Celestial Bodies and the Solar System

Celestial Bodies

• The sun, moon, and all objects shining in the night sky are celestial bodies
• Stars possess their own heat and light, for example, the sun
• Planets do not have their own heat and light
• Planets are lit by starlight, such as Earth, which receives its light from the sun
• Constellations are various patterns formed by different groups of stars, such as Saptarishi (seven sages)

Solar System

• The Solar System includes the Sun, eight planets, satellites, asteroids, and meteoroids
• The sun is the center of the solar system
• The sun is huge, composed of extremely hot gases, and the ultimate source of heat and light
• The sun is about 150 million kilometers away

Planets

• There are eight planets
• All eight planets revolve around the sun in fixed, elongated paths called orbits
• Mercury is the closest planet
• Venus, known as Earth's twin, is very similar in size and shape

Earth

• Earth: the third nearest planet to the Sun
• In size, it is the fifth largest planet
• Earth's shape is described as geoid, slightly flattened at the poles
• Earth is a unique planet that supports life, neither too hot nor too cold
• Earth contains life-supporting gases like oxygen
• Water covers 2/3 of Earth's surface, possibly from outer space (BLUE PLANET)
• Earth's natural satellite is the moon, about 384,000 km away

Satellites

• Satellites are celestial bodies that move around planets, similar to how planets revolve around the sun
• Human-made satellites are artificial bodies created by scientists
• They help to gather information and communication, with examples like INSAT and IRS
• The first man to step on the surface of the moon ws Neil Armstrong on July 20, 1969
• INSAT = Indian National Satellite System
• IRS = Indian remote sensing

Asteroids

• Asteroids are numerous, tiny bodies that orbit the sun
• Most asteroids are found between the orbits of Mars and Jupiter

Milky Way Galaxy

• The Milky Way galaxy is a white, glowing path across the sky, a cluster of millions of stars
• Our solar system is part of the Milky Way galaxy
• The Milky Way Galaxy is a vast system of stars, clouds of dust, and gas

Meteoroids

• Meteoroids are small pieces of rocks moving around the sun
• Sometimes, they enter Earth's atmosphere and burn due to friction, creating a flash of light

Other Concepts

• Earth, Solar System, Milky Way Galaxy, Universe, in that order
• Universe: Million of galaxies together make universe

Globe: Latitudes and Longitudes

• A globe is a miniature model of Earth
• A needle is fixed through the globe in a tilted manner. The needle is called Axis, an imaginary line

Latitudes

• Latitudes are imaginary horizontal lines running from east to west
• The Equator (0° latitude) divides Earth into two equal parts: the Northern and Southern Hemispheres
• Parallels of latitude are all the parallel circles from the equator to the poles
• 90°N represents the North Pole, and 90°S represents the South Pole
• North latitudes are parallels north of the equator
• South latitudes are parallels south of the equator
• The size of parallels decreases from the equator to the poles

Important Latitudes

• Tropic of Cancer: 23½°N
• Tropic of Capricorn: 23½°S
• Arctic Circle: 66½°N
• Antarctic Circle: 66½°S

Heat Zones of Earth

• Torrid Zone: hottest region, located between 23½°N and 23½°S, sun is exactly overhead at least once a year
• Temperate Zone: moderate region, between 23½°-66½° N and S, the Sun is never overhead
• Frigid Zone: coldest region, between 66½°-90° N and S, the Sun is very low, always slanting and provides less heat

Longitudes

• Longitudes are imaginary vertical lines that run North to South
• All meridians are of equal length

Prime Meridian

• The Prime Meridian is 0° longitude
• The Prime Meridian passes through Greenwich
• The Prime Meridian divides Earth into the Eastern and Western Hemispheres
• You can locate any place/point on a globe if you know its latitude and longitude

Time

• The Prime Meridian is 0° longitude
• Earth rotates from west to east, so places east of 0° will be ahead of time
• Indian Standard Time has the longitude of 82½°E, 5 hours 30 minutes ahead of GMT

Standard Time

• Standard Time is needed because of different times in local places due to different meridians/longitudes
• This makes it difficult to function as a nation; trains run on certain times for example