Earth Science Astronomy What is Astronomy l Astronomy

Earth Science - Astronomy

What is Astronomy? l Astronomy is the study of anything we see in the sky, and beyond l Overlaps with physics, chemistry, geology, and other sciences

The Scientific Method in Astronomy l Astronomy is one of the most difficult sciences to do, because we can’t do very many things in a lab l We have to combine our observations with our understanding of other sciences to make good predictions l Sometimes, our “lab” is a computer

Astrology l Astrology - the belief that the stars and planets affect your life u Despite the –ology, it’s not a science! l Gravity of other planets is not as strong as the gravity of your obstetrician! l Does not use the scientific method l It’s complete poppycock

Observing the Universe l Astronomy began with people observing their surroundings u What did the sky look like when herds moved? When a season changed? u When was it good to plant? u Planets, sun, moon, and stars all seemed to move independently

What have you Observed? l An incomplete list: Moon u Planets (Venus, Mercury, Mars, Jupiter, Saturn) u Stars u Meteors (shooting stars) u Aurora u Comets u

What’s Out There, Anyway? l Atmospheric phenomena l Solar System u Sun and planets; comets, asteroids, etc. l Milky Way u Our galaxy l Extra-galactic Other galaxies u Some objects like our galaxy u Some completely different phenomena u Things between galaxies u

Atmospheric phenomena l Auroras l Meteor Showers

Solar System Objects and Phenomena l The Sun l Eclipses l Planets & Moons l Asteroids l Comets

Galactic Objects and Phenomena l l Stars & star clusters Nebulas Supernova Remnants Dead Stars u u u White Dwarfs Neutron Stars Black Holes l Dark Matter

Extra-Galactic Objects and Phenomena l Other Galaxies l Galaxy Clusters l Super Clusters l Dark Matter l Dark 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 l Terrestrial Planets Include: u Mercury, Venus, Earth and Mars l Jovian Planets Include: u Jupiter, Saturn, Uranus & Neptune l Also Interesting: Jovian moons l Not sure what to do with them: u Pluto/Charon u 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. 2. 3. 4. Mercury Venus Earth Mars

Mercury l Mercury has a lunar-like geology. Caloris Basin

Mercury l Mercury is almost tidally locked, like the Moon.

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

Venus l The surface of Venus is like the surface of hell.

Venus l Venus has a young, basaltic surface.

You Probably Know This One

Mars l Mars has the most Earth-like geology.

Mars l Mars has a thin atmosphere of CO 2.

Mars l Familiar geologic features/processes

Mars l Familiar geologic features/processes

Mars l 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. 2. 3. 4. Jupiter Saturn Uranus Neptune

Jupiter l Jupiter’s geologic features are all atmospheric.

Moons of Jupiter l Io is the most active body in the Solar System.

Moons of Jupiter l “All these worlds are yours except Europa…”

Moons of Jupiter l Ganymede and Callisto are two of the larger bodies in the Solar System.

Saturn l Saturn is the furthest out of the historical planets.

Saturn’s moons

First ever color picture of Titan’s surface January 14, 2005 Water and hydrocarbon ice ESA/NASA/Univ. of Arizona

Uranus & moons l Uranus orbits the Sun on its side.

Neptune & moons

Pluto & Charon

Units for Measuring Astronomical Distances l Astronomical Units (AU) Defined as the distance from the Sun to the Earth u About 1. 496 x 1011 m (about 150 million km) u l Light-years Defined as the distance light travels in one year u About 9. 46 x 1015 m u l Parsecs Derived from the way stars appear to shift slightly in the sky as the Earth orbits the Sun u Equal to about 3. 26 light-years u

How Big Is It? l Our Earth u 12, 756 km across l Earth to the Moon u 384, 400 km l Earth to the Sun u 150 million km u = 1 AU u = 500 light-seconds

How Big Is It? , cont. l Sun to Jupiter u 5. 2 AU l Sun to Pluto u Between 30 and 49 AU l Oort Cloud u Theoretical, unobserved edge of the Solar System u Out to about 50, 000 AU (= 0. 79 light-year)

How Big Is It? , cont. l Nearest star u 4. 2 light-years away l Our Galaxy u 100, 000 light-years across l To the nearest large galaxy u 2. 5 million light-years away

How Big Is It? , cont. l Virgo Cluster of Galaxies u Nearest cluster of galaxies to us u About 50 million light-years (debated) l Quasar 3 C 273 u One of the nearest and brightest quasars u About 2 billion light-years l Edge of the observable Universe u About 13. 7 billion light-years away

Light travel times… l Across earth: 0. 04 seconds l From moon: 1. 3 seconds l From sun: 8 minutes l From Neptune: 4 hours

Light travel times… l From nearest star: 4 years l From galactic center: 25, 000 years l From Andromeda galaxy: 2 million years l From hot early universe: 14 billion years