Astronomy 201 Cosmology Prof Jill Bechtold Graduate TA Ken Wong Pick up hard copy of syllabus Pick up HW 1 http boojum as arizona edu jill astro201 html The Textbooks 21st Century Astronomy Stars and Galaxies by Hester et al 3rd Edition Unbound version available at UA bookstore for low cost 45 50 However this version is not refundable or re sellable The bound edition is available through Amazon com for 71 An ebook version is also available Stars and Galaxies is a subset of 21st Century Astronomy 45 or 71 115 Two other books Dancing With the Universe From Creation Myths to the Big Bang by Marcelo Gleiser paperback 23 new 5 10 used From Eternity to Here The Quest for the Ultimate Theory of Time by Sean Carroll paperback will come out in October Bookstore 17 Amazon 11 Do I need to buy the books Class notes will be posted Exams will be on lecture material If you like to also read the material in a textbook get the Hester et al book If you like to read prose the other books are readable and enjoyable especially if you like history culture and philosophy What Is Modern Astronomy Science of the nature of everything outside of the Earth s atmosphere planets stars interstellar gas galaxies etc What is the content of the Universe What is its history What is its future How do humans fit in The science that studies the history future of the Universe is called cosmology kosmos order harmony logos word law My goal is simple It is complete understanding of the universe why it is as it is and why it exists at all Stephen Hawking Our Cosmic Address STEWARD OBSERVATORY Ca 1930 Steward Observatory THE UNIVERSITY OF ARIZONA Steward Observatory The University of Arizona TUCSON Steward Observatory The University of Arizona Tucson ARIZONA Steward Observatory The University of Arizona Tucson Arizona UNITED STATES NORTH AMERICA Steward Observatory The University of Arizona Tucson Arizona United States North America EARTH EARTH Planet Diameter 7900 miles Mass 6x1024 kilograms Age 4 5 billion years 4 5 x 109 years 4 500 000 000 years Earth has one moon which orbits it The Moon Earth Moon distance 240 000 miles or 30 Earth Diameters Steward Observatory The University of Arizona Tucson Arizona United States North America Earth SOLAR SYSTEM Not to scale SUN Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Solar system to scale SUN THE SUN Star produces energy by nuclear fusion Hydrogen helium 93 million miles from Earth 93 million miles 1 Astronomical Unit or A U Visible light image More on units of distance Instead of miles kilometers etc astronomers often use light seconds light minutes light years 1 Light Year the distance light travels in one year 1 Light Year 5 9 x 1012 miles THE MOON IS ABOUT 1 3 LIGHT SECONDS FROM EARTH THE SUN IS ABOUT 8 3 LIGHT MINUTES FROM EARTH Practical matters Astronomers use scientific notation to write large small numbers 3 10 1000 1 000 000 000 109 3 10 0 001 2 200 000 2 2 x 106 1 light minute the distance light travels in one minute 1 light year the distance light travels in one year almost 10 trillion kilometers or 6 trillion miles one trillion 1012 1 000 000 000 000 Because light takes time to travel through space when we look farther away in distance we look farther back in TIME The farthest we can see in space is 13 7 billion light years because we think the Universe is 13 7 billion years old Orbit of Quaor Q and Pluto P versus the planets STARS NEAR THE SUN Nearest Nearest Star Star to to Sun Sun Alpha Alpha Centauri Centauri Triple Triple star star in in S S hemisphere hemisphere 4 2 light years from the Sun Alpha Centauri A and Alpha Centauri B are orbiting each other with period 80 years separation 23 Astronomical Units Proxima Centauri is 13 000 AU from Alpha Centauri A and B Space Travel Speed Time to get Time to get to Mars To Jupiter Time to get to Saturn Time to get to Alpha Centauri Freeway speed 75 mph 80 years 600 years 1200 years 38 million years Jetliner speed 500 mph 12 years 90 years 180 years 6 million years Concorde Speed Mach 2 1350 mph 4 4 years 33 years 66 years 2 million years 2 months 1 5 years 3 years 70 000 years Spacecraft Speed 40 000 mph Back to our COSMIC ADDRESS Steward Observatory The University of Arizona Tucson Arizona United States North America Earth Solar System Milky Way Galaxy The Sun is one star of many in the Milky Way The Milky Way as seen from Earth Spiral Galaxy Our Milky Way Plus many dwarf satellite galaxies The LOCAL GROUP The Andromeda Galaxy The other big spiral galaxy in the Local Group About 2 5 million Light years from The Milky Way The Local Group is on the edge of the VIRGO CLUSTER OF GALAXIES A photograph of the center of the VIRGO CLUSTER OF GALAXIES SUPERCLUSTERS OUR COSMIC ADDRESS Steward Observatory The University of Arizona Tucson Arizona United States North America Earth Solar System Milky Way Galaxy Local Group of Galaxies Virgo Cluster of Galaxies Local Supercluster of Galaxies The UNIVERSE