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Astronomy 161, Introduction to the Solar System, is the first quarter of a 2-quarter introductory Astronomy for non-science majors taught at The Ohio State University. This podcast presents audio recordings of Professor Richard Pogge's lectures from his Autumn Quarter 2006 class. All of the lectures were recorded live in 100 Stillman Hall on the OSU Main Campus in Columbus, Ohio.
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Similar to its big friend Uranus, a thick soup of water, ammonia and methane makes up this planet's composition. Some other facts that fall into the composition of Neptune is that Neptune has a solid center. It's atmosphere is made of hydrogen, helium and methane. This methane gives methane the blue color that is has, similar to Uranus.…
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Ura, ura, ura, Uranus! Uranus is the seventh planet away from the Sun, and the least massive of the four Jovian planets. It was discovered on March 13, in 1781 by a man named William Hershel. There are actually rings surrounding Uranus, but they aren't visible.
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Our planetary neighbor is one of the terrestrial or rocky planets, which are planets made of denser material like iron. Venus is known as Earth's twin due to its similar size and density. They are fraternal twins, though, so don't think we could live there.
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Mars is covered in rock, dirt and dust made from iron oxide, which is why it appears red. It also has thick ice sheets, which gives signs that at one point along its 4.5 billion years in the solar system there was water on this planet.
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A new podcast, Astronomy 141, Life in the Universe, is availablefor those interested in continuing an exploration of topics inmodern astronomy.Richard Pogge
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Are there planets around other stars? Are there Earth-like planetsaround other stars? Do any of those harbor life? Intelligent life?We'd like to know the answers to all of these questions, and in recentyears we've made great progress towards at least answering the first. To date, more than 200 planets have been found around other stars, most in the…
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What is a planet? Is Pluto a planet? This lecture traces the debate onthe nature of what it means to be a planet by taking an historical approach, looking at how the question has arisen with the discovery of the asteroids andlater Pluto and the Kuiper Belt. Many of the issued raised at the 2006IAU General Assembly meeting were raised two centuries …
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Comets are occasional visitors from the icy reaches of the outer SolarSystem. This lecture discusses the orbits, structure, and properties ofcomets, and introduces the "dirty snowball" model of a comet nucleus.The end of class was a demo where I created a model of a comet nucleusfrom common household and office materials. Imagine a twistedcombinati…
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Beyond the orbit of Neptune is the realm of the icy worlds, ranging insize from Triton, the giant moon of Neptune, and the dwarf planets Plutoand Eris, all the way down to the nuclei of comets. This lecturediscussed the icy bodies of the Trans-Neptunian regions of the SolarSystem, discussing the basic properties of Triton (the best studied suchobje…
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Asteroids are the leftover rocky materials from the formation of theSolar System that reside mainly in a broad belt between the orbits ofMars and Jupiter. Meteoroids are fragments of asteroids or bits ofdebris from passing comets that occasionally pass through our atmosphereas meteors, and even more rarely survive the fiery passage to reach thegrou…
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All Jovian planets have rings. We are most familiar with the bright,spectacular rings of Saturn, but the other Jovian planets have ringssystems around them. This lecture describes the different ring systemsand their properties, and discusses their origin, formation, and thephysics - resonances and shepherd moons - that govern their evolution.Record…
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Saturn is attended by a system of 56 known moons and bright, beautifulrings. The Moon system is the focus of our attention today. Saturn hasone giant moon, Titan, which is the 2nd largest moon in the SolarSystem, and the only one with a heavy atmosphere. On Titan, theatmosphere is mostly nitrogen and methane, but the temperature andpressure are suc…
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Jupiter is surrounded by a solar system in miniature of 63 known moons.Most (59) are tiny, irregular bodies that are a combination of capturedasteroids and comets. The 4 largest are the giant Galilean Moons: Io,Europa, Ganymede, and Callisto. Each is a fascinating world of its own,with a unique history and properties: volcanically active Io, icy Eu…
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Uranus and Neptune are the smallest and outermost of the 4 Jovianplanets. While superficially similar to Jupiter and Saturn, there aresubstantial differences. Uranus and Neptune have smaller rocky coressurrounded by deep, slushy ice mantles and relatively thinner hydrogenatmospheres, quite different from the massive cores and deep metallichydrogen …
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Jupiter and Saturn are the largest planets in the Solar System,and the prototype of the Jovian Gas Giant planets. This lecturefocusses on the planets themselves, looking at their composition,atmospheres, and internal structures. We will leave discussionof their fascinating systems of rings and moons for next week.Recorded 2006 Nov 15 in 100 Stillma…
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Having completed our tour of the terrestrial planets, we want to stepback and compare their properties. In particular, we want to look atthe processes that drive the evolution of their surfaces, theirinteriors, and their atmospheres. Recorded 2006 Nov 14 in 100 StillmanHall on the Columbus campus of The Ohio State University.…
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Mars, fourth planet from the Sun, is a cold desert planet with a thin,dry carbon-dioxide atmosphere. The geology of Mars, however, showssigns of an active past, with hot-spot volcanism, and tantalizing signsof ancient water flows. While a cold, dead desert planet today, Mars'past may have been warmer and wetter, with liquid water during the firstth…
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Venus, the second planet from the Sun, is perpetually veiled behindopaque clouds of sulfuric acid droplets atop a hot, heavy, mostly carbondioxide atmosphere. In size and apparent composition, however, it is anear twin-sister of the Earth. Why is it do different? This lecturereviews the basic properties of Venus, and examines the similarties anddif…
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Mercury is the innermost of the planets, a hot, dead world that has beenheavily battered by impacts. This lecture reviews the basic propertiesof Mercury, particularly its surface and interior. Recorded 2006 Nov 8in 100 Stillman Hall on the Columbus campus of The Ohio StateUniversity.Richard Pogge
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How did the Solar System form? This lecture examines the clues in thepresent-day dynamics (orbital and rotation motions) of the planets andplanetary composition to the formation of the solar system. We willthen describe the accretion model, where grains condense out of theprimordial solar nebula, grains aggregate by collisions intoplanetesimals, th…
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We start our exploration of the Solar System with a quick overview ofits constituent parts. I will take as my starting point that Pluto,Eris, and Ceres are Dwarf Planets according to the 2006 IAU decision.This decision, which is not without controversy, will be one of thequestions we will revisit during these lectures. Recorded 2006 Nov 6 in100 Sti…
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What is the structure of the Moon, and what physical processes haveshaped its surface? In this lecture we turn to our nearest celestialneighbor, the Moon, to see a world quite different than the dynamicEarth. We will discuss the surface features of the Moon (the Mariaand cratered highlands), see how crater density tells us the relativeages of terra…
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What is the composition and structure of the Earth's atmosphere? Why isit as warm as it is, and how did it form? These are the questions fortoday's lecture. The Earth's atmosphere is a complex, dynamic, andevolving system. We will discuss the composition and structure of theatomsphere, the nature of the different thermal layers, the GreenhouseEffec…
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What is the structure of the Earth? What better place to begin ourexploration of the Solar System then with the best-studied planet, theEarth. This lecture discusses the interior structure of the Earth,introducing the idea of differentiation, how geologists map the interiorof the Earth using seismic waves, and the origin of the Earth's magneticfiel…
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How old is the Earth? This lecture reviews the idea of cyclic andlinear time, since how you view time determines whether the question ofthe age of the Earth is even meaningful. We then review various wayspeople have estimated the age of the Earth, starting with historicalages that equate human history with the history of the Earth proper, andthen s…
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Telescopes, equipped with advanced electronic cameras and spectrographs,are the primary tools of the astronomer. This lecture reviews the typesof telescopes and observatory sites, and discusses radio and spacetelescopes, and reviews briefy the observing facilities at Ohio State.Recorded 2006 Oct 27 in 100 Stillman Hall on the Columbus campus of The…
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Why does each chemical element have its own unique spectral-linesignature? How do emission- and absorption-line spectra work? Thislecture is the second part of a two-part exploration of the interactionbetween matter and light, today discussing how the unique spectral-linesignatures of atoms are a reflection of their internal electronenergy-level st…
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How do matter and light interact? This lecture is the first of atwo-part lecture on the physical basis of spectroscopy. Today we willdiscuss the Kelvin Absolute Temperature scale, which provides a measureof the internal energy content of matter, and Kirchoff's empirical Lawsof Spectroscopy, along with the Stefan-Boltzmann Law and the Wein Law todes…
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What is Matter? This lecture reviews the nature of matter fromsubatomic to atomic scales, and introduces the ideas of atomicstructure, atomic number (number of protons), the elements, isotopes,radioactivity, and half-life. We conclude with a brief overview of thefour fundamental forces of nature: gravitation, electromatgnetic, andthe strong and wea…
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What is Light? This lecture reviews the basic properties of light,introducing the inverse square law of brightness and the Doppler Effect.Recorded 2006 Oct 23 in 100 Stillman Hall on the Columbus campus of TheOhio State University.Richard Pogge
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How do we prove physically that the Earth rotates on its axis andrevolves around the Sun? Newtonian physics was so compelling that itwas mostly accepted before there were ironclad physical demonstrationsof the Earth's daily rotation about its axis and annual revolution(orbit) around the Sun. This lecture reviews three of thesedemonstrations: the Co…
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Why are there two high tides a day? This lecture examines another ofthe consequences of gravity, the twice-daily tides raised on the Earthby the Moon. Tides are a consequence of differences in the gravityforce of the Moon from one side to the other of the Earth (stronger onthe side nearest the Moon, weaker on the side farthest from the Moon).The Su…
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Why do Kepler's Laws work? This lecture discusses how Newton appliedhis Three Laws of Motion and the Law of Universal Gravitation to theproblem of orbits. Newton generalized Kepler's laws to apply to any twomassive bodies orbiting around their common center of mass. We discussthese new, generalized laws of orbital motion, introducing the familiesof…
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What is Gravity? This lecture reviews the law of falling bodies firstdescribed by Galileo, and then Newton's explanation in terms of his Lawof Universal Gravitation. Gravity is a mutually attractive force thatacts between any two massive bodies. Its strength is proportional tothe product of the two masses, and inversely proportional to the squareof…
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The work of Copernicus, Kepler, and Galileo all contributed to a new wayof looking at the motions in the heavens, but did not explain why theymove that way. Enter Isaac Newton, who within a few years swept awaythe last vestiges of the Aristotelian view of the world and replacedwith a new, powerfully predictive synthesis, in which all motions, inthe…
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Tycho did as much as could be done with the naked eye, a new technologywas required to extend our vision, the telescope. This lectureintroduces Galileo Galilei, the contemporary of Kepler who was in manyways the first modern astronomer, and his discoveries with thetelescope. These observations were to electify Europe in the early 17thcentury, and b…
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In the generation following Copernicus, the question of planetarymotions was picked up by two remarkable astronomers: Tycho Brahe, thebrilliant Danish astronomer whose precise measurements of the planetsrepresented the highest expression of pre-telescope astronomy, andJohannes Kepler, the brilliant and tormented German mathematician whoused Tycho's…
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In 1543, Nicolaus Copernicus re-introduced the Heliocentric idea ofAristarchus of Samos in an attempt to purge Ptolemy's geocentric systemof the un-Aristotelian idea of the Equant. His goal was to derive amodel that, in his words, pleased the mind as well as preservedappearances. What he started, without intending, was a profoundrevolution in thoug…
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What are the origins of the Geocentric and Heliocentric modelsput foward to explain planetary motion? This lecture begins a newunit that will chart the rise of our modern view of the solar system byreviewing the highly influential work by Greek and Roman philosopherswho elaborated the first geocentric and heliocentric models ofthe Solar System. We …
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How do the planets move across the sky? This lecture will reviewplanetary motions, specifically the apparent motions of the fiveclassical planets (Mercury, Venus, Mars, Jupiter, and Saturn) as seenfrom the Earth. We will discuss the classical division of the naked-eye planets into inferior (Mercury and Venus) and superior (Mars, Jupiter, and Saturn…
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Why are there leap years? This lecture explores the astronomicalorigins of the calendar. We will discuss lunar and solar calendars andtheir hybrids in history and tradition (for example, the Islamic LunarCalendar and the Jewish Luni-Solar Calendar), and the Julian andGregorian Calendar reforms. Recorded 2006 Oct 4 in 100 Stillman Hall onthe Columbu…
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What time is it? This lecture is the first part of a two-partexploration of the astronomical origins of our time-keeping and calendarconventions. Today we will discuss the division of the year intoseasons by the motions of the Sun, and the oft-forgotten origins of ourholidays in in the solar Quarter and Cross-Quarter days, the division ofthe year i…
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