The milky way is one of about 100 billion galaxies in

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Unformatted text preview: observable Universe? The Milky Way is one of about 100 billion galaxies in the observable Universe ‣ 1011 stars per galaxy x 1011 galaxies = 1022 stars! That’s 10,000,000,000,000,000,000,000 STARS! ‣ Joshua Davis As many stars as grains of sand on all Earth’s beaches… 22 So, how many stars are there in the observable Universe? The Milky Way is one of about 100 billion galaxies in the observable Universe. It contains about 100 billion stars. 100 billion stars per galaxy times 100 billion galaxies = 10 sextillion stars! (That’s a 1 followed by 22 zeroes!) There are about as many stars in the Universe as there are grains of sand on all of Earth’s beaches combined. Remember last summer.. you went to the beach...That grain of sand that got into your bathing-suit.. and was so very, very uncomfortable? That grain of sand represents a single star in the Universe. How do our lifeNmes compare to the age of the Universe? 23 It is not only distances and numbers of stars and galaxies that can be “astronomical”, but also time. The Universe began 13.7 billion years ago with an event called the Big Bang, a time when all the matter & energy of the visible universe was contained in a volume smaller than an atom. From this incredibly dense, energetic state, the Universe began to expand. The first stars formed 400 million years after the Big Bang. The first galaxies formed 1 billion years after the Big Bang. Our solar system formed about 4.6 billion years ago (9 billion years after the Big Bang). But billions of years are an unimaginably long time compared to our lifetimes. So lets create a scale model of time. Scale the history of the Universe into one year 24 We will scale the 13.7 billion year history of the Universe to a length of time we can understand one year. On this scale, 1 month is about 1.2 billion real years, 1 day is roughly 40 millio...
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This note was uploaded on 10/23/2013 for the course ASTR 100 taught by Professor Dunne during the Fall '12 term at University of Illinois, Urbana Champaign.

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