What is a Star? - Stars for Kids - Galaxies for Kids - Space Facts for Kids - What is a Galaxy?

Welcome to Learning More. Today I am going to take you on a journey, a journey across the galaxy. This is one of my very favourite subjects, space. Did you know that scientists think that there could be more than 170 billion galaxies in the universe? Some, called dwarf galaxies, are very small, with about 10 million stars, while others are huge, containing an estimated 100 trillion stars. This is totally mind-blowing, but for today we will stick with our galaxy. Our solar system is located within the Milky Way. Let's jump into my rocket and start our mission to the Milky Way. But let me start by explaining what a galaxy actually is. Simply put, galaxies are huge collections of matter, possibly dark matter, dust, gases and of course stars. These are all held together by gravity. There are many different types of galaxies and many different shapes and sizes of these galaxies. These are all weird and wonderful places, with most of them yet to be discovered. Hold on tight. 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, Blast off. Look at the window now and you will see some great examples of the different types of galaxies. Elliptical galaxies. It's shaped like an elliptical or stretched out circle. The stars in it orbit the centre in random directions. Among them are actually some of the oldest stars in existence. Spiral galaxies, like the Milky Way. The main feature of spiral galaxies is their spiral shape. At their centre is a very bright circle with lots of old stars. Yet their spiral arms are full of young and new stars. How awesome is that? Let's stop here for a moment and have a good look around. Welcome to our galaxy, the Milky Way. First we will look out for some stars. Now be careful, these will be very bright. Stars are giant spheres of super hot gas made up mostly of hydrogen and helium. Our sun is a star which is over 4.5 billion years old. Did you know that stars have a life cycle? First stars are born. Stars start out as giant clouds of dust called nebulae. Nebulae are basically clouds of dust and gases like helium and hydrogen. Gravity forces this dust together. As more and more dust comes together, gravity gets stronger and it starts to get hot. Once the centre gets hot enough, nuclear fusion will begin and a young star is born. This is called a protostar. Once the star is created, it will continue to burn energy and for billions of years. The star will remain this way until it runs out of hydrogen. Then another amusing thing happens. The star becomes a red giant. When the hydrogen runs out, the outside of the star expands and it becomes a red giant. Finally the star will collapse. Eventually the core of the star will start to make iron. This will cause the star to collapse. The average star will become a white dwarf star. Larger stars will create a huge nuclear explosion called a supernova. Let's pop outside the rocket and have a good look at these different types of stars. Can you spot some? The smallest stars are red and don't give off much of a glow. Medium sized stars are yellow like the sun. The largest stars are blue and are hugely bright. Our sun is actually a yellow dwarf. Some supergiant stars are as big as the entire solar system. However, this is crazy. The smaller the star, the longer it lives. Giant stars are bright but tend to burn out fast. If you look carefully, you will see the nearest star to Earth. After the sun, of course, it's called Proxima Centauri. It is 4.2 light years away, meaning you will have to travel at the speed of light for 4.2 years to get there. Now that will be a long journey. Well, I think it is time to get back down to Earth. Back to the rocket! If you look out the window, you will see lots of stars. However, there are between 200 to 400 billion stars in our Milky Way galaxy alone, so we might not get to see all of them today. In fact, each galaxy contains hundreds of billions of stars and there is estimated to be over 100 billion galaxies. The total number of stars in the universe is mind-boggling. Estimated to be at least 70 sextillion and possibly as high as 300 sextillion, that's three-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero, zero-zero-zero! That leaves Mayseen stars. Get it? Hold on tight! We are about to enter the Earth's atmosphere. I am going to be busy landing, so here is something to think about. Stars range in colour, depending on how hot they are. In order from lowest to highest temperature, they can be brown, red, orange, yellow, white or blue in colour. Ah, back to Earth! I will leave you with my favourite, craziest, mind-blowing star fact. The light from the stars takes millions of years to reach Earth. Therefore, when you look at the stars, you are literally looking back in time. I hope you enjoyed our journey through space. What exciting facts did you learn? Let's recap on all the facts you've learned about galaxies and stars. Our solar system is located in the Milky Way galaxy. Elliptical galaxies are shaped like an elliptical or a stretched out circle. The main feature of spiral galaxies like the Milky Way is their spiral shape. Stars are actually giant spheres of super hot gases like hydrogen and helium. Stars have a life cycle. First, they are born. This is called a protostar. Once created, the star continues to burn energy and glow brightly for billions of years. When all the hydrogen runs out, the star will start to expand on the outside and become a red giant. Finally, the star will collapse and become a white dwarf star. Here are some key words that are really going to help you think about the stars and galaxies. Star, Galaxy, Spiral, Elliptical, Protostar, Supernova. I really hope you enjoyed learning all about the stars and galaxies today. I hope you enjoyed learning with us today. We will see you soon.