When we look up into the night sky, it can be difficult to imagine what could be out there. This article explains some of the things that astronomers (scientists who study space) have discovered in our universe.
The Universe contains everything that exists, and it is nearly 14 billion years old. The Universe is infinitely large, meaning if you traveled through it, you would never find the edge. Astronomers believe our Universe began at the ‘Big Bang’. In the beginning, everything in the Universe was condensed into a tiny point, which suddenly started to rapidly expand. We don’t know how or why this happened, but the Universe has been growing ever since.
It might seem strange to say that the Universe is growing when it is already infinitely large. By this, we mean that the Universe is stretching, in the same way that two ends of a rubber band get further apart as you pull on them.
Planets can be made up of different things. For example, Earth is mostly made of rock, but Jupiter and Saturn are mostly gas.
Most planets are very different to Earth. Some experience extreme temperatures, where the night is hundreds of degrees colder than the day. Also, Earth has an atmosphere, which is a layer of gas around the planet. This provides the air we breathe, and it allows us to survive. Other planets have atmospheres made of different gases, and some have no atmospheres at all. This means that life as we know it could not survive on these planets.
In fact, Earth is the only planet that we know has life on it. Scientists think this is because Earth has one very special feature – water. All things on Earth need water to survive, and so far we have not found any other planets with water on the surface.
Sometimes if you look up into the night sky, you can see other planets. They often look bigger and brighter than stars, and are sometimes a different colour. For example, Mars is red.
STARS AND SOLAR SYSTEMS
Stars are mostly made up of a gas called helium. This helium gets extremely hot, and burns, giving off light. The nearest star to Earth is the Sun.
Sometimes stars have planets orbiting around them. This is called a solar system. Earth is in a solar system with seven other planets.
A galaxy is a very large group of stars. Some galaxies contain billions of stars and solar systems. The galaxy that we are in is called the Milky Way, and it is shaped like a spiral.
So far, we have discovered 100 billion galaxies – almost 100 galaxies for every person in Africa! As we build better telescopes, we are likely to discover even more.
From planets very different to our own, to whole other galaxies, the night sky contains a lot of interesting things. Astronomers have learnt a lot by studying our universe.