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Physics 320: Astronomy and Astrophysics – Lecture I

Physics 320: Astronomy and Astrophysics – Lecture I. Carsten Denker Physics Department Center for Solar–Terrestrial Research. Introduction. History of Solar Physics Prehistoric era Ancient Greek Paradigm shift in planetary models “Modern” Solar Physics Why bother … ?

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Physics 320: Astronomy and Astrophysics – Lecture I

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  1. Physics 320: Astronomy and Astrophysics – Lecture I Carsten Denker Physics Department Center for Solar–Terrestrial Research

  2. Introduction • History of Solar Physics • Prehistoric era • Ancient Greek • Paradigm shift in planetary models • “Modern” Solar Physics • Why bother … ? • Most of the material has been stolen from theHAO Education Pagesby Paul Charbonneau (NCAR, HAO) NJIT Center for Solar–Terrestrial Research

  3. Stonehenge (3000 – 1600 BC) NJIT Center for Solar–Terrestrial Research

  4. Solar Observations BC • 3 May 1375 BC or 5 March 1223 BC: eclipse record on clay tablet uncovered in the ancient city of Ugarit, Syria • 8th century BC: Babylonians were keeping a systematic record of solar eclipses, predictions based on numerological rules • 800 BC: Oldest record of a sunspot observations are found in the Book of Changes, China • 250 BC: Measurement of the distance to the Sun by Aristarchus of Samos (ca. 310-230 BC). NJIT Center for Solar–Terrestrial Research

  5. Physical (geocentric) model of the cosmos by Aristotle (384 – 322 BC) Mathematical model of planetary motion by Ptolemy (100 – 170), terrestrial/celestial sphere, basic elements: earth, water air, and fire/quintessence Ancient Greek The Aristotelian cosmos. The Earth sits motionless at the center of the universe, and the outer sphere, the Primum Mobile, is assumed to undergo a full revolution in 24 hours. NJIT Center for Solar–Terrestrial Research

  6. Report of solar eclipse observations by the Byzantine historian Leo Diaconus (950 – 994) on December 22nd, 968 from Constantinople (now Istanbul, Turkey). Possible eclipse record on oracle bones dating from the Shang dynasty in China (1766 – 1123 BC) Chronicle of Novgorod describes a prominence during the May 1st, 1185 solar eclipse: "In the evening there as an eclipse of the sun. It was getting very gloomy and stars were seen ... The sun became similar in appearance to the moon and from its horns came out somewhat like live embers." Early Observations of the Corona Annales Sangallenses: "...at the fourth hour of the day ... darkness covered the earth and all the brightest stars shone forth. And is was possible to see the disk of the Sun, dull and unlit, and a dim and feeble glow like a narrow band shining in a circle around the edge of the disk". NJIT Center for Solar–Terrestrial Research

  7. Sunspot Observations • Official records of the Chinese imperial courts starting in 165 BC • Theophrastus (374 –287 BC) including details of umbra and penumbra • Aristotelian views concerning the incorruptibility of the heavens meant that sunspots were "physically impossible", sightings were ignored or ascribed to transit of Mercury or Venus across the solar disk "... from morning to evening, appeared something like two black circles within the disk of the Sun, the one in the upper part being bigger, the other in the lower part smaller. As shown on the drawing." From the Chronicles of John of Worcester: one of the first surviving sunspot drawing from a sighting on December 8th, 1128. NJIT Center for Solar–Terrestrial Research

  8. Nicholas Copernicus (1473–1543) • De Revolutionibus Orbium Coelestum in 1543 • Heliocentric planetary model:The Sun is at the center of all planetary motions, except for the Moon which orbits Earth. Under this arrangement the orbital speed of planets decreases steadily outwards, and the outer sphere of fixed stars is truly motionless. In Copernicus' original model the Earth has three motions: a daily 24-hr axial rotation, a yearly orbital motion about the Sun, and a third motion, somewhat related to precession which Copernicus thought necessary to properly reproduce ancient observations. NJIT Center for Solar–Terrestrial Research

  9. Collection of 20 years of accurate planetary positions by Tycho Brahe (1546 – 1601) Johannes Kepler (1571 – 1630) 1609: Astronomia Nova 1619: Harmonice Mundi 1627: Rudolphine Tables Orbital Paths of Planets NJIT Center for Solar–Terrestrial Research

  10. Galileo Galilei (1564 – 1642) First telescopic observations of the Sun! NJIT Center for Solar–Terrestrial Research

  11. Sun as a Star – Maunder Minimum • René Descartes (1596 – 1650) describes the Sun as a star in his 1644 book Principia Philosophiae • Maunder minimum 1645 –1715: sunspots vanish even though a systematic solar observing program was underway under the direction of Jean Dominique Cassini (1625 – 1712) at the newly founded Observatoire de Paris NJIT Center for Solar–Terrestrial Research

  12. Isaac Newton (1642 – 1727) • 1686: Principia Mathematica, universal law of gravitation • Stable planetary orbits result from a balance between centripetal and gravitational acceleration • Sun–to–Earth mass ratio (MEarth/MSun= 28700 instead of 332945), wrong value for solar parallax, better estimate in later edition of the Principia (within factor of two) NJIT Center for Solar–Terrestrial Research

  13. Infrared Radiation • In 1800, William Herschel (1738 –1822) extended Newton's experiment of separating chromatic light components via refraction through a glass prism by demonstrating that invisible "rays" existed beyond the red end of the solar spectrum. NJIT Center for Solar–Terrestrial Research

  14. Spectroscopy • The English chemist and physicist William Hyde Wollaston (1766 – 1828) noticed dark lines in the spectrum of the Sun while investigating the refractive properties of various transparent substances • Joseph von Fraunhofer (1787-1826) independently rediscovered the “dark lines” in the solar spectrum NJIT Center for Solar–Terrestrial Research

  15. Chemical Composition of the Sun Reproduction of part of the map of the solar spectrum published in 1863 by Kirchhoff, showing the identification of a large number of spectral lines with various chemical elements. Note numerous clear matches for Iron (Fe). NJIT Center for Solar–Terrestrial Research

  16. Heinrich Schwabe (1789 –1875) Sunspot Cycle NJIT Center for Solar–Terrestrial Research

  17. The First Solar Photograph 1845 The first successful daguerrotype of the Sun, reproduced below, was made on April 2nd, 1845 by the French physicists Louis Fizeau (1819-1896) and Léon Foucault (1819-1868). The exposure was 1/60 of a second. This image shows the umbra/penumbra structure of sunspots, as well as limb darkening. NJIT Center for Solar–Terrestrial Research

  18. Sunspot Numbers • Statistics of sunspot number by Swiss astronomer Rudolf Wolf (1816-1893) • Relative sunspot number: r = k (f + 10 g), where g is the number of sunspots groups visible on the solar disk, f is the number of individual sunspots (including those distinguishable within groups), and k is a correction factor that varies from one observer to the next (with k = 1 for Wolf's own observations) Sunspot drawings by Johann Hieronymus Schroeter (1745 – 1816), an active solar observer between 1785 and 1795. Schroeter's sunspot drawings were a primary source for Wolf's reconstruction of activity cycle number 4 (1785 –1798) NJIT Center for Solar–Terrestrial Research

  19. Differential Rotation • Richard C. Carrington (1826 – 1875) • Gustav Spörer (1822 –1895) Spörer's Law of sunspot migration. The thick lines shows the latitude] at which most sunspots are found (vertical axis, equator is at zero), as a function of time (horizontal axis). The dashed line is the Wolf sunspot number, showing the rise and fall of the solar cycle. NJIT Center for Solar–Terrestrial Research

  20. First Observation of a Solar Flare 1859 On September 1st, 1859, the astronomer R. C. Carrington was engaged in his daily monitoring of sunspots, when he noticed two rapidly brightening patches of light near the middle of a sunspot group he was studying. NJIT Center for Solar–Terrestrial Research

  21. First Observations of a Coronal Mass Ejection 1860 NJIT Center for Solar–Terrestrial Research

  22. George Ellery Hale (1868–1938) The Magnetic Nature of Sunspots 1908 The magnetically–induced Zeeman splitting in the spectrum of a sunspot. Reproduced from the 1919 paper by G.E. Hale, F. Ellerman, S.B. Nicholson, and A.H. Joy (in The Astrophysical Journal, vol. 49, pp. 153–178). NJIT Center for Solar–Terrestrial Research

  23. The Celestial Sphere • Greek Tradition  • Copernican Revolution  • Positions on the Celestial Sphere • Physics and Astronomy NJIT Center for Solar–Terrestrial Research

  24. Positions on the Celestial Sphere Earth precession period is 25,770 years. Reference Epoch 1950: m = 3.07327s yr –1 n = 20.0426’’ yr –1 NJIT Center for Solar–Terrestrial Research

  25. Law of sines: Law of cosines for sides: Law of cosines for angles: Spherical Geometry NJIT Center for Solar–Terrestrial Research

  26. v: transverse or tangential velocity vr: radial velocity Proper Motion NJIT Center for Solar–Terrestrial Research

  27. (inferior) (superior) Synodic and Sidereal Period NJIT Center for Solar–Terrestrial Research

  28. Retrograde Motion of Planets NJIT Center for Solar–Terrestrial Research

  29. NJIT Center for Solar–Terrestrial Research

  30. Zodiac NJIT Center for Solar–Terrestrial Research

  31. Physics and Astronomy • Astronomy = natural extension of human curiosity in its purest form • Paradigm shifts • Physical causes for observable phenomena • Astronomy + Physics = Astrophysics • Observations  analyze photons and particles • Tools: telescopes, post–focus instrumentation, and computers NJIT Center for Solar–Terrestrial Research

  32. Homework • Homework is due Wednesday September 10th, 2003 at the end of the lecture! • Homework assignment: Problems 1.5, 1.6, and 1.7 • Late homework receives only half the credit! • The homework is group homework (2–3 students)! • Homework should be handed in as a text document! NJIT Center for Solar–Terrestrial Research

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