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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
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