The Earth and the Universe
Concept: The Solar System
The universe means everything. It includes the whole of space, matter and energy. The Earth and the Moon are part of the universe, along with the Sun and the other planets.
Features of the universe:
- The universe is almost 13.5 billion years old.
- It has no centre and is constantly expanding. The universe has kept on changing every day since it was formed.
- The size of the universe is too big to be defined. It has many galaxies.
- Our solar system is part of the Milky Way galaxy, which is also called Akash Ganga.
- The scientific study of the universe is called cosmology. So, the other name for the universe is ‘cosmos’.
- The solar system consists of the Sun and all the celestial objects that travel around the Sun.
- The solar system includes eight planets, their moons, dwarf planets, asteroids, comets, and other objects.
The planets in the solar system can be broadly classified into two groups—Jovian planets and Terrestrial planets, based on specific characteristics.
- Jovian planets:
Planets with the following characteristics are called Jovian planets—
- Massive size.
- Presence of more than one moon.
- Existence of ring systems.
- Occurrence of high force winds and short rotations.
- Examples Jupiter, Saturn, Uranus and Neptune are jovian planets.
Planets with the following characteristics are called terrestrial planets—
- The core is made up of heavy metals in their liquid forms.
- Presence of valleys, volcanoes and craters.
- An outer solid surface.
- Examples Mercury, Venus, Earth and Mars, are terrestrial planets.
Let us now look at all the planets of the solar system.
- It is the closest planet to the Sun and is one of the four inner planets.
- The diameter of Mercury is 4878 km, which makes it the smallest planet in the solar system.
- The name ‘Mercury’ originated from the Roman Messenger God.
- The temperature on this planet’s surface rises to 425 oC.
- Mercury does not have any rings or moons.
- It takes 88 days to complete one revolution around the Sun.
- Mercury is called Budh in Hindi.
- It is the second planet from the Sun and is slightly smaller in size than the Earth.
- The diameter of this planet is 12104 km.
- The name ‘Venus’ originates from the Roman God of love and beauty.
- It is the thickest of all the four terrestrial planets.
- Too much heat and pressure make the environment of this planet unsuitable for the existence of life.
- Because of its proximity to the Earth, Venus is visible in the night sky.
- Venus does not have any moons.
- It takes this planet 225 days to complete one revolution around the Sun.
- Venus is called Sukra in Hindi.
- It is the third planet from the Sun and is the fifth-largest planet in the solar system.
- The diameter of Earth is 12742 km.
- It is the only planet that has water and tectonic plates and can sustain life.
- A large area of the Earth’s surface is covered with water.
- The Earth is surrounded by a blanket of gas mixture that majorly comprises nitrogen, oxygen, carbon dioxide, argon, etc.
- The Earth has one moon.
- It takes 365 days to complete one revolution around the Sun.
- The Earth is called Prithvi in Hindi.
- It is the fourth planet from the Sun. It is also called the ‘red planet’ due to the large amount of iron oxide present in the soil.
- The name ‘Mars’ originated from the Roman God of war.
- The diameter of this planet is 4127 km.
- Mars is colder than Earth and shows some dry river beds on its surface. It hints toward the possibility of the presence of water on this planet. Scientists are still working on this possibility.
- Mars has two moons.
- It takes 687 days to complete one revolution around the Sun.
- Mars is called Mangal in Hindi.
- It is the fifth planet from the Sun.
- It is the largest planet in the solar system and the first of the outer gas giant planets.
- The diameter of Jupiter is 86881 km.
- Its name originated from the Ruler of the Roman Gods.
- It has very faint rings around it.
- Jupiter has 63 moons.
- It takes 4333 days to complete one revolution around the Sun.
- Jupiter is called Brahspati in Hindi.
- It is the sixth planet from the Sun.
- Saturn has rings around it, making it a unique planet.
- It is named after the Roman God of agriculture.
- The diameter of Saturn is 120500 km.
- It is the least dense of all the planets in the solar system.
- It has 62 moons, including Titan, the second-largest moon in the solar system.
- The interior of Saturn mostly constitutes hydrogen and helium.
- It takes 10,756 days to complete one revolution around Sun.
- Saturn is called Shani in Hindi.
- It is the seventh planet from the Sun.
- The planet is named after the personification of heaven in ancient myth.
- The diameter of Uranus is 51120 km.
- It is different from other planets as it revolves on an axis parallel to its orbit.
- It is a cold planet, and its atmosphere mainly comprises methane.
- It has 27 moons.
- It takes 30,687 days to complete one revolution around the Sun.
- Uranus is called Arun in Hindi.
- Also known as a blue planet, Neptune is located farthest from the Sun.
- It is named after the Roman God of water.
- Because of its considerable distance from the Sun, the temperature of this planet is extremely low.
- The atmosphere mainly comprises methane, which gives it a characteristic blue colour.
- The diameter of Neptune is 49530 km.
- It has 3 moons
- It takes 60,190 days to complete one revolution around the Sun.
- Neptune is called Varun in Hindi.
Diameter: A line segment that passes from the centre of a circle with end-points located on the circumference of the circle.
Tectonic plate:Movable pieces of the solid crust of the Earth.
Revolution:The movement of a planet around the Sun in a fixed path called its orbit.
Did You Know?
- The solar system was formed around 4.6 billion years ago from a solar nebula which is considered a cloud of dust and gas.
- The distance you will cover while taking 1000 trips to Australia would equal the distance between the Sun and the Moon.
- Venus is the second brightest object in the night sky after the Moon.