Lecture 2: Course Overview Introduction to the Solar System AST2003 Section 6218 - Spring 2012 Instructor: Professor Stanley F. Dermott Office: 216 Bryant Space Science Center Phone: 352 294 1864 email [email protected] Lecture time and place: Tuesdays (4th period: 10:40 am – 11:30 am) Thursdays (4th and 5th period) (10:40 am – 12:35 pm), FLG 210 Office hours: Tuesdays 11:45 – 12:45 pm, Thursdays 12:45 pm - 1:45 pm or by appointment Teacher Assistant: Dr Naibi Marinas (Help with Mastering Astronomy and Exam Reviews) Office: 312 Bryant Space Science Center Phone: 325 294 1848 Email: [email protected]!! Class Website: http://www.astro.ufl.edu/~marinas/astro/AST2003.html A bit about myself Russian Translation Worked with Carl Sagan while at Cornell Carl Sagan: Author and presenter of COSMOS Two papers in Nature Radar images of hydrocarbon lakes on Titan taken by Cassini spacecraft This movie, comprised of several detailed images taken by Cassini's radar instrument, shows bodies of liquid near Titan's north pole. Biggest Discovery! Published in Nature in 1994 © 1994 Nature Publishing Group © 1994 Nature Publishing Group © 1994 Nature Publishing Group Last sentence in the paper © 1994 Nature Publishing Group Structure in Debris Disks Structure in Debris DebrisDisks disks imply >km planetesimals around Debris disks imply >km main sequence stars, but planetesimals around also evidence for planets: main sequence stars, but •! inner regions are empty, also evidence for planets: probably cleared by planet formation •! inner regions are empty, probably cleared by •! disks are clumpy/ planet formation asymmetric, probably caused by unseen •! disks are clumpy/ equivalent of Neptune asymmetric, probably caused by unseen Planets are lower mass equivalent of Neptune and further out than those detected with other means Planets are lower mass and further out than those detected with other means OVERVIEW OF THE COURSE spring 2012 calendar This is a tentative schedule and it will change !! ! January 10 - Introduction and course Overview! 12 - course overview 17 - charting the heavens (chapter 1) 19 - charting the heavens!! (Chapter 1) 24 - the copernican revolution!!! (Chapter 2) 26 - the copernican revolution!!! (Chapter 2) 31 - radiation!!! (Chapter 3) February 02 - spectroscopy and telescopes!!! (Chapters 4 & 5) 07 - review exam 1 09 - exam 1 (Chapters 1-5) 1. Evolving perspectives - a historical prologue • The wandering planets move in a narrow track against the unchanging background stars, and some of these vagabonds can suddenly turn around, apparently moving in the opposite direction before continuing on their usual course. • The ancient Greeks noticed that the Earth always casts a curved shadow on the Moon during a lunar eclipse, demonstrating that our planet is a sphere. • For centuries, astronomers tried to describe the observed planetary motions using uniform, circular motions with the stationary Earth at the center and with the distant celestial sphere revolving about the Earth once a day. • Around 145 AD, Claudius Ptolemy devised an intricate system of uniform motion around small and large circles to model the motions of the Sun, Moon and planets around a stationary Earth; his model was used to predict their location in the sky for more than a thousand years. 1. Evolving perspectives - a historical prologue • The stars seem to be revolving around the Earth each night, but the Earth is • Theinstead wandering spinning planets beneath move the in stars. a narrow This trackrotation against also thecauses unchanging the Sun to move backgroundacross the sky stars, each and day. some of these vagabonds can suddenly turn around, apparently moving in the opposite direction before continuing on their usual • course.Mikolaj Kopernik, better known as Nicolaus Copernicus, argued in 1543 that the Earth is just one of several planets that are whirling endlessly about the Sun, • Theall movingancient inGreeks the same noticed direction that the but Earth at different always castsdistances a curved from shadow the Sun on and the with Moonspeeds during that decrease a lunar eclipse, with increasing demonstrating distance. that our planet is a sphere. •• ForAlmost centuries, four centuriesastronomers ago, tried Johannes to describe Kepler the used observed accurate planetary observations, motions usingobtained uniform, by Tycho circular Brahe, motions to conclude with the that stationary the planets Earth move at the in center ellipses, and or with ovals, thewith distant the Sun celestial at one sphere focus, revolving and to infer about a precise the Earth mathematical once a day. relation between the mean orbital distance and period of each planet. • Around 145 AD, Claudius Ptolemy devised an intricate system of uniform • motionMore distantaround planets small and take large longer circles to move to model once the around motions the of Sun the and Sun, they Moon move andwith planets slower around speeds; a theirstationary orbital Earth; periods his are model in proportion was used to to predict the cubes their of their locationdistances. in the sky for more than a thousand years. •• TheAstronomy stars seem is anto beinstrument-driven revolving around science the Earth in which each night, novel buttelescopes the Earth and is new insteadtechnology spinning enable beneath us to discoverthe stars. cosmic This rotation objects alsothat causesare otherwise the Sun invisibleto move and acrosshitherto the unknown. sky each day. •• MikolajMany major Kopernik, astronomical better known discoveries as Nicolaus have Copernicus,been unanticipated argued andin 1543 that theserendipitous, Earth is just made one of while several new planets telescopes that arewere whirling used to endlessly study other, about known the Sun, allcosmic moving objects; in the thesame earliest direction of these but ataccidental different discoveries distances from include the theSun four and largewith speedsmoons that of Jupiter, decrease the with planet increasing Uranus, distance. and the first known asteroid, Ceres, • Almost four centuries ago, Johannes Kepler used accurate observations, obtained by Tycho Brahe, to conclude that the planets move in ellipses, or ovals, with the Sun at one focus, and to infer a precise mathematical relation between the mean orbital distance and period of each planet. • More distant planets take longer to move once around the Sun and they move with slower speeds; their orbital periods are in proportion to the cubes of their distances. • Astronomy is an instrument-driven science in which novel telescopes and new technology enable us to discover cosmic objects that are otherwise invisible and hitherto unknown. • Many major astronomical discoveries have been unanticipated and serendipitous, made while new telescopes were used to study other, known cosmic objects; the earliest of these accidental discoveries include the four large moons of Jupiter, the planet Uranus, and the first known asteroid, Ceres, The Geocentric Paradigm Below is an image of the universe as conceived of by Aristotle and Ptolemy.! The earth is composed of four elements:! Earth, Water, Fire and Air.! It is in the center (notice the trees, mountains and water).! In this cosmology, the earth does not revolve around anything else or rotate around its own axis.! It is surrounded by ten concentric spheres made of a perfectly transparent substance known as "quintessence."! These spheres revolve around the earth, carrying the other celestial bodies.! As you can see, one is the sphere "of the Moon" ("Lunae"), two is Mercury ("Mercurii"), three is Venus ("Veneris"), four is the Sun ("Solis"), five is Mars ("Martis"), six is Jupiter ("Iovis"), seven is Saturn ("Saturni"), and spheres eight, nine and ten hold the "fixed stars" (so-called because they do not move relative to each other, unlike the planets, which move among the other stars).! (The symbols by the names of the planets are the traditional astrological symbols for them.! The symbols in spheres eight, nine and ten are for the twelve astrological constellations, Gemini, Ares, etc.)! Beyond the tenth sphere is, as the words in the periphery say in Latin, "The Kingdom of Heaven, the Abode of God and of the Elect."! This photograph shows the apparent movements of the planets against the background stars. Mars, Jupiter and Saturn appear to stop in their orbits, then reverse direction before continuing on – a phenomenon called retrograde motion by modern astronomers. Ptolemy: Epicycles - “Wheels within wheels” To explain the occasional retrograde loops in the apparent motions of Mars, Jupiter and Saturn, astronomers in ancient times imagined that each planet travels with uniform speed around a small circle, known as the epicycle. The epicycle’s center moves uniformly on a larger circle, the deferent. A similar scheme was used by Ptolemy (fl. AD 150) to explain the wayward motions of the planets in his Almagest. In the Ptolemaic system, the Earth was displaced from the center of the large circle, and each planet traveled with uniform motion with respect to another imaginary point, the equant, appearing to move with variable speed when viewed from the Earth. Mikolaj Kopernik, better known as Nicolaus Copernicus, argued in 1543 that the Earth is just one of several planets that are whirling endlessly about the Sun, all moving in the same direction but at different distances from the Sun and with speeds that decrease with increasing distance. Almost four centuries ago, Johannes Kepler used accurate observations, obtained by Tycho Brahe,