 Since the launch of the artificial satellites thousands of pictures or reviews of the planet The earth are taken from the space. So what is One of the minor part of the universe or we can say is like a sand particle of the even milky way Which is the name of our galaxy? So when we are talking about the universe Universe actually is all the matter and energy in the form of light and heat That exists anywhere in space and time is called the universe So this universe includes the planners the stars the galaxies and the component of the other intergalactic space So when we are talking about the universe Universe is actually expanding from an extremely dense and hot state and continues to expand today It is gathered into about 100 billion galaxies most galaxies contain Millions or billions of stars and large cloud of gas and dust From the earth we can see for a maximum of 13 to 15 billion light years in any direction So when we are talking about the light year a light year is the distance light travels in a year The universe is probably far larger than this visible matter in the universe is dominated by the simple elements as Hydrogen and helium but gravity reveals that Normal matter is heavily Outrage by invisible dark matter the nature of the dark matter is unknown the dark energy Which is a mysterious phenomena and helps keeps the universe expanding So the size of the universe is unknown It may be infinite with a radius of about 46 billion light years In 2010 astronomers estimated that observable universe contains 300 billion billion stars So we have a picture of the universe which is actually a Sposed we can suppose that this is actually a universe So most of the You galaxies and you can see that in different patches you can see here But this is actually the center of the universe The solar system is the part of the galaxy which is called the milky way The milky way is a part of the local group Which is actually part of another system which is called the super local cluster and super local cluster is part of the known universe So this actually a hierarchy of the system which is in the universe The diameter of our galaxy milky way is 100,000 light years local group has about 5 million light years And the known universe has 20 billion light years in diameter So these are actually the astronomical distances which when we are discussing the diameters or the radius of the celestial bodies So this actually is a picture of the milky way, which is our home galaxy Is a disk like in situation The most of the planets and stars are moving around the center of the known A milky way the center is actually is a hand dense mass which has a high density So that's where all the things are moving around the center of the milky way So a light year is the distance when a beam of light travels with a speed of 300,000 Kilometers per second and covered a distance of about 9.446 trillion kilometer in a year The light year is most Often used when expressing distances to stars and other distances on the galactic scale The unit usually used in professional astronomy