1. Geocentric Model Geo = earth, Centr= centre Ptolemy during 2 nd century AD (C.E) Lasted 1500 years Earth is the center of the solar system (instead of the sun) Models of the Solar System
2. Heliocentric model Helio = sun, centr= centre Nicolaus Copernicus (early 1500’s) Orbits with perfect circles 3. Johannes Kepler (1571-1630) demonstrated elliptical orbits Current model = heliocentric with elliptical orbits
Key Terms Planet Orbits a star Is not a star itself Spherical (requires sufficient mass/gravity) Dominates its orbit Solar system Solar = sun (like a solar panel) System: involves many components A group of planets that orbit one or more stars ** Where does the solar system end?
722 kg spaceprobe launched on sept 5, 1977 Purpose: to explore Jupiter and Saturn Moved on to explore the outer heliosphere Sept 12, 2013 crossed the heliopause farthest human-made object from the sun Now exploring the interstellar medium Expected to send signals until 2025 http://voyager.jpl.nasa.gov/ Voyager 1 leaves the solar system!
http://solarsystem.nasa.gov/planets/ IMAGE Sun Inner planets = Terrestrial planets = Mercury, Venus, Earth, Mars Asteroid belt Outer planets = gas giants = Jupiter, Saturn, Uranus, Neptune Kuiper belt Layers
-Small, non-spherical objects -Left over debris from solar system formation -Most are in the asteroid belt -Size : sand to 500km across -Can have moons (Example: Ida and its moon, Dactyl) -Ceres (a dwarf planet) also is in the asteroid belt -65 million years ago an asteroid struck earth. -Caused climate changes -May have caused mass extinctions (dinosaurs!) Asteroids and the Asteroid Belt
Impact Events Haughton Crater in Nunavut: 23 km across. 39 million years ago Barriger Meteroite Crater in Arizona Equivalent to 1000 atomic bombs. 40-50000 years ag0. Tunguska Event 1908 in Siberia: destroyed 2000 km 2 (larger than Kingston, ON) 120 ft across, 220-million pounds Heated to 44,500 F Explosion equal to 185 Hiroshima bombs
Comets -Originate in Kuiper belt and Oort cloud -Composed of dust, ice and rock -Can move into the inner solar system by Jupiter’s gravity -when near the sun, forms two tails -Gas tail (blue) ionized gases -Particle tail (white) light reflects off of particles -Periodic comets have stable orbits Can be short period (<200 year orbit) or long period Other Celestial Bodies
Meteoroids: chunks of rock moving through space (broken from asteroids, comets or planets) Meteors: Meteroids burning up in the earth’s atmosphere (shooting stars!) Shooting stars are NOT stars Meteor showers: when earth passes through trail of comet debris Meteorites: Meteoroids that impact the earth’s surface (~ 100 metric tonnes/year) Meteoroids, Meteors, and Meteorites
The distance light travels in one Earth year. 1 light year = 9.46 x 10 12 km ALL electromagnetic radiation (light) travels at a constant speed: Speed of light = 300 000 km/s What is a light year?
Galaxies A collection of stars, gas, dust, and planets held together by gravity. All stars are part of a galaxy Spiral and elliptical and irregular are the primary types William Herschel Discovered Uranus Coined the term asteroid Built and sold telescopes w/his sister First to discover galaxies beyond the Milky Way
A hazy white band, which appears brightest in summer Named by Greeks. Milk spilled by Hera while feeding Hercules Everything you can see in the sky is part of the milky way ~100 billion stars The Milky Way Galaxy
Local Group Milky way is part of the LOCAL GROUP of ~40 galaxies Milky way and Andromeda are the largest in our local group If Andromeda was brighter, this is what it would look like in the sky!
Collection of stars held together by gravity Open clusters (50-1000 stars) in milky way arms Globular clusters (100000-1000000 stars) Spherical Superclusters: clusters of 4-25 clusters of galaxies Star clusters
Harlow Shapley noticed globular clusters only in the direction of Hercules, Scorpius, Ophiuchus and Sagittarius. Thus we must be far away in one of the major arms Mapped the milky way with radio waves to determine diameter and shape. 100000 light years in diameter Bulge at the center (looks like UFO from the side) Two major spiral arms and several minor Sun is 28000light years from the center