Unit 2 - The Solar System (Chapters 4 - 5)

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Western University
Earth Sciences
Earth Sciences 1086F/G

Introduction February-03-14 7:18 PM - Our solar system consists of a central star called Sun surrounded by 8 major planets, 3 dwarf planets, too many comets to num ber, and a whole lot of space debris GEOCENTRIC MODEL: Earth is at the center of the solar system HELIOCENTRIC MODEL: Sun is at the center of the solar system The Pioneers and Their Models Pythagorus/Plato - Pythagorus developed one of the earliest models of the solar system - Geocentric model - He pictured Earth as a stationary object in space, surrounded by a sphere which contained everything else (including Sun), an d the objects inside the sphere rotated slowly east at speeds depending on how far they were from Earth Aristarchus - He experimented with placing Sun at the center of the solar system - Heliocentric model - Satisfied that the geometry seemed to work — and seemed able to predict events in the solar system — he immediately moved on to other topics of interest Ptolemy - He was extremely religious, and under direction of the Catholic Church, he obediently put Earth back at the center of things and placed all the other objects he could see on various moving spheres Unit 2 - The Solar System Page 1 could see on various moving spheres - Geocentric model Copernicus - He put Sun at the center of the system, had Earth rotate about the Sun, and had Earth revolve on an axis once per day - Heliocentric model - He believed passionately that the model was right, but he could not publish it as the Church would not allow it - His friends published a book about this new model on his behalf but inserted a preface that indicated: the contents were hand y for calculating planetary position but should not be taken as anything representing reality" - This preface protected the ideas within the book from Church attack Tycho Brahe - The King of Denmark gave Tycho a grant with which he built the world's first state-of-the-art observatory, and the records of star and planet positions he mapped have been used by astronomers ever since - Tycho believed Sun moves around Earth, dragging the rest of the planets with it Johannes Kepler - He worked as Tycho's assistant - Kepler realized that Copernicus had gotten things almost right, but not quite - Kepler noted that the series of celestial spheres had somehow been pushed into their orbits by Sun - He figured that force was strongest near Sun and weakened with distance outward - Kepler believed that this mysterious force was magnetic - Kepler's laws define the geometry of planets moving about stars - Kepler's First Law defines the construction of an ellipse because he realized that planets did not move in perfectly circular paths - Here, with Sun as one focal point and the other a hypotheticalpoint in space, the sum of the distanced of any point on the e llipse from the two foci is a constant — which means that the Earth-Sun distance is constantly changing as the planet goes around its orbit PERIHELION: The point of nearest approach of a planet to Sun APHELION: The point of greatest separation Galileo Galilei - He was the first to observe the planets through a telescope, and what he saw convinced him that Copernicus was right (Heliocentric model) - Galileo did not invent the telescope, but he greatly improved upon the existing version by polishing the lenses himself - He observed Moon, sunspots, and four satellites orbiting around Jupiter - Galileo declared himself a Copernican, as far as cosmic models were concerned, and because of this he was called before the officials of the Inquisition and told to stop teaching the nonsense of Copernicus - After publishing a book promoting the Copernicus theory, he was again called before the officials of the Inquisition and was found guilty of heresy and placed under house arrest Learning Goals - Understand the contributions made to the science of astronomy by Pythagoras, Aristarchus, Copernicus, and Galileo - Know the 4 new definitions in the Introduction - The sun is a middle-range star on the Main Sequence of the Hertzsprung-Russell diagram — it is essential to know its history from birth to death - The problems with the Nebular Hypothesis have mainly to do with the evolution of the different planets and their present loca tions in the solar system — it is essential to learn how the positions of planets changed as the system developed Unit 2 - The Solar System Page 2 Chapter 4: A Star Called Sun February-03-14 7:15 PM - Malina (the Sun goddess) lived with her brotherAnningan (the Mood god) - One day they got into a terrible fight and Malina spread dirty, black grease all over her brother's face - In fear of retaliation, she ran as far as she could into the sky and became Sun - Anningan chased after her and became Moon - Anningan often forgets to eat, so he gets thinner as the days go by - Every month, Moon disappears for three days while he eats - He then returns to chase his sister once again— this eternal chase makes Sun alternate in the sky with Moon The Anatomy of Sun - Sun is a bunch of gas that becomes denser as you move from space toward the solar core PHOTOSPHERE: The visible outer layer of a star - The photosphere represents the depth at which we can see no deeper toward the core CHROMOSPHERE: The layer surrounding the photosphere that is invisible to the naked eye and made up of irregular gases CORONA: Sun's atmosphere Basic Sun Physical Facts - Diameter about 1.4 million km - Volume about 1.3 million times that of the Earth - Mass is about 330 000 times that of the Earth - Age is just over 4.6 billion years - At Sun's equator: 25 Earth days - At Sun's poles: 35 Earth Days - Temperature: → Interior: 15 000 000 K → Surface: 5800 K Distance Measurements Inside the Solar System - The distance between Earth and Sun is about 150 million km Chemical Composition Spectroscopy SPECTROSCOPY: The measurement and analysis of energy spectra to determine the composition of matter using a spectrometer or a spectrograph which records the spectrum of light emitted (or absorbed) by a given material, where the light can be used to determine the chemical composition of a substance because particular elements emit unique and characteristic wavelengths of energy Unit 2 - The Solar System Page 3 elements emit unique and characteristic wavelengths of energy - The dark, absorption lines are characteristic of particular elements allowing the composition of the matter generating the spectrum to be identified The Genesis Experiment - NASA's Genesis mission set out to capture particles of the solar wind and return them for study to Earth to better understand the connectionbetween the solar wind and the evolution of our solar system - The spacecraft's collector arrays, collected samples and stored them for the journey back to Earth - The mission went perfectly except for when the sample was returning to Earth via parachute, the capsule's parachutes failed to open and it crashed into the desert which contaminated the samples - Some of the samples were recovered and it turned out that theisotopic compositions of oxygen and nitrogen implanted in the wafers are significantly different to those in most of the solar system objects for which we have measurements Sun in Action PROMINENCES: Arcs of gas in the chromosphere that begin on the bright surface and soar to as much as 10 000 km into the corona FLARES: Short-lived gas eruptions that generally last for no more than 20 minutes or so Magnetic Fields - Earth has a strong magnetic field, which is produced by an interaction between an inner solid metal core inside a liquid metal layer - Sun also has a magnetic field whose generator has to do with the interaction of the unique properties of matter in the different layers inside Sun - In both Earth and Sun, we can crudely express the magnetic fields as giant bar magnets: north at one end, south at the other,and a field surrounding them that we commonly express as lines of different strength and orientation - The magnetic "generators" sometimes become "confused" and become unstable causing the poles of the magnet to switch - Sun's switch happens every 11 years (the complete 22 year cycle is referred to as a "solar cycle") - The clearest manifestation of "switch-time" for Sun is the development of a great number of sunspots SUNSPOT: A region of Sun's photosphere marked by lower than average temperature, thus appearing black - Flares and all other magnetically-controlled eruptions follow the same cycle - During intense flares, corresponding intense magnetic storms occur on Earth - There are two obvious effects: 1) Interf
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