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Astronomy 201: Cosmology

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. 21 st Century Astronomy: Stars and Galaxies by Hester et al. 3 rd Edition.

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Astronomy 201: Cosmology

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  1. 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

  2. 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

  3. “Stars and Galaxies” is a subset of “21st Century Astronomy” $45 or $71 $115

  4. 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

  5. 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

  6. 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?

  7. 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

  8. Our Cosmic Address STEWARD OBSERVATORY Ca. 1930

  9. Steward Observatory THE UNIVERSITY OF ARIZONA

  10. Steward Observatory The University of Arizona TUCSON

  11. Steward Observatory The University of Arizona Tucson ARIZONA

  12. Steward Observatory, The University of Arizona Tucson, Arizona UNITED STATES, NORTH AMERICA

  13. Steward Observatory, The University of Arizona Tucson, Arizona United States, North America EARTH

  14. EARTH • Planet • Diameter = 7900 miles • Mass = 6x1024 kilograms • Age = 4.5 billion years • = 4.5 x 109 years • = 4,500,000,000 years

  15. Earth has one moon, which orbits it The Moon Earth-Moon distance = 240,000 miles or 30 Earth Diameters

  16. 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)

  17. Solar system to scale: SUN

  18. THE SUN • Star, produces energy by nuclear fusion (Hydrogen  helium) • THE SUN • Star, produces energy by nuclear fusion (Hydrogen  helium) • 93 million miles from Earth • 93 million miles = 1 Astronomical Unit, or A.U. THE SUN Visible light image

  19. 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 More on units of distance: • More on units of distance: • Instead of miles, kilometers, etc. astronomers often • use light seconds, light minutes, light years • 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 THE MOON IS ABOUT 1.3 LIGHT SECONDS FROM EARTH

  20. Practical matters: Astronomers use scientificnotation to write large & small numbers. 1000 = 1,000,000,000 = 0.001 = 2,200,000 = 103 109 10-3 2.2 x 106

  21. 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) 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. 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.

  22. Orbit of Quaor (Q) and Pluto (P) versus the planets

  23. STARS NEAR THE SUN

  24. Nearest Star to Sun: Alpha Centauri • Triple star in S. hemisphere • 4.2 light years from the Sun • Nearest Star to Sun: Alpha Centauri • Triple star in S. hemisphere • Nearest Star to Sun: Alpha Centauri • Triple star in S. 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. • Nearest Star to Sun: Alpha Centauri • Triple star in S. 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.

  25. Space Travel

  26. 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

  27. Spiral Galaxy

  28. Our Milky Way, Plus many “dwarf” satellite galaxies

  29. The LOCAL GROUP

  30. The Andromeda Galaxy The other big spiral galaxy in the Local Group About 2.5 million Light years from The Milky Way

  31. The Local Group is on the edge of the VIRGO CLUSTER OF GALAXIES

  32. A photograph of the center of the VIRGO CLUSTER OF GALAXIES

  33. SUPER- CLUSTERS

  34. 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

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