The Solar System and Its planets.

The Solar System comprises of the Sun and eight planets (excluding Pluto) which revolve around it in fixed orbits. The Sun is the center of the Solar system. Distanc-wise Mercury is closest to the Sun followed by Venus, Earth, Mars, Jupiter, Saturn, Neptune. Pluto was excluded from the Solar system by the Scientists and was declared a dwarf planet.

The Sun.
The Sun is a large bright star which forms the center of the Solar System. The speed of 285 km/s and 224 million years to complete one revolution. This period is called cosmic year. The Sun is 400,000 times brighter than the full Moon. At the core of Sun, temperature is about 36 million Fahrenheit (20 million degree Celcius) because the Hydrogen is converted into Helium at the rate of 600 million tons per second. The energy released by these nuclear reactions is in the form of x-rays which heats up the surrounding area extending over millions of miles. The surface temperature of the Sun is about 6000 degree Celsius. It is very large in size with a diameter of 865,400 miles.

The Planets of Solar System:

Mercury:

Mercury is the nearest planet to the Sun. It has a diameter of 4,880 km and revolves in 88 days. The temperature of its surface ranges between -346 degree Fahrenheit on dark side to 950 Fahrenheit on the side facing the Sun. Its surface is highly cratered.

Venus:

Venus has a diameter of 12,100 km and is the second closest planet to the Sun. It completes a revolution in 224.7 days. Venus has an atmospheric pressure equal to 94.5 times that of Earth. American space craft Magellan reached Venus on 10th August, 1990 and explored its surface. A channel 1.8 km wide, 4,200 miles long was discovered on its surface.

Earth:

Earth is the third closest planet to the Sun which maintains a distance of 149.6 million kilometer. It has a diameter of 12,756 km and completes a revolution in 365.2 days with a speed of 67 thousand miles per hour. Moreover, it rotates on its axis completing on revolution in 23 hours 56 minutes and 4.09 seconds. Earth has a mass of 6.6 sextillion tons. Atmosphere of Earth comprises of 78 % Nitrogen, 21 % Oxygen, and 1% other gases. The air blanket has a height of 60 miles. The atmosphere of Earth is divided into 5 zones. Troposphere (0-7 miles), Stratosphere (7-30 miles), Mesosphere (30-50 miles), Thermosphere (50-400 miles), Exosphere (above 400 miles). Main data of Earth is as given below.

Mars:

Mars is the brightest planet in the sky. It is the fourth planet from the Sun with a distance of 227,9 km. It complets one revolution in 687 days. its surface comprises of many craters, volcanoes, chasms and a huge grand canyon. The canyon is 50 miles wide and 2.5 miles deeps and 3000 miles long. The highest elevation is Olympic Mons with a height of 78,000 ft. Mars has two small satellites names Deimos and Phobos. Out of these, Deimos (15 km long) completes a round in 30 30.35 hours whereas Phobos (27 km long) takes 7.6 hours for a revolution. Probing of Mars began in July, 1979 when a space craft Viking I landed on its surface. Later on many other missions provided data about this planet. These included Mars Pathfinder (1996), Mars Global Surveyor (2001), Mars Express (2003), Spirit and Opportunity (2004) and Mars Reconnaissance Orbiter (2005). According to the scientists Mars (Red Planet) is the only planet where chances of life exist due to its similarities with Earth.

Jupiter:

It is the fifth closest planet to the Sun with a diameter of 778.3 million km. Jupiter is the largest planet of the Solar with a diameter of 142,000 km. It completes a revolution around the Sun 11.86 years. Its equatorial diameter is 88,786 miles. Jupiter also completes a revolution around its axis in 9 hours and 55 minutes. It is known as giant planet due to its size which is 1,300 times bigger than Earth. Surface of Jupiter has an oval red spot which is equal to the size of Earth. Spacecraft Galileo probed its surface on 7th December, 1995. Jupiter has 63 satellites, out of which the largest are Ganymede (diameter 3,275 miles), Europa (1,950 miles), Calllisto (2,400 miles) and Lo (2,262 miles)

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