All the planets and moons of the solar system.

Solar system: Formation, Evolution, Sun, Planets, Terrestrial, Gas Giants, Interstellar Medium, Space

Solar system

The planets and moons in the solar system in their true color.
The planets and moons in the solar system are in their true color. Credits –
CactiStaccingCrane/Source/CC BY-SA 4.0.

The Solar System is a gravitationally connected system containing all the planets orbiting the Sun. This 4.6 billion-year-old structure formed after a massive interstellar molecular cloud collapsed. Almost all the mass is found in the Sun. The rest is on the planet Jupiter. Mercury, Venus, Earth, and Mars have been classified as terrestrial planets which contain the main component – Rock and Metal. The 4 gigantic worlds of the outer system were significantly larger and heavier than the earth and its atmosphere.

Formation and evolution

A protoplanetary disk which formed the solar system (illustration).
A protoplanetary disk which formed the solar system (illustration). Credits – NASA/Source.

Our Solar System has formed 4.6 billion years ago when a Giant Molecular Cloud collapsed under the force of its own gravity. Most of the mass in this collapse formed the Sun. The remaining mass turned into a Proto-planetary disk. This later formed the planets, their moons, asteroids, and all other bodies.

After the initial formation, there have been a lot of changes that have taken place. Many moons of planets have formed due to collisions between different bodies. The orbits may have been altered due to gravitational interaction.

Interplanetary medium

The interplanetary medium consists of cosmic dust, cosmic rays, and plasma. There is Solar Wind blowing through the Interplanetary medium. The interplanetary medium is filled with plasma and hence shows some remarkable properties such as a difference in the strength of the magnetic field than expected due to the presence of plasma.

Heliosphere interacting with the interstellar wind.
Heliosphere interacting with the interstellar wind. Credits – NASA/Source.

The interplanetary medium extends until the Heliopause. The interaction of the interplanetary medium with the planets depends on whether the planet has a magnetic field or not. If the planet or a moon has a magnetic field, they won’t be impacted by the solar wind.

For most of scientific history, the interplanetary medium was thought to be either vacuum or filled with aether. In the 1950s radical discoveries found that interplanetary space is filled with plasma due to the solar wind which flows at supersonic velocities.

Pluto: Once a planet, now a dwarf planet

Pluto is the largest dwarf planet in our Solar System. It is found in the Kuiper belt on the outer edges of our Solar System. It was considered a planet from its discovery in 1930 to 2006 when it was stripped of its planetary status. Kuiper Belt is a disc of rocky bodies on the edge of the solar system from 30 AU to 50 AU from the Sun.

Pluto in true color.
Pluto in true color.
Credits – NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker/Source.

Five moons of Pluto have been discovered to date: Charon, Styx, Nix, Kerberos, and Hydra. Pluto is visited by only one space probe until now: New Horizons. New Horizons made a flyby of Pluto. The closest it came was 12,500 km from Pluto on July 14, 2015.

Sun

The Sun is the largest solar system body present in its center. The Sun is the primary source of energy on Earth. The Sun is a hot ball of plasma giving out an enormous amount of energy due to the process of nuclear fusion taking place at its core.

Sun as seen from the International Space Station (ISS).
Sun as seen from the International Space Station (ISS). Credits – NASA/Source.

The Sun converts 600 mil tons of hydrogen into helium every second. The Sun has an average distance of about 150 mil kilometers from Earth. About 73% of the Sun is hydrogen, the remaining being mostly helium and a minute percentage of other elements. Its surface temperature is nearly 6000 kelvin.

See all the facts about the Sun here The Mighty Sun: Facts that will blow your mind forever.

Mars: The solar system’s Red Planet

Mars in its true color.
Mars in its true color. Credits – ESA & MPS/Source/CC BY-SA IGO 3.0

Mars is the fourth planet from the Sun. It is reddish-pink in color due to the presence of iron oxide and other minerals. Mars was a great source for humans since the beginning of time. It is named after the Roman God of War. Mars is visited by various space probes.

Landers and Rovers have landed on its surface. Sophisticated overs are exploring Mars. Mars has many similarities to Earth. This has made people think of Mars as a Plan B in case something happens to our Earth.

If you want to know about the search for life on Mars and Mars exploration check Life on Mars: The fascinating history of Mars

Mercury: The closest planet to the sun

Mercury is the first planet from the Sun and is the smallest. It is very difficult to spot Mercury from Earth due to its close proximity to the Sun. Hence it is visible just before sunrise and just after sunset. Hence not much of the planet was studied before space probes could reach Mercury. However, radio and radar astronomy made some observations of Mercury.

Mercury in its true color.
Mercury in its true color.
Credits – NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington/Source.

It is also difficult to send space probes to Mercury as it is closer to the Sun’s gravitational field. Since Mercury’s orbital speed around the Sun is ~1.59 times that of Earth, it is difficult to enter into orbit around Mercury for space probes. As a matter of fact, for space probes, more fuel is needed to go to Mercury than to get out of the Solar System.

If you are interested in space exploration, you might want to see V-2: Story of the First Object to reach Space.

Types of planets in the solar system

There are two types of planets in the solar system depending on their distance from the Sun; Terrestrial planets and Gas giants. 4/8 planets in our solar system are terrestrial, remaining four are gas giants. Terrestrial planets have solid rocky structures and are made of soil and rock. Gaseous planets are made of different gases. The Gas Giants are huge in size compared to the Terrestrial planets.

Uranus: The tilted, sideways planet in our solar system

Uranus in its true color.
Uranus in its true color.
Credits – NASA/JPL-Caltech/Source

Uranus is the seventh planet from the Sun in our Solar System. The planets Uranus and Neptune are further classified as ice giants to distinguish themselves from gas giants since they contain lots of ice as well as gas. Uranus was discovered by William Herschel in 1781.

Uranus is named after the Greek God of the Sky. It takes 84.02 years to orbit the Sun once. 27 moons of Uranus are discovered. Its atmosphere is mostly made of hydrogen and helium and a little bit of methane. It also has ammonia and water in ice form.

You might be interested in Exciting Visit of an Interstellar Object Will Make You Feel Eerie.

Saturn: The ringed jewel of the solar system

Saturn is the sixth planet from the Sun. It is also the second-largest. It is well known for its characteristic rings. It takes 29.46 years to orbit the Sun once. The Titan is the largest moon of Saturn, among its 83 known moons. Titan is also the second-largest moon in the solar system after Ganymede.

Saturn in its true color.
Saturn in its true color. Credits – NASA/JPL/Source.

Saturn is well known for its density being less than that of water at 0.687 g/cc. Saturn is visited by various space probes since 1979. The first to enter into orbit around Saturn was Cassini-Huygens in 2004. Huygens probe landed on Saturn’s moon Titan.

Venus: Earth’s twin in the solar system

Venus is the second planet in our solar system from the Sun. It is also the hottest. Even though Mercury is the closest planet to the Sun, it is not the hottest. Because, Venus has a dense atmosphere 96.5% carbon dioxide. The average temperature is 467 degrees celsius.

Venus is seen as a bright spot in the sky. Venus is seen in the center-right in this picture.
Venus is seen as a bright spot in the sky. Venus is seen in the center-right in this picture. Credits – Brocken Inaglory/Source/CC BY-SA 3.0

Venus is also the third brightest object seen in the sky after the Sun and the Moon. Its physical features are similar to those of Earth. Its radius is 0.95 times the Earth. Its mass is 0.815 times the Earth and its surface gravity is 0.904 times the Earth. The first space probe to fly by Venus was the Soviet Venera 1 way back in 1961.

You might want to read Exoplanets: Super-Earth and Sub-Neptune types Found Transiting a Star.

Jupiter: The largest planet in our solar system

The Jupiter is the largest planet in the solar system. It is the fifth planet from the Sun. It is also the first gas giant. 80 of the Jupiter’s moons are known till date, with Ganymede being the largest in the solar system. Jupiter takes 11.862 years to complete one orbit around the Sun. It is visited by a few space probes beginning Pioneer 10 in 1973. Galileo was the first to orbit Jupiter in 1995.

Jupiter as seen by the Juno spacecraft.
Jupiter as seen by the Juno spacecraft. Credits – NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill/Source.

The Great Red Spot on Jupiter is the largest storm in the solar system. Jupiter has a mass of 317.8 times that of the Earth. Almost 90% of its atmosphere is hydrogen and 10% helium, with other gases in minute quantities. Its escape velocity is 59.5 km/s.

Neptune: A giant stormy blue planet

Neptune is the last planet in our solar system. It was the most recent planet to be discovered (1846). It takes 164.8 years to orbit the Sun once. It has 14 known moons with Triton being the largest. The atmosphere is primarily made of hydrogen and helium, with a small quantity of methane.

Neptune planet in its true color.
Neptune in its true color. Credits –
Justin Cowart/Source.

It has a Great Dark Spot comparable to the Jupiter’s Great Red Spot. Neptune is visited by only one space probe till date: Voyager 2 in 1989. Neptune also possesses rings but is smaller than those of Saturn. It weighs 17.147 times the Earth. Its escape velocity is 25.3 km/s.

You might want to see Voyager Probes: Top 10 Amazing Facts To Make You Awestruck.

Earth: Our home planet, filled with life

The Earth is our home planet. It is the only planet known to sustain life in our solar system to date. It has large bodies of water, which cover almost 3/4th of its surface area. It has a magnetic field which shields the life on it from the solar wind and cosmic rays. It is at an average 150 million kilometers from the Sun. It is the third planet from the Sun.

Earth as seen from the lunar orbit taken by Lunar Reconnaissance Orbiter.
Earth as seen from the lunar orbit taken by Lunar Reconnaissance Orbiter. Credits – NASA / GSFC / ASU/Source.

It has one natural satellite, the moon. It has more than 4500 artificial satellites orbiting it, with still higher space debris. The water bodies on the Earth led to evolution, thus plants and animals were born. The most dominant species on Earth are the Humans.

You might want to see ASTROCHEMISTRY: RELEVANCE OF CHEMISTRY IN THE STUDY OF COSMOS.

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