Chapter 1: A Modern View of the UniverseBasic DefinitionsComparable Sizes for Each of these things in our solar systemDistances in AstronomyThe SunWhere did all the “stuff” in the universe come from?Cosmic CalendarSpaceship EarthMonday, January 14, yChapter 1: A Modern View of the UniverseBasic Definitions -Most points of light in the night sky you can see are stars-Star- A large, glowing ball of gas (actually it’s a plasma) that generates heat andlight through nuclear fusion-Sometimes you are able to see planets in the sky, not only stars• You can see about 5 without a telescope• Some of the brightest objects in our night sky are planets-Planet- A moderately large round object that orbits a star; it shines by reflected light. planets may be rocky, icy, or gaseous in composition• Tatooine: a fictional planet orbiting a binary star (YES STAR WARS)-Binary star- The two stars orbit each other, and a planet orbits the two who are in orbit-Solar system- The system of planets and smaller objects that orbit a star or stars• 4 inter-terrestrial planets Mercury, Venus, Earth, Mars• Jupiter (biggest planet) and Saturn, if they were larger would be stars• Pluto is a dwarf planet• Ceres, largest asteroid known -Galaxy- Large collection of stars orbiting a common center, held together by gravity1Monday, January 14, y• 100 Billion (1011) stars in our galaxy• Milky Way galaxy…. Our home…. We are about 1/2 way out from the center-Universe- All matter and energy; everything within and in between all galaxiesComparable Sizes for Each of these things in our solar system-How Big is Earth compared to the sun?• Scaled down by a factor of 10 billion, the Sun in the size of a large great fruit 14 cm diameter)-the Earth is the size of a ball point-The sun is about 100x bigger than the Earth (actually 109x)-how far appart are they?• the pair are 15 meters apart-How big is our planetary system• on a 1- to -10 billion scale:-The sun and neptune are about 450 m apart• most of space is very empty• (about 1/2 way across campus)-How far would you have to walk to reach the nearest star system, Alpha Cen-tauri?• San fransisco (4400 km)2Monday, January 14, y-Real distance is…41,500,000,000,000 kmDistances in Astronomy-Astronomical Unit (AU)= the average distance between the Earth and Sun• =1.5 X 108 km= 150,000,000 km-Example Distances• Mercury to Sun= .39 AU• Earth to Sun= 1 AU• Mars to Sun 1.52 AU• Jupiter to sun 5.20 AU-Light Year= distance light travels in one year• You should know the speed of light: -c= 300,000 km/s-c= 3 X 105 km/s-Distance= Velocity X Time• d=vt• or v=d/t• Distance= 300,000 km/s X 1 year• = 300,000 km/sD (365X24X60X60)s• =9,460,800,000,000 km3Monday, January 14, y-A light year is a unit of distance not time!-The Orion Nebula is 1,500 light years away.• How long does it take light emitted from this nebula to get to Earth?• Since light travels at a finite speed, we see objects as tehy were in the past.• The farther away we look in distance, the further back we look in time.• Moon- 1 sec• Sun- 8 min• Alpha Centauri- 4.4 years• Andromeda Galaxy- 2.5 million years -THe universe is only about 14 billion years old• Light from more distant objects has not had to to get to us yet-Where does 14 billion come from?• in 1929 Edwin Hubble (and others) discovered that we live in an ever expand-ing universe-Every part of the universe is expanding away from every other part of the universe. No true center to universe• if you know the rate of expansion (which we do), you can predict how long ago it began. The beginning is called the Big Bang-The moment that the expansion began-Term was given by those that did not believe that this could have happened, almost poking fun at their expense4Monday, January 14, y• The age of the universe defines the size of the (or our) observable universe is everything within about 14 billion light years• The universe is potentially infinite in sizeThe Sun-98% H and He: the remaining 2% is all of the other elements• Like most stars-Different colors represent different temperatures-The sun is not “ on fire” or “burning”. It is bright because it is hot and gives off ther-mal radiation (light), like a hot poker iron-Not a solid surface, not a liquid but a boiling gas• Sun spots are about 4,000 K as apposed to the general temp of the sun being 6,000 k• turbulance in atmosphere causes images of the sun’s surface to pour in and out (same reason it seems that stars “twinkle”)-The Sun produces energy via fusion- process of combining light elements into heav-ier elements• Sun fuses H into He.-Same process that occurs in a Hydrogen bomb• Do not confuse fusion with fission- the process of splitting heavier elements into lighter ones-Fission is how nuclear power plants produce energy5Monday, January 14, yWhere did all the “stuf” in the universe come from?-All matter and energy were created in the Big Bang. However the matter it create was in the form of hydrogen and helium only. Heavier elements were created in the center of stars.• “…We are made of star-stuff” -Carl SaganCosmic Calendar-History of the universe compressed into 1 yr-All recorded human history occurred in the last 30 seconds. -(most people about 20 y/o were born in the last .05 seconds of this year)6Monday, January 14, y-galaxies formed soon, solar system 2/3rds along primitive life on Earth soon there af-ter, dinosaurs came and went in a few days…..Spaceship Earth-Earth rotates around it’s axis once every day (about 1400 km/hr)-Earth orbits the sun once a year ( about 100,000 km/hr)-Solar system orbits the galaxy once every 230 million years ( about 800,000 km/hr)-There is no “rest frame” of the universe. Objects in motion will stay in motion forever, unless some force slows them down (inertia; Chapter