Solar System - Planets and their Moons
Our solar system comprises the following 8 planets:
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
It also includes dwarf planets like Pluto, dozens of moons, and millions of asteroids, comets, and meteoroids.
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The term “Planet,” is an ancient word with ties to science, history, astrology, mythology, and religion. It is a celestial body that orbits the Sun and it carries enough mass to be circled by its own gravity, where each planet has a varying number of moons and natural satellites.
On this page, we will discuss planets and their moons in our solar system, and planets and their satellites in detail.
Moons of Planets in Solar System
Do you know the meaning of the Moons of Planets in the Solar System? If not, let’s understand it:
We all hear that planets and their natural satellites exist in the sky, among these, we have a moon. So, do you know what Moon is?
Moons are natural satellites that vary in shapes, sizes, and types. They are solid bodies, and few have atmospheres.
Most planetary moons probably formed from the rotating discs of gas and dust, circling around planets in the early solar system.
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Do you know the Planets and Satellites of our Solar System? If not, let’s understand the moons of different planets:
The below table comprises the Planets and their Moons:
Planets and their Moons List
Planets and Moons
Planets of the inner solar system: Earth has one and Mars has its two small moons.
However, in the outer solar system: the gas giants: Jupiter and Saturn, and therefore, the ice giants: Uranus and Neptune have dozens of moons.
Do You Know?
1. Property of a Moon
A moon is Earth’s only natural satellite. At 1/4th the diameter of the Earth, a moon is the largest natural satellite within the system relative to the dimensions of its planet, and therefore the fifth largest satellite within the system overall.
2. Moons in Asteroids
There are many moons in our system - even a couple of asteroids are found to possess small companion moons.
3. Provisional Moons
Moons that start with a letter and a year are provisional moons. However, they will be given a proper name when their discoveries are confirmed by additional observations.
Discovery of Our Solar System
For millennia, astronomers have followed points of sunshine that appeared to move among the celebs. the traditional Greeks named them planets, meaning "wanderers."
Mercury, Venus, Mars, Jupiter, and Saturn were known in antiquity, and therefore the invention of the telescope added the belt, Uranus, Neptune, Pluto, and lots of of those worlds' moons.
The dawn of time saw dozens of probes launched to explore our system, an adventure that continues today. just one spacecraft thus far, Voyager 1, has crossed the edge into the region.
The discovery of Eris began a rash of the latest discoveries of dwarf planets, and eventually led to the International Astronomical Union revising the definition of a "planet." The revision changed Pluto's status from planet to dwarf planet in 2006, a choice that is still controversial – especially after the New Horizons mission found immense geological variety on the planet in 2015.
Now, we will understand the Planet Definition:
Definition of a Planet
As per the definition of a planet given by IAU in 2006 officially, it is:
"Planets" under the present definition are some celestial bodies, like Ceres, Pallas, Juno, and Vesta (each an object within the solar asteroid belt), and Pluto (the first trans-Neptunian object discovered), that were once considered planets by the scientific community, are not any longer viewed as planets under the present definition of a planet.
Formation of Planets
Many scientists think our system formed from an enormous, rotating cloud of gas and mud referred to as the solar nebula. because the nebula collapsed due to its gravity, it spun faster and flattened into a disk. Most of the fabric was pulled toward the middle to make the sun. While, other particles within the disk collided and stuck together to make asteroid-sized objects named planetesimals, a number of which combined to become the asteroids, comets, moons, and planets.
Fun Facts:
Our solar system carries inner rocky planets, which are Mercury, Earth, and Mars.
Apart from the Earth itself, five planets within the system are visible to the eye. These were regarded by many early cultures as divine/ as emissaries of deities. Because of the knowledge base advancement, human perception of the planets changed, incorporating a spread of disparate objects.
Astronomers are now trying to find another planet in our system, a true ninth planet, after evidence of its existence was unveiled on Jan. 20, 2016.
The reputed "Planet-Nine," as scientists are calling it, is assumed to be about 10 times the mass of Earth and 5,000 times the mass of Pluto.
FAQs on Planets and their Moons
1. What officially defines a body as a 'planet' in our solar system?
According to the International Astronomical Union (IAU), a celestial body is officially classified as a planet if it meets three specific criteria:
- It must orbit the Sun.
- It must have sufficient mass to assume hydrostatic equilibrium, which means its own gravity has pulled it into a nearly round shape.
- It must have 'cleared the neighbourhood' around its orbit, meaning it has become gravitationally dominant, removing other smaller objects from its orbital path.
2. What is the fundamental difference between terrestrial planets and gas giants?
The fundamental difference lies in their composition and location. Terrestrial planets (Mercury, Venus, Earth, Mars) are inner planets primarily composed of rock and metal with solid surfaces. In contrast, gas giants (Jupiter, Saturn) and ice giants (Uranus, Neptune) are outer planets that are much larger and composed mainly of gases like hydrogen and helium, and ices, without a solid surface to stand on.
3. Which planets in our solar system have moons, and which do not?
Not all planets in our solar system have moons. The two innermost planets, Mercury and Venus, have no moons at all. Earth has one moon, and Mars has two small moons. The outer planets, however, host extensive moon systems:
- Jupiter: Over 90 confirmed moons.
- Saturn: Over 140 confirmed moons.
- Uranus: 27 known moons.
- Neptune: 14 known moons.
4. How are moons believed to be formed, and why do gas giants have so many?
Moons are formed through several processes. Many, like Earth's Moon, are thought to have formed from debris left over after a massive collision. Others may have been captured by a planet's gravitational pull. The gas giants have so many moons because their immense mass creates a powerful gravitational field, allowing them to capture passing asteroids and comets. Additionally, the large discs of gas and dust that surrounded these giant planets in the early solar system provided abundant material for moons to form in orbit around them.
5. Which planet currently holds the title for the most moons?
As of recent discoveries, Saturn holds the title for the planet with the most moons in our solar system, with over 140 confirmed natural satellites. It has surpassed Jupiter, which has over 90 confirmed moons. These numbers can change as new, smaller moons are continuously being discovered by astronomers.
6. Why do we always see the same side of Earth's Moon?
We always see the same face of the Moon because of a phenomenon called tidal locking. Over billions of years, Earth's gravity has influenced the Moon's rotation to the point where the time it takes for the Moon to rotate once on its own axis is exactly the same as the time it takes to complete one orbit around Earth (approximately 27.3 days). This perfect synchronisation keeps one hemisphere of the Moon permanently facing us.
7. Besides our own, what are some examples of significant moons in the solar system?
Our solar system has many fascinating moons with unique characteristics. Some significant examples include:
- Ganymede (Jupiter): The largest moon in the solar system, even bigger than the planet Mercury.
- Titan (Saturn): The second-largest moon, and the only one with a thick, dense atmosphere and liquid lakes on its surface.
- Europa (Jupiter): Famous for its smooth, icy crust which is believed to cover a vast saltwater ocean, making it a key target in the search for extraterrestrial life.
- Triton (Neptune): A large moon that orbits its planet in the opposite direction of the planet's rotation (a retrograde orbit), suggesting it was a captured object.
8. How is a 'dwarf planet' like Pluto different from a regular planet?
A dwarf planet is a celestial body that meets the first two criteria for being a planet: it orbits the Sun and has a nearly round shape. However, it fails to meet the third criterion. A dwarf planet like Pluto has not 'cleared its neighbourhood' of other objects. Its orbit is located in a region with many other celestial bodies of comparable size, such as the Kuiper Belt, which it has not gravitationally dominated.
