Astronomy 14 CSU: Exploring the Universe

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Astronomy 14 (CSU)Exploring the Universe

• Dr. David Sowards-Emmerd
• And Todd Rigg

Credit NASA APOD
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Syllabus

• Short class (6 weeks)
• Lots of info in a short time
• July 4th Holiday?
• Website

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Read Ahead
Theres a reason the syllabus lists what chapter
well talk about read it before you get to
class! If you get behind in this class, it may
be very difficult to get caught up. Much of the
later chapters will build on things learned in
the earlier chapters
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Ancient Astronomy
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Observatories
Canada-France-Hawaii Telescope (Credit
Wainscoat)
The Very Large Array Image courtesy of NRAO/AUI
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Physics Gravity and Light
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Our Solar System
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Stars
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Nebulae,and Supernovae
M78 Nebula Credit SDSS Collaboration
Credit X-ray NASA/CXC/Rutgers/J.Hughes et al
Optical Rutgers Fabry-Perot
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Compact Objects
Crab Pulsar/Nebula (X-ray) Credit
NASA/CXC/ASU/J. Hester et al.
Credit http//www.mpe.mpg.de/ir/GC/index.php
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Galaxies
Credit SDSS Collaboration
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Groups, Clusters, and Larger Structures
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Active Galaxies
Images courtesy of NRAO/AUI
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Cosmology and the Fate of the Universe
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Why is Astronomy/Astrophysics Interesting

• Curiosity about our origins and fate
• Its night half of the time
• Great laboratory for experiments we cant
• hope to perform on earth (energy, density, and
  
• length scales)
• Curiosity about what else is out there.
• Natural beauty.
• Everyday uses
• Theres money in it

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The Power of Science

• Hypotheses, trial and error, theories, laws etc
• Describing something is only part of the goal,
• repeatability and the ability to predict new
  phenomena
• Physics and its applications (chemistry,
  engineering)
• Huge leaps in technology in the past century
• Should be objective and unbiased (maybe not so
  much once money is involved)

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Connections with Us
The current theories/models/observations lead us
to believe that after the Big Bang, the only
elements present were H (almost all), He, and Li
(scarce). Where does the carbon, oxygen,
molecules, etc., come from? How did all the
heavier elements form?
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Some Definitions
Solar System Galaxy Cluster/group of Galaxies
Universe Density Rotation Revolution
Star Planet Moon/Satellite Asteroid
Comet Is Pluto a planet?
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Astronomers Convention
Galaxy ? The Milky Way (our galaxy) galaxy ? a
galaxy
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Distances
Solar System Scales Astronomical Unit (AU)
average distance between the sun, 150 million
(1.5 x 108) km. Galactic/Extragalactic
Scales Light Year distance light travels in a
year (in vacuum), 9.46 trillion (9.46 x 1012)
km. Parsec (pc) - 3.26 light-years, related to
parallax. Most extragalactic astronomy use kpc
and Mpc for distances. Well be working in
SI/MKS units for most of this class.
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Sizes in the Solar System
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The Distance Ladder
(Lots of empty space)
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Powers of Ten
1 m LCD TV 10 m Bus 100 m Soccer field 1
km Skyscraper (2 on top of each other) 100 km My
commute 1,000 km Length of CA 10,000 km
Radius of Earth 100,000 km 1,000,000 km
Radius of Sun 10,000,000 km 100,000,000 km
AU 1,000,000,000 km 10,000,000,000 km Solar
System 100,000,000,000 km 1,000,000,000,000
km 1013 km Light Year
?
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Making Sense of Large Numbers

• People generally cant grasp the concept of large
  
• Numbers. So we make up ways to deal with them
• Comparison
• Subdivision
• Ignore any contact with reality and count the
  digits.

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Examples How Far Do We Walk?
Low estimate ? 3 miles per day walking 365 days
per year Long lifespan ? 100 years ?3 miles/day
x ()365 days/year x 100 years ?100,000 miles
?160,000 km (almost half way to moon!)
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How Far Does a Business Traveler Fly?

• London to SFO ? 8,700 km
• Double this (account for return trip) ? 17,000
  km
• Every week ? 52 times per year
• Years of service ? 30 years
• 30 x 52 x 17,000 km
• 26.5 million km
• gt1/6 of the way to the sun

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Typical Sizes of Astronomical Objects
How big is a comet? 10 km Asteroid? varies Moon
(ours) 1,700 km (1/100,000 of an
AU) Planet? 6,400 km Star (non-compact)? 700,000
km (1/200 of an AU) Solar system? 50 AU
(1/4,000 of a pc) Galaxy? tens of kpc Cluster
of Galaxies? several Mpc Observable
Universe? Depends on how old the universe
is Kilo (k) ? x 1,000, Mega (M) ? x
1,000,000 Giga (g) ? x 109
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Size/Length Scales
How far to the nearest star? How far across the
Galaxy? How far to our nearest neighboring
galaxy? How big is the universe?
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Were Always Seeing the Past

• Light travels as a finite speed, so the further
  away an object is, the longer it takes the light
  to reach us.
• ? Due to this delay, we see the object as it
  appeared when the signal left it.
• This is true in everyday life the delay is
  just
• too short to notice (important for electronics
  though).

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Timescales in Astronomy
Age of the Universe ? 14 billion yrs Age of the
Earth/Solar System ?4.6 billion yrs Compare
with tens of thousands to millions of years
timescale of life on Earth. Millisecond
timescales in pulsars
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Calendar of the Universe
See image in your textbook.
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Calendar of the Universe
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Where Did the Heavier Elements Originate?
Only H, He, and Li were produced in the big
bang. How was everything else formed?
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Stellar Evolution
Stars account for the reprocessing of hydrogen
and helium into the metals we see
today. Gravitational collapse/pressure ?
fusion Supernovae ? heavier elements (beyond
iron) Fraction converted is small (not very
efficient)
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Why Do the Stars Move?
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Motion About the Sun
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Motion in the Solar System
Click Here
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Relative Motions
How fast are we moving? Depends on your frame of
reference With respect to Speed Center of
Earth 1,500 km/hr Sun 100,000
km/hr Galactic center 800,000 km/hr Local
Group 300,000 km/hr Other distant
objects depends So, why does the sky appear
static?
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The Universe is Expanding
The underlying fabric of the entire universe is
expanding that is all points are moving away
from each other (unless theyre gravitationally
bound). Baking a blueberry/currant
cake/muffin/scone is the usual example.
Resizing a photo is the same thing (in 2-d)
its just a re-scaling of the universe. And
recently (1990s) evidence has been presented
that suggests its expanding faster and faster.