While we have been learning about the nine planets in our solar system since childhood, of late there has been a bit of confusion about the number of planets with Pluto being knocked off the list.
Solar system is a minute component of the vast universe which was formed billions of years ago. It consists of the Sun and several celestial bodies revolving around it. These include planets (and their satellites), asteroids, meteoroids, etc. Until 2006 the number of planets in our solar system was nine, but the exclusion of Pluto has left us with only eight planets.
Planets in Our Solar System
The Sun is the center of our solar system and has eight planets orbiting it. These include―starting from the nearest to the Sun―Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Initially considered a planet, Pluto was officially declared a dwarf planet by the International Astronomical Union (IAU) in 2006, thus bringing the number of planets down to eight. Let's have a brief look at each of these planets.
Mercury: Mercury is the smallest planet in our solar system. At 3031.670 miles, its diameter is 38 percent the diameter of the Earth. It has extreme climate with temperature ranging between −180 to 430 °C. It is located at a distance of 0.39 AU. On the basis of information sent by Mariner 10 spacecraft, scientists suspect that some volcanic activity is occurring on Mercury.
Venus: Venus is a small, rocky planet, typically characterized by a thick blanket of yellowish clouds of sulfuric acid. With a diameter of 7521.076 miles, Venus is bigger than Mercury, but smaller than the Earth.
It is located at a distance of 0.72 AU from the Sun and has an average temperature of 465 °C. Venus is also referred to as the morning star or evening star, owing to the probability of its sighting at dawn and dusk.
Earth: The Earth has a diameter of 7926.210 miles. It is 1 AU away from the Sun, owing to which its temperature ranges between −89 to 58 °C. The Moon, which happens to be the planet's natural satellite, plays an important role in its gravitational force. Approximately 71% of the planet is covered with water, while the remaining 29% is land. Its physical properties make planet Earth the only planet in the solar system to support life.
Mars: Mars is the fourth planet in the solar system. With a diameter is 4217.246 miles, it is smaller than planet Earth. It is also referred to as the 'Red planet' due to the distinct reddish appearance it gets from the presence of iron oxide on it.
Mars has two moons revolving around it. It is located 1.52 AU away from the Sun, due to which its temperature ranges between −82 to 0 °C, making it a cold and lifeless planet.
Jupiter: Jupiter is a giant gas planet, which holds the distinction of being the largest planet in the solar system. With a diameter is 88731.806 miles, it is large enough to accommodate a thousand planets the size of the Earth. It is located at a distance of 5.20 AU from the Sun and has a temperature of −150 °C. With 63 moons revolving around it, Jupiter also boasts of having the most number of moons.
Saturn: Saturn, with a diameter is 74564.543 miles, is the second largest planet in the solar system, next only to Jupiter. It lies at a distance of 9.54 AU from the Sun and hence, its temperature is −170 °C. It has the second most number of moons―60 to be precise―again, next only to Jupiter. It is composed of material which is much lighter than water. The planet is famous for its unique planetary ring system.
Uranus: Uranus is the seventh planet in the solar system. It has a diameter is 31763.252 miles, which makes it the third largest planet after Jupiter and Saturn. It is located at a distance of 19.18 AU and thus, has a temperature of −200 °C.
Uranus has 27 moons and 13 rings of dark particles, varying in size, around it. The planet is mostly composed of rock and ice. Unlike other planets, which spin right side upwards, Uranus is a bit tilted and spins sideways.
Neptune: Neptune is the last planet in our solar system (since Pluto has been officially classified as a dwarf planet.) It has a diameter of 30775.272 miles.
The temperature of Neptune is −210 °C, which can be attributed to its remote location―a distance of 30.06 AU from the Sun―and the fact that it is mostly composed of ice and rock. Neptune has 13 moons and reddish planetary rings around it. A trip by Voyager 2 in 1989, the only visit by a spacecraft, is our lone source of credible information about it.
The re-classified of Pluto as a 'dwarf planet' in 2006, has left the solar system with only eight planets. According to the IAU, a dwarf planet is a celestial body orbiting the Sun, which is massive enough to be rounded by its own gravity, but not capable of clearing its neighboring region of the planetesimals.
Other dwarf planets identified by IAU include Eris, Ceres, Haumea, and Makemake.