The Universe, The Milky Way and The Solar System

The Universe

The universe is a name for all matter and energy. It includes The Earth (our planet), other planets, stars, satellites and comets, the Solar System and other galaxies. It has other names such as the cosmos or the world.

The Universe is full of astronomical bodies. We can classify them in two big groups:

luminous astronomical bodies: They give off light and heat. For example: Stars.
non-luminous astronomical bodies: They don't give off light; they only reflect the light from the stars. For example: planets, satellites and comets reflect light from the Sun and other stars.

Sometimes people name the Universe like Solar System or The Milky Way, but they are not the same.

Universe, The Milky Way and The Solar System.

Do you understand the difference between them? No?
Ok. We will try to explain the differences:

The Earth is our planet. It is one of the planets of our Solar System; The Solar System is a small part of our Galaxy (the Milky Way); and the Milky Way is a Galaxy of the Universe.

Our Earth orbits the Sun in our Solar System. Our Sun is one star among the billions in the Milky Way Galaxy. Our Milky Way Galaxy is one among the billions of galaxies in our Universe. You are unique in the Universe!

Do you understand it now? Not yet? Ok, we will learn more...

The Universe is made up of billions of galaxies. NASA's telescopes allow us to study these galaxies in detail.

The Hubble Space Telescope made the one of the most beautiful images of the universe called the Hubble Extreme Deep Field. Soon the James Webb Space Telescope will be exploring galaxies forming at teh very beginning of the universe.

This is the famouse Hubble Extreme Deep Field made by the NASA. Every spot is a galaxy.

One of these Galaxies is The Milky Way (Vía Láctea in Spanish). It is made up of between 200 and 400 billion stars. The Milky Way is a big galaxy but there are some galaxies much bigger, like our neighbour Andromeda Galaxy (Galaxia de Andromeda in Spanish).

One of these hundreds of billions of stars is our Sun. the Sun is the centre of our Solar System.

The Solar System is a part of the Milky Way. It consists of: the Sun and other astronomical bodies like planets (including the Earth), asteroids and comets that orbits the Sun and other like satellites that orbit the planets.
For example: The Earth is a planet that orbits the Sun, and the Moon is a satellite that orbits the Earth.

Here, there is a picture of our galaxy, The Milky Way. Can you find the Solar System?

What we used to study is our Solar System, so here there are some basic notions about it:

There are eight planets orbiting the Sun:

Mercury is the closest planet to the Sun and the smallest planet of the Solar System.
Venus is a rocky planet and teh second closest planet to the Sun.
The Earth is our planet. It is called the Blue Planet because it has a lot of water.
Mars is a rocky planet and it is called "The Red Planet" because it has a lot of iron oxide.
Jupiter is the largest planet in the Solar System. It is a gaseous planet.
Saturn is the second larges planet in the Solar System. It is a gaseous planet and it is famous by its ring system, that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with rocks and dust.
Uranus is the seventh planet from the sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System.
Neptune: is the farthest planet from the Sun. It is a gaseous planet and it is the fourth-largest planet by diameter and the third-largest by mass.

Pluto was considered a planet between 1845 and 2006. In 2006 Pluto was not considered a planet anymore. However, in the 19th Century (between 1807 and 1845) some astronomical bodies such as Ceres, Pallas and Vesta were considered as planets.

Here you can find a song about the planets for children. It is very easy to understand.