The people, places, experiences that are associated with a particular person, place or thing.

All of space and everything in it including stars, Planets and galaxies.

An area of space or a world that is similar to but separate from the one that we live in.

  • The study of universe is known as Cosmology.
  • The universe is commonly defined as the totality of everything that exists including all physical matter and energy, the planets, stars, galaxies and the contents of intergalactic space.
  • Galaxy A galaxy is a vast system of billions of stars, dust and light gases bound by their own gravity. There are 100 billion galaxies in the universe and each galaxy has, on average, 100 billion stars.
  • Our galaxy is Milky way Galaxy (Akash Ganga) formed after the Big Bang. Andromeda is the nearest galaxy to the Milky way.
  • The Big Bang Theory Big Bang was an explosion of concentrated matter in the universe that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.
  • Stars are the heavenly bodies made up of hot burning gases and they shine by emitting their own light.
  • Black Hole Start having mass greater than three times that of the sun, have very high gravitational power, so that not even light can escape from its gravity and hence called black hole.
  • Comets Made up of frozen gases. They move around the sun in elongated elliptical orbit with the tail always pointing away from the sun.
  • Constellations The sky is divided into units to enable the astronomers to identify the position of the stars. These units are called constellations. There are 88 known constellations.
  • Satellites are the heavenly bodies that revolve around the planets. Moon is the natural satellite of the Earth.

Solar system

The sun together with the group of celestial bodies that are held by its attraction and revolve around it also.

A Star other than our Sun and the planets that move around it.

  • The solar system consists of the sun, the eight planets and their Satellites (or moon’s) and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
  • The sun is at the centre of the Solar system and all these bodies revolve around it. It is the nearest star to the Earth.
  • Sun
  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune

Facts about Sun

  • Average distance from the sun 149,597,870 km.
  • Diameter 1391980 km
  • Temperature of the core 15000000°C
  • Rotation speed 25.38 days (with respect to Equator) 33 days (with respect to poles)
  • Time taken by sunlight to reach the Earth 8 min and 16.6 sec

Facts about planets

  • Biggest planet Jupiter
  • Biggest Satellite Ganymede (Jupiter)
  • Blue planet Earth
  • Green planet Uranus
  • Brightest planet Venus
  • Brightest planet outside Solar system Sirius (Dog star)
  • Closest star of Solar system Proxima Centauri
  • Coldest planet Neptune
  • Evening star Venus
  • Farthest planet from Sun Neptune
  • Planet with maximum number of Satellites Jupiter
  • Fastest Revolution in Solar system Mercury
  • Hottest planet Venus
  • Densest planet Earth
  • Fastest rotation in Solar system Jupiter
  • Morning star Venus
  • Nearest planet to Earth Venus
  • Nearest planet to Sun Mercury
  • Red planet Mars
  • Slowest Revolution in Solar system Neptune
  • Slowest Rotation in Solar system Venus
  • Smallest planet Mercury
  • Smallest Satellite Deimos (Mars)
  • Earth’s Twin Venus
  • Only Satellite with an atmosphere like Earth Titan


  • They are small planetary bodies that revolve around the sun and found in between the orbits of Mars and Jupiter. They are also known as mknor planets.

Meteors and Meteorites

  • They are also called as shooting stars. Meteors are fragments of rocks comings towards the Earth.
  • They are formed due to collision among the asteroids.
  • Meteors that do not burn up completely in Earth’s atmosphere and land on the Earth, are called meteorites.
  • Meteorites are composed of various proportions of a nickel-iron alloy (10% nickel and 90% iron) and silicate minerals.

Classification of Planets

Inner Planets Include Mercury, Venus, Earth and Mars.

Outer Planets Include Jupiter, Saturn, Uranus and Neptune.

Inner Planet

  • They are called as Terrestrial or Rocky Planets.
  • They are nearer to the Sun.

Outer Planet

  • They are called as Jovian or Gaseous planets.
  • They are far away from the Sun.

Dwarf planet

According to IAU, it is a celestial body in direct orbit of the sun, that is massive enough that it’s shape is controlled by gravitational forces, but has no clear neighborhood. eg, Ceres, Pluto, Eris Makemake and Haumea.

  • A light year is the distance light travels in one year at the speed of 3×10 m/s.
  • Astronomical unit it is the average distance between Earth and the Sun. 1 AU=93 million miles.

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