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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

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
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

two other books
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
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
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?
slide7

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

slide8

Our Cosmic Address

STEWARD OBSERVATORY

Ca. 1930

slide9

Steward Observatory

THE UNIVERSITY OF ARIZONA

slide10

Steward Observatory

The University of Arizona

TUCSON

slide11

Steward Observatory

The University of Arizona

Tucson

ARIZONA

slide12

Steward Observatory, The University of Arizona

Tucson, Arizona

UNITED STATES, NORTH AMERICA

slide13

Steward Observatory, The University of Arizona

Tucson, Arizona

United States, North America

EARTH

slide14

EARTH

  • Planet
  • Diameter = 7900 miles
  • Mass = 6x1024 kilograms
  • Age = 4.5 billion years
  • = 4.5 x 109 years
  • = 4,500,000,000 years
slide15

Earth has one moon, which orbits it

The Moon

Earth-Moon distance

= 240,000 miles

or 30 Earth Diameters

slide16

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)

slide19

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

slide20

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

practical matters astronomers use scientific notation to write large small numbers
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

slide23

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.

slide31

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.
slide34

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

slide37

Our Milky Way,

Plus many “dwarf”

satellite galaxies

slide39

The Andromeda

Galaxy

The other big

spiral galaxy in

the Local Group

About 2.5 million

Light years from

The Milky Way

slide40

The Local Group is on the edge

of the VIRGO CLUSTER OF GALAXIES

slide42

SUPER-

CLUSTERS

slide45

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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