Universe and the Solar Family - Class 5 Notes & Olympiad Questions

The Universe

a) The universe is a vast expanse that includes everything we know, from planets and stars to galaxies and beyond.
b) The universe is about 13.8 billion years old.
c) The universe is made up of billions of galaxies, and each galaxy contains billions or even trillions of stars.
d) Our galaxy is called the Milky Way, and it's just one of many galaxies in the universe.

The Solar System

a) The solar system is a fascinating part of the universe that includes the Sun, eight planets, numerous moons, asteroids, comets, and other smaller objects.
b) The sun is the centre of our solar system.
c) Studying the solar system helps us understand the formation and evolution of planets, the conditions necessary for life, and the vast diversity of celestial objects in our cosmic neighbourhood.

The Planets

a) Planets are celestial objects that orbit around stars, just like how Earth orbits around the Sun.
b) There are eight planets in our solar system, and each one has its own characteristics.

Classification of Planets

Planets can be classified into two main categories based on their characteristics.

Terrestrial Planets

a) Terrestrial planets are made up of rocks and metals, and they have solid surfaces. They are closer to the Sun compared to the other category of planets.
b) Terrestrial planets are also called “Inner Planets”.
c) Mercury, Venus, Earth and Mars are terrestrial planets.

Jovian (Jupiter-like) Planets

a) Jovian planets are giant planets that are much larger than terrestrial planets.
b) They are called Jovian because they are similar to Jupiter, the largest planet in our solar system.
c) There are four Jovian planets in our solar system: Jupiter, Saturn, Uranus, and Neptune.
d) All four giant planets in our solar system have rings around them.
e) Jovian planets, also known as gas giants, are mainly made up of hydrogen and helium gases, with some other elements.
f) They are also known as the outer planets because they are located farther away from the Sun compared to the terrestrial planets.

It's important to note that there is also a category called "dwarf planets."

Dwarf Planets

a) Dwarf planets are celestial bodies that orbit around the Sun, just like the regular planets. However, dwarf planets are usually smaller in size compared to the regular planets.
b) They can be round or have odd shapes, just like their bigger counterparts.
c) Another difference is that dwarf planets don't have as much gravitational influence as regular planets, which means they may not be able to clear their orbits of other objects like planets do.
d) When a planet clears its orbit, it means that its gravitational influence is strong enough to either pull those smaller objects towards itself or push them away, ensuring that its path is relatively free of other objects.
e) Some famous examples of dwarf planets are Pluto and Ceres.

Planets in Our Solar System

Mercury

a) Mercury is the smallest planet in our solar system, just a little bigger than Earth's Moon.
b) Mercury is the planet that orbits closest to the Sun out of all the planets in our solar system.
c) Mercury is the fastest planet. Because it's so close to the Sun, it has the shortest year of all the planets—only 88 days.
d) Mercury is a rocky planet, like Earth's Moon. It has a solid and cratered surface.
e) Unlike some other planets, Mercury doesn't have any moons.
f) Mercury has really extreme temperatures, and it gets hit by a lot of harmful rays from the Sun. These conditions make it impossible for living things to survive there.

Venus

a) Venus is often called Earth's twin because it's similar in size and structure, but it has extreme heat and a thick, toxic atmosphere.
b) Venus is the second planet closest to the Sun.
c) Venus rotates very slowly, so one day on Venus lasts 243 Earth days. However, it orbits the Sun faster than Earth, so one year on Venus is shorter than its day.
d) Venus has a solid surface with dome-like volcanoes, rifts, mountains, and volcanic plains.
e) It's the hottest planet in our solar system.
f) Venus rotates backwards on its axis compared to most planets. This means the Sun rises in the west and sets in the east, opposite to what we observe on Earth.
g) Venus doesn't have any moons.
h) Venus is referred to as both the morning and evening star is because it orbits closer to the Sun than Earth. As a result, Venus can sometimes be seen on one side of the Sun (before sunrise) and at other times on the opposite side (after sunset). This makes it visible at different times of the day, depending on its position in relation to Earth and the Sun.

Earth

a) Our Home Planet Earth is the third planet from the Sun and the only place we know of so far that has living things.
b) Although Earth is the fifth largest planet in our solar system, it is the largest among the four rocky planets closest to the Sun.
c) Earth has a solid and dynamic surface with various features like mountains, canyons, and plains. It also has a significant amount of water, with most of the planet covered by oceans.
d) Earth has one moon that orbits around it.
e) Earth's atmosphere acts as a shield, protecting us from incoming meteoroids. Most of them burn up in the atmosphere before reaching the surface.

Mars

a) Mars is the fourth planet from the Sun. It's a cold and dusty desert world with a thin atmosphere.
b) One day on Mars is a little over 24 hours, similar to Earth. But it takes Mars about 687 Earth days to complete one orbit around the Sun, which we call a year in Martian time.
c) Mars is a rocky planet, and its surface has been shaped by volcanoes, impacts, winds, and other forces over time.
d) Mars is often called the Red Planet because iron minerals in the Martian soil oxidize or rust, giving the soil and atmosphere a reddish colour.
e) Mars has two moons called Phobos and Deimos.
f) Currently, Mars cannot support life as we know it. Scientists are studying Mars to understand its past and potential for life in the future.

Jupiter

a) Jupiter is the largest planet in our solar system. It is the fifth planet from the Sun.
b) Jupiter spins very quickly, completing one rotation in about 10 hours. However, it takes about 12 Earth years for Jupiter to complete one orbit around the Sun.
c) Jupiter is a gas giant, which means it doesn't have a solid surface like Earth.
d) Jupiter's atmosphere is mostly made up of hydrogen and helium, which are light elements.
e) Jupiter has 95 moons orbiting around it. These moons come in different sizes and have their own unique features.
f) Just like Saturn, Jupiter also has a faint ring system.
Jupiter is famous for its Great Red Spot, which is a massive storm that has been raging for over a century. It's about twice the size of Earth and is a fascinating feature of the planet.

Saturn

a) Saturn is the sixth planet from the Sun and the second-largest planet in our solar system.
b) It is known for its beautiful and intricate ring system, made of chunks of ice and rock. Saturn has 7 rings.
c) A day on Saturn is about 10.7 hours (approximately), which is shorter than a day on Earth. However, it takes Saturn about 29 Earth years to complete one orbit around the Sun.
d) Saturn is a gas-giant planet, which means it doesn't have a solid surface like Earth. It's mostly made up of hydrogen and helium, similar to Jupiter.
e) Saturn has a total of 146 moons.

Uranus

a) Uranus is the seventh planet from the Sun and has the third-largest diameter in our solar system.
b) A day on Uranus lasts about 17 hours (approximately), which is shorter than a day on Earth. However, it takes Uranus about 84 Earth years to complete one orbit around the Sun.
c) Uranus is classified as an ice giant.
d) Many Moons: Uranus has 27 known moons.
e) Uranus has 13 known rings.
f) Similar to Venus, Uranus rotates from east to west. However, what makes Uranus unique is that it rotates on its side, unlike any other planet in our solar system.

Neptune

a) Neptune is the eighth planet in our solar system and the farthest one from the Sun. It is a dark, cold, and windy place with extreme conditions.
b) Neptune is about four times wider than Earth.
c) Neptune spins on its axis, completing a full rotation in about 16 hours (approximately). However, it takes about 165 Earth years for Neptune to orbit around the Sun.
d) Neptune has 14 known moons.
e) Neptune has five main rings and four additional ring arcs. These rings are made up of dust and debris, likely formed by the gravity of a nearby moon.

Earth’s Movements

Rotation

a) Earth spins around an imaginary line called its axis. This spinning motion is called rotation, and it takes about 24 hours for Earth to complete one full rotation.
b) As Earth rotates, it gives us day and night. When your side of Earth is facing the Sun, it's daytime, and when your side is facing away from the Sun, it's nighttime.
c) Also, the changing length and position of shadows throughout the day are a direct result of the Earth's rotation and the movement of the Sun across the sky.
d) Shadows are created when an object blocks light. When the Sun is low in the sky, like in the early morning or late afternoon, the shadows appear long because the Sun's light has to pass through more of Earth's atmosphere to reach us. This makes the shadow stretch out.
e) As the Sun gets higher in the sky during the middle of the day, the shadows become shorter. That's because the Sun's light has to pass through less of Earth's atmosphere to reach us, creating a shorter shadow.

Revolution

a) Earth also moves around the Sun in a path called an orbit. This movement is called revolution.
b) It takes about 365.25 days (or one year) for Earth to complete one revolution around the Sun.
c) As Earth travels in its orbit, different parts of the planet receive different amounts of sunlight, which is why we have different seasons throughout the year.

Tilted Axis

a) Another important aspect of Earth's movement is its tilted axis. Earth's axis is not straight up and down but tilted at an angle.
b) This tilt causes the changing seasons we experience. When one hemisphere (half) of Earth is tilted towards the Sun, it receives more direct sunlight, creating summer.
c) In the other hemisphere, which is tilted away from the Sun, it receives less direct sunlight, creating winter. As Earth continues its orbit, the tilt causes the seasons to change.