OUR SOLAR SYSTEM AT A GLANCE
Our solar system comprises of anything that orbits around the Sun – planets, dwarf planets, moons, asteroids, and comets. According to the present estimation, the age of our solar system is around 4.6 billion years. The Sun is the most massive member of the solar family accounting for about 99.86 % of the total solar system mass. Surprisingly, 99% of the rest of the mass is locked in Jupiter, whereas, the total mass share of the rest of the planets such as Mercury, Earth, Mars, etc. of our solar system is only a miniscule fraction of our solar system.
SUN
The main composition of the Sun is hydrogen accounting about 75% of its mass and rest is in the form of helium. The sun derives its energy from nuclear fusion inside the core. Presently, two hydrogen is fusing into a helium atom and in this process a huge amount of energy is produced. The Sun is already 4.6 billion years old and has sufficient hydrogen fuel to continue burning for another 5 billion years. The temperature inside the Sun’s core is more than 15 million Kelvin whereas the surface (photosphere) has only a temperature of about 6000 Kelvin. Variable dark spots are seen on the Sun’s surface called Sunspot. The Sunspots correspond to the regions of high magnetic field which inhibits transport of energy, therefore remain cooler than the surrounding regions. Sunspots are temporary phenomena, which are constantly varying with time. The distance between the Sun and Earth has been adopted as the unit of 1 A U, which is also equal to eight-light seconds.
Members of our Solar systems:
In our Solar system there are numerous number of heavenly objects with a wide range of sizes and masses, which are orbiting around the Sun. Only eight among tens of thousands such objects qualify to be planets based on their size. The planets of our solar system are divided into two broad categories – Inner planets and outer planets. The inner planets are predominantly composed of rocks and silicates which is why these planets are also called terrestrial planets. On the other hand the outer planets are mainly composed of gaseous elements so they are called gas planets.
Inner Solar System:
Mercury, Venus, Earth and Mars are the terrestrial planets of our solar system. These planets are primarily composed of heavy elements such as iron and rocks. They are closer to the Sun compared to the rest of the planets. Among the four, only Earth and Mars have moons. Mars have two moons namely Deimos and Phobos. Between the inner and outer planetary zone, in the space between Mars and Jupiter lies the famous Asteroid belt. This region is the home to minor planets and thousands of asteroids, orbiting around the Sun. The dwarf planet called Ceres is the biggest celestial body among the members of the Asteroid belt. Its diameter is about 950 km.
Outer Solar System:
Jupiter, Saturn, Uranus and Neptune are composed of thick layers gas (primarily hydrogen and helium) – belong to the Outer Solar System. Jupiter is the largest planet of our Solar system. These planets have larger number of moons than the terrestrial planets. Jupiter has about 67 identified satellites, among them the most notable moons are Ganymede, Io, Europa, and Callisto. Saturn is about 95 times more heavier than the Earth and known to have around 62 satellites. Titan and Enceladus are the two notable moons of Saturn. Titan is the second largest moon of our solar system. Uranus and Neptune also have about 27 and 14 known satellites, respectively.
Kuiper Belt is a disk of debris in the outer Solar system beyond Neptune. Unlike the Asteroid Belt, debris of Kuiper Belt are mostly composed of frozen methane, ammonia and water. Pluto is the largest member of the Kuiper Belt. Since 2006, Pluto ceases to be a planet anymore rather called as a dwarf planet. In 2006, IAU imposed an additional qualification for any solar system member to be called as a planet is to have a cleared neighborhood around its orbit. Pluto being a member of Kuiper Belt is surrounded by Kuiper Belt debris, could not satisfy this criteria. Pluto has 5 moons, they are – Charon, Styx, Hydra, Nix and Kerberos.
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