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Where are we in the universe?Where are we in the universe?
Planet?
Star-orbiting system?
Galaxy?
Cluster Group?
Supercluster?
Universe?
Our Cosmic AddressOur Cosmic Address
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USA
Our Cosmic AddressOur Cosmic Address
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USAEarth
Our Cosmic AddressOur Cosmic Address
SPaydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USAEarth Solar System
Our Cosmic AddressOur Cosmic Address
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USAEarth Solar SystemMilky Way Galaxy
Our Cosmic AddressOur Cosmic Address
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USAEarth Solar SystemMilky Way GalaxyLocal Group
Our Cosmic AddressOur Cosmic Address
Paydirt PeteUTEP500 W. University Ave.El Paso, TX 79968USAEarth Solar SystemMilky Way GalaxyLocal GroupLocal Supercluster
Our Cosmic AddressOur Cosmic Address
How do we know? How do we know? Who is responsible?Who is responsible?
Early AstronomersEarly Astronomers
• 500 BC Pythagoras - thought Earth was round from moon observations
• 350 BC Aristotle - Earth at center of “universe”, planets/stars moved around Earth
• 250 BC Aristarchus - measured (relative) distance to Sun & moon using
angles; Sun very BIG; at center of “universe”
• 200 BC Eratosthenes - measured size of the Earth using angles of sun at noon at 2 places
500 250 0 250 1500 1600 1700 1800 1900 AD
PythagorasAristotle
Aristarchus Eratosthenes
Ptoo bad for PtolemeyPtoo bad for Ptolemey
Claudius Ptolemey (100 - 170 A.D.)
PythagorasAristotle
Aristarchus Eratosthenes Ptolemy
Ptolemy geocentric diagram(Earth at center)
• claimed that all planets & stars orbited the Earth (wrong!)
• Earth-Centered model = Geocentric Model
• ideas last 1300 years!
500 250 0 250 1500 1600 1700 1800 1900
Nicholas Copernicus (1473-1543)
Crazy (but not really) CopernicusCrazy (but not really) Copernicus
AD
PythagorasAristotle
Aristarchus Eratosthenes Ptolemy Copernicus
Copernicus heliocentric diagram(sun at center)
• proposed Earth NOT AT CENTER, but SUN IS!
• Sun-Centered model = Heliocentric Model
500 250 0 250 1500 1600 1700 1800 1900
Galileo the GreatGalileo the Great
Galileo Galilei (1564 - 1642 A.D.)
AD
PythagorasAristotle
Aristarchus Eratosthenes Ptolemy Copernicus Galileo
• The Great Observer!
• 1st to observe moons orbiting Jupiter (Galilean
satellites) - proved geocentric model wrong
Galileo’s moon phases
• Venus phases
500 250 0 250 1500 1600 1700 1800 1900
Keeping up with KeplerKeeping up with Kepler
Johannes Kepler (1571 - 1630 A.D.)
AD
PythagorasAristotle
Aristarchus Eratosthenes Ptolemy Copernicus Galileo
Kepler
Kepler’s Laws (3)
• Used catalogs of planets’ positions to form equations that described all planetary motion
500 250 0 250 1500 1600 1700 1800 1900
Kepler’s Law # 1Kepler’s Law # 1
Planets orbit the Sun in ellipses with Sun at one focus
focus
xx
circle ellipse
x xx
Kepler’s Law # 2Kepler’s Law # 2
A line joining a planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse
C Dclose to sun
A Bfar from sun
time to go from C D = time to go from A B
travels slowesttravels fastest
Kepler’s Law #2 Kepler’s Law #2
equal area, equal times
fastspeed
slowspee
d
P2 ~ a3
Kepler’s Law # 3Kepler’s Law # 3
orbital period orbital radius
€
≈
P = orbital period (years), time to complete 1 orbita = orbital radius (AU, astronmomical unit)
*note: 1 AU is distance from Earth to Sun, 1.5x108 km
like lanes on a race track
• Percival Lowell (1855 - 1916 A.D.) - observed canals on Mars
Modern AstronomersModern Astronomers
AD
PythagorasAristotle
Aristarchus Eratosthenes Ptolemy Copernicus Galileo
Kepler
• Carl Sagan (1934 - 1996 A.D.) - discovered hot, dense atmosphere on Venus - lead many searches for extra-terrestrial life
• Eugene & Carolyn Shoemaker - Eugene: linked Earth and moon craters to asteroid impacts - Carolyn: discovered more comets (32) than any other person
Lowell SaganShoemakers
500 250 0 250 1500 1600 1700 1800 1900
We use electromagnetic waves (or light) (or radiation)
How do we know? How do we know? Who is responsible?Who is responsible?
What is a wave?What is a wave?
Ocean waves Sound waves Seismic waves
Waves are traveling energy
a wave
Light (electromagnetic) wavesLight (electromagnetic) waves
medium waves = visible
BIG wavelengths
small wavelengths
Light (electromagnetic) wavesLight (electromagnetic) waves
infrared image
visible imagex-ray image
Tools of AstronomyTools of Astronomy(telescopes)(telescopes)
• Objective - telescopes collect light (all kinds)
• Types - optical telescopes (for visible waves) - radio telescopes (for radio waves) - plus many others (x-ray, gamma, etc.)
• Determining factor: the bigger aperture (size), the better
Optical TelescopesOptical TelescopesTwo types: Reflecting & Refracting
• Reflecting: uses a curved mirror to reflect & focus light
(more common)
light in
eyepiece
mirror
• Refracting: uses a lense (like eye-glasses) to focus light
eyepiece
light in
lense
Main functions of optical telescopes?Main functions of optical telescopes?
• Sharpen images (resolving power)
Make things look larger?
• Make objects look brighter (light-gathering power)
yes, but….
Radio TelescopesRadio Telescopes
• Radio waves collected in large dish and reflected to center antenna
light in
What do radio telescopes do?What do radio telescopes do?
• Detect radio waves emitted by space objects
• Allow us to “see” different properties of space that are invisible to us - temperature, magnetic field, composition
The Moon
visible radio
Galaxy M81
visible radio
Where should they go?Where should they go?
Problem: Earth’s atmosphere blurs objects in the sky
• how about a mountain top? in space?
Ideal locations:• Places away from city lights & pollution• Places high in elevation
US light pollution Mauna Kea, Hawaii
• Hubble Space Telescope
Telescopes and ObservatoriesTelescopes and Observatories(you should visit)(you should visit)
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Clark: Lowell Obs., AZ
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Clark: Lowell Obs., AZ
• Shane: Lick Obs., CA
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Clark: Lowell Obs., AZ
• Shane: Lick Obs., CA
• Kitt Peak Obs., AZ
• Hubble Space Telescope
• Keck: Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Clark: Lowell Obs., AZ
• Shane: Lick Obs., CA
• Kitt Peak Obs., AZ
• Aricebo, Puerto Rico
• Hubble Space Telescope
• Keck (et al.): Mauna Kea, Hi
• Hale: Palomar Obs., CA
• Clark: Lowell Obs., AZ
• Shane: Lick Obs., CA
• Kitt Peak Obs., AZ
• Aricebo, Puerto Rico
• Very Large Array (VLA), NM