Hello everyone and welcome to our universe. Today we'll be answering the question, how big is the Milky Way? So we probably know by now that we live in a galaxy called the Milky Way. But the thing is, we always say that galaxies are big, but relative to what? Usually if we talk about something big on this planet, we talk about something like cars or planes or mountains or mobile phones that can't quite fit in your hand because the screen's too big. Nevertheless, people don't quite understand how big our home galaxy really is. So let's first of all start off with the location of our planet. So the planet earth and the solar system and the sun etc, everything like that is not located within the centre. In fact, it resides in somewhat of a suburban area, around about two thirds of the way out. If you want to know that in miles, it is 165 quadrillion miles from the black hole at the Milky Way centre. So our galaxy is around about 100,000 light-years across. And the thickness of the galaxy ranges on depending how close you are to the centre. This can be tens of thousands of light-years across. Our galaxy is also part of a larger collection called the local group. Some of these galaxies in the local group tend to look quite familiar to our very own galaxy. Our biggest closest neighbour is called the Andromeda Galaxy. This is quite a similar galaxy because it has a spiral shape. It is though rather large compared to our Milky Way, at around about 250,000 light-years across. This makes the Milky Way the second largest member in the local group. The bronze medal for this goes to the Triangulum Galaxy, or Messier 33. There are about 30 members of the local group. And Andromeda seems to be the brightest in the night sky. This is basically because of its size and because it is actually relatively close, at 2.5 million light-years. From the Earth's point of view to the Milky Way, we're actually inside of the galaxy. So therefore, when we do see the Milky Way in the night sky, we are basically seeing the Milky Way's arms. These arms consist of lighter areas and darker areas that obscures any light from stars, galaxies or any other bright object behind it. From the outside, the Milky Way would look completely different. It would be a bar-spiral galaxy. This basically means that it has a spiral shape with a bar running through the center. If you are looking for the center of the Milky Way, it is mainly located in the constellation of Sagittarius. This constellation also contains a massive radio source known as Sagittarius A star. Astronomers using very powerful telescopes have discovered that this is a supermassive black hole, but compared to black holes around the universe, this is a rather quiet black hole. The Milky Way also has objects called globular clusters. These are basically clusters of stars and usually reside within the halo of the central bulge of the galaxy. These can also show you the overall age of the galaxy, because these clusters themselves are nearly as old as the universe itself. Estimations show that the Milky Way's inner halo of stars are about 11.5 billion years old, and by looking at different points of the galaxy, scientists are beginning to think the different parts of the galaxy formed at different times. This could probably mean that our galaxy was probably formed from smaller galaxies merging together. They also used white dwarf stars, the burnt out remnants of sun-like stars, to make this measurement. But the main thing about the Milky Way is not what we can see, it's what we can't see. The Milky Way might be 100,000 light tears across, and might be a relatively large spiral galaxy, but estimations show that the galaxy is made up from something else. This is known as dark matter. Dark matter can only be seen indirectly. Dark matter seems to be very elusive, but we definitely know it's there because we can detect it for its gravitational effects. This means that NASA estimates that our galaxy is about 10 times the mass of what we can actually see. Dark matter makes most of the mass in our galaxy, and therefore makes it a lot larger than we can actually see with our own eyes. So I hope that's giving you a great insight into how big is the Milky Way, or how big is the Milky Way open brackets with dark matter closed brackets. It definitely is a very mysterious thing. If you want to know any more about our Milky Way, about its size, about the studies that are going on with globular clusters and white dwarfs, and also anything about dark matter, I'll put some links in the description below. And as always, if you've enjoyed the video, click the like button, and if you want to support the channel, click subscribe. Thank you for watching.