3. Our Solar System
3. Our Solar System
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Identify the components of the solar system and label them
Group planets as terrestrial or gas giants
Exploring our solar system is like going on a cosmic adventure! It's all about understanding the Sun, planets, moons, and other fascinating things in space. We'll learn how our planet fits into this big picture. Get ready for a fun and educational journey through our solar system!
Fig. 3.1 Our Solar System
At least one star and the planets and other celestial bodies make up a solar system. A few of these things are planets—enormous spheres that orbit stars. Moons, asteroids, comets, and pieces of rock and dust are some of the other objects in a solar system. An object's orbit is the path it takes as it travels around another object in space. The pull of gravity keeps objects in orbit.
Fig. 3.2 Celestial Objects in Our Solar System
There are eight planets in our solar system and one star, the sun. There are several stars in other solar systems.
a. The Sun
a. The Sun
The Sun is an ordinary star, one of the billions of stars in the universe. It sits at the centre of the solar system and influences the motion of every other body by its gravitational pull that holds the solar system together2.
It is enormous and composed of incredibly hot gases primarily hydrogen and helium.
The sun serves as the solar system's primary source of heat and light. Although it is our nearest star, we do not feel its intense heat very much because it is so far away3.
Fig. 3.3 The Sun As Seen Under UV Light
b. The Planets
b. The Planets
Our Solar System has 8 Planets. The planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, listed in order of their distance from the Sun2.
Our solar system consists of some rocky planets and some gaseous planets.
Fig. 3.4 Rocky and Gaseous Planets
1. Rocky Planets
1. Rocky Planets
Mercury, Venus, Earth, and Mars are known as the ‘rocky' or 'terrestrial' planets. These planets are known as such because they are primarily made of rocks and metal. These first four planets from the sun have a solid surface1.
Fig. 3.5 Rocky Planets
Let us look at some fun facts about these planets.
It is the smallest and closest planet to the sun in our solar system. It is a little bit bigger than the Earth’s moon. It has no moon of its own.
1 Mercury year = 88 earth days5
It is the second planet from the sun, also known as the Earth’s twin. Venus, our nearest planetary neighbour, is the hottest planet in our solar system.
It is the only planet to spin backward and has 1 day longer than its 1 year5.
Our home planet, also known as the ‘Blue Planet', is the third planet from the sun and the only habitable planet we know of. It is the only known planet to sustain life, as it has water, a stable and suitable atmosphere, and sources of energy. Earth happens to have a unique set of conditions that support life.
Our planet has 1 moon, its natural satellite.
The moon crosses the earth
The fourth planet from the sun, is dry, rocky, and cold. One of the easiest planets to locate in the night sky is Mars, which resembles a brilliant red dot. Mars has 2 moons5.
Moons of Mars
Mars is a planet that scientists find really interesting because they want to learn about how it has changed over time and if there could be any life there. We used to think Mars was warm and wet, but now we know it's dry with a very thin atmosphere.
India sent its first spacecraft, the Mars Orbiter Mission (MOM), to Mars on November 5, 2013. This was a big deal because it made India the fourth space agency in the world to successfully send a spacecraft to orbit Mars.
Even though the mission was supposed to last for 6 months, MOM kept working for a whole 7 years in Mars' orbit until September 24, 2021, which was an impressive achievement6.
Mars
2. Gaseous Planets
2. Gaseous Planets
The last four planets—Jupiter, Saturn, Neptune, and Uranus—are the gaseous planets of our solar system. They are known as the ice giants or gas giants. They are spinning balls of gas with rocky cores (centres)4.
Fig. 3.6 Gaseous Planets
The fifth planet from the Sun, Jupiter is by far the largest planet in the solar system, more than twice as massive as all the other planets together. It has 95 moons5.
Jupiter and the Red Spot
Saturn is the second largest planet in our solar system and is located six planets from the Sun. With its brilliant system of ice rings, Saturn stands out from the other planets.
Similar to Jupiter, Saturn is a huge sphere primarily composed of hydrogen and helium. It has the most number of moons, i.e., 2745.
Saturn and its Rings
Uranus is the first planet discovered with the help of a telescope. Uranus is windy and quite cold. It rotates at roughly a ninety-degree angle from the plane of its orbit, encircled by weak rings and twenty seven tiny moons. Uranus appears to rotate on its side because of this unusual tilt5.
Uranus with its rings
It is the farthest planet in our solar system. It takes 165 Earth years to complete its orbit. It has 14 moons5.
Neptune
Watch this video to see actual images of the planets of our solar system:7
Vid. 3.1 Planets of our Solar System
c. Moon
c. Moon
Objects formed naturally that orbit around planets are called moons or planetary satellites. These moons differ greatly in terms of their shape, size, and characteristics. There are hundreds of moons within our solar system.9
Our solar system has over 891 known moons, and new ones continue to be discovered regularly. Approximately 369 of these moons revolve around Jupiter and Saturn, while others orbit different planets and dwarf planets, such as Pluto.13
Earth’s Moon
Watch this video14 to know more about the moons of our Solar System:
Vid. 3.2 What are Moons?
d. Asteroid Belt
d. Asteroid Belt
In the early days of the solar system, bits of rock and dust were swirling around the Sun. Thanks to gravity, some of these bits came together to form planets. However, not all of these materials turned into new worlds. Here, small objects, mostly rocky and some metallic, orbit the sun.
Many of these objects, known as planetoids or asteroids (which means "star-like"), travel in orbits between Mars and Jupiter. They form a group called the main asteroid belt.
Fig. 3.7 Asteroid Belt between Mars and Jupiter
People sometimes wonder if the asteroid belt was once a complete planet that got destroyed, or maybe a world that never quite got going. But according to NASA, the total amount of mass in the belt is way less than even our moon. It's just not enough to be considered a planet. Instead, Jupiter plays the role of a guardian. It prevents all the debris in the belt from coming together to form other planets by herding them around10.
Watch this video to learn more about our solar system:11
Vid. 3.3 Our Solar System
Glossary
celestial body: any object in space, such as a planet, moon, or star.
orbit: the path one object in space takes around another, like Earth around the Sun.
star: a giant ball of burning gas in space that gives off light and heat.
composition: what something is made of.
crater: a hole or pit on a surface (like Mercury or the Moon) formed by a collision with a meteorite or asteroid.
UV Light (Ultraviolet Light): type of light from the Sun that we can't see but can be observed with special tools
Summary
Our solar system consists of the Sun, planets, moons, and other space objects like asteroids, comets, and dust particles.
Objects in space follow orbits, which are determined by gravity, keeping them in motion around other celestial bodies.
The Sun, a massive star, is at the centre of our solar system, providing heat and light.
The eight planets in our solar system, in order of distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Four of these planets (Mercury, Venus, Earth, and Mars) are rocky or terrestrial planets, primarily composed of rocks and metals.
The other four planets (Jupiter, Saturn, Uranus, and Neptune) are gaseous or ice giants with rocky cores.
There is an asteroid belt located between Mars and Jupiter, which consists of leftover rock and dust that did not form planets. Jupiter's gravity prevents the debris in the belt from coalescing into new planets.
References
1 Astronomy Space Systems. Core knowledge, n.d, link
2 Solar System. Britannica, 2023, link
3 The Earth in the Solar System. NCERT, n.d, link
4 Gas Giants. NASA Exoplanet Exploration, n.d, link
5 The Planets. NASA, n.d, link
6 Mars Orbiter Mission. ISRO, n.d, link
7 Real Images From Our Solar System. Youtube, n.d, link
8 Moon. NASA, n.d, link
9 Moons of our Solar System. NASA, (n.d), link
10 Asteroid Belt: Facts and Information. Space.com, 2017, link
11 Asteroids: Facts. NASA, n.d, link
12 Solar System 101. Youtube: National Geographic, n.d, link
13 Our favorite moons of the Solar System. The Planetary Society, (2023), link
14 What are moons? Youtube, (n.d), link
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