Solar System

Solar System Important Facts:

• Sun account for 99.85% of mass of the solar system. It continuously gives us energy in the form of Visible light, infra-red, ultra-violet, x-rays etc.
• The period of revolution of sun around the galactic centre is 250 million years and is called as cosmotic year or galactic year.
• Like all other stars sun is mainly composed of Hydrogen and Helium. Nuclear fusion in the core of sun is a source of all energy.
• The glowing surface of sun that we see is called photosphere.
• Diameter of sun is 100 earth diameters.
• Core temperature = 15 million degree centigrade.
• Surface temperature = 6000 degree centigrade.
• Sun rotation time = 25 days.
• Age = 5 billion years.
• Composition of sun- Helium(26.5%), Hydrogen(71%), Rest(2.5%).

Terrestrial Planets: 

• Mercury, Venus, Earth, Mars.
• These are earth like planets which have dense rocky body and also called as inner planets.

Jovian Planets:

• Jupiter, Saturn, Uranus, Neptune.
• Means Jupiter like which are gaseous, gigantic, having large satellite families and high rotational velocities. These are also called as outer planets.

Mercury:

• Called as swiftest planet, low atmosphere and has a crater surface.
• It has maximum diurnal range of temperature.
• Has the shortest year.

Venus:

• It is second only to the moon in brilliance in the night sky.
• Closest to Earth.
• Morning star, evening star and also the brightest star.
• Twin of earth because of its similar size, density and mass.
• Similar year length as of earth.
• Its a planet where length of day is longer incomparison to the length of year.
• Days are 243 earth days and year length 224.7 days.
• All planets rotates from west to east except for U-V (Uranus & Venus).
• Venus rotates from east to west so here sun rises from the west and sets in the east on contrary Uranus tumbles down from north to south.
• Slowest rotation.
• It is the hottest planet (atmosphere contain 97% CO2).

Earth:

• It is called as the blue planet because of presence of water.
• Densest of all the planets and is unique for the presence of higher form of life.

Mars:

• It is called as the red planet.
• It has evoked greatest interest than any other planet.
• It has two moons named as Phobos and Demos (Smallest satellite).
• It has the same angle of inclination as that of earth and has the same length of day as that of earth.
• There is a possibility of life on mars and habitability by humans and is being extensively probed.

Jupiter:

• Known as lord of the heaven.
• Largest planet in our solar system.
• The zone / region between Mars & Jupiter is known as Asteroid belt.
• Fastest rotational time = 9 hr 55 minutes.
• Important satellites- Europa, Ganymede (largest satellite) and heaviest of all satellite in the solar system.

Saturn:

• Known as allegiant planet.
• Second largest and is surrounded by a set of seven rings which are made up of primordial dust and ice particles. It has more prominent ring than Jupiter.
• Largest satellite of Saturn is titan.

Uranus and Neptune:

• These are called as jovians twins and these are better twins in comparison to earth and venus.
• Beside being similar in size, they appear pale greenish blue in colour because of the presence of methane in the atmosphere.
• The largest satellite of Neptune is triton.
• Neptune has a great depression and is called as the grey dark spot and is of earth size.
• Important satellite of uranus is Mirand.

1. Closest star to Earth – Sun.
2. Closest star to solar system – Proxima Centauri also called as Alpha Centauri.
3. Brightest star outside solar system – Sirius also called as dog star.
4. Brightest star – Venus.
5. Astronomical Unit – It is the mean distance between the Earth and the Sun. It is used to measure distance within the solar system.
6. Light Year – Distance travelled by light in vacuum for a period of one year.