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NJIT
Physics 320: Astronomy and Astrophysics – Lecture I
Carsten Denker
Physics DepartmentCenter for Solar–Terrestrial Research
NJIT Center for Solar–Terrestrial Research September 3, 2003
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 the HAO Education Pages by Paul Charbonneau (NCAR, HAO)
September 3, 2003NJIT Center for Solar–Terrestrial Research
Stonehenge (3000 – 1600 BC)
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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).
September 3, 2003NJIT Center for Solar–Terrestrial Research
Ancient Greek 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
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.
September 3, 2003NJIT Center for Solar–Terrestrial Research
Early Observations of the Corona
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."
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".
September 3, 2003NJIT Center for Solar–Terrestrial Research
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 the Chronicles of John of Worcester: one of the first surviving sunspot drawing from a sighting on December 8th, 1128.
"... 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."
September 3, 2003NJIT Center for Solar–Terrestrial Research
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.
September 3, 2003NJIT Center for Solar–Terrestrial Research
Orbital Paths of Planets
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
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Galileo Galilei (1564 – 1642)
First telescopic observations of the Sun!
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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
September 3, 2003NJIT Center for Solar–Terrestrial Research
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)
September 3, 2003NJIT Center for Solar–Terrestrial Research
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.
September 3, 2003NJIT Center for Solar–Terrestrial Research
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
September 3, 2003NJIT Center for Solar–Terrestrial Research
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).
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Sunspot Cycle
Heinrich Schwabe
(1789 –1875)
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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.
September 3, 2003NJIT Center for Solar–Terrestrial Research
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)
September 3, 2003NJIT Center for Solar–Terrestrial Research
Differential Rotation
Richard C. Carrington (1826 – 1875)
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.
Gustav Spörer (1822 –1895)
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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.
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First Observations of a Coronal Mass Ejection 1860
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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).
George Ellery Hale (1868–1938)
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The Celestial Sphere
Greek Tradition Copernican
Revolution Positions on the
Celestial SpherePhysics and
Astronomy
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Positions on the Celestial Sphere
sin tan
cos
m n N
n N
Reference Epoch 1950:
m = 3.07327s yr –1
n = 20.0426’’ yr –1
Earth precession period is 25,770 years.
September 3, 2003NJIT Center for Solar–Terrestrial Research
Spherical Geometry
sin sin sin
sin sin sin
a b c
A B C
Law of sines:
Law of cosines for sides:
cos cos cos sin sin cosb c b c A
Law of cosines for angles:
cos cos cos sin sin cosA B C B C a
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Proper Motion
d v t
vdt
r rvd
dt r
v: transverse or tangential velocity
vr: radial velocity
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Synodic and Sidereal Period
1/ 1/1/
1/ 1/Earth
Earth
P PS
P P
(inferior)
(superior)
Planet Sidereal Orbital Period [yr]
Mercury
0.2408
Venus 0.6152
Earth 1.0000
Mars 1.8809
Jupiter 11.862
Saturn 29.458
Uranus 84.014
Neptune
164.79
Pluto 248.54
September 3, 2003NJIT Center for Solar–Terrestrial Research
Retrograde Motion of Planets
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Zodiac
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Physics and Astronomy
Astronomy = natural extension of human curiosity in its purest form
Paradigm shiftsPhysical causes for observable
phenomenaAstronomy + Physics = AstrophysicsObservations analyze photons and
particlesTools: telescopes, post–focus
instrumentation, and computers
September 3, 2003NJIT Center for Solar–Terrestrial Research
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!