Where are we in the universe? Planet? Star-orbiting system? Galaxy? Cluster Group? Supercluster?...

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

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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.)

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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.)

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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

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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