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New Unit Astronomy: Structure of the Universe 42 Question of the Day What is the evidence for the Big Bang Theory? Celestial Object Any object outside Earth’s atmosphere Universe Everything that exists Big Bang Theory ● Universe started as a small, concentrated area of matter & energy that exploded ~13 billion years ago. ● Expanding ever since. In the beginning there was Energy… Which cooled into the first matter: Hydrogen 75% Helium 25% Evidence for the Big Bang 1. Background Radiation Energy (microwaves) from explosion found in all parts of universe 2. Electromagnetic spectrum of radiation from stars Spectral Lines Every element has a distinct pattern Helium Hydrogen Neon Oreos 2a. Doppler Effect – • Wavelength shifting of electromagnetic energy. • Caused by motion between energy source & observer (star and Earth). 2b. Red Shift • Shift in spectrum toward longer red wavelengths • Star is “RUNNING” AWAY • Farther away, greater red shift. • Almost all galaxies show red shift proof that universe is expanding. Blue Shift • Shift toward shorter blue wavelength • Object is “BARRELING” TOWARD Earth. Doppler Effect Red Shift = Object Moving Away Blue Shift = Object Moving Toward Questions 1. What are the 2 major pieces of evidence to support the Big Bang Theory? 2. If spectral lines are red-shifted, is the object moving toward or away from Earth? Question of the Day What is the structure of the universe? Warm Up What evidence supports the theory that the universe is expanding? http://htwins.net/scale/index.html 43 Planet Celestial body in orbit around the Sun. Solar System A sun and its orbiting planets, moons, and other celestial objects. Galaxies • 100+ billions of stars + gas and dust, held together by gravity. • 100+ billion galaxies. Milky Way Galaxy • Our spiral-shaped galaxy, with 200+ billion stars. We’re 2/3rds distance from center You are here! Universe Everything that exists Biggest 1. Universe 2. Galaxies 3. Solar Systems Smallest 4. Planets Distances in Space - Vast! FYI: 240,000,000,000,000 (240 trillion) miles to closest Star (other than Sun) Light-Year (LY): Distance traveled by light in a year (FYI: 9.47 x 1012 km). Astronomical Unit (AU): Average distance from Earth to Sun (FYI: 149,597,870.691 km) = 1 AU. FYI: At 100 miles per hour (160 kph) it would take over 100 years to go 1 AU. Solar System is about 80 AU in diameter 1 AU Earth Nearest star is 4.4 light-years away (7.866402828x1026AU) Nearest galaxy is 50 million light-years away (8,939094122x1027AU) 80-100,000 light-years Each dot on this screen is an entire GALAXY!!! Order from biggest to smallest Biggest Galaxies Planets Solar Systems Universe Universe Galaxies Solar Systems Planets Smallest Question of the Day What is the structure of our solar system? Warm Up What is LY? What is AU? 44 Solar System • Held together by sun’s gravity. • Formed 5 billion years ago. 1. Clumping of gas & dust 2. Sun forms – nuclear fusion. 3. More clumping – planets form. 4. Planets separate by density. Densest near Sun. 5. Present solar system. Formation Parts of Solar System 1. Planet • Celestial body in orbit around the Sun. • 8 in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune • Distance from the sun determines characteristics (ESRT) • Density generally decreases with distance from the sun 2. Moon • Body that orbits a planet or an asteroid, as those objects orbit the sun. • Over 175 moons in our solar system 3. Asteroids • Small, solid, rocky or metallic bodies that orbit the sun. • Most are in a belt between Mars and Jupiter 4. Comets • Balls of ice & rock or metal that turn to gas when heated by the sun • Heating by sun forms a tail, which is blown away from sun by solar wind. 4. Comets Particles and radiation from sun pushes tail of comet away. Meteoroid - Very small solid fragment that orbits the sun. Most are size of a dime or grain of sand. Meteor - Meteoroid that makes a streak when it burns up in Earth’s atmosphere Also called “shooting stars”. Meteorite - Meteoroid that hits Earth, forming an impact crater Impact Event Collision of comets, asteroids, meteoroids or any other celestial body. Meteor Crater, AZ 180 meters deep and 1.2 km in diameter with an eroded rim standing 30-60 m high Lunar Impact Crater Terrestrial (Rocky) Planets Mercury, Venus, Earth, Mars Close to sun, mostly solid Small diameters, high densities, few or no moons, no rings, have impact craters Mercury Ball of rock with iron core, -279°F to 800°F, many impact craters, no atmosphere or water Caloris Basin Venus Runaway Greenhouse Gases Thick clouds, acidic rain, poisonous atmosphere, 890°F, many volcanoes Earth - The Water Planet Mars - The Red Planet Thin atmosphere, many dust storms, impact craters, presence of water in ice caps, and ??? Jovian Planets - Gas Giants • Jupiter, Saturn, Uranus, Neptune • Far from sun, largely gaseous • Large diameters, low densities, many moons, may have small solid core, no impact craters Jupiter – The Largest Planet The Great Red Spot – a hurricane that has lasted 300 years so far, and is large enough to fit Earth inside! Saturn • Least dense planet (< water). • Rings made of ice & rock (possibly debris from a destroyed moon) Uranus • Tilted almost completely on its side. So during summer the sun never sets, during winter the sun never rises! Neptune • Mainly hydrogen atmosphere, -225oC Solar System Scavenger Hunt In notebook, answer the following using ESRT: 1. Most massive object in solar system. 2. Most massive planet. 3. Least massive planet. 4. Densest planet. 5. Least dense planet. 6. Planet with diameter most similar to Earth. 7. Planet farthest from Sun. 8. Distance from Earth to our Moon (units!) Answers 1. Sun 2. Jupiter 3. Mercury 4. Earth 5. Saturn 6. Venus 7. Neptune 8. .386 million km = 386,000 km Question of the Day How are stars formed? 1. In your notebook, categorize the 8 planets as either Terrestrial or Jovian. 2. Name 2 characteristics of Terrestrial planets and 2 of Jovian planets. 45 Terrestrial • Mercury, Venus, Earth, Mars • Close to the sun and mostly solid • Small diameters, high densities, few or no moons, no rings, have impact craters Jovian • Jupiter, Saturn, Uranus, Neptune • Far from sun & largely gaseous • Large diameters, low densities, many moons, may have small solid core, no impact craters Star • Large ball of gas held together by gravity that produces tremendous amounts of energy and shines. • Sun - Our closest star. Nebulas • Gas & dust held together by gravity. • Birthplace of stars. A Star is Born Step 1 - Cloud Collapses Nebula clouds of gas & dust begin to collapse due to gravity. Eagle Nebula Step 2 - Fusion • Cloud begins to spin & heat up. • Eventually, it gets hot enough for fusion • Protostar is born. Nuclear Fusion Combination of smaller elements form into larger elements. Some mass is converted to energy. Star Formation • In core, 4 H atoms fuse together to make 1 new He atom. • This releases huge amounts of energy, and makes the star expand. Step 3 - Equilibrium Opposite forces keep star in balance: 1. Fusion in core produces radiation (light) that pushes out. 2. Gravity pulls everything in. Birth of a Star 1. Cloud Collapses 2. Fusion 3. Equilibrium Question How is a star born? 1) Fusion, cloud collapses, equilibrium. 2) Equilibrium, cloud collapses, fusion. 3) Cloud collapses, fusion, equilibrium. 4) Get discovered, get an agent, get a movie contract. How Long Do Stars Live? It depends on the mass of the star. • LARGE stars live a short time, ~ 10 million years. Think SUV. • SMALL stars live a long time, hundreds of billions of years. Think Prius or VW Beetle. • Our SUN will live 10 billion years. It’s now 5 billion years old. What happens next? It depends on the mass of the star. Question of the Day What is the life cycle of stars? Write down in notebook: 1. The 3 steps in a star’s formation 2. What determines how long a star lives. 46 1. Low-Mass Stars Gas/Dust Star Red (Main Giant Sequence) White Dwarf Black Dwarf 1. Low-Mass Stars < 8 times our Sun’s mass. ● Fusion in core begins to run out, but continues in outer shell. ● Expands to Red Giant. White Dwarf ● In shell, outward pressure from fusion continues. ● Star explodes into a planetary nebula that leaves the core of a White Dwarf. Ring Nebula White Dwarf Burned-out core of a planetary nebula. • A sugar cube of White Dwarf weighs several tons. • Eventually cools down & becomes a “dead star” - Black Dwarf. • This is the destiny of our Sun….billions of years from now. 2. High-Mass Stars Gas/Dust Star (Main Sequence) Neutron Star Super Supernova Giant Black Hole 2. High-Mass Stars > 8 times Sun’s mass. ● Higher temperatures fuse heavier elements, e.g., iron. ● Fusion in core begins to run out, but continues in outer shell. ● Expands to Super Giant. Supernova Collapse of iron core triggers an enormous explosion into a Supernova. Supernova remnant Crab Nebula Neutron Stars & Black Holes Iron core of a high-mass star continues to collapse and becomes a super-dense Neutron Star. A teaspoon weighs 10 million tons! BUT iron core of a very-high-mass star collapses further and becomes … a Black Hole. 1. Low-Mass Stars Gas/Dust Star Red (Main Giant Sequence) White Dwarf Black Dwarf 2. High-Mass Stars Gas/Dust Star (Main Sequence) Neutron Star Super Supernova Giant Black Hole Question A low-mass Red Giant star becomes a 1) White Dwarf 2) Black Hole 3) Neutron Star 4) Supernova Question The life cycle of a star depends on the star’s 1) Color 2) Shape 3) Mass 4) Movie agent Organize into a flow chart: Black dwarf Supernova White dwarf Neutron star Main sequence Nebula Black hole Red giant Super giant ___________ Black dwarf, Supernova White dwarf, Neutron star ______________ Main sequence, Nebula Black hole, Red giant ______________ ________________ _______________ Super giant ________________ _______________ _________________ ________________ Nebula Main Sequence Red giant Super giant White dwarf supernova Black dwarf Black hole Neutron star You are made of stardust! Live Long and Prosper … Spirograph Nebula Cat’s Eye Nebula Boomerang Nebula Question of the Day How are stars classified? Warm Up: Categorize Giants, Supergiants, Main Sequenc & White Dwarfs under these stages: Early Stage Intermediate Stage Late Stage 47 Star Classification Luminosity: Actual brightness. Depends on size & temperature. Bigger is brighter Hotter is brighter Absolute Magnitude: Actual brightness if all stars same distance from Earth. Apparent Magnitude: How bright a star appears to be to an observer on Earth. - Depends on distance. Closer = brighter Characteristics of Stars (ESRT) Groups stars by luminosity and temperature (HR Diagram) Y-Scale: Luminosity – Brightness compared to sun. Sun = 1 < 1 = Dimmer than Sun > 1 = Brighter BEWARE: The Scary Scale!!!! X-Scale: Temperature DANGER: IT’S BACKWARDS! 10,000 L U M I N O S I T Y A B C D 1,000 100 10 30,000 20,000 10,000 Temperature (K)