Earth in the Solar System - Lesson 1

Celestial Bodies

• Celestial bodies include the sun, moon, and objects shining in the night sky.
• Stars are large, hot bodies made of gases, emitting their own heat and light.
• The sun is classified as a star and serves as the primary heat and light source for the solar system.
• Patterns formed by stars in the night sky are called constellations; Ursa Major is a notable example.

Navigation and Planets

• In ancient times, the North Star (Pole Star) helped people determine directions.
• Planet is derived from the Greek word “Planetai,” meaning 'wanderers'; these celestial bodies do not emit their own light.
• Earth is a planet and shines in the sky due to sunlight reflection; it has one natural satellite, the moon.

The Solar System

• The solar system comprises the sun, eight planets, satellites, asteroids, and meteoroids, often referred to as a solar family.
• The sun is at the center, surrounded by planets—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Memorization of Planetary Order

• An easy mnemonic to remember the order of planets: "MY VERY EFFICIENT MOTHER JUST SERVED US NUTS."

Planetary Characteristics

• Mercury, the closest planet to the sun, takes about 88 days to complete its orbit.
• Venus, similar in size and shape to Earth, is often called "Earth's twin."
• Pluto was reclassified as a 'dwarf planet' by the International Astronomical Union in 2006.

Earth’s Unique Features

• Earth is the third planet from the sun and the fifth largest by size.
• Its shape is described as a geoid, indicating a slightly flattened appearance at the poles.
• Earth's only satellite is the moon, which is about 3,84,400 km away and has a diameter one-quarter that of Earth.

Moon and Other Celestial Bodies

• The moon orbits Earth approximately every 27 days.
• Asteroids, small rocky bodies, are primarily located between the orbits of Mars and Jupiter.
• Meteoroids are smaller rocks that may approach Earth, heating up and burning upon atmospheric entry, creating meteors.

Galactic Context

• The solar system exists within a galaxy, which is a massive system of billions of stars and cosmic dust.
• The universe contains millions of galaxies, contributing to its vastness and complexity.