Universe : Our Solar System, Sun & Planets
The Solar System, Sun & Planets
INTRODUCTION
In Hindi geography is called “Bhugol”. “Bhu” means the Earth and “goal” means round. Father of geography is Eratosthenes.
Universe
- 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.
- The study of universe is known as Cosmology.
- Radius of the universe is 108light years.
- A galaxy is a vast system of billions of stars, which also contains a large number of gas clouds (mainly of hydrogen gas) and dust in space from similar systems.
- Our nearest galaxy is “Andromeda”.
- Latest known galaxy is the “Dwarf Galaxy”.
The Solar System
- Our solar system consists of the sun, the eight planets and their satellites (or moons), and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
- Our galaxy is Milky Way galaxy. It is spiral in shape.
- The Brightest star outside our solar system is Sires, also called Dog Star.
- The coolest star of solar system is Proxima Centauri. Then Alpha Centauri.
Sun
- The sun is the centre of the solar system.
- It is situated 30000 light years apart from the Milky Way galaxy.
- The sun is rotating about its own axis.
- It is the nearest star to the earth.
- It is an ultimate source of energy for life on earth.
- Its diameter is 14 lacs km. It is 110 times of earth.
- Hydrogen and helium are the main gases present in the sun. Hydrogen is 71% and Helium is 26%.
- In sun hydrogen is converted to helium due to nuclear fusion releasing a tremendous amount of light and heat.
- The centre portion of sun is called core and its temperature is 1.5 x 107°C. Temperature of the outer portion of the sun is 6000°C.
- Shining surface of sun is called photosphere.
- At the time of solar eclipse the visible portion of sun is called corona. It radiates x ray.
- Age of sun is 5 billion years.
- The sun is about 150 million km away from the earth.
- Light (at the speed of 30,000 km per second) takes about 8.5 minutes due to reach the earth from the sun.
- Sun is 13 lacs time bigger than earth and we get only 2 billionth amount of heat from Sun.
Planets
Planets are classified into two groups Terrestrial or Inner Planet and Jovian or Outer Planet.
- Terrestrial or Inner planet: Mercury, Venus, Earth, and Mars
- Jovian or outer planet: Jupiter, Saturn, Uranus, and Neptune.
- According to size (descending order):
Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars and Mercury
Mercury
- It is the closest planet of sun.
- It is the smallest planet. It has no satellite. It has magnetic field.
- It rotates about sun in 88 days – the smallest time period compared to other planet.
Venus
- It is the closest planet of earth.
- It is hottest as well as brightest planet in solar system.
- It is called evening star as well as morning star.
- Venus is similar to earth in size and mass, and hence also known as the “Earth’s Twin”.
- Unlike others it rotates anti clockwise.
- It also has no satellite.
Mars
- Because of presence of Iron oxide its color is red so it is called Red Planet.
- Revolution-687days
- Rotation- 24.6 hours
- It has signs of water. It has 2 satellites – Phoebes and Demos.
- The largest Volcano of solar system is situated here named Alipus Messy and the highest mountain named Nix Olympia is also situated here. It is 3 times of Mount Everest.
Jupiter
- It is the biggest planet of the solar system.
- It rotates about its own axis in 10 hours and rotates about the sun in 12 years.
- It has 63 satellites and Ganymede is the largest of them. Ganymede is a yellow colored satellite.
Saturn
- It is the 2nd largest planet of solar system.
- It is yellow colored planet.
- Revolution – 29 years
- Rotation- 10.3 hours
- It has 60 satellites and Titan is the biggest of them, and also biggest satellite in the solar system.
- It is 30 times less dense than earth.
- It is surrounded by some light rings. They consist of countless small particles, ranging in size from micrometers to meters that orbit about Saturn.
Uranus
- It is the 3rd largest planet of solar system. Its size is 4times of Earth. Its color is green.
- Uranus is surrounded by 5 rings namely, Alpha, Beta, Gamma, Delta and Epsilon.
- It is the first planet which was discovered by Telescope in 1781 by Sir William Hershel.
- Revolution – 84years
- Rotation-10.8hours
- It has 27 satellites, Ariel and Miranda are important of them
- Its rotation is anti clock wise like Venus.
Neptune
- It is the 8th planet of solar system.
- Its temperature is low.
- Neptune is very similar to Uranus and considered as its twin.
- Neptune is surrounded by methane ring of sub zero temperature.
Earth
- It is 5th largest planet in solar system. But it is the largest one among the inner planets.
- It is the only planet in solar system having life.
- The Earth is 23½° tilted on its axis and thus makes 66½° angle with its orbit.
- It takes 23hr 56min 4sec to complete a single rotation on its axis.
- It takes 365yrs, 5hr, 48min to complete one revolution around the sun.
- Earth is known as the watery planet or the Blue planet due to the presence of huge amount of water on it.
- The earth is neither too hot nor too cold. It has goldilocks zone.
- It has only one satellite that is Moon.
Moon
- Only 59% of its surface is directly visible from earth circumference-11,000km.
- Distance from earth-382,200km.
- Moon light takes 1.3sec to reach earth.
- It takes 27days 7hrs 43min and 11.47sec to complete one revolution around earth.
- Rotation & revolution time are same.
- Neil Armstrong and Edwin Aldrin reached moon on July 21, 1969 on Apollo XI (landing spot is called Sea of Tranquility).