Exploring Our Galaxy: Formation, Evolution, and Features

1. UNIT 1 DYNAMIC EARTH AND BEYOND Beyond Earth • Tools of Astronomy • Electromagnetic Radiation • Satellites & Telescopes • Moon • Creation, Features, & Phases • The Space Race • Synergy of the Sun-Earth-Moon • Solstices and Equinoxes • Influences and Effects • Our Galaxy • Type • Location Within • Our Solar System • Terrestrial Planets • Gas Giants Science of the Earth • Parts of Earth Science • 4 Major Areas • 4 Major Systems • Dynamic Earth • Tornados, Tsunamis, & Earthquakes • Exacerbation and Mitigation Unit I: DYNAMIC EARTH AND BEYOND

2. BEYOND EARTH Our Galaxy OUR GALAXY – Where we are in the MILKY WAY • Formation and Evolution of the Milky Way • The halo and bulge are exclusively made up of old stars suggesting these formed first • Astronomers hypothesize that the galaxy began as a spherical cloud • The cloud eventually collapsed under the force of its own gravity • Rotation therefore gave it its disc like shape • Stars forming afterward have orbits lying on the plane of the disc • Greater quantities of heavier elements • Formed by gasses enriched from previous generations of stars • Spiral arms are thought to be under constant development and evolution Unit I: DYNAMIC EARTH AND BEYOND

3. BEYOND EARTH Our Galaxy OUR GALAXY – Where we are in the MILKY WAY • Our viewing perspective • Appears as a band of stars stretching across the sky • We are part of that band • The real view is one of a disc’s edge • What we do not know • How large the galaxy is • Where the center is • Where we actually are in it • From our perspective, a hazy band of light across the sky • Not something we are looking at • Something we are looking outward from • We are within it and in fact, we are a very small part • To really see, we must be away from the lights of civilization and the Moon • Our Sun is one of 100,000,000,000 or so stars within this galaxy Unit I: DYNAMIC EARTH AND BEYOND

4. BEYOND EARTH Our Galaxy OUR GALAXY – Where we are in the MILKY WAY • Suggested that the Milky Way Galaxy has some interesting features • Spiral Arms – Speculation on the part of Astronomers that our galaxy, like many others, also contains spiral arms. Hydrogen mapping is again the source. • Supposedly we have four major spiral arms • Numerous minor spiral arms • The Sun is in the minor arm Orion • Orbital speed is 220 Km/sec • Orbital period is 240 million years • Has orbited the galaxy approximately 20 times • Mapping of the Milky Way Galaxy is largely through radio waves • Radio waves can penetrate interstellar gas and dust without scatter or absorption • There is also a measure of infrared radiation • Found the center, the “Galactic Center” to be surrounded by a nuclear bulge • Sticks out of the galactic disc like a yolk in an egg • Around the bulge and the disc are a halo • Spherical region • Globular clusters present Unit I: DYNAMIC EARTH AND BEYOND

5. BEYOND EARTH Our Galaxy OUR GALAXY – Where we are in the MILKY WAY • Mass • About 100 Billion times that of our Solar System • Astronomers have found significantly more mass towards the disc’s outer area • Indication the mass is more outward than at the center (90% is in the halo) • Part of the mass includes burnt out stars (e.g., white dwarfs) • Galactic Black Hole • Near the center, Sagittarius, is an area smaller than our solar system • 2.6 million times the mass of the Sun • Stars Within • The halo of the Milky Way contains the oldest known objects • Globular clusters, estimated to be 12 to 14 billion years old • Have traces of elements heavier than hydrogen an indication of their extreme age • Younger stars are in the spiral arms • Here there is a concentration of gasses and dust • Star formation occurs here • Population I Stars: Those in the disc and arms with heavy elements • Population II Stars: Those in the halo and bulge with only traces of heavy elements Unit I: DYNAMIC EARTH AND BEYOND

6. BEYOND EARTH Solar System OUR SOLAR SYSTEM – Terrestrials and Gas Giants • Also called rocky or telluric planets • Mostly rock and heavy metals • These have a core made of heavy metals • Mostly iron • Surrounded by a mantle of silicate rock • Much smaller than gas giants • Varied terrain • Volcanoes • Canyons, • Mountains • Craters • Few or no moons • No planetary rings • Atmospheres vary • Venus’ thick CO2 • Almost nothing on Mercury Terrestrial Planets Mercury Venus Earth Mars The Gas Giants Jupiter Saturn Uranus Neptune The Asteroid Belt • Almost entirely formed of various gases with a rocky center • Layers of hydrogen and helium molecules • Rocky center is actually molten “heavy metals” • These have numerous similar characteristics • All are outer planets (furthest from the Sun) • Massive • Low density • Fast rotations • Extreme cold • Numerous satellites (moons) • Ring systems • Astronomers have found gas giants in other solar systems • Extra-solar planets • Some in the habitable zones of other solar systems Located between Mars and Jupiter • Asteroids/Minor/Dwarf • Some small as a dust particle Unit I: DYNAMIC EARTH AND BEYOND