- The full moon only once in about a month’s time is Full moon night or Poornima.
- A fortnight later, you cannot see it at all. It is a New moon night or Amavasya.
- On this day, you can watch the night sky best, provided it is a clear night.
- We can't see the moon during day time because the very bright light of the sun does not allow us to see all these bright objects of the night sky.
- The sun, the moon and all those objects shining in the night sky are called celestial bodies.
- Some celestial bodies are very big and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars. The sun is a star.
- Various patterns formed by different groups of stars are called constellations. Ursa Major or Big Bear is one such constellation.
- One of the most easily recognisable constellation is the Saptarishi (Sapta- seven, rishi-sages). It is a group of seven stars that forms a part of Ursa Major Constellation.
- The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky.
- Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets.
- The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
- The moon is a satellite. It is a companion of our earth and moves round it.
- The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
- The sun is in the centre of the solar system. It is huge and made up of extremely hot gases. It provides the pulling force that binds the solar system. The sun is the ultimate source of heat and light for the solar system.
- The sun is about 150 million km away from the earth.
- There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
- An easy way to memorise the name of the planets in order of their distance from the sun is: MY VERY EFFICIENT MOTHER JUST SERVED US NUTS.
- All the eight planets of the solar system move around the sun in fixed paths. These paths are elongated. They are called orbits.
- Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit.
- Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
- Till August 2006, Pluto was also considered a planet. However, the International Astronomical Union decided to call it a ‘dwarf planet.”
- The earth is the third nearest planet to the sun. In size, it is the fifth largest planet. It is slightly flattened at the poles. That is why, its shape is described as a Geoid. Geoid means an earth-like shape.
- Conditions favourable to support life are probably found only on the earth. The earth is neither too hot nor too cold. It has water and air, which are very essential for our survival. The air has life-supporting gases like oxygen. Because of these reasons, the earth is a unique planet in the solar system.
- From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.
- Our earth has only one satellite, that is, the moon. Its diametre is only one-quarter that of the earth. It appears so big because it is nearer to our planet than other celestial bodies. It is about 3,84,400 km away from us.
- A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.
- The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the moon is visible to us on the earth.
- Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter.
- The small pieces of rocks which move around the sun are called meteoroids.
- A cluster of millions of stars is the Milky Way galaxy. Our solar system is a part of this galaxy. It was named Akash Ganga in India.
- A galaxy is a huge system of billions of stars, and clouds of dust and gases.
- There are millions of such galaxies that make the Universe.
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