Astronomy

What is Astronomy?

Astronomy is the study of anything we see in the sky, and beyond

Overlaps with physics, chemistry, geology, and other sciences

The Scientific Method in Astronomy

Astronomy is one of the most difficult sciences to do, because we can’t do very many things in a lab

We have to combine our observations with our understanding of other sciences to make good predictions

Sometimes, our “lab” is a computer

AstrologyAstrology - the belief that the stars and planets

affect your life Despite the –ology, it’s not a science!

Gravity of other planets is not as strong as the gravity of your obstetrician!

Does not use the scientific method

It’s complete poppycock

Observing the Universe

Astronomy began with people observing their surroundings What did the sky look like when herds

moved? When a season changed? When was it good to plant? Planets, sun, moon, and stars all seemed

to move independently

What have you Observed?

An incomplete list: Moon Planets (Venus, Mercury, Mars, Jupiter, Saturn) Stars Meteors (shooting stars) Aurora Comets

What’s Out There, Anyway?

Atmospheric phenomenaSolar System

Sun and planets; comets, asteroids, etc.Milky Way

Our galaxyExtra-galactic

Other galaxies Some objects like our galaxy Some completely different phenomena Things between galaxies

Atmospheric phenomena

AurorasMeteor Showers

Solar System Objects and Phenomena

The SunEclipsesPlanets & MoonsAsteroidsComets

Galactic Objects and Phenomena

Stars & star clusters Nebulas Supernova Remnants Dead Stars

White Dwarfs Neutron Stars Black Holes

Dark Matter

Extra-Galactic Objects and Phenomena

Other GalaxiesGalaxy ClustersSuper ClustersDark MatterDark Energy

Neighborhood Tour - Our Solar System

The Solar System

• Condensed from Solar nebula about five billion years ago

• Contains Sun, planets, asteroids, comets, and dust

Terrestrial verses Jovian Planets

Terrestrial Planets Include: Mercury, Venus, Earth and Mars

Jovian Planets Include: Jupiter, Saturn, Uranus & Neptune

Also Interesting: Jovian moons Not sure what to do with them:

Pluto/Charon Xena

Sol (our sun)

SOHO/Extreme Ultraviolet Imaging Telescope (EIT) consortium

The Solar System

Terrestrial Planets

Small and rocky, composed of Oxygen, Silicon, Aluminum, Calcium, Iron, and Magnesium

1. Mercury2. Venus3. Earth4. Mars

MercuryMercury has

a lunar-like geology.

Caloris Basin

MercuryMercury is

almost tidally locked, like the Moon.

Venus

Venus’ surface has only been revealed in the past 10 years.

Venus

The surface of Venus is like the surface of hell.

Venus

Venus has a young, basaltic surface.

You Probably Know This One

Mars

Mars has the most Earth-like geology.

Mars

Mars has a thin atmosphere of CO2.

Mars

Familiar geologic features/processes

Mars

Familiar geologic features/processes

Mars

Mars’ geologic history was once warmer and wetter than now.

The Real Face of Mars

Mars from Pathfinder

Sojourner

Olympus Mons

Mars’ Polar Caps

Martian Meteorite

Martian Fossils ?

Deimos and Phobos

Jovian Planets

Large, gaseous, composed mainly of hydrogen and helium

1. Jupiter2. Saturn3. Uranus4. Neptune

Jupiter

Jupiter’s geologic features are all atmospheric.

Moons of JupiterIo is the most active

body in the Solar System.

Moons of Jupiter“All these worlds are

yours except Europa…”

Moons of JupiterGanymede and

Callisto are two of the larger bodies in the Solar System.

SaturnSaturn is the

furthest out of the historical planets.

Saturn’s moons

First ever color picture of Titan’s surface

Water and hydrocarbon ice

January 14, 2005

ESA/NASA/Univ. of Arizona

Uranus & moonsUranus orbits the

Sun on its side.

Neptune & moons

Pluto & Charon

Units for MeasuringAstronomical Distances

Astronomical Units (AU) Defined as the distance from the Sun to the Earth About 1.496x1011 m (about 150 million km)

Light-years Defined as the distance light travels in one year About 9.46x1015 m

Parsecs Derived from the way stars appear to shift slightly

in the sky as the Earth orbits the Sun Equal to about 3.26 light-years

How Big Is It?

Our Earth 12,756 km across

Earth to the Moon 384,400 km

Earth to the Sun 150 million km = 1 AU = 500 light-seconds

How Big Is It?, cont.

Sun to Jupiter 5.2 AU

Sun to Pluto Between 30 and 49 AU

Oort Cloud Theoretical, unobserved edge of the Solar

System Out to about 50,000 AU (= 0.79 light-year)

How Big Is It?, cont.

Nearest star 4.2 light-years away

Our Galaxy 100,000 light-years across

To the nearest large galaxy 2.5 million light-years away

How Big Is It?, cont.

Virgo Cluster of Galaxies Nearest cluster of galaxies to us About 50 million light-years (debated)

Quasar 3C 273 One of the nearest and brightest quasars About 2 billion light-years

Edge of the observable Universe About 13.7 billion light-years away

Light travel times…

Across earth: 0.04 secondsFrom moon: 1.3 secondsFrom sun: 8 minutesFrom Neptune: 4 hours

Light travel times…

From nearest star: 4 yearsFrom galactic center: 25,000 yearsFrom Andromeda galaxy: 2 million yearsFrom hot early universe: 14 billion years