World Geography

Evolution of Earth The earth broke off about 4.5 billion years ago with an explosion. It was a burning hot white mass of gas and dust. Over a long period, dust and gas gradually condensed to form solid rock. Such … Continue reading →

Asteroid Belt Asteroids are remnants of planetary formation that failed to coalesce because of the gravitational interference of Jupiter.  They circle the Sun in a zone lying between Mars and Jupiter.  The circular chain of asteroids is called the asteroid … Continue reading →

Planets in Solar System Our Solar System consists of the sun and eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) which are placed in the Milky Way Galaxy. Classification Planets  in Solar System Inner Planets Mercury Mercury is … Continue reading →

Planets Criteria It is in orbit around the Sun It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and It has cleared the neighbourhood around its orbit. … Continue reading →

Basics of Sun Age – 4.6 billion years Diameter – 1.39 million km Temperature –  6000 °C on the surface The surface gravity of the Sun is 274 m/s2 Period of rotation – 25 days 9 hrs. Rotation – counterclockwise … Continue reading →

A pole star is a star or a star system situated in the direction of the earth’s axis.  At present, Polaris or North Star (a system of 3 stars) is the earth’s pole star. It is visible only from the … Continue reading →

What is it? The stars forming a group that has a recognisable shape is called a constellation. Types of Constellations Ursa Major It is also known as the Great Bear or Saptarishi.  It consists of seven bright stars, which appear … Continue reading →

Life Cycle of Star Associated Terms Nebula A cloud of gas (mostly hydrogen and helium) and dust in space. Nebulae are the birthplaces of stars. T Tauri Star A young star still undergoing gravitational contraction. It represents an intermediate stage … Continue reading →

What is it? A galaxy is a sprawling space system which is composed of stars, dust, interstellar gas, stellar remnants,  and dark matter and all held together by gravity. Types of Galaxy Spiral Galaxy The most common type of galaxy … Continue reading →

Other Name: It is also called the expanding universe hypothesis. About Theory Discovery: Edwin Hubble, in 1920, provided evidence that the universe is expanding. Period: Took place 13.7 billion years ago. Findings Galaxies move further and further apart. Similarly, the … Continue reading →