Solar System – Various Planets, Inner and Outer Planets

Welcome to DataFlair Tutorial on our Solar System. Let’s learn about the Solar system and its planets in detail.

 

What is the Solar System?

The Solar System is a gravitationally bound system of a star and astronomical objects orbiting around the star either directly or indirectly. In our very own galaxy, astronomers have found more than 500 solar systems.

The number for the entire universe is estimated to reach a figure of about tens of billions, or perhaps as many as 100 billion.

Talking about the solar system of the Sun, it consists of the Sun, eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), five dwarf planets (three universally accepted – Ceres, Pluto, Eris; and two more expected – Haumea, Makemake), 796354 minor planets and several smaller objects including satellites, asteroids, etc.

What are Planets?

Planets (meaning ‘wanderers’ in Greek) are the relatively large astronomical bodies revolving in an orbit around a star that does not radiate energy from a nuclear fusion reaction.

Some scientists impose restrictions on size (should be more than 1000 km), shape (should be squeezed into a sphere under its own gravity), and mass (must have mass insufficient of its core that has experienced even temporary nuclear fusion).

In order of their distance from the Sun, planets are – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Let us discuss all of them in detail.

MERCURY

• The smallest planet in the Solar System (radius – 2439.7 km)
• Planet closest to the Sun
• It is dark grey in color.
• Has a surface temperature of about 800°F (430°C) during the day and -290°F (-180°C) at night.
• Has no known moon revolving around it.
• Completes one rotation in 58 days 15 hours 30 minutes.
• Completes one revolution in 88 days.
• Has a very thin atmosphere with the presence of Sodium and Helium on the surface.
• Travels around Sun faster than any other planet, hence got its name after the swift messenger of gods in ancient Roman mythology.
• The surface has holes because of striking meteoroids and asteroids.

VENUS

• Is almost the same size as that of Earth (radius – 6051.8 km).
• The planet is closest to Earth but it cannot support life.
• Also known as Earth’s twin and Evening Star.
• Has a surface temperature of about 880°F (471°C).
• Has no known moon revolving around it.
• Completes one rotation in 116 days for 18 hours.
• Completes one revolution in 225 days.
• The atmosphere consists of Carbon Dioxide and small amounts of Nitrogen.
• Has very thick rapidly spinning clouds to cover its surface. Clouds contain heat in them and reflect sunlight, making the planet shine brighter.
• It looks very bright with a white or yellowish hue.
• It has several large inactive volcanoes.
• Rotates in the opposite direction than all planets.

EARTH

• Earth has a radius of about 6371 km.
• The only planet that supports life.
• 70% of the planet’s surface is covered by water, hence known as the Water planet.
• Has a surface temperature of about 61°F (16°C).
• Has one named moon revolving around it.Completes one rotation in 23 hours 56 minutes.
• Completes one revolution in 365 days.
• It is blue in color with white clouds.
• The atmosphere consists of Nitrogen and a small amount of Oxygen.
• Earth’s axis is tilted at an angle of 23.5 degrees, which gives rise to different seasons.

MARS

• Has a radius of about 3389.5 km.
• Martian dirt has been found to be rich in Iron, which results in its red color.
• Also known as Red Planet.
• Has a surface temperature of about minus 20°F (-28°C).
• Has two named moons (Phobos and Deimos) revolving around it. It is believed that they are potato-shaped asteroids that were pulled by Mars’ gravity.
• Completes one rotation in 1 day 36 minutes.
• Completes one revolution in 687 days.
• Has a thin atmosphere consisting of Carbon Dioxide and small amounts of Nitrogen.
• It has many craters caused because of colliding meteorites and asteroids.
• Has tallest volcanoes and deepest valleys in the solar system.

JUPITER

• The largest planet in the Solar system (radius – 69911 km).
• Made mostly of Hydrogen and Helium gases.
• Has a surface temperature of about minus 162°F (-108°C).
• Has 79 known moons revolving around it. One of its moon, Io, has active volcanoes on it.
• Completes one rotation in 9 hours 56 minutes.
• Completes one revolution in 4333 days.
• Has thin rings around it. Rings are thin discs of dust and rocks orbiting around the planet.
• Is visible in the night sky from Earth for nine months of a year.
• It is orange in color with white bands.
• Huge areas of swirling lights have been found on Jupiter. Largest of them is called the Great Red Spot, which is believed to be a large hurricane-like storm swirling on its surface from hundreds of years.
• Large lightning bolts have also been seen in its atmosphere.

SATURN

• Is a large gas planet (radius – 58232 km).
• Its atmosphere is mostly made up of Hydrogen and Helium.
• Has a surface temperature of about minus 218°F (-138°C).
• Has 82 known moons revolving around it.
• Completes one rotation in 10 hours 42 minutes. Its fast spin has resulted in the flat top and bottom of the planet with a bulge near the equator.
• Completes one revolution in 10759 days.
• It is pale gold in color.
• The atmosphere has winds blowing at a speed of around 1800 km/hr. White spot on Saturn is assumed to be these storms.
• Has over 1000 rings revolving around it. Rings are probably made of ice and dust caused due to destructed moons revolving around it.
• Some moons revolve in between the rings, hence creating gaps between them.

URANUS

• Has a radius of about 25362 km.
• Its atmosphere is mostly made up of Hydrogen, Helium, and Methane.
• The cold methane gas in the upper atmosphere gives it a blue-green color.
• Has a surface temperature of about minus 320°F (-195°C).
• Has 27 named moons revolving around it.
• Completes one rotation in 17 hours 14 minutes.
• Completes one revolution in 30687 days.
• It is tilted at an angle of 97.77 degrees. This tilt is so high that it results in Uranus spinning on its sides with its centre facing the Sun.
• Its atmosphere has storms swirling at a speed of about 600 km/hr.
• It has 13 known rings that contain dark and boulder-sized particles.
• It is also known as Neptune’s twin.

NEPTUNE

• Has a radius of about 24622 km.
• Its atmosphere is mostly made up of Hydrogen, Helium, and Methane.
• Has a surface temperature of about minus 331°F (-201°C).
• Has 14 named moons revolving around it. Four of them revolve within the rings. One of the moons, Triton, orbits the planet in the opposite direction to other moons.
• Completes one rotation in 16 hours 6 minutes.
• Completes one revolution in 60190 days.
• Also known as Blue Planet.
• Its atmosphere has storms swirling at a speed of about 2000 km/hr.
• It has six known rings surrounding it.

What are Dwarf Planets?

These are the astronomical objects that are massive and round. They orbit the Sun, but they have not cleared their orbital path of other materials. There are five dwarf planets – Ceres, Pluto, Makemake, Haumea, and Eris. Amongst them, Ceres lies in the asteroid belt and the other four lie in the Kuiper belt.

Inner and Outer Planets

The four planets closest to the Sun, namely Mercury, Venus, Earth, and Mars, are termed as Inner or Terrestrial Planets. The four planets farthest from the Sun, namely Jupiter, Saturn, Uranus, and Neptune, are Outer Planets.

Separating them is an asteroid belt, that consists of thousands of asteroids (small rocky bodies orbiting the sun) revolving around the Sun and lying in between Mars and Jupiter. Though all planets are different, inner planets have some resemblance to each other.

The same is the case with outer planets. Let’s look at some differences between the Inner and Outer planets.

Inner Planets	Outer Planets
They are small in size. Earth (radius – 6371 km) is the largest inner planet Mercury (radius – 2439.7 km) is the smallest inner planet	They are very huge Jupiter (radius – 69911 km) is the largest outer planet Neptune (diameter – 24622 km) is the smallest inner planet
Inner planets have solid surfaces and a thin atmosphere.	Most of the Outer Planets are made of gas. They have a much smaller solid or liquid centre.
Inner Planets have a very high density.	They are not densely packed.
The atmosphere of the Inner Planets varies. Mercury – a very thin atmosphere with the presence of Sodium and Helium on the surface. Venus – the atmosphere has Carbon Dioxide and small amounts of Nitrogen. Earth – atmosphere has Nitrogen and small amounts of Oxygen. Mars – the atmosphere has Carbon Dioxide and small amounts of Nitrogen, similar composition to that of Venus but is thinner.	The atmosphere of all outer planets is almost similar which consists of Hydrogen and Helium with small amounts of other gases. Methane is also found in significant amounts in the atmosphere of Uranus and Neptune.
Inner Planets spin slowly comparatively to Outer Planets. Earth spins quickest. It takes about 23 hours 56 minutes to spin about its axis. Venus spins most slowly. It takes 116 days 18 hours to complete one rotation.	Outer Planets spin very quickly. Jupiter spins quickest. It takes about 9 hours 56 minutes to spin about its axis. Uranus spins most slowly. It takes 17 hours 14 minutes to spin about its axis.
Being close to the Sun, Inner planets orbit the Sun quickly. Mercury has the smallest revolution period i.e. 88 days Mars completes one revolution in 687 days and has the biggest revolution period.	Outer planets take much time to complete a revolution. Jupiter takes 12 years and has the smallest revolution period. Neptune has the biggest revolution period of about 184 years.
Inner planets have few moons orbiting around them. Mercury and Venus have no moon. Earth has one and Mars has two moons.	Outer planets have lots of moons orbiting around them. Jupiter has 79, Saturn has 82, Uranus has 27 and Neptune has 14 moons.
Inner planets have no rings orbiting around them.	All outer planets have rings orbiting around them. Saturn has the most visible rings.
There have been several spacecraft missions to Inner Planets. Mercury has been visited by 2 spacecraft, Venus by 40 (most visited planet) and Mars by 16.	There have been comparatively fewer spacecraft missions to Outer planets. Jupiter has been visited by 12 spacecraft, Saturn by 5, Neptune, and Uranus by only one.

Conclusion

In this article, we learned about, the Solar System, all the eight planets, and their characteristics. We also learned about dwarf planets, inner and outer planets. We learned about many differences between inner and outer planets.