physics320 lecture01

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)


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).


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.


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".


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."


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.


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


Galileo Galilei (1564 – 1642)

First telescopic observations of the Sun!


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


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)


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.


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


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).


Sunspot Cycle

Heinrich Schwabe

(1789 –1875)


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.


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)


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)


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.


First Observations of a Coronal Mass Ejection 1860


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)


The Celestial Sphere

Greek Tradition Copernican

Revolution Positions on the

Celestial SpherePhysics and

Astronomy


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.


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


Proper Motion

d v t

vdt

r rvd

dt r

v: transverse or tangential velocity

vr: radial velocity


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


Retrograde Motion of Planets


Zodiac


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


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!

physics320 lecture01

Technology

solar solar observations

njit center

solar disk

solar parallax

solar spectroscopy

solar stonehenge

solar spectrum

solar early observations