The Sizes and Distances of Objects in Space PDF

The Sizes and Distances of Objects in Space The Universe 1 The most distant objects in the Universe are 47 billion light years away, making the size of the observable Universe 94 billion light years across. How can the observable universe be larger...

The Sizes and Distances of Objects in Space The Universe 1 The most distant objects in the Universe are 47 billion light years away, making the size of the observable Universe 94 billion light years across. How can the observable universe be larger than the time it takes light to travel over the age of the Universe? This is because the universe has been expanding during this time. This causes very distant objects to be further away from us than their light travel time. 2 The Hubble Key Project, conducted by the Hubble Space Telescope from 1991 to 2000 verified the age of the Universe. Results from the WMAP satellite further confirmed and refined the age of the Universe to be 13.7 billion years. Galaxy Basics 1 Galaxies consist of stars, planets, and vast clouds of gas and dust, all bound together by gravity. The largest contain trillions of stars and can be more than a million light-years across. The smallest can contain a few thousand stars and span just a few hundred light-years. Most large galaxies have supermassive black holes at their centers, some with billions of times the Sun’s mass. 2 Galaxies come in a variety of shapes, mostly spirals and ellipticals, as well as those with less orderly appearances, usually dubbed irregular. 3 Most galaxies are between 10 billion and 13.6 billion years old. Some are almost as old as the universe itself, which formed around 13.8 billion years ago. Astronomers think the youngest known galaxy formed approximately 500 million years ago. 4 Galaxies can organize into groups of about 100 or fewer members held together by their mutual gravity. Larger structures, called clusters, may contain thousands of galaxies. Groups and clusters can be arranged in superclusters, which are not gravitationally bound. Superclusters, empty voids, “walls” of galaxies, and other large-scale structures make up the cosmic web of matter in the universe. Our Milky Way Structure and Composition 1 The galaxy we live in, called the Milky Way Galaxy, is a barred spiral galaxy composed of at least 100 billion stars. It is approximately 100,000 light years across and about 1000 light years thick. It has a central bulge that is about 10,000 light years in diameter. 2 Our solar system is about a third of the way towards the edge of the Galaxy from the central bulge. If the Solar System were inside the bulge, at night we would be able to see a million stars as bright as Sirius (the brightest star in our night sky). The night sky would be so This illustration shows the Milky Way, bright, that it would not seem much different than day. The Sun and our home galaxy. NASA/JPL-Caltech Solar System are within the 1,000 light year thick disk, and we are only about 95 light years from the central plane.  Nebula 1 Nebulae are interstellar clouds of gas and dust. Many nebulae are formed from the remnants of dying stars. Nebulae are often also regions where new stars are born. 2 Nowadays, the term ‘nebula’ refers to an interstellar cloud of dust and gas. Nebulae are often formed from the remnants of dying stars: from planetary nebulae or the dispersed debris from supernova explosions. They are also often regions of intense star formation, as the rich reservoirs of dust and gas provide the necessary raw material from which new stars are born. Nebulae are often mind-bogglingly big, spanning several light years in size. Solar System 1 While some astronomers are content to claim that the size of the solar system is around 122 AU, others point out that the solar system should really be defined by the reach of its gravity. In other words, if an object can be said to orbit the Sun, then it should be considered part of the solar system. 2 Using this expanded definition, astronomers point to the theoretical Oort Cloud as the approximate boundary of the solar system. A cloud of icy objects that could be the source of comets that The layout of the solar system, including the Oort Cloud, on a enter the inner solar system from time to logarithmic scale. Credit: NASA time, the Oort Cloud sits more than 100,000 AU away from the Sun. 3 Using the Oort Cloud as an approximate boundary would mean that the size of our solar system approaches nearly 2 light years! That's equivalent to almost 12 trillion miles. Try to wrap your mind around that. And once you have wrapped your mind around that, remember that's just the size of our tiny solar system, which is just a speck in terms of the whole universe!  Sources Galaxy Basics https://science.nasa.gov/universe/galaxies/ The Milky Way Galaxy https://lco.global/spacebook/galaxies/the-milky-way-galaxy/ Nebula https://esahubble.org/wordbank/nebula/#:~:text=Nebulae%20are%20often%20mind%2Dbogglingly,we %20now%20know%20as%20galaxies. How Big Is the Solar System? https://wonderopolis.org/wonder/how-big-is-the-solar-system How Big is The Solar System? https://www.universetoday.com/104486/how-big-is-our-solar-system/#google_vignette