turns to fall as the axis of the northern hemisphere moves sideways. When the Sun is directly overhead at the equator, it is called fall or autumnal equinox
• The Autumnal Equinox happens on September 23, with equal night and daytime
• December, January, February: The North Pole faces away from the Sun, so the Northern Hemisphere experiences winter while the South Pole experiences summer
• The Winter Solstice is around December 22, with longer nights
• March, April, May: Earth's axis is not pointed to the Sun, so both hemispheres receive equal amounts of solar energy, called spring
• Spring starts on March 21
• The northern hemisphere has a spring equinox around March 21
• The Philippines, being near the equator, has only two seasons: wet and dry