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Complete 1st midterm study guide

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Astronomy 2021A/B

1 Midterm Study guide Chapter 1 – A Universe of Life - Extraterrestrial life: any sign of life, whether it be complex, simple or intelligent - 3 disciplines ply an important role in framing the search for life: Astronomy, Planetary Science (geology and atmospheric science) and biology o Biology may be common throughout the universe (don’t have evidence yet doe) o Planetary science is the study of almost anything to do with planets 1. Helps us learn how planets form 2. Extrasolar Planets: planets orbiting stars other than our sun 3. Habitable worlds: contain the basic necessities for life • Not necessarily where people can survive but more microbes - Geocentric view: Earth is the center of the universe (discarded this view) - Laws of physics and chemistry are universal Places to Search - Solar system o Possibilities: 8 planets + dwarf planets + moons + asteroids o Mars (ice, past water, present water?) o Jupiter moons: Europa – best candidate for life (subsurface ocean), Ganymede, Calisto o Saturn moon: Titan (atmosphere, no liquid water) o More subsurface liquids: (Saturn’s moon) Enceladus & Triton (Neptune’s moon) – liquid water found - Nearest star is 4 light years away (100,000 years) - Search for extraterrestrial life – SETI o Search for signal from alien civilizations - Astrobiology: combination of astronomy (study of universe) and biology (study of life) o Most astrobiology research is focused on these 3 areas: 1. Searching for conditions conducive to formation and development of life 2. Looking for such conditions on other planets in our S.S 3. Looking for actual occurrences of life elsewhere Matter - Atomic Structure: (made of protons, neutrons and electrons) o Nucleus (protons and neutrons found here)  Electrons surround nucleus  Electrical charge measures how strongly it will interact with other particles  Ions = when atoms lose or gain electrons • Positive ion is one that has lost one or more electron • Negative ion is one that has gained one or more electrons - Phases of matter o Solid, liquid, gas and plasma - Atomic number = # of protons - Atomic mass # = number of protons and neutrons - Different isotopes contain the same # of protons but a different # of neutrons - Organic molecules contain carbon (and usually a hydrogen) - Compounds are molecules made from atoms of two or more elements - Molecules are two or more atoms o Bonds are broken at melting and boiling points allowing substances to change forms (from solid to liquid… etc) - Temperature = average motion of particles in a substance - Solid  liquid = sublimation and liquid  gas = evaporation Energy - What makes matter move - Kinetic energy: energy of motion. o Ex. Falling rocks, orbiting planets and molecules in air - Radiative energy: energy carried by light o Ex. Light allowing us to see or warming the surface of the planet - Potential Energy: stored energy – waiting to become kinetic or radiative o Ex. A rock on a ledge has gravitational potential energy because if it slips it falls o Ex. Gasoline contains chemical potential energy that can be converted into kinetic energy of a moving car o Mass is a form of stored energy e=mc^2 (Einstein) - ENERGY CAN CHANGE FORM FROM ONE TO THE OTHER - LAW OF CONSERVATION OF ENERGY: energy cannot be created or destroyed Light - Form of energy that travels at 300,000 km/second - Made up of electromagnetic waves (measured in hertz) o Wavelength: distance between adjacent peaks of wave o Frequency: rate at which waves vibrate/change - Speed of light = wavelength x frequency o Longer wavelength = lower frequency o Shorter wavelength = higher frequency o Energy is proportional to frequency so higher frequency = higher energy - Electromagnetic Spectrum o Consists of (shortest to longest): 1. Gamma rays 2. X-rays 3. Ultraviolet • Light shorter than blue light 4. Infrared • Light longer than red light 5. Microwaves 6. Radio waves o Visible light is in between ultraviolet and infrared - Spectroscopy: collecting light through a telescope o 3 basic types of spectrums: 1. Continuous spectrum: smooth light across a broad range of wavelengths 2. Emission Line Spectrum: bright lines on a dark background 3. Absorption line spectrum: Dark lines on a continuous background - Thermal radiation: light emitted by any dense object Chapter 2 – The science of Life in the Universe - Sky is made up of 88 constellations (an area that fills the sky) - Greeks were the first to understand astronomy using math(in the form of geometry) and facts o Greeks created models which influence science today o Reason, debate and challenge o Formal geometry  scientific deduction o Observations  scientific induction o Scientific model - Planets known in ancient times o Mercury o Venus o Mars o Jupiter o Saturn - Thales: origin of greek science (he answered “what is the universe made of?” o Said earth was a flat disk - Anaximander: heavens form a complete sphere – the celestrial sphere o Stars move in circle around polar star o Thought earth was a cylinder (first to think it was curved) - Pythagorus: first to think world was a sphere - Plato and his student Aristotle: o Aristotle  shadow of sphere on moon o Systematization of scientific thought - Eratosthenes (c. 276c. 196 BC): Measured the circumference of the Earth - Retrogade motion: planets sometimes reverse course and go backwards o Don’t actually go backwards but appear like it - Ptolemaic model: planets moved around earth on small circles that turn around larger circles - Aristarchus: said earth revolved around the sun o Stellar Parallex – shift in stars which prove that earth does go around the sun - Greeks believed the world was built from water, fire earth and air. o Two distinct schools of thought: 1. Atomists: world is made from an infinite number of indivisible atoms of each of the four elements • natural to assume that the same process created other worlds • atomism = atheism 2. Aristotelians: the four elements were confined to Earth, while heavens were made of a fifth element: ether or the quintessence • world must be unique Copernican revolution: Copernicus revived Aristarchus’ radical suggestion of a sun centered solar system  heliocentric model - Tycho: measured planet positions for 3 decades - Kepler: Tycho’s student o Trusted tycho’s measurements o Came up with a solution: planetary orbits take the shapes of special ovals known as ellipses • Kepler’s law of planetary motion • Kepler’s first law: the orbit of each planet about the sun is an ellipse with the sun at one focus • When the earth is colsest to the sun it is called perihelion • When the earth is farthest from the sun it is called aphelion • Average distance from sun is its semimajor axis • Kepler’s second law: Planet moves around its orbit, it sweeps out in equal areas at equal times • Planets move faster when closer to the sun and slower when it is further • Keplers third law: more distant planets orbit the sun at slower average speeds (p^2 =a^3) • P = planet in years • A = average distance from sun in astronomical units • One AU (astronomical Unit) = earths average distance from the sun or 149.6 million km - Order of planets = mercury, venus, earth, and mars, Jupiter and Saturn - Galileo: a moving object remians in motion unless a force stops it o First observed sun spots o Moon had mountains o OBSERVED FOUR MOONS ORBITING JUPITER AND NOT EARTH o OBSERVED VENUS ORBITS THE SUN AND NOT EARTH • Earth is not the center of everything - - Newton explained why the planets moved in ellipses (NEWTONS 3 LAWS OF MOTION) 1. An object moves at a constant velocity unless an object acts against it 2. Force = mass x acceleration 3. For any force there is always an equal and opposite reaction force Nature of Science - The idealized scientific method o Based on proposing and testing hypotheses (hypothesis = educated guess) - 3 major hallmarks of science o Modern science seeksexplanatuons for observed phenomena that rely on natural science o Science creates and tests models o Scientific model must make testable predictions about a natural phenomena 1. Eyewitness testimony should never be used as evidence in science - Occam’s Razor o If you have two methods or theories the simpler should be chosen - Induction: hypothesis driven science o Empirical science: observation(s)  interpretation  explanation  questions  more observation(s) o E.g., water on Europa: Voyager observations  interpreted as moving icebergs  explanation of motion by underlying water  question whether there can be life in the underlying water  plan a space mission to Europa - Deduction: Hypothesis driven science o Theoretical science: model or theory  prediction(s)  experimental or observational test(s)  refutation or consistency  modification of the model  new questions  new model(s) or theory(ies) o E.g., theory that amino acids can form under natural conditions  Miller-Urey experiment  consistency  the range of natural conditions?  models for the formation of RNA and DNA - Astronomy vs astrology o Astronomy is a science focused on learning about how stars, planets, and other celestial objects work. o • Astrology is a search for hidden influences on human lives based on the positions of planets and stars in the sky. - Nonscience = outside the domain of science (example love or religion) - Pseudoscience = observational evidence about natural world that are not treated in scientific way o Example: a psychic who sees the future (CAN’TBE TESTED) - Science must be objective: All people get the same results - Paradigm = accepted pattern of thought by scientists ( a bias) - When a model survives rigorous testingby scientists it is elevated to a theory Gravity (law details) - Mass attracts other mass because of gravity - Strength of force of one is proportional to their mass - Strength of gravity decreases with the square of the distance between the centers Chapter 3 – The Universal Context of Life - Earth is 14 billion years old Our Cosmic Address - Earth is a planet in our  solar system which consists of the sun and other orbiting objects. Our sun is a star which like all stars we can see with the naked eye make up the  Milky Way Galaxy. This galaxy contains 100 billion stars. The milky way galaxy is located in  the local group which it is one of the two largest galaxies. Our local group is a  Supercluster which is essentially a cluster of galaxies. Finally all these clusters make up our  Universe o Universe is sum of all matter and energy - Voyage model: o A walkable scale of the distance between planets o Sun = grapefruit, Jupiter = marble and earth = ballpoint pen o Planets in order  - We measure distance to stars in Light years o 1 light year = 10 trillion kilometers o How long light takes to reach us from another planet (when we see a planet that is 5 light years away we are seeing how it looked five years ago) - Galaxy is a flat disk o Consists of dark matter = unseen mass in halo surrounding the disk o Most of mass in universe is made of dark matter o Dark energy = force pushing galaxies apart even tho gravity is pulling them together o Dark matter and energy are main ingredients in universe • There is way more dark energy than dark matter - Big Bang created universe o Have evidence of cosmic microwave background left over from bang o Universe is three fourths hydrogen and one-fourth helium which was what was predicted from big bang theory o Universe expands, not the clusters and galaxies - Stars are born when gravity compresses material into a cloud and center becomes dense and hot enough to generate energy through nuclear Fusion o Atomic nuclei smash/stick together as a result and form planets o Stars then die in explosions called supernova o Stars generate energy by fusing helium into carbon Cosmic Calendar (compresses entire life of universe – 14 billion years) - Our solar system and planet formed in early September (4.5 billon years ago) - Animals only became prominent in mid December - Dinosaurs appeared the day after Christmas o Died yesterday - 9pm on december 31 early hominoids began to walk upright - Human civilization falls within last half minute o Modern humans appear a couple of minutes before midnight (quiz answer) - Observable Universe: things within 14 billion light years away as universe didn’t exist any further than that o We are the center of our observable universe o #of stars in universe is comparable to # of grains of sand on every beach on earth - Anthropic principle: o If one thing had occurred differently in the past we wouldn’t be here today Worlds - Moon was thought to have oceans but instead were maria - Terrestrial Planets: o Mercury, Venus, Earth and Mars o Much smaller than outer planets o Made of metal and rock o Solid surfaces o Have few moons] o Have Higher densities o Closer to sun - Jovian Planets: o Jupiter, Saturn, Uranus and Neptune o Jupiter is largest o Made up of helium, hydrogen and hydrogen compounds such as water, methane and ammonia o Have lower densities o No solid surface o Farther from Sun - Dwarf Planets: large enough objects to have gravity made them round (Pluto and Eris) - Asteroids: made mostly of metal and rock o Orbit in region called asteroid belt (between mars and Jupiter) - Comets: made mostly of rock and ice o Come from the Kuiper belt (region beyond Neptune) • Both Pluto and Eris live in the Kuiper belt • The OoRt cloud lies here too • Oort cloud comets originated in regions where they crossed orbits of jovian planets - Asteroids and comets can have their own moons - Not all moons are small Nebular Theory - Solar system was born from the gravitational collapse of an interstellar cloud - Particular cloud that gave birth to our solar system is the solar nebula o Cloud began to collapse o It heated up and spun faster and faster until it flattened into a disk o Center become hot were the sun formed (law of conservation of energy) o Particles collided and condensed (process in which solid/liquid particles form in a gas) and stuck together • Process of particles sticking together is called accretion • Particles that grew to the size of planets were called planetesimals o In inner part of disk only rock and metal condensed but in outer ice condensed as well as the other two - Current idea of how solar system formed is a theory because of its strength - The Close encounter hypothesis: planets formed when the sun nearly collided with another star Chapter 4 – Habitability of Earth - Geology = study of earth - 3 aspects of earth’s geology are important: o Volcanism • Outgassing  controls atmosphere and oceans o Plate Tectonics • Stabilizes climate o Earth’s magnetic field • Shields from solar wind - Fossils and rocks reveal earths history o Rock = structure and composition (Climate) o Fossils = environment at time and evolution o Make up our geological record (not synonymous with fossil record) Types of Rocks - Igneous Rocks: molten rock that cools and solidifies - Metamorphic Rock: rock that ahs been structurally or chemically transformed by high pressure or heat - Sedimentary rock: gradually compressed sediments over time (such as sand and silt) o Majority of fossils are found in sedimentary
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