INTRODUCTION

 

 

TO

 

 

ASTRONOMY

 

 

 

 

 

 

 

 

 

INSTRUCTOR: Dr. MAHMOUD KHALILI

 

 

 

 

 

 

TEXT BOOK: Astronomy

 

A Beginner Guide to the Universe, Second Edition:

 By

 Chaisson & Mc Millan

 

 

 

 


                1: Project                        10 Point

 

                2: Quiz                             20 Point

 

Grade     3: Midterm Exam           35 Point

 

                4: Final Exam                 35 Point

 

                5: Attendance                 10 Point

 


                      Total          110 Point

 

 

Final Letter Grade:

 

                 Point                      Grade

                85-110                        A

                75- 84                         B

                60- 74                         C

                50  59                         D

                Less 50                       F

 

 

 

 

 

 

 

 

 

 

 


                      1: Introduction

 

                      2: Biography of Person

 

   Project          3: Scientific Contribution

                              (Any Discovery, Invention, Development.   )

 

                      4: Conclusion

 

                      5: Reference

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


OBJECTIVE OF PROLOGUE

 

 

1: System of Measurement

 

2: Scientific Notation

 

3: Concept of the Celestial Sphere

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

System of Measurement

 


Quantity                SI*                  C g S                 British System

 


Length ( L )               meter ( m )     centimeter (cm)             foot ( ft )

 


Mass( M )          Kilogram ( Kg )         gram ( gr )             slug

 


time ( t )                     second                   second                   second

 


Weight ( W )         Newton ( N )          dyn                     pound ( Ib )

 


Area ( A )              square meter square centimeter     square foot

                                  ( m2 )                      ( cm2 )                ( ft2 )

 


Volume( V )           cubic meter        cubic centimeter          cubic foot

                                  (m3 )                       (cm3 )                     (ft3 )

 


Speed( v )                  ( m / s )               ( cm / s )             ( ft / s )

 


Acceleration(a)     ( m / s2 )                 ( cm / s2 )                   ( ft / s2 )

 


Force( F )              Newton(N)                dyn                 pound( Ib )

 

 

 


SI* : System International( Metric System)

 

Conversion Factors:

 

1 m = 100 cm                                       1 mile = 1.609 Km

1 m = 3.28 ft                                        1 mile = 5280 ft

1 Kilometer = 1000 meter                       1 ft = 0.3.5 m

1 Kg 1000 gr = 2.2 Ib                              1 Ib = 0.455 Kg = 455 gr

1 Angstrom ( A0 ) = 10-10 m                 1 ft = 12 inch

1 nanometer ( nm ) = 10-9 m                1 inch = 2.54 cm

1 micron ( µm ) = 10-6 m

 

 

 

 

 

 

 

SCIENTIFIC NOTATION:

 

 

                 0.1  =  1 x 10-1                                                  1  =  1 x 100

 

                0.01  =  1 x 10-2                                               10  =  1 x 101 

 

               0.001  =  1 x 10-3                                            100  =  1 x 102

 

             0.0001  =  1 x 10-4                                           1,000  =  1 x 103

 

           0.00001  =  1 x 10-5                                         1,0000  =  1 x 104

 

         0.000001  =  1 x 10-6                                    1,000,000  =  1 x 106

                                                                            (million)

            0.0231  =  2.31 x 10-2                          1,000,000,000  =  1 x 109

                                                                               (billion)

 

 0.00000936815  =  9.37 x 10-6                 1000,000,000,000  =  1 x 1012

                                                                            (trillion)

 

                                                                                    6400  =  6.40 x 103

 

                                                                            2453700  =  2.45 x 106

 

 

 

 

 

 

 

 

 

ASTRONOMY: The scientific study of the universe beyond the Earth, especially the observation, calculation, and theoretical interpretation of the positions, dimensions, distribution, motion, composition, and evolution of celestial bodies and phenomena.

UNIVERSE: The totality of all space, time, matter and energy.

EARTH: Earth is an ordinary rocky planet orbiting an average star called Sun, one star near the edge of huge collection of stars called the Milky Way Galaxy.

     The age of Earth is about five to six billion years ( 5 x109 years)

 

SPEED OF LIGHT : 300,000 kilometers per second

                                          ( 186,000 miles per second)

LIGHT YEAR: The distance light travels in a year, at the rate of 300,000 kilometers per second; one light-year is equivalent to 9.46 x 1012 kilometers or 5.88x1012 miles.(About 6 trillion miles).

CONSTELLATIONS. A human grouping of stars in the night sky into a recognizable patterns are called constellations, from Latin words meaning together and stars. Today 88 constellations are recognized by astronomers. Orion, Canis Minor, Canis Major, Capricorn, Libra are some of famous constellations.

In a clear night between sunset and sunrise, we can see about 3000 stars on sky.

 

CELESTIAL SPHERE: An imaginary sphere surrounding the Earth, to which all objects in the sky were once considered to be attached.

NORTH CELESTIAL POLE: The point where the Earth’s axis intersects the celestial sphere is known as the north celestial pole, and it is directly above the Earth’s North pole.

SOUTH CELESTIAL POLE: The point where the Earth’s axis intersects the southern celestial sphere is known as the south celestial pole, and it is directly above the Earth’s south pole.

CELESTIAL EQUATOR: The projection of the Earth’s equator onto the celestial sphere.

 

PARALLAX: The apparent motion of a relatively close object with respect to a more distant background as the location of the observer changes. The amount of parallax is inversely proportional to the object distance.

 

                                                                              A

 


                                                                        a

 

AH = Distance to the object

 

BC = Base ( Diameter of Object)

a = Angular Diameter

 

 

                                                      B                    H                    C

 

 


               Diameter of object                   Angular Diameter( In degree)

               2 p x Distance                                                360

 

 

 

                                                                            BC                    Base

 PARALLAX (a Radian ) = tg ( a Degree ) =   ---------    =   --------------

                                                                            AB                  Distance

 

CONVERSION BETWEEN DEGREE AND RADIAN

 

 

 


              D                 R                                                    360 Degree

                         =                                                               or

            360               2 p                                                    2 p Radian

 

             Where  p = 3.14

              1o  = 60’ =  3600’’               1’ = 60’’

 

 

 

 

 

 

 

OBJECTIVE OF CHAPTER ONE

 

 

1: Account for the apparent motions of the Sun, Moon, and stars in terms of the actual motions of Earth and the Moon.

2: How the relative motions of Earth, the Sun, and the Moon lead to eclipses.

3: how the observed motions of the planets led to our modern view of a Sun-centered solar system.

4: Contributions of Galileo and Kepler to the development of our understanding of the solar system.

5: Kepler's laws of planetary motion.

6: Newton's laws of motion and his law of universal gravitation.

 

 

 

 

 

 

SOLAR DAY: The time from one sunrise to the next is called a solar day.

SIDEREAL DAY: The time between successive rising of any given star is called a Sidereal day. Because of Earth’s revolution around the sun, the solar day is a 3.9 minutes longer than the Sidereal Day.

ECLIPTIC : The Sun’s yearly path around the celestial sphere or, equivalently, the plane of Earth's orbit around the Sun is called the ecliptic.

ZODIAC: The twelve constellations lying along the ecliptic are collectively called the zodiac

SEASONS : Because Earth’s axis is inclined to the ecliptic plane (23.5o ) we experience seasons, depending on which hemisphere ( northern or southern ) happened to be ‘tipped” toward the Sun.

 

 

 

 

 

 

 

THE SUN AND THE SEASONS

People have always watched the sun for signs of the passing seasons. Those living in the Northern Hemisphere learned early that the noon sun is highest in the sky about June 22 and lowest about December 22. These positions are called the solstices.

SUMMER SOLSTICE: The Sun is the highest in the sky, and the length of the day is greatest.

WINTER SOLSTICE: The Sun is the lowest in the sky, and the length of the day is shortest.

VERNAL EQUINOXES: The date on which the sun crosses the celestial equator moving northward, occurring on or near March 21.

AUTUMNAL EQUINOXES: The date on which the sun crosses the celestial equator moving southward, occurring on or near September 22.

 

 

 

APPARENT CHANGES OF SUN’S POSITION:

   Two facts account for the apparent changes in the sun's position. First, the Earth revolves around the sun once during the year while rotating daily on its own axis. Second, the Earth's axis is tilted about 23 1/2 degrees from the vertical. Thus in June the Northern Hemisphere is tipped slightly toward the sun, and the Southern Hemisphere slightly away from the sun. In December the opposite is true. In March and September both hemispheres are equally exposed to the sun.

TROPICAL YEAR: The time interval between one vernal equinoxes and the next is one tropical year .

SIDEREAL YEAR: The time required for the same zodiac constellations to reappear at the same location in the sky, as viewed from a given point on Earth, is one sidereal year.

 

 

 

 

 

PRECESSION: The slow change in the direction of the axis of a spinning object, caused by some external force.

 

EARTH PRECESSION: In addition to its rotation about its axis and its revolution around the Sun, Earth undergoes a motion called precession , where the influence of the Moon causes Earth's axis to wobble slightly. As a result, the particular constellations that happen to be visible on any given night change slowly over the course of many years.

 

 

 

 

 

 

 

 

 

 

 

 

NOTE: It takes 365 days the Earth orbits once the sun, and 24 hours to orbit around its axis.

 

 

 

Day                           Angle

 

365                            360

 

  1                                 x = 360/365 = 0.9860 

 

 

Hours                  Angle

 

24                          360                    24 x 0.986

 

Y                         0.986     

 

 

               24 x 0.986

  Y = -------------------- =  0.0657 h = 3.94 minutes

                   360

 

 

 

 

 

THE MOTION OF THE MOON

 

The Moon our nearest neighbor in space. It emits no light of its own. It shines by reflected sunlight.

 

LUNAR PHASE: The appearance of the Moon at different points along its orbit is called LUNAR PHASE.

 

FULL MOON: At full Moon the entire illuminated side can be seen.

 

QUARTER MOON: At quarter Moon only the half  illuminated side can be seen.

 

NEW MOON: At new Moon illuminated side points away Earth, and the Moon is invisible from Earth.

 

 

 

 

 

SYNODIC MONTH: Time required for the Moon to complete a full cycle of its phases is called synodic month.( 29.5 days)

 

SIDEREAL MONTH: Time required for the Moon to complete one trip around the celestial sphere is called sidereal month.( 27.3 days)

 

ASTRONOMICAL ALIGNMENTS

ECLIPSE: . The eclipse is named for the object that is being eclipsed, or obscured. eclipse have long been a source of mystery and spectacle. These events were viewed with fear and dread in the past and, even today, still thrill.

LUNAR ECLIPSE: A celestial event during which the Moon passes through the shadow of the Earth, temporarily darkening its surface. The eclipse may be total, if the entire Moon is temporarily darkened, or partial, if only a portion of the Moon’s surface is affected.

 

 

 

 

SOLAR ECLIPSE: A celestial event during which the Moon passes directly between the Earth and the Sun, temporarily blocking the Sun’s light.

 

UMBRA: The entire Sun is obscured, and the solar eclipse is

     total.

 

PENUMBRA: The portion of  Sun is obscured, and the partial solar eclipse can be seen.

 

 

 

 

 

 

 

 

 

 

 

 


                           I: Observation of the problem

                           II: Data and information

SCIENTIFIC     III: Theory

   METHOD       IV: Test and experiment

                           V: Scientific law

 

 

 

 

 

 

 

 

RETROGRADE MOTION: Backward or westward loop traced out by a planet with respect to the fixed stars is called retrograde motion. (Fig. 1.13)

 

PTOLEMAIC MODEL (PTOLEMY THEORY): A solar system model developed by the 2nd century astronomer and mathematician, Claudius Ptolemaeus (Ptolemy). Although his work has survived, almost nothing is known about his life. Ptolemy published his astronomical data in an encyclopedic volume known as 'Almagest'. It synthesized Greek astronomical knowledge and provided an expanded catalog of 1,022 stars. He proposed a geocentric, or Earth-centered, universe in which the planets and fixed stars were embedded in concentric crystalline spheres that revolved around the Earth. Outside the spheres of fixed stars were other spheres, ending with the "prime mover," which provided the motive power for all the spheres. The Ptolemaic system was the official dogma of Western Christendom until the 1500s, when it was replaced by Nicholas Copernicus's heliocentric, or Sun-centered, system. (Fig. 1.15)

 

 

 

 

 

ASTRONOMICAL UNIT (AU): The mean distance between the Earth and sun is called Astronomical Unit. Each AU is about 93,000,000 mil (149,600,000 km); used for expressing distances within the solar system

 

 

GEOCENTRIC THEORY(ARISTOTLE MODEL): The earliest model of the solar system. Base on this model the Earth is at the center of universe and all other heavenly bodies revolve(orbit) around it.

 

HELIOCENTRIC MODEL (COPERNICUS THEORY): A model of the solar system. Base on this model the Sun is at the center, Earth and other planet heavenly bodies revolve(orbit) around it.

 

 

 

 

 

 

KEPLER'S LAWS OF PLANETARY MOTION

 

Kepler's great work on planetary motion is summed up in three principles, which have become known as " Kepler's Laws "

 (1) The path of every planet in its motion about the sun forms an ellipse, with the sun at one focus.

 

(2) An imaginary line connecting the sun to any planet sweeps out equal areas of the ellipse in equal times. Thus the speed of a planet in its orbit varies, so the speed of the planet increases as it nears the sun and decreases as it recedes from the sun. (Fig. 1.22)

 

(3) The squares of a planet’s orbital period (P) is proportional to the cubes of the its orbital semi-major (a)

P2 (in years) = a3 (in astronomical units)

 

 

 

 

 

 

 

 


                     F                  O                        F/

 

 

 

 


                                             <             a            >

 

 

              <                            2a                           >

 

 

2a : major axis                                     2b : minor axis

a : semi-major axis                              2b : semi-minor axis

O : center of Ellipse                             e : Eccentricity

F and F : Focus                                   

FF’ = 2 Ö a2 - b2

 

 


e =  Ö a2 - b2 /a

 

 


x2 / a2  +  y2 / b2  = 1          (Equation of Ellipse)

 

 

NEWTON'S LAWS OF MOTION:

     (CLASSICAL MECHANIC):

1: Every body continues in a state of uniform motion in a straight line unless it is compelled to change that state by a force acting on it.

S F = 0     Þ  a =  0 ( a straight line motion with constant velocity)

d = v x t

F : Force                                              d: Distance

V: Velocity                                          T: time

 

2: When a force acts on a body of mass m, it produces in it an acceleration equal to the force divided by the mass.

m = F / a                        oR                F = m a

ACCELERATION: The rate of change of speed is called acceleration.

       V2 - V1

a = -----------

       t2 - t1

 

3: To every action, there is an equal and opposite reaction.

 

 

 

 

THE LAW oF UNIVERSAL GRAVITATION.

(NEWTON'S LAW oF GRAVITY)

 

                m2 x m1

Fg  =  G  ------------

                R2

 

 

 

 


  m1                                         R                                                                 m2

                    O1                                                                O2 

                         

 

 

 

 

 

G: 6.67 x 10-11 ( m3 /Kg . s2 )       Gravitational Constant

                                             Newton's Constant

 

 

 

 

 

 

 

THE CIRCULAR VELOCITY ( VC ):

The minimum velocity ( speed) required to sustain an object ( spacecraft ) in its orbit is called the circular velocity (VC). The circular velocity of an objet orbiting around another objet equal to:

VC =  

G: 6.67 x 10-11 ( m3 /Kg . s2 ) gravitational constant

 

 ESCAPE VELOCITY ( VEscape ):

( VEscape ) =  

 

 

 

NEWTON'S MODIFIED VERSION OF KEEPER’S LAWS

1: (1) The path of every planet in its motion about the sun forms an ellipse, with the common center of mass of the planet and the sun at one focus. (Fig. 2.5)

2: An imaginary line connecting the sun to any planet sweeps out equal areas of the ellipse in equal times. Thus the speed of a planet in its orbit varies, so the speed of the planet increases as it nears the sun and decreases as it recedes from the sun.

3:  The squares of a planet’s orbital period (P) is proportional to the cubes of the its orbital semi-major axis (a), and inversely proportional to total mass of two object.

 

                                            a3 (in astronomical units)

   P2 (in years) =

                                   total mass of two object ( in solar masses)

 

 

 

 

 

 

ASTRONOMICAL MEASUREMENTS

 

Length                                                        Time

meter (m )                                                   Second (s)

1 Angstrom ( Ao ) = 10-10 m                      1 minute = 60 s

1 nanometer ( nm ) = 10-9 m                     1 hour ( h ) = 3600 s

1 micron ( mm ) = 10-6 m                           1 day  = 86400 s

Earth radius( RO ) = 6378 Km                  1 year = 3.16 x 107 s

Solar radius( RO ) = 6.96 x 108 m

Astronomical Unit (AU) =  1.496 x 1011 m

1 Light year (L y) = 9.46 x 1015 m = 63200 AU

parsec ( pc ) = 3.09 x 1016 m = 3.26 Ly

 

Mass

Kilogram ( Kg )

Earth Mass (MO ) = 5.98 x 1024 Kg

Solar ( Sun) Mass (MO ) = 1.99 x 1030 Kg

 

 

 

 

 

 

 

 

 

 

OBJECTIVE OF CHAPTER TWO

 

1: The nature of electromagnetic radiation and way that radiation transfers energy and information through interstellar space.

2: Name the major regions of the electromagnetic spectrum.

3: How determine an object's temperature by observing the radiation it emits.

4: The characteristics of continuous, emission, and absorption spectra, and the conditions under which each is produced.

5: The basic components of the atom and our modern conception of its structure.

6: How electron transitions within atoms produce unique emission and absorption spectra.

 

 

 

 

 

 

 

LIGHT: Light is a particular type of radiation and travels through space in the form of a wave with speed of C = 3 x 108 m/s in vacuum (186,000 miles/s)

 

COMPONENT OF VISIBLE LIGHT: The small part of electromagnetic spectrum between 4000 Ao and 7000 Ao is visible light, which consists of Red, Orange Yellow, Green, Blue, and Violet. ( Fig. 2.7 )

 

 

 Infrared    Red   Orange  Yellow  Green  Blue  Violet   Ultraviolet

 

 

 


                7000 A0                                            4000 A0

 

 

FIGURE 2.7 Spectrum of visible light.

 

 

 

 

THE ELECTROMAGNETIC SPECTRUM

 

 

f(Hz)     103      105    107      109     1011     1013     1015     1017    1019   1021 

 


                  Radio frequency                          V                     X          Gamma

                FM(88-108 MHz)              Infrared  I    UV          Ray          Ray

             AM(540-1650 KHz)                            s

 


l(cm)         106      104     102      1    10-2         10-4       10-6       10-8      10-10 

 

 

 

 

FIGURE 2.8 Spectrum of electromagnetic radiation

 

 

OPACITY: A quantity that measures a materials ability to block electromagnetic radiation. Opacity is the opposite of transparency.

 

WAVE PROPERTIES

 

WAVELENGTH ( l ): The distance between two similar point of the wave which they have the same wave character. The unit of wavelength is meter ( m )

WAVE PERIOD ( P ): The time required for wave to complete one full cycle is called period. The unit of period is second ( s )

WAVE FREQUENCY ( f ): The number of full cycle in one second is called frequency. The unit of frequency is Hz (cycle/s )

AMPLITUDE: The maximum deviation of a wave above or below the zero point

 

 

 

RELATION BETWEEN WAVES CHARACTERISTICS

 

 

 


FREQUENCY = 1 / PERIOD

 

or

 

PERIOD = 1 / FREQUENCY

 

 

 

 


WAVELENGTH = WAVE VELOCITY X PERIOD

 

or

 

                                          WAVE VELOCITY

  WAVELENGTH  =  --------------------------------------

                                             FREQUENCY

 

 

 

 

 

TEMPERATURE AND ITS UNITS: A measure of the amount heat in an object, and an indication of the speed of the particles that comprise it. The unit for temperature are:

1: Fahrenheit ( F )

2: Celsius ( C )

3: Kelvin ( K ) or degree absolute

 

 

 


    F - 32          C

  ---------- = --------               and K  = C + 273

      180          100

 

 

 

 

 

 

 

 

 

 

 

 


Hydrogen          18,000,032                  10,000,000          10,000,273

fuses

 

 

 

 

 


Water boils                 212                       100                         373

 

 

 

                   180{                    100{          100{

 

 

 

Water freezes              32                            0                         273

 

 

 

 

 

 

 

 

All molecular boils   -459                      -273                              0

motion stops

 

 

 

 


                         F               C           K

 

 

 

 

 

 

 

BLACK-BODY SPECTRUM ( PLANK, CURVE ): The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. (Fig. 2.9)

 

 

 

 

 

 

 

FIGURE 2.9 The black-body, or plank, curve represents the distribution of the intensity of radiation emitted by any heated object.

 

 

 

 

WEIN’S LAW: The temperature is inversely proportional to the emitted wavelength of hot object

 

                                                   

                                                            1

 Wavelength of peak emission a   -------------------

                                                    temperature

 

or

 

lA                 TB

=  

lB                 TA

 

 

 

lA : wavelength of object A     TA : temperature of the object A

 

lB : wavelength of object B     TB : temperature of the object B

 

 

 

 

STEFAN’S LAW: The amount of energy radiated from a hot object is proportional to the temperature of the object.

 


ENERGY a [ TEMPERATURE]4

 

or

 

EA                 TA

=  

EB                  TB

 

 

 

EA : Energy of object A     TA : temperature of the object A

EB : Energy of object B     TB : temperature of the object B

 

DOPPLER EFFECT: The apparent change in wavelength (or frequency ) of sound or light caused by the motion of the source, observer or both.

1: Source stationary, detector moving toward

                                                                                                   v + vD

                                                                                       f/  =  f  ---------

                                                                                                        v

 

2: Source stationary, detector moving away

                                                                                                v   -   vD

                                                                                    f/  =  f  ------------

                                                                                                      v

3: Source moving toward, detector stationary

                                                                                                        v

                                                                                       f/ = f  ----------

                                                                                                  v  - vs

4: Source moving away, detector stationary

                                                                                                    v

                                                                                    f/ = f  ------------

                                                                                               v  + vs

5: Source and detector both moving

 

          v  +   vD

f/ = f  ------------

          v  +   vs

 

 

vs: Speed of detector                         vD : Speed of Source

f Source frequency                           f/ : apparent frequency

v: Speed of sound

 

 

 

 

SPECTROSCOPY: The study of the way in which atoms absorb and emit electromagnetic radiation.

 

SPECTROSCOPE: Instrument used to analyze the electromagnetic radiation spectrum.

 

DIFFERENT KIND OF SPECTRA:

 

1: CONTINUOUS SPECTRUM: Spectrum in which the radiation is distributed over all frequencies sUCH AS; black-body radiation emitted by a hot, dense object.

 

2: EMISSION LINE SPECTRUM: Bright line in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency. A heated gas in a glass container produces emission lines in its spectrum

 

3: ABSORPTION LINE SPECTRUM: Dark line in an otherwise continuous bright spectrum, where light within one narrow frequency range has been removed.

 

 

 

 

(a)        Violet   Blue Green  Yellow   Orange Red

 

 

 

 

 

 

 

 

 

 

 

 


(b )

 

 

 

 

 

 


(c )

 

 

 

 

 

 

 

Fig 2.3: Three Kind of Spectra: (a) Continuous; (b) Bright Line; (c) Dark Line.

 

 

 

 

 

 

 

KIRCHHOF’S LAWS: The relation between the three type of spectra: continuous, emission line, and absorption line.

 

1. A luminous solid or liquid, or a sufficiently dense gas, emits light of all wavelengths and so produces a continuous spectrum of radiation

 

2. A low-density hot gas emits light whose spectrum consists of a series of bright emission lines. These lines are characteristic of the chemical composition of the gas.

 

3. A low-density cool gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place, superimposed on the continuous spectrum. These lines are characteristic of the composition of the intervening gas; they occur at precisely the same wavelengths as the emission lines produced by that gas at higher temperatures.

 

 

 

 

 

 

OBJECTIVE OF CHAPTER THREE

 

 

1: The basic designs of the major types of optical telescopes.

2: Comparison of reflecting and refracting telescopes. Need for very large telescopes for most astronomical studies.

3: Effects of Earth's atmosphere on astronomical observations.

4: how interferometry can enhance the usefulness of radio observations.

5: Advantages, limitations, and chief uses of infrared, ultraviolet, high-energy, and full-spectrum astronomies.

6: Advantages and disadvantages of radio astronomy.

7: The importance of making astronomical observations in different regions of the EM spectrum.

 

 

 

 

 

 

 

 

 

 

 

 

TELESCOPE: A device designed to collect as much Light as possible from some distant source and then deliver it to a detector for detailed studies. There are two basic types of optical telescopes:  refractors which use lenses and reflectors which use mirrors. ( Fig. 3.4 )

 

CHROMATIC ABERRATION:  The tendency for lens to focus red and blue lights differently, causing images to become blurred.

 

DIFFRACTION: The ability that waves have to bend around the corners. The diffraction of light establishes its nature as a wave. The amount of diffraction is proportional to the wavelength and inversely proportional to the size of the mirror.

 

 

 

 

 

COLLECTING AREA The total area of a telescope that is capable of capturing incoming radiation. The larger the telescope, the greater its collecting area, and the fainter the objects it can detect

 

THE LIGHT-GATHERING POWER OF A TELESCOPE : It depends on its collecting area, which is proportional to the square of the mirror ( or lens ) diameter

 

 

 


Power of A Telescope    a     Square of Diameter

 

 

 

ANGULAR RESOLUTION: The ability of a telescope to distinguish between adjacent objects in the sky.

 

 

 

DISADVANTAGE OF REFRACTING TELESCOPES

1: the light pass through the lens, creating chromatic aberration.

2: Absorption of some passing light by lens. Glass blocks most of infrared and ultraviolet radiation.

3: Lens can be supported only around its edge. In large lens they tends to deform under its own weight.

4: Lens has two surfaces that must accurately cut and polished.

 

DIFFERENT KIND OF REFLECTING TELESCOPES:

1: Prime Focus Telescope

2: Newtonian Focus Telescope: A reflecting telescope in which incoming light is intercepted before it reaches the prime focus and is deflected into an eyepiece at the side of the instrument

3: Cassegrain Telescope: A type of reflecting telescope in which incoming light hits the primary mirror and is then reflected upward toward the prime focus, where a secondary mirror reflects the light back down through a small hole in the main mirror, into a detector or eyepiece

4: Coude Focus Telescope:

 

 

NON OPTICAL TELESCOPE:

1: RADIO TELESCOPE:

2: INFRARED TELESCOPE:

3 ULTRAVIOLET TELESCOPE:

4: HIGH-ENERGY TELESCOPES

 

 

CHARGE-COUPLED DEVICE (CCD): Electronic device used for data acquisition, composed of many tiny pixels, each of which records a buildup of charge to measure the amount of light striking it.

ADVANTAGES OF CCD OVER PHOTOGRAPHIC PLATES: CCD are many times more sensitive than photographic plates, and the resultant data are easily saved directly on disk or tape for later image processing.

 

 

 

 

 

 

RADIO TELESCOPES: Radio telescopes are conceptually similar in construction to optical reflecting telescopes. Radio telescopes are generally much larger than optical instruments, for two reasons.

First, the amount of radio radiation reaching Earth from space is much less than the amount of visible radiation, so a large

collecting area is essential.

Second, the long wavelengths of radio waves mean that diffraction severely limits resolution unless large instruments are used. In order to increase the effective area of a telescope, and hence improve its resolution, several instruments may be combined into an interferometer.

Using interferometry, radio telescopes can produce images much sharper than those from the best optical equipment.

 

 

 

 

 

 

INFRARED AND ULTRAVIOLET TELESCOPES: They are similar in basic design to optical systems. Infrared studies in some parts of the infrared range can be carried out using large ground-based systems. Ultraviolet astronomy must be carried out from space.

 

HIGH-ENERGY TELESCOPES: These telescopes designed to detect radiation in X-rays and gamma rays. X-ray telescopes can form images of their field of view, although the mirror design is more complex than for lower-energy instruments.

Gamma-ray telescopes simply point in a certain direction and count photons received. Because the atmosphere is opaque at these short wavelengths, both types of telescope must be placed in space.

Radio and other nonoptical telescopes are essential to studies of the universe because they allow astronomers to probe regions of space that are completely opaque to visible light and to study the many objects that emit little or no optical radiation.

 

 

 

 

Table 3.1 Astronomy at Many Wavelengths

 

 


Radiation              General Considerations                  Common Applications

 


                        Can penetrate dusty regions of interstellar space.    Radar studies of planets

                        Earth's atmosphere largely transparent to radio  Planetary magnetic fields

                             wavelengths.                                                            Interstellar gas clouds

                        Can be detected in daytime as well as at night.         Center of Milky Way Galaxy,

     Radio       High resolution at long wavelengths requires       Galactic structure,

                             very large telescopes.                                             Active galaxies

                                                                                                             Cosmic background radiation

 


                        Can penetrate dusty regions of interstellar space.    Star formation

                        Earth's atmosphere only partially transparent to Cool stars

Infrared            IR radiation, so some observations must be         Center of Milky Way Galaxy

                             made from space.                                                    Active galaxies

                                                                                                             Large-scale structure of universe

 


                                                                                                             Planets,

                        Earth's atmosphere transparent to visible light         Stars and stellar evolution

    Visible                                                                                           Galactic structure

                                                                                                             Large-scale structure of universe

 


                        Earth's atmosphere opaque to UV radiation, so        Interstellar medium

Ultraviolet            observations must be made from space.               Hot stars

 


                        Earth's atmosphere opaque to X rays, so                   Stellar atmospheres

          X                observations must be made from space.               Neutron stars and black holes

        ray             Special mirror configurations needed to           Hot gas in galaxy clusters

                             form images.                                                           Active galactic nuclei

 


Gamma       Earth's atmosphere opaque to gamma rays,              Neutron stars

     ray                 so observations must be made from space.           Active galactic nuclei

                        Cannot form images.

 

 

 

 

 

 

 

 


OBJECTIVE OF CHAPTER FOUR

 

 

1: Scale and structure of the solar system and basic differences between the terrestrial and the jovian planets.

 

2: Orbital and physical properties of the major groups of asteroids.

 

3: The composition and structure of a typical comet.

 

4: The orbital and physical properties of meteoroids and Their relation to asteroids and comets.

 

5: The major facts that any theory of solar system formation must explain and indicate how the leading theory accounts for them.

 

 

 

 

 

 

SOLAR SYSTEM: The sun, and all the planets ( Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. ( Fig. 4.1 ) & ( Fig. 4.2 ) and (Table 4.1)

PLANET: The major bodies that orbit the Sun and reflect its light, such as: Earth, Mars, Jupiter, ...

MOON: A small body in orbit about a planet.

DENSITY: The ratio of mass to volume of an object is called the density of the object. Its unit In MKS ( SI ) system is Kg/m3

 

                                            MASS ( Kg )

DENSITY (Kg/m3 )  =  --------------------------

                                           VOLUME (m3 )

 

 

TITIUS-BODE RULE: The distance to the next planet out is about twice that to the next planet in.

 

 

Table 4.1 Properties of Some Solar System Objects

 


                     Orbit           Orbit

                  Semi-Major  Period       Mass      Radius       Number      Average

                     Axis            (Earth     (Earth     (Earth       of Known    Density

Object         (A.U.)            years)    masses)    radii)         Moons       (kg/m3)

 


 Mercury        0.39                0.24        0.055      0.38        0                 5400

 


 Venus        0.72                0.62        0.81        0.95        0                 5200

 


 Earth         0.72                0.62        0.81        0.95        0                 5200

 


 Moon        0.72                0.62        0.81        0.95        0                 5200

 


 Mars         0.72                0.62        0.81        0.95        0                 5200

 


 Jupiter      0.72                0.62        0.81        0.95        0                 5200

 


 Saturn       0.72                0.62        0.81        0.95        0                 5200

 


 Uranus      0.72                0.62        0.81        0.95        0                 5200

 


 Neptune    0.72                0.62        0.81        0.95        0                 5200

 


 Pluto         0.72                0.62        0.81        0.95        0                 5200

 


 Sun            0.72                0.62        0.81        0.95        0                 5200

 

 

 

 

 

 

 

 

 

 

 


Table 4.2 Comparison of the Terrestrial  and Jovian Planets

 


Terrestrial                                     Jovian

 


close to Sun                                  far from Sun

closely spaced orbits                      widely spaced orbits

small masses                                large masses

small radii                                    large radii

predominantly rocky                  predominantly gaseous

solid surface                                 no solid surface

high density                                 low density

slower rotation                            faster rotation

weak magnetic fields                   strong magnetic fields

no rings                                        many rings

few moons                                    many moons

 

 

 

 

 

 

 

 

 

 

 

 

Table 4.3 Some Prominent Meteor Showers

 


Morning of                            Rough

Maximum        Shower         Hourly            Parent

Activity            Name            Count              Comet

 

Jan. 3            Quadrantid        40                     -

 

Apr. 21         Lyrid                   10               1861I

                                                                      (Thatcher)

 

May 4           Eta Aquarid       20               Halley

 


June 30         Beta Taurid        25               Encke

 


July 30          Delta Aquarid    20                     --

 


Aug. 12         Perseid                   50               1862III

                                                                   (Swift­Tuttle)

 


Oct. 9            Draconid             up to              Giacobini-

                                                500                Zimmer

 


Oct. 20          Orioni              30                  Halley

 


Nov. 7            Taurid              10                  Encke

 


Nov. 16          Leonid             121              1866I (Tuttle)

 


Dec. 13             Geminid           503200       Phaeton2

 

    

1 : Every 33 years, next expected to occur in 1999

2 : Phaeton is actually an asteroid.

 

 

TERRESTRIAL PLANET: One of the four innermost planets (Mercury, Venus, Earth, Mars ) of the solar system, resembling the Earth in the general physical and chemical properties. ALL of them are :

1: within 1.5 AU of their parent star

2: All of them are small and of mass

3: All of them have generally rocky composition and solid surfaces.

JOVIAN PLANET: One of the four giant outer planets of the solar system, which resembling the Jupiter in the general physical and chemical properties. ALL of them are :

1: widely spaced through the outer solar system

2: All of them are large and gaseous, made up predominantly of hydrogen and helium

3: All of them have strong magnetic fields.

 

 

ASTEROIDS OR MINOR PLANET: A group of small bodies, non of them larger than Earth’s moon, that orbit in a broad band called the asteroid belt between the orbits of Mars and Jupiter. ( Fig. 4.4 )

COMET: A small body, composed mainly of ice and dust, in an elliptical orbit about the Sun. As it comes close to the Sun, some of its material is vaporizes to form a gaseous head and extended tail. Haley’s comet was first observed in 1531. ( Fig. 4.7 ) and ( Fig. 4.9 )

 

METEOROID: Chunk of interplanetary debris prior to encountering Earth’s atmosphere, or in brief a small rock in space.

METEOROID SWARM: Pebble-sized cometary fragments dislodged from the main body of a comet moving in nearly the same orbit as the parent comet.

METEOR: The luminous phenomenon seen in the sky, when a meteoroid enters the Earth’s atmosphere, commonly known as a shooting star.

METEOR SHOWER: Event during which many meteors can be seen each hour, caused by the yearly passage of the Earth through the debris spread along the orbit of a comet. (Fig. 4.13 ) Table 4.3 lists some prominent Meteor Showers.

METEORITE: A part of a meteoroid that survives passage through the Earth's atmosphere and lands on the surface of Earth.

NEBULA: A diffuse mass of interstellar dust and gas or any “fuzzy” patch on the sky.

SOLAR NEBULA: The large cloud of gas and dust surrounding the early Sun during the epoch of solar system formation, also referred to as the primitive solar system from which the Sun and planets condensed about 5 billion years ago.

NEBULAR THEORY: One of the earliest models of solar system formation, dating back to Descartes, in which a large cloud of gas began to collapse under its own gravity to form the Sun and planets. (Fig. 4.18 )

CATASTROPHIC THEORY: According to this theory, changes occur abruptly, as the result of accident or chance.

CONDENSATION THEORY: Currently favored model of the solar system formation, which is built base on the nebular theory by the incorporation of the effects of particles of interstellar dust, which help to cool the nebula and act as condensation nuclei, allowing the plant-building process to begin. (Fig. 4.21 )

INTERSTELLAR DUST: Microscopic dust grains that populate the space between stars, having their origins in the ejected matter of long-dead stars.

 

 

 

CONDENSATION NUCLEI: dust grains in the interstellar medium which acts as seeds around which other material can cluster. The presence of dust was very important in causing matter to clump during the formation of the solar system.

ACCRETION: Gradual growth of bodies, such as planets, by the accumulation of other, smaller bodies, or accumulation of dust and gas into larger bodies.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OBJECTIVE OF CHAPTER FIVE

 

1: compare the basic properties of Earth and the Moon, and explain why the two bodies differ.

2: Consequences of gravitational interactions between Earth and the Moon.

3: How Earth's atmosphere helps heat us as well as protect us.

4: How dynamic events early in the Moon's history formed its surface features.

5: Current model of Earth's interior structure

6: The nature and origin of Earth's magnetosphere.

7: The evidence for continental drift

8: Discuss theories of the formation and evolution of Earth and the Moon.

 

 

 

 

 

 

 

 

 

Comparing the properties of the Earth and the Moon

 

 


                         Earth                       Moon         Earth / Moon

 


     Radius       6400 Km               1740 Km             1/4

 


      Mass        6 x 1024 Kg         7.4 x 1022 Kg          1/80

 


     Volume   1.098 x 1021 m3     2.207 x 1019            1/50

 


    Density       5500 Kg/m3        3300 Kg/m3           3/5

 


         g             9.81 m/s2             1.63 m/s2              1/6

 


   Escape         11.2 Km/S           2.4 Km/S             1/5

   Speed

 


   Rotation         23 h                     27.3 day             1.1

    Period            56 m                    

 

 

 

 

 

 

 

 

 

 

 

 

 


THE SIX MAIN REGIONS OF THE EARTH (Fig. 5.1a)

1: INNER CORE

2: OUTER CORE

3: MANTLE

4: CRUST

5: HYDROSPHERE

6: ATMOSPHERE ( Composed primarily of nitrogen and oxygen)

 

EARTH’S ATMOSPHERIC STRUCTURE (Fig. 5.4 ): The Earth’s atmosphere base on its properties can be divided to five different region:

1: Troposphere : Convection happens in this region

2: Stratosphere: At this region air is calm, the temperature increases with altitude as incoming solar ultraviolet radiation is absorbed by oxygen, ozone, and nitrogen gases.

3: Ozone layer: This is the insulting layers that serve to protect life on Earth from the harsh realities of outer space.

4: Mesosphere

5: Ionosphere

 

 

 

 

THE MAIN SURFACE FEATURES ON THE MOON(Fig. 5.1b)

 

1: MARIA ( Sea of shower ): Flat region on the moon

2: HIGHLANDS: Relatively light-colored regions on the surface of the Moon which are elevated several kilometers above the maria. Also called terrae.

3: CRATERS Bowl-shaped depression on the surface of moon, resulting from a collision with interplanetary debris.

 

TIDES: Rising and falling motion that bodies of water follow, exhibiting daily, monthly, and yearly cycles. Ocean tides on Earth are caused by the competing gravitational pull of the Moon and Sun on different regions of the Earth. (Fig. 5.3)

 

 

 

 

SYNCHRONOUS ORBIT: State of an object when its period of rotation is exactly equal to its average orbital period. The Moon is in Synchronous orbit, and so presents the same face toward Earth at all times.( 27.3 days )

CONVECTION: Churning motion resulting from the constant upweling of the warm fluid and the concurrent down ward flow of the cooler material to takes its place. (Fig. 5.5 )

GREEN HOUSE EFFECT: The partial absorption and trapping by atmospheric gases ( primarily carbon dioxide and water vapor ) of infrared radiation emitted by Earth’s surface. Visible light from the Sun is not significantly absorbed by these gases. It makes more difficult for Earth to radiate its energy back into space. The green house effects makes our planets surface some 40 K warmer than would other wise be the case. (Fig. 5.6 )

 

 

SEISMIC WAVE: A wave that travels out ward from the site of an earthquake through the Earth. Most of the information about the deep inner structures of the Earth has come from the study of seismic waves.

DIFFERENTIATION: Variation in the density and composition of a body, such as the Earth, with low density material on the surface and higher density material in the core.

VAN ALLEN BELTS: Two doughnut-shaped regions of magnetically trapped charged particles high above Earth’s atmosphere. (Fig. 5.18 )

AURORA: When atmospheric molecules are exited by incoming charged particles from the solar wind, then emit energy as they fall back to their ground states  Aurora generally occur at high latitudes, near the north and south magnetic poles.

 

PLATE TECTONICS ( CONTINENTAL DRIFT ): Earth’s surface is made up of about a dozen enormous slabs, or plates. The slow movement of these plates across the surface is called continental drift or Plate tectonics.