Science Test 4 PDF

The Stars Stars are stationary because our planet is spinning. This gives us the impression that the stars are moving. Polaris is the north star. It is perfectly aligned with Earth's axis. Why are stars important? -​ Navigation life cycle of stars eg. hydr...

The Stars Stars are stationary because our planet is spinning. This gives us the impression that the stars are moving. Polaris is the north star. It is perfectly aligned with Earth's axis. Why are stars important? -​ Navigation life cycle of stars eg. hydrogen, -​ Culture helium, and lithium) -​ Light and Energy -​ Elements (nearly all elements were formed at some point during the What is a star? -​ Stars are immense balls made mainly of hydrogen and helium, where fusion goes on inside. Astronomy: -​ A natural science that studies celestial objects and phenomena. -​ It uses math, physics, and chemistry to explain their origin and evolution. -​ Objects of interest include planets, moons, stars, galaxies -​ Our primary source of info on stars is electromagnetic radiation -​ Electromagnetic radiation can be visible to humans, or take the form of radio waves that we cannot see (optical telescopes, radio telescopes) -​ Astronomers measure and investigate 4 aspects of this radiation: wavelength, intensity, direction/position, and variations in these through time. -​ Galileo Galilei: First recorded astronomical observations with a telescope in 1609. Coined the term ‘tele’ meaning far and ‘skopos’ meaning seeing. He used the Refracting Telescope. Telescopes: -​ Refracting Telescope: Rely on 2 lenses. Incoming light is focused on the objective lens, causing the parallel line to converge. At the focal point, the lines cross so that the image becomes upside down. The eyepiece lens then re-bends the light and makes it parallel for the viewer. -​ Reflecting Telescope: rely on mirrors rather than lenses so they are more efficient. Light enters and is bounced off curved mirrors. -​ Satellite observations allow us to have a more unobstructed view of the cosmos. -​ Modern large telescopes use multiple mirrors that can be angeled and adjusted. -​ Most are built in the Atacama Desert in Chile The Anatomy of Stars The Sun: -​ Not just a giver of life, but a giver of knowledge. -​ The Surface: Image of the surface of the Sun, showing hot material following magnetic field lines. It is the only part of the Sun that we see is the thin outer layer, perhaps 150km into the sun. -​ The Outer Layer is called the photosphere. The sun doesn't have a sharp boundary. What we call “the sun” is a mass of gas and energy that is not like Earth or a planet. These gaseous layers are not usually visible from the Earth. However, during a total eclipse of the Sun, the Moon passes in front of the Sun, and we can sometimes view the chromosphere and the corona. -​ Aurora Borealis: Charged particles from the sun blow into Earth's magnetic field. The interactions of these particles with atmospheric gases (Oxygen and nitrogen) cause intense, dancing colours. The Northern Lights: -​ The Sun emits charged particles that form plasma. -​ The Earth's magnetic field usually protects the Earth's surface from these particles. -​ Sometimes the sun emits larger amounts, which can overpower the magnetic field. -​ When the charged particles enter the atmosphere, chemical reactions release photons that we view as lights in the sky. Nuclear Fusion: -​ The sun is not powered by coal and is instead powered by nuclear fusion of hydrogen. -​ Hydrogen is the most common element in the universe -​ Fusion converts hydrogen into helium and in the process releases energy. Nuclear Fusion in the Sun: 1.​ Two protons come together to form deuterium. One proton turns into a neutron. By-products include energy, a neutrino and a positron. 2.​ Another proton collides with a deuterium, producing a hydrogen isotope. By-products include energy and a photon. 3.​ Two of the helium-3 isotopes collide to form the final helium. By-products include energy, protons, and a photon. Hertzsprung-Russel Diagram: -​ In the 1900s, 2 astronomers discovered a way to organize and name stars -​ Energy is calculated based on distance and brightness -​ Temperature is determined by the colour spectrum of light -​ Most stars seemed to align with a sloping line called the ‘main sequence stars’  -​ Most stars conform to a trend where there are hot stars emitting lots of energy, and cooler stars emitting less -​ These are burning hydrogen and include the Sun -​ Some stars do not conform, and emits lots of energy but seem cool. They produce lots of energy is distributed across a huge area.. So they appear cooler. They are often red and are called the red giants. -​ Other stars are super hot but produce little energy. These are so small to explain why so little energy is emitted despite the heat. These are called white dwarfs. Where do Stars come from? -​ The Nebular Hypothesis is the most widely accepted model. -​ It is a large cloud of dust and gas collected forming a nebula. -​ They are common in our galaxy. -​ Gravitational pull causes the particles to attract and the nebula collapses on itself. -​ Gravitational forces cause the cloud to spin faster and faster What keeps a Star together? -​ Internal heat and pressure cause the star to push apart -​ The gravity of the star is pulling it together -​ The size of the star is dependent on how massive it is and how much heat/pressure it is producing Life Cycle of Stars 1.​ Stars begin as an immense ball of hydrogen and helium. Most stars “burn hydrogen” for billions of years. The burning hydrogen create pressure that pushes back against gravity so that there is a balance and it does not completely collapse. 2.​ Depletion of hydrogen reduces fusion, and the lower production of energy allows gravity to dominate. The star contracts and heats up, consuming any remaining hydrogen. 3.​ Helium burning produces heat and causes the star to expand in size. Our sun is expected to expand out to where many planets orbit now. However, the planets will shift and only Mercury and maybe Venus will be consumed by the Sun. 4.​ Once helium is depleted, the star will collapse under gravitational forces. This generates large amounts of heat and energy. 5.​ Eventually, most stars cool and become a white dwarf. Our Sun will decrease to the size of Earth, but hundreds and thousands of times more massive. Basically, any star depends on the total mass of HYDROGEN and HELIUM.  SUMMARY -​ Astronomy is the study of celestial objects and phenomena, and astronomers have discovered much of the nature and origins of stars. -​ Stars are studied with telescopes that detect electromagnetic radiation. -​ Extreme temperature and pressure within a star cause hydrogen to undergo nuclear fusion, creating helium and heat energy. -​ These reactions create nuclear winds that create amazing views of the night sky on Earth. -​ Stars form from nebulae, which are clouds of interstellar dust that collapse on themselves due to gravity. -​ The life of a star is a struggle against gravity, and ultimately gravity wins. -​ Stars that burn hydrogen are the main-sequence stars. -​ After depleting hydrogen, stars briefly burn helium and expand into a red giant. As all nuclear fuel is exhausted, gravity dominates and the star collapses into a small but very hot white dwarf. -​ Larger and smaller stars undergo different paths (Brown dwarfs and supernovas) Cosmology Astronomy: The science that deals with celestial bodies and the universe. Cosmology: The branch of astronomy that deals with the origin and evolution of the universe. Galaxy: A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. Nebula: Cloud of dust and gas in space. The Milky Way: spiral-armed galaxy Andromeda: A cloud of gas and dust within the Milky Way, or was it a distant galaxy? Andromeda is a galaxy! It is the nearest major galaxy to the Milky Way. Edwin Hubble -​ A telescope with an unprecedented 100-inch mirror was built near LA -​ Named the Hooker Telescope after the philanthropist that funded it -​ He helped us realize that the universe is bigger than our galaxy and that there are billions of galaxies, each with millions to billions of stars  -​ He observed many more galaxies and saw a pattern: they were redder than expected (Red Shift) Hubble’s Law -​ Galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther away they are, the faster they are moving away from Earth. The Big Bang Theory -​ The universe began at a specific time in the past, and it has been expanding ever since. -​ The theory describes how the universe expanded from an initial state of high density and temperature. -​ The Big Bang Theory Evidence 1.​ Universal Expansion: Hubble's observation of the expansion of the universe was the first strong evidence for the big bang theory. Ongoing expansion suggests that in the past things were together. This is not conclusive evidence because other theories could explain expansion, such as the steady-state universe. 2.​ Cosmic Microwave Background: Scanning the skies for radio signals, 2 radio astronomers found a hiss coming from all directions. Checked for interference- including pigeon poop- but found a constant microwave radiation. Importantly, the steady-state theory does not predict this radiation, whereas the Big Bang theory predicts this precise wavelength. 3.​ Abundance of Light Elements: Big Bang models predict that, for a short time, elements could form from only hydrogen, helium, and lithium. The others would form from the nuclear fusion in stars. The observed abundance of isotopes matches predictions. SUMMARY -​ The great debate is whether these nebulas are nearby dust clouds or something farther away. -​ Edward Hubble solved this with a giant telescope and showed that they existed outside our galaxy. He also found that the universe is expanding, and founded the field of cosmology. -​ If everything is expanding, then at one time everything must have been together. -​ The best theory to explain universal expansion is the big band theory. -​ The entire universe was extremely small, then got incredibly large during inflation. In the beginning, all forces were united into a single force, with gravity separating first.  -​ Gravity continues to be an exceptionally important part of our universe, stars, and more. -​ Test: what happens with really big stars? supernova – (collapses on itself because of gravity The Future of Our Universe The universe is expanding, but will it expand forever? There are 3 models that depend on the ability of gravity to slow things down. -​ ‘Closed’ ‘Open’ and ‘Flat’ actually refer to the shape, or curvature, of space-time itself. -​ Impossible to picture in three spatial dimensions, this is easy enough in two: 1.​ A closer universe would resemble the surface of a sphere (returns to its original state). It's like trying to stretch apart a rubber band that eventually pulls your fingers back together. 2.​ An open universe would be like the surface of a saddle or a Pringles potato chip (Expansion goes forever) when stretching the rubber band until it pops. 3.​ A flat universe would resemble a sheet of paper (stops the expansion after infinite time but does not reverse it). Like a stretching band that eventually stops and doesn't expand or contract. Dark Matter (unrelated to dark energy): -​ The further from the center, the faster an object must move to stay in line. -​ That is, there needs to be more force/energy to stay in line when an object is far from the middle. -​ So, if forces are equal on all objects, the distant ones should orbit at a slower rate. That is, they should fall behind. -​ Gravity holds galaxies together. Kepler’s laws of planetary motion says distant objects should orbit more slowly. -​ In the early 1970s, Vera Rubin was studying the rotation of galaxies and found they were rotating much faster than expected given their mass: fast enough that they should break away from gravity and fly apart. -​ Rubin did the calculations: how much more massive would the galaxy have to be for there to be enough gravity to hold this speeding galaxy together? -​ Answer: at least 10x more massive. -​ Dark matter is a very strange form of matter. -​ Although it has mass, it does not interact with everyday objects and it passes straight through our bodies. -​ Physicists call the matter dark because it is invisible. (remember, astronomers often require indirect observation to detect celestial objects and forces). -​ Yet, we know it exists. Because dark matter has mass, it exerts a gravitational pull.  -​ Dark matter is >5x as abundant as all known normal matter: “most of the universe can’t even be bothered to interact with you” -​ We have not actually detected dark matter, and theory suggests it can Dark Matter vs Dark Energy: Dark Matter Dark Energy -​ Matter that reflects little to no light, -​ An unknown energy causing the but does have a gravitational universe to expand at an influence. accelerating rate. -​ Maybe subatomic particles with -​ Recent observations of supernovae extremely small mass, but also provide estimates that the universe EXTREMELY abundant. is ~70% dark energy. -​ Weakly interacting massive particles (WIMPS). Review Q’s: -​ How is cosmology different from astronomy? -​ How are galaxies distributed across the universe? -​ Explain redshift. -​ Who discovered galaxies that exist beyond the milky way? How did he do it? -​ Why is the big bang theory often called the ‘hot big bang’? -​ What theory competed with ‘big bang’ and why was it dismissed? -​ How was dark matter discovered? -​ What effect does dark energy have on the universe? Key Terms to Know: -​ Milky way -​ Cosmic microwave background -​ Galaxy radiation -​ Cosmology -​ WIMPs -​ Redshift -​ Dark energy -​ Hubble’s law -​ Dark matter -​ Big bang theory PLANETS Planet: A large rounded astronomical body that is neither a star nor its remnant. Asteroid: Small rocky body orbiting the sun. They are materials that never accumulate enough mass to form a planet. Pluto: Classified as a dwarf planet: it isn't big enough to produce enough gravity to clear away objects of similar size near its orbit. Astronomical Units (AU): The length of the solar system is the AU, which is the average distance from Earth to the sun. -​ Mercury is about halfway from Earth to the Sun -​ Venus is about halfway to Mercury -​ Mars is about the same distance from Earth as Mercury but in the other direction -​ Jupitur is 5AU, Saturn is 10AU, Uranus 20AU, Neptune 30AU, Pluto 40AU REMEMBER Terrestrial Planets The protoplanetary disc was a mess of dense mineral grains and other solids, whizzing around the sun. Over time, grains collide, stick together and grow into larger objects called Planetesimals (the size of a boulder to a small mountain). These slammed into each other and formed protoplanets. -​ 20-30 protoplanets orbited the sun -​ Some were sucked into the sun -​ Some broke free of the gravitational pull and shot into space -​ Many collided -​ Generated lots of heat The Great Bombardment -​ Caused so much heat that the forming planets completely melted -​ As Earth gained mass, gravity intensified and the heaviest materials sank to the center of the planet, forming the solid and liquid core -​ Less dense material floated above the core, forming the mantle and crust -​ This process called (differentiation) occurred in all 4 terrestrial planets The 4 Terrestrial Planets 1.​ Mercury -​ Closest to the sun -​ Visible as a fast-moving star -​ About ⅓ size of Earth, but just as dense -​ No atmosphere -​ The surface has craters, no weathering process 2.​ Venus -​ %85 of Earth's Mass -​ Most earth-sized planet -​ The atmosphere is mostly C02 and it has suffered from the runaway greenhouse effect  3.​ Earth -​ 3rd closest to the sun 4.​ Mars -​ 1/10th the mass of Earth -​ Very thin atmosphere, mainly C02 -​ Most explored and studied -​ 6 rovers have landed on Mars -​ Mars has ice and liquid water may exist below its surface Asteroid Belt -​ The region between the terrestrial and Jovian planets -​ Although portrayed as a fairly dense collection of asteroids, it is incredibly sparse. -​ Once thought to be a broken-up planet, it is not understood to be material that never formed a planet, probably due to the gravitational influence of Jupiter. Jovian Planets 1.​ Jupiter: -​ Largest planet. Has rings made up of dust. Has the most moons. -​ 2 distinguishing characteristics are the coloured bands and the Great Red Spot -​ Has 61 Moons (Europa) -​ Europa is the size of Earth’s moon -​ Gravitational pull and flexing from Jupiter keep it liquid 2.​ Saturn -​ Jupiter and Uranus have rings but none compare to Saturn -​ Similar to Jupiter but less dense -​ The spectacular rings are only spectacular looking “down” -​ Composed of countless small pieces of rock and ice that orbit the planet 3.​ Uranus -​ “Ice Giant” -​ 21 moons -​ Looks bland because methane in the upper atmosphere absorbs red wavelengths, leaving a plain, bluish ball. -​ It has rings but they are made of sparse and very dark material -​ It is the only planet that rotates as if it were lying down. -​ Important: It is not dense, it is cold and glassy, it is lying down, and it has rings and moons around it. 4.​ Neptune -​ Gassy “Ice Giant” -​ 14 moons Saturns Moons:  1.​ Titan: largest moon in the solar system. The only moon with an atmosphere. 2.​ Enceladus Plate Tectonics Hypothesis: Theory: -​ Proposes an explanation for a -​ Well-demonstrated and widely phenomenon: a tentative accepted explanation for a explanation which can be tested phenomenon. -​ Based on observations (an -​ Based on a wide range of data and educated guess) well tested. Plate Tectonics explains how a few thin, rigid tectonic plates of crustal and upper mantle material are moved across Earth’s surface by mantel convection. Convection is the flow of fluid or gas due to thermal differences. (Hot air rises) Theory of Tectonic Plates: 1.​ Geological features of ocean floors 2.​ Magnetic reversals: Stripping 3.​ Rock ages: Seafloor spreading Biogeography: The study of the distribution of species and ecosystems in geographic space and through geographic time. It started because people wanted to understand better why species were distributed. Disjunction: When two species that are similar live super far apart. The Atlantic Ocean: Formed via seafloor spreading at the mid-Atlantic ridge -​ We can estimate the age of the ocean like how we would estimate how long it takes to drive from point A to point B Mantle convection causes movement: -​ Where two plates meet, there are 3 general ways in which they can interact with each other. 1. Divergent plate boundaries -​ Pulling apart doesn't produce earthquakes 2. Convergent plate boundaries -​ Pulling toward produces earthquakes 3. Transform plate boundaries -​ Plates move past each other; friction keeps the plates moving PLATE TYPES: 1.​ Continent-Ocean (denser, ocean plate subducts below the continental plate) 2.​ Ocean-Ocean (When colliding, one plate goes beneath the other and drags the edge of the other plate down) 3.​ Continent-Continent (less dense, the plates buckle and fold producing mountains) Volcanoes: -​ Emerge in 3 different areas -​ Form on hot spots which are the middle of plates Rock Cycle The process by which rock is created, destroyed, and altered. Types of Rocks: 1.​ Igneous -​ Any rock can be melted down and become an igneous rock -​ First rocks formed on earth 2.​ Sedimentary -​ Any rock could be weathered and lithified into sedimentary rocks 3.​ Metamorphic -​ Any rock can be warped by heat/pressure into a metamorphic rock