the birth of a star You may think that the only time you can see stars is at night but you’d be wrong our Sun is actually a star and you see it every day The Sun is quite an ordinary star and has kept a stable temperature and brightness since there has been life on Earth All the other stars are much further away than our Sun which is why they look so small in the night sky but they all have their own extraordinary stories to tell So how did they begin The stars formed out of clouds of hydrogen gas which were left over either from the Big Bang or from earlier exploded stars Over time gravity pulled this gas together into clumps where it started to spin and heat up This continued until the gas was dense and hot enough to combine and then in a flash of light a new star was born That is just incredible WOAH 6
types of stars Giant stars are very large which means they are extremely hot and bright Sadly this incredible power causes them to burn their fuel very quickly so they have a shorter lifespan than our Sun RED DWARF STAR Red dwarf stars are smaller than our Sun but live for an incredibly long time They are so small that they have a relatively slow and stable nuclear reaction at their cores that will last for hundreds of billions of years Brown dwarf stars are the smallest stars in the Universe They are not big enough to fuse hydrogen together but can be big enough to create other elements Brown dwarfs are very small and don’t give off much light so they are very difficult to discover GIANT STAR BROWN DWARF STAR MAIN SEQUENCE STAR Our Sun is known as a main sequence star and there are many others like it Main sequence stars make up 90 of the stars we can see and are the most likely to have planets that support life They are so beautiful Amazing 7
galaxies All of the stars we see from Earth are part of a big group of stars called a galaxy Galaxies are made up of vast swarms of stars swirling around like a giant space whirlpool Our galaxy is called the Milky Way and looks a bit like a Catherine wheel firework It contains more stars than anyone could count in a lifetime and is constantly spinning very very slowly so slowly in fact that it takes 225 million years to complete a full cycle You can see the Milky Way in the night sky with your own eyes if you go far into the countryside away from the city lights It forms a milky band of light stretching across the sky and is quite a beautiful thing to see 8 We are here
Outside the Milky Way are lots of other galaxies all made of countless numbers of stars These galaxies come in all shapes and sizes some swirling around like our own and others are big disordered balls of stars that look like giant swarms of bees You can see a couple of galaxies with your eyes but most of them are so far away that you need a big telescope to spot them There are galaxies stretching away into the depths of space as far as our most powerful telescopes can see and there are certainly even more beyond that The closest spiral galaxy to the Milky Way is the Andromeda galaxy around 2 5 million light years away It is so far away that the light we see from it has been travelling through space for 2 5 million years This means that we see the Andromeda galaxy as it was in the ancient past before humans even existed on Earth The further you look into space the further you are looking into the past so the furthest galaxy we have discovered is very very old It is called UDFj-39546284 and because it is at the very edge of the visible Universe we see it as it was not long after the Big Bang THE SPEED OF LIGHT Because things in space are so far away we don’t measure distances in miles or kilometres but in light years One light year is the distance that light travels in one Earth year Light is the fastest thing in the Universe and it can cover mind-boggling distances in a short space of time it is so fast that it could travel all the way around the Earth 7½ times in a second 9
