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GRADE –IX

CONTENTS

SECTION-I- GENRAL SCIENCE (20 MCQs) (PHYSICS, CHEMISTRY & BIOLOGY)

1. • LIFE SCIENCE:

1.1 Life Process.

1.2 The Fundamental Unit of Life.

1.3 Tissues.

1.4 Diversity in Living Organisms.

1.5 Reproduction in Animals.

1.6 Cell Structure and Function.

2. • PHYSICAL SCIENCE:

2.1 Motion.

2.2 Force and Laws of Motion.

2.3 Work and Energy.

2.4 Light.

2.5 Sound.

2.6 Gravitation.

3. • CHEMICALCAL SCIENCE:

3.1 Matter in Our Surroundings. 3.2 Atoms & Molecules. 3.3 Structure of an Atom. 3.4 Natural Resources.

SECTION-II- ASTRONOMY ( 30 MCQs)

(Earth Science)

4. • EARTH SCIENCE:

4.1 History of Astronomy. 4.2 Overview of Solar System. 4.3 The distribution and orbits of Planets. 4.4 Physical Characteristics of Planets. 4.5 Earth and its Motion. 4.6 Moon. 4.7 Terrestrial Planets. 4.8 Jovian Planets. 4.9 Smaller Bodies in Solar System. 4.10 Asteroids, Comets & Meteoroids. 4.11 Stars and Galaxies. 4.12 Lunar & Solar Eclipses. 4.13 Hubble’s law. 4.14 Cosmology.

[NATIONAL ASTRONOMY & SCIENCE OLYMPIAD] GRADE-IX

1. During a lunar eclipse, the Moon has the phase____?

A. Full B. Last Quarter C. New

2. A solar eclipse can only happen during ________?

A. First quarter moon. B. Perihelion passage of the Sun. C. New moon.

3. The Red shift of a galaxy is_________.

A. The rate at which a galaxy is expanding in size B. How much the galaxy appears when observed at large distances? C. The velocity of a galaxy, expressed as a fraction of the speed of light.

4. A solar eclipse always occurs___________.

A. At sunrise B. At sunset C. At midday

5. The small cluster of galaxies to which the Andromeda galaxy belongs is?

A. The Milky Way Neighbourhood B. The Local Group C. The Solar Neighbourhood

6. Why is a black hole referred as “black”?

A. light coming from behind shines right through it. B. it is so small you can’t see it. C. light can’t escape from it.

7. What are comets made of?

A. Ice and dust B. Rock C. Hydrogen

8. What are asteroids closely similar to?

A. Comets B. Meteorites C. Meteors


9. What are meteors called that exploding with a thunder sound?

A. Meteoroids B. Asteroids C. Bolides.

10. What happens when a comet goes toward the sun?

A. Develops a tail

B. Brightens

C. Melts 11. What type of galaxy is the Milky Way?

A. Barred spiral B. Elliptical C. Spiral

12. How many basic types of galaxies are there?

A. 2 B. 3 C.4.

13. What do scientists think are in the middle of the Milky Way?

A. The sun B. A black hole C. An asteroid belt

14. What kind of stars are in the Milky Way?

A. Blue stars B. Red stars

C. Both blue and red stars

15. What do you need for an eclipse to occur?

A. The sun

B. The moon and the sun

C. Earth, the moon, and the sun


16. What kind of eclipse occurs when the sun, moon, and Earth doesn't line

up completely?

A. Total B. Partial C. Annular

17. When a lunar eclipse occurs, what phase should the moon be in?

A. Anning B. Half moon C. Full moon

18. How long does a lunar eclipse last up to?

A. 2 hours B. 4 hours C. 8 hours

19. What are stars mainly made of?

A. Balls of gas B. Rock C. Ice

20. What are the terms astronomers use to measure the brightness of star?

A. Light year B. Magnitude C. Scale

21. What is the cloud of material stars are made of called?

A. Galaxies B. Nebulae C. comets

22. What is the name of the remains of the sun after its nuclear reactions

stops?

A. Neutron star B. Black holes C. White dwarf stars

23. How many moons does Mercury have?

A. None B. 1 C. 3.


24. What is the storm on Jupiter called?

A. The Great Red Spot B. The Great Dark Spot C. The Small Red Spot

25. Which planet has a moon that is nearly that is half the size of itself?

A. Jupiter B. Neptune C. Pluto

26. Which planet is called the Sister Planet?

A. Mercury B. Venus C. Mars

27. How many rings does Uranus have?

A. 8 B. 20 C. 11

28. Which of Mars's moons is the smallest in the solar system?

A. Phobos B. Callisto C. Demios

29. What is Earth mostly made of?

A. Land B. Mountain ranges C. Water

30. Which planet has the most moons?

A. Jupiter B. Saturn C. Uranus

31. Which storm disappeared on Neptune?

A. Dark Spot 2 B. The Great Dark Spot C. The Great Red Spot

32. When Galileo was released from the Inquisition, what did they put him

under?

A. House arrest B. But him in jail C. Execution


33. What instrument did Galileo improve?

A. Telescope B. Magnifying glass C. Microscope

34. When Galileo left Pisa, where did he go to teach?

A. University of Rome B. University of Italy C. University of Padua

35. Out of these four stars, which one is the brightest (as seen from Earth)?

A. Betelgeuse B. Vega C. Achernar

36. Which constellation is sometimes referred to as the thirteenth sign of the

zodiac?

A. Ophiuchus B. Cetus C. Cancer

37. In September 29, 2010, an unconfirmed extra solar planet 20.5 light-

years from Earth in the constellation of Libra was discovered. What was its

name?

A. Gliese 581g B. Kepler 22-b

C. Upsilon Andromeda 38. What is the theoretical boundary between the Sun's solar wind and the

interstellar medium?

A. Heliopause B. Heliosphere C. Solar flares

39. In the constellation of Serpens, this Messier object consists of noticeable

features such as the Spire and the Pillars of Creation. What is it called?

A. Crab Nebula B. Eagle Nebula C. Helix Nebula


40. Which two co-ordinates are used to find a celestial object in the sky?

A. Declination and right ascension B. Latitude and longitude

C. Equatorial diameter and radius 41. What is the term that defines the maximum mass of a white dwarf star,

approximately equal to 1.38 solar masses?

A. Red shift B. Roche's limit

C. Chandrasekhar limit 42. By July 14 2015, the New Horizons spacecraft will arrive to study what

celestial object?

A. Pluto B. Sedna C. Eris

43. Which of these is classified by astronomers as the largest star

(actual diameter)?

A. VY Canis Majoris B. Rigel C. Mu Cephei

44. What is the tight open cluster of stars located in the heart of the Orion

Nebula named?

A. Beehive Cluster B. The Trapezium C. Butterfly Cluster

45. Rounded to the nearest day, the Mercurial year is equal to?

A. 111 days B. 88 days C. 50 days

46. One of the largest volcanoes in our solar system-if not the largest-is

named Olympus Moons this volcano is located on?

A. Venus B. Saturn's moon Titan C.Mars


47. One Jupiter day is equal to which of the following?

A. 30 hrs 40 min B. 9 hrs 50 min C. 3 hrs 20 min

48. The sunspot cycle is: ____________.

A. 3 years B. 11 years C. 26 years

49. When two heavenly bodies occupy the same longitude, the bodies are

said to be in?

A. Sympathy B. Conjunction C. Parallel

50. The study of the origin and evolution of the universe is known as?

A. Tomography B. Cystoscopy C. Cosmolog

BIOLOGY SYLLABUS SAMPLE QUESTIONS

1. DNA structure was first described by____________?

a. Catcheside b. Nirenberg c. Lederberg d. Watson and Crick

2. The food which gives an athlete instant energy is_________?

a. Glucose b. Protein c. Butter d. Vitamin

3. Identical twins are born, when______?

a. Two sperms fertilize two ova b. Two sperms fertilize one ovum c. One sperm fertilize one ovum d. One sperm fertilize one ovum.


4. The ABO blood groups were discovered by__________?

a. Charles Darwin b. Karl Landsteiner c. Gregor Mendel d. Watson

5. Acromegaly is caused by irregular secretion of_______?

a. Pituitary b. Adrenal c. Thyroid d. Pancreas

6. The blood which leaves the liver and moves to the heart has a

higher concentration of_____?

a. Glucose b. Bile Pigments c. Bile d. Urea

7. The children of a colour-blind mother and a normal father will

be__________?

a. Normal daughters and sons b. Normal sons and carrier daughters c. Colour blind sons and carrier daughters d. Colour blind sons and daughters

8. Which of the following hormones is responsible for the emotional states such

as fear, anger and tension and a rise in blood pressure and heart rate?

a. Somatotrophin b. Oxytocin c. Thyroxine d. Adrenaline


9. Gene mutation takes place in____________?

a. Deoxyribonucleic acid b. Chloroplast c. Mitochondrion d. Ribosome

10. The kinds of ribonucleic acid present in any plant cell will be____?

a. 2 b. 4 c. 3 d. 5

11. Which part of the human brain is the centre of memory, learning,

thinking and reasoning?

a. Cerebrum b. Hypophysis c. Cerebellum d. Medulla

12. Mark the correct statement__________?

a. All sperms fertilize all eggs b. Eggs are fertilized by many sperms c. Each egg is usually fertilized by one sperm d. Each sperm fertilizes one egg.

13. Mark the correct statement__________?

a. Foramen magnum is in the skull b. Foramen magnum is an aperture in the heart c. Foramen magnum is a large hole in the voice box d. Foramen magnum does not exist anywhere

14. Survival of the fittest' was proposed in his theory of evolution

by__________?

a. Darwin b. Lamarck c. Mendel d. Hugo de vries


15. The pteridophyte produces two kinds of spores_________?

a. lycopodium b. Psilotum c. Selaginella d. Adiantum

16. Ozone hole refers to__________?

a. Hole in ozone layer b. Decrease in the ozone layer in troposphere c. Decrease in thickness of ozone layer in stratosphere d. Increase in the thickness of ozone layer in troposphere

17. Pine, fir, spruce, cedar, larch and cypress are the famous timber-

yielding plants of which several also occur widely in the hilly regions of India. All these belongs to__________?

a. Angiosperms b. Gymnosperms c. Monocotyledons d. Dicotyledons

18. Pollination is best defined as____________?

a. Transfer of pollen from anther to stigma b. Germination of pollen grains c. Growth of pollen tube in ovule d. Visiting flowers by insects

19. Movement of cell against concentration gradient is called__________?

a. Osmosis b. Active transport c. Diffusion d. Passive transport


20. How do marine animals survive in water without air contact?

a. They do not require any oxygen b. They take oxygen from water c. They only produce oxygen in their body d. They get oxygen from water plants

21. The most advanced evolutionary inflorescent is found in?

a. Dahlia b. Calotropis c. Saliva d. Yucca

22. Kidney stones are mainly formed by which of the following compound?

a. Sodium chloride b. Silicates c. Calcium bicarbonate d. Calcium Oxalate

23. Potatoes are borne on?

a. Primary roots b. Stem branches c. Lateral roots d. Adventitious roots

24. Which one of the following has haustoria or sucking roots?

a. Orchids b. Mango c. Chestnut d. Cuscuta

25. The Phylloclade commonly found in xerophytic plants is the modified?

a. Stem b. Roots c. Leaf d. Flower


26. Which one among the following is the largest edible bud found in

nature?

a. Cauliflower b. Agave c. Cabbage d. Drpsera

27. The fruit after ripping becomes soft. It is due to?

a. Dissolution of tannin in sap b. Dissolution of middle lamella c. Formation of ethylene gas d. Formation of auxin.

28. Which one among the following parts of castor seed yields oil?

a. Nucleolus b. Caruncle c. Endosperm d. Cotyledon

29. Which one among the following vitamins is necessary for blood clotting?

a. Vitamin - A b. Vitamin - D c. Vitamin - K d. Vitamin - C

30. The macro nutrients provided inorganic fertilisers are?

a. Carbon, Iron and boron b. Magnesium, manganese and sulphur c. Magnesium, zinc and iron d. Magnesium, phosphorus and potassium


31. Which of the following impart yellow colour to urine in humans?

a. Cholesterol b. Lymph c. Urochrome d. Bile Salts

32. Which of the following vitamin is considered to be a para - thormone?

a. Vitamin - A b. Vitamin - C c. Vitamin - D d. Vitamin - K

33. Which are among the following organs is involved in the conversion of

ammonia, the main end product of protein digestion to excretory product

urea?

a. Kidney b. Lung c. Intestine d. Liver

34. Which of the following organism does not obey the 'Cell Theory'?

a. Virus b. Bacteria c. Fungi d. Plants

35. What is the amount of blood filtered by the Kidney within a minute?

a. 1200 ml b. 1600 ml c. 600 ml d. 800 ml


36. The unit structure of genes is made up of?

a. RNA b. DNA c. Endoplasmic reticulum d. Magnesium

37. The vitamin which is generally excreted by human in urine is?

a. Vitamin - A b. Vitamin - D c. Vitamin - C d. Vitamin - E

38. Which one among the following is known as 'animal starch'?

a. Cellulose b. Glycogen c. Pectin d. Chitin

39. Which of the following diseases is caused by a virus? a. Plague b. Polio c. Tetanus d. Leprosy

40. Which of the following parts of human body is affected by Florid?

a. Bronchus b. Small intestine c. Teeth and gums d. Large intestine

41. The branch of agriculture which deals with the feeding, shelter, health

and breeding of the domestic animals is called? a. Animal Husbandry b. Dairy Science c. Veterinary Science d. Poultry


42. The branch of agriculture which deals with the feeding, shelter, health

and breeding of the domestic animals is called?

a. Animal Husbandry b. Dairy Science c. Veterinary Science d. Poultry

43. Hay fever is a sign of?

a. Malnutrition b. Allergy c. Old Age d. Over Work

44. Heart attack occurs due to?

a. Bacteria b. Stopping of heart beat c. Lack of blood supply to the heart itself d. Impairment of heart's working due to unknown reason

45. Plants die in winter by frost because?

a. There is no transpiration b. No photosynthesis takes place at such low temperatures c. Respiration ceases at such low temperatures d. Of desiccation and mechanical damage to tissues

46. Which is the chief nitrogenous waste in humans?

a. Urea b. Ammonia c. Uric acid d. Ammonium nitrate

47. Which is the largest living bird?

a. Ostrich b. Peacock c. Dodo d. Turkey


48. Root nodules are commonly found in?

a. Leguminous plants b. Parasitic plants c. Epiphytic Plants d. Aquatic plants

49. The function of Trypsin is to?

a. Break down fats b. Break down proteins c. Synthesize proteins d. Break down Carbohydrates

50. What is "ALZHEIMER'S" disease?

a. It affects liver b. It affects Kidney c. It affects human immune system d. It is a disorder of the brain


PHYSICS & CHEMISTRY SAMPLE QUESTIONS

1. What is the state of water at 100° C?

a. Solid

b. Vapour

c. liquid & vapour

d. Liquid

2. Human cheek cells, observed under the microscope looks like?

a. Circular in shape with a nucleus in the centre

b. Spindle shaped with nucleus in the centre

c. Irregular in shape with nucleus in centre

d. Rectangular in shape with nucleus towards periphery

3. Mata nil Yellow is ____________?

a. Yellow grains

b. Dye

c. Nutritional supplements

d. A yellow metal 4. In a school laboratory most commonly used chemical to test the presence of metanil yellow in dal is______________?

a. Concentrate HCL

b. Alcohol

c. Safranin

d. Iodine Solution 5. When dilute sulphuric acid is added to zinc granules, it is observed

that___________?

a. Bubbles comes out from surface of zinc granules b. Brown fumes evolves

c. Mixture turns blue

d. Yellow colour mixture is formed.


6. Which of the following is characteristic feature of parenchyma tissue?

a. Cells are thin walled and loosely packed

b. Cells have thickenings at corners

c. Cells are thinking walled.

d. Cells are long narrow without inter cellular space 7. Which of the following will form a clear & transparent solution?

a. Common salt with water

b. Sand with water

c. Starch with water d. Gum with water

8. Which one of the following food sample would give a positive iodine test?

a. Sugars

b. Pulses

c. Boiled egg

d. Potato 9. When Magnesium ribbon in air, the colour of magnesium oxide will be______?

a. Red

b. Blue

c. White

d. Black

10. When you observe slide of nerve cells, the branches around cell body is ______?

a. Cyton

b. Axon

c. Dendrite

d. Nerve ending

AIR CONDITIONING AIRPLANE ALEXANDER FLEMING ALEXANDER GRAHAM

BELL ARTHUR GRANJEAN BEN FRANKLIN BIFOCALS BINNEY SMITH BLOOD BANK CAMERA CAN OPENER CHARLES DREW CHRISTOPHER LATHAM

SHOLES COTTON GIN CRAYOLA DENIM JEANS EDWARD JENNER ELEVATOR BRAKE ELIJAH MCCOY ELISHA G. OTIS ELI WHITNEY ETCH A SKETCH ETIENNE LENOIR EZRA WARNER FOUNTAIN PEN GAS ENGINE ISAAC MERRITT SINGER JAMES WATT

Inventor’s Challenge JOHANNES GUTENBERG

P S E L B Y Z Z Q U R E G N I S T T I R R E M C A A S I LEVI STRAUSS

C H T L S L H M E B C Q N V N A E J N A R G R U H T R A L.E. WATERMAN

G K O E I E O Q Z Q S H L E W H I T C O M B J U D S O N LIGHT BULB

D W M N A W L O D C R Z A N P Q P V W A B R C B R S E G LIQUID PAPER

F N E W O M H O D X W P S R Q N N S L W M E A I E T F A MICROWAVE OVEN

V O N E L G E I H B I B L T L S I E F U K P M F I E B S MORSE CODE

G S I M G T R N T S A Y A E W E X A Y P T P E O R A L E PENICILLIN

R I C C G E S A G N M N S V S A S E T T V I R C R M U N PHONOGRAPH

E D C R T L A B P I E A K S N E B D L N T Z A A A B B G PRINTING PRESS

B E A R T E L Q X H N Y H D E E M E R I U U T L C O T I RICHARD DREW

N A V E A P O M K H W E E T E R N A N E S O P S H A H N RICHARD JAMES

E V X N W H Y R A G T R E C A T P I J F W H F Y W T G E ROBERT FULTON

T L O E S O A V C Y G K N R Y L I G H D R Z A T L G I V SAMUEL F.B. MORSE

U A P P E N R O P R A E E F M S R E N C R A Q G S L L T SCOTCH TAPE

G S L O M E C E A R V S V A L E E E N I A A N P O W I U SEWING MACHINE

S A L N A R W H B O R R D E L T L R H N T M H K G T Y S SILLY PUTTY

E M A A J R A R E O E N L I C E F T E P E N G C L W I C SLINKY

N O M C I M O V M N O H J H V W J C N P O L I N I I V S SMALL POX VACCINE

N H S T B T A B N T T A A I E S R P E A A T E R I R N N STEAM BOAT

A T E E A W F E L I H S S R N E E P N N M P S N P W Y C STEAM ENGINE

H R L V O L J U M M K T D A N N A U T A T R D I O S E K TELEPHONE

O L E R E D F S C E R D E R I T Y K N I L S E I R I J S THOMAS ALVA EDISON

J L C U R T Y C T A R J A C H E N A L P R I A T U H R G TYPE WRITER

E I M A R E O C U A M W I C M O R S E C O D E F A Q C Z W.H. CARRIER

M A W E N Y H S H I A L T C O T T O N G I N K J G W I M WHITCOMB JUDSON

S D B N Q N S C N R L O S R E H T O R B T H G I R W E L WRIGHT BROTHERS

E O I B O B I E Z I C A I R C O N D I T I O N I N G V L ZIPPER

R B A T W R D E N S A L E X A N D E R F L E M I N G J X

9th

Grades Syllabus

History of Astronomy

Astronomy is the oldest science of mankind, and our records of the

movements of the heavenly bodies date back to prehistoric times. The

oldest surviving text record of astronomical phenomena is a fragment of

bone from around 30,000 years ago with representations of the phase of

the moon, and the oldest artifact related to astronomy is the megalithic

structure located in the outskirts of London, England. This stone structure

was erected in positions that coincide with the directions in which the sun

and the moon rise and set on the horizon. Astronomy developed

independently in various regions including the Middle East, China, India

and the American continent. In ancient cultures, the celestial bodies and

religion were closely correlated. For example, in ancient Babylonia,

astronomy developed to serve the purpose of astrology. In this context, the

attempt to distinguish astronomy and astrology in ancient cultures is

meaningless.

Pythagoras, who set the foundation of geometry and trigonometry, argued that the earth is round and that all of the heavenly bodies follow circular orbits. Plato, meanwhile, argued that since our observations reveal only an incomplete portion of the cosmos, insights into the mystery of the universe ought to be pursued through reason rather than through observation. Such Platonic teachings thereafter remained enrooted as one of the dominant ideas of Western society for nearly two millennia, up to the time of the Renaissance.

Aristotle was the first to adopt the law of physics and to posit that the features of the current universe were attributable to the fact that the universe conformed to this law. He also claimed that circular movement was the only natural form of movement, and that the earth was the center of the universe. Aristarchus was the first scholar to argue that the center of the universe was not the earth but instead the sun, preceding Copernicus’ heliocentric theory by 1700 years.

Eratosthenes accurately determined the size of the earth using a very

simple geometric method, and around the 2nd century B.C., Ptolemy improved upon the epicycle theory honed by Hipparchus, the theory in which planets were assumed to move in a small circle called an epicycle, to identify the retrograde motion which served as the basis for Ptolemy’s own geocentric theory. For a long period thereafter, there were no significant developments in astronomy. Upon the arrival of the 15th century, however, Copernicus espoused his heliocentric theory, and Kepler, based on his analysis of the observational data regarding Mars compiled by Tyco Brahe, established the three laws which are known as Kepler’s laws even to this day. Meanwhile, Galileo used the telescope to observe the moon and the planets, most notably the phases of Venus, which allowed Galileo to verify that Copernicus’ heliocentric theory was correct. Newton established dynamics as an important field of science, and applied this knowledge to understand the movements of the moon and planets and induced the law of gravity.

Overview of the Solar System

The solar system was formed when an enormous cloud of gas and dust contracted by gravity to create a proto planetary disk, which then grew into planetesimals, which ultimately formed the planets. The solar system consists of 8 planets, and in general these are categorized into terrestrial planets that are composed of rocks and metal components on the interior and Jovian planets (or giant planets) composed of gas on the exterior. This is because the temperature became lower toward the exterior of the solar nebula. The orbits of the planets are ellipses that are nearly circular, with the exception of Pluto and Mercury. Between Mars and Jupiter, there is an asteroid belt with a distribution of asteroids with rock and metal components, and asteroids exist in the Kuiper belt outside Neptune. Comets are found all across the solar system, and are emitted from Oort clouds that exist as a heavy spherical exterior on the outer boundary of the solar system. The surfaces of planets have diverse appearances, but almost all members exhibit craters made from collisions with asteroids or comets. Areas with few craters are where the surface has recently changed, indicating that the area is a young region. On inner planets, we see traces of volcanoes and lava flow.

The Distribution and Orbits of Planets

The distance from the sun to a planet is calculated according to the Titius-Bode Law. This law is astoundingly accurate when applied to the seven interior planets, but the difference becomes larger beginning with Neptune. Planetary movement is characterized in revolutions in direct motion counter clockwise around the sun. Also, the orbital planes of the planets’ revolutions are all within the zodiac in a 16 degree range from the ecliptic plane, with the exception of Pluto. The revolution orbit is all close to a circle, with the exceptions of Mercury and Pluto. Pluto exhibits a high degree of eccentricity, and hence there are cases when it enters inside

Neptune’s orbit. The rotational axes of the planets are around 25 degrees tilted in relation to the rotation orbital plane in the case of the earth, Mars, Saturn and Neptune, but all other planets have an axis that is nearly vertical. The direction of rotation is the same as the direction of revolution for all planets with the exceptions of Venus and Uranus. Venus exhibits a retrograde motion by rotating in the opposite direction, while Uranus has a rotational axis that lies on the equatorial plane. The rotational velocity of Mercury and Venus is very slow, and this is explained as the result of the combination of rotation and revolution.

The Physical Characteristics of Planets

The mass of a planet can be determined by applying Kepler’s Third Law to the satellites that are attached to the planet.

Here, P refers to the revolution period, A to the semi-major axis of the orbit, and m1 and m2 respectively to the mass of the planet and the mass of the satellite. In general, the mass of the satellite is extremely small compared to that of the planet, and therefore we are able to obtain the mass of the planet using the formula above.

Also, in cases where no satellite exists, we can obtain the planetary mass by measuring the perturbation effect of gravity that the planet has on the orbital movement of other planets, asteroids, comets or our space probes. The size of a planet can be obtained by directly measuring the size of the visible disk of the planet, by measuring the accurate time intervals at which the planet obscures stars, its own satellite, or a space probe, or, in the case of planets close to the earth, by measuring the time it takes for a radar pulse emitted from the earth to return by reflecting from various points on the planet in question. Though we are unable to directly explore the interior of the planets, we can build a model of the estimated interior based on the average density, chemical composition, oblations, etc., factors that have been determined based on observation.

From the planet’s surface, we can obtain information regarding color, albedo and temperature.

From the color, we learn the chemical composition of the surface and the atmosphere. The oceans and the land on earth makes the earth appear to be a blue sphere mottled with green, brown and orange, while regions covered in clouds or snow appear white. The desert regions on Mars make this planet appear brown, while the surface of Io, a satellite of Jupiter, is observed to be yellow due to the sulfur emitted from volcanic eruptions. Meanwhile, the albedo of a celestial body is defined as the ratio of reflected radiation from the surface to incident radiation upon it. Planets with no atmosphere or very little have extremely low albedo, and this is because their surfaces are composed of low rocks that have low albedo. The surfaces of the Jovian planets or Venus reflect a lot of the light from clouds,

and therefore have high Albedo.

The temperature of planet surfaces can be estimated based on Stefan’s law by assuming the planet to be a blackbody. This law is expressed as , where E stands for the total amount of energy emitted per unit area per unit of time from the surface of the blackbody, T for the effective temperature, and s for the proportional constant. If the total energy received by the planet from the sun is equal to the total energy emitted by the planet, the planet is in equilibrium, and we can determine the temperature of the planet by measuring these two quantities. However, we must take into consideration that we have omitted factors such as the planet’s atmospheric circulation, convection, ?the atmosphere’s heat conductivity, the existence of an interior heat source, and greenhouse effects. Also, by measuring the wavelength corresponding to the maximum amount of radiation according to Wien’s law regarding blackbodies whereby λmax=(0.002898m)/T, we are able to determine the temperature. Also, by applying the escape velocity Ve = (2Gm/R)0.5 to the planet’s surface, we can find out what components are included in the planet’s atmosphere. Here, R stands for the radius of the planet.

The Unsolved Questions Regarding the Solar System

There remain many questions regarding the solar system’s structure and

various aspects of its members, and among these the most fundamental

question is how the solar system originated and evolved to reach its

current state. Meanwhile, the distribution of angular momentum in the

solar system is another issue that is challenging to explain.

The Earth’s Motion

To understand the movement of the earth, we need to apply the system of coordinates. For the celestial coordinate system, we use the horizontal coordinate system, the equatorial coordinate system, the ecliptic coordinate system, and the galactic coordinate system, etc. with each having its respective advantages and drawbacks. We therefore select one that is most convenient depending on our purpose. The revolutionary and rotational movements of the earth serve as the standard of time, and the mean solar time that we currently use has been obtained by eliminating the problems inherent in the use of true solar time. When the mean sun twice consecutively culminates, then we consider one mean solar day to have passed. Sidereal time is based on the vernal equinox, while in the mean solar time, because the transit time of the mean sun differs according to the longitude, we have established standard times for each country for our usage. All observation data is expressed in terms of the Universal Time. One year is the time it takes for the earth to revolve once around the sun, but depending on the definition of the base point, the sidereal year, the tropical year, and the anomalistic year are formed. The calendar that we currently use is the Gregorian calendar that is made to approximately coincide with the changes of the seasons. The earth’s varying seasons occur because the earth’s equatorial plane is 23.5 degrees tilted in relation to the ecliptic plane.

The evidence of the earth’s rotation can be found in the Carioles effect, Foucault’s pendulum, and the oblate spheroid shape of the earth, etc. while the revolution of the earth is evidenced by the aberration of starlight, stellar parallax, and the Doppler effect, etc. Tidal friction due to differential gravity reduces the energy of the earth’s rotation and therefore the length of the day increases at a rate of approximately 0.002 seconds per century and causes the synchronous rotation of the moon and tidal evolution, thereby increasing the distance between the moon and the earth. In the distant future, the length of a day and one month will become the same, approximately 50 times the present length. Meanwhile, the differential gravity that exercises on the rise along the earth’s equator creates torques and gives rise to precession motion, causing the vernal equinox to move in 26,000 year periods. As a result, the values of the right ascension and the declination of celestial bodies change and the stellar constellations also

change, so that around A.D. 14,000, Vega will be located on the North Pole.

Also, since the moon and the sun? move above and beneath the earth’s equatorial plane, the torques that are exercised in the rise of the earth’s equator cause periodic changes, resulting in notation, a phenomenon in which the rotational axis of the earth shakes.

The Earth and the Moon

The size of the earth was first determined by Eratosthenes of Ancient Greece. When compared to the parent planet, the moon is an immense satellite that is the largest in the solar system. Considering that the mass of the moon is very small compared to the mass of the earth, we can apply

Kepler’s Law of Harmonization to obtain the earth’s mass from the orbit of an artificial satellite, and the mass of the moon can be determined by observing the earth’s movement in relation to the earth and moon’s center of mass. Today, we can deduce the distribution of the moon’s interior mass based on the orbit of artificial satellites that revolve around the moon, and we can measure the accurate mass of the moon. The interior of the moon was investigated by Apollo’s seismic waves, and we have thus learned that a mascon exists and that the nucleus is not in the center of the shape but instead located closer toward the earth.

The elements of the earth’s motion include its revolutionary motion in relation to the sun that is the center of mass for the earth-moon system, the earth’s rotational movement, the rotational motion in relation to the center of mass of the earth’s center, the precession motion of the earth’s rotational axis, notation, and the decrease of the earth’s rotational period due to tidal friction, etc. The movements of the moon are even more complex. The phases of the moon are created by an eclipse phenomenon, because the size of the area that receives sunlight varies when viewed from the earth depending on the elongation of the moon.

The surface of the moon is modeled by collision craters of varying sizes, and these have been formed by collision with meteoroids. The surface of the moon is divided into the highlands and the Maria. The highlands is an area covered with countless craters that is around 3 km higher than the

Maria and aged approximately 4.6 billion years, making it the oldest area on the earth’s surface. The Maria is a large black region, a plain of black basaltic lava that is nearly circular in shape. This circular basin was been created by lava that filled the area upon eruption due to the impact of a meteor.

The Earth’s Atmosphere

The earth’s atmosphere absorbs and scatters stellar light and causes refraction effects. The atmospheric effects that affect visible light include scattering, extinction, refraction, seeing, dispersion, etc.

The light scatters when interacting with particles according to Rayleigh’s scattering law determined by the wavelength of the light and the size of the particle. The earth’s magnetic field is distorted by the solar wind and forms the earth magnetosphere: the magnetosphere is the zone affected by the earth’s magnetic field. Solar winds change direction at the magnetopause and disappear far away from the earth, but nonetheless many protons and electrons seep in and are caught in the annular Van Allen belt that is symmetrical to the earth’s magnetic axis and here the motions of the particles follow the Lorentz Force Law, (F = q (VxB)). The light of an aurora occurs when low energy electrons escape the inner belt and collide with atmospheric gases, causing them to arise or become ionized and emitted.

Terrestrial Planets

The interior structure of the earth is known from various direct and indirect evidences. The lithosphere that includes the crust and the upper part of the mantle is known based on our analysis of the types of rocks, and the lower part of the mantle and the structure and components of the nucleus can be investigated through seismic waves. The asthenosphere just below the lithosphere are zones with sufficiently high pressure and temperature so that the matter that composes the asthenosphere can have fluidity even in a solid state. Ultimately, in this zone heat is usually transferred through convection. The lithosphere is the exterior layer of solids in which convection is impossible, and the internal heat is transferred through conduction. In cases such as the earth or Io with high

geological activity, the heat may sometimes be transferred through the processes of volcanic activities or the circulation across the entire lithosphere. This phenomenon causes the plate tectonics, which is the movement of the plates. The earth’s lithosphere is composed of the crusts of the oceans and the continents as well as the upper mantle. Heat transfer through convection and conduction can occur to a similar degree in objects that are mainly composed of rocky matter and ice.

The evolutionary patterns of terrestrial planets are all quite similar.

Primordial heat is the remainder from the early stages of a planet’s formation, and is one of the important sources of heat for terrestrial planets and other similar celestial bodies. Two other types of heat sources are radiation decay heat and tidal heating. Generally, decay occurs in 235U, 238U, 232Th, 40K, etc. that are located in the mantle and crust which contain a lot of silicon. Radiation decay occurred frequently in the early evolutionary stages of a planet when there was a lot of radiation matter, while tidal heat is a major heat source with strong tidal effects as in the case of large planets such as Jupiter that have large satellites. Among terrestrial planets, the amount of heat that the planet possessed from the beginning of that is continually generated determines the condition of the planet’s surface.

Jovian Planets

The internal structure of Jovian planets can be estimated based on factors that have been determined by observation, including their density, gravity, gravitational field strength, radiation and the chemical components of the atmosphere. The surfaces of Jupiter and Saturn are thought to probably lack clear liquid or solid states. According to a theoretical model, their interiors form five layers. The two layers near the center comprise the nucleus of rock and ice matter, and their nuclei are surrounded by hydrogen and helium, which constitutes the majority of these planets’ masses. The hydrogen near the nucleus is believed to be in a metal state. The central zones of Jupiter and Saturn have high temperatures, exceeding 15,000K in the case of Jupiter.

Uranus and Neptune also lack surfaces of clear liquid or solid states, and

are believed to have rocky nucleus. The results of the most recent model indicate that the rock and ice matter remain incompletely separated. The mantle that is mostly composed of ice matter surrounds the nucleus, and the mantle is surrounded by a layer composed mostly of hydrogen and helium. Overall, compared to Jupiter and Saturn, the roles of hydrogen and helium are significant in Uranus and Neptune, and the layers are chemically separated to a lesser degree. Jupiter, Saturn and Neptune exhibit an excess heat phenomenon, whereby they emit more energy than they receive from the sun. In the case of Jupiter, the excess heat is caused by the continuing emission of heat that remained from the early formation period in addition to the heat arising from radiation decay, and in Saturn, it is believed that the heat is caused by helium droplets sinking after separating from metallic hydrogen.

The magnetic fields of Jupiter and Saturn are thought to be created in the metallic hydrogen layer that is in a liquid state, while in Uranus and Neptune, the magnetic field arises from the layer of ice matter in a liquid state containing ions such as H3O+, OH-, and NH4+. The atmosphere of a Jovian planet is mostly composed of H, H2, and helium, and other molecules include CH4, NH3, etc. The majority of molecules contained in the atmosphere are detected through ultraviolet and infrared spectral observation. The Galileo spacecraft was equipped with a mass spectrometer and was able to research the relative content of molecules in the region upon entering the atmosphere. The cloud layer at the outermost of Jupiter and Saturn is ammonia, and in Uranus and Neptune, methane clouds have been detected. In Jovian planets, the atmospheric layer can be divided into two according to the changes in temperature along depth: in the lower troposphere, the temperature drops when moving upward, but in Uranus, the drop in temperature occurs more slowly. ?In the upper zone known as the thermosphere, the temperature increases when moving upward.

The wind velocity on Jovian planets is identified by observing the movements of spots such as clouds. The value obtained by this method includes the planet’s rotational effect, and therefore we must subtract the rotational speed. In Jupiter and Saturn, we verified the evidence that convection cells exist in a series in a deep location, based on the patterns of

the observed wind velocity. In Jupiter, the major change in wind velocity occurs at the borders of bands with alternating colors, but this does not apply to Saturn. Jovian planets all have large scale spherical magnetic fields, and the overall appearance is similar to that of the earth. In Uranus and Neptune, the rotational axis and the magnetic axis differ significantly, and therefore there appear changes in the strength of the magnetic field over the course of time.

Small Solar System Bodies

The ring of Jupiter is composed of minute particles, and was formed by the influx of gas erupting from a volcano on Io, the nearest satellite. This differs markedly from the ring of Saturn, which is composed of chunks of ice that are tens of centimeters in size. The ring of Uranus is presumed to have been formed in the early stages of the solar system’s creation. Among the planets, an object of our keenest interest is Europa in Jupiter, where we have recently discovered the existence of an ice sea, making Jupiter emerge as the most promising site in the solar system in terms of searching for potential life forms. Meanwhile, Miranda, located in the innermost area of Uranus, shows large regional variations in surface features, leading to questions over its origin. Computer simulations on Pluto and its satellite Charon have indicated that they were originally the satellites of Neptune, but escaped due to the gravitation perturbation by a third celestial body.

Asteroids

Asteroids are widely distributed across the asteroid belt between Mars and

Jupiter, and the location of the Trojan Group has been identified as one of the

Lagrangian points. The majority of asteroids follow orbits with large

inclination angles and eccentricity and in terms of their composition; asteroids are categorized into the C type containing a lot of carbon and the S type which contain a lot of silicates or stony matter. Recently, we have identified asteroids that approach the earth as NEO (Near Earth Object) and are conducting international monitoring campaign for early detection of potentially hazardous asteroids.

Comets

Comets consist of the nucleus, the coma, the hydrogen cloud, the dust tail and the ion tail, and can be categorized by the orbital period with a criterion of 100 years into long period comets and short period comets. The ion tail interacts with the solar wind, so that it extends in the direction opposite to the solar wind. Originally, the orbit of a comet is a hyperbola or a parabola and leaves the solar system after once approaching the sun, but in cases where the comet has approached Jupiter, its orbit changes and it becomes a periodic comet. Comets are dirty chunks of ice and are believed to come from the Oort cloud. Research into comets began in earnest when an exploration satellite was able to observe Haley’s comet when it approached in 1998 and we learned that the nucleus of the comet is peanut-shaped and that the nucleus is made of the darkest matter in the solar system.

Meteoroids

Meteoroids include all celestial bodies that exist in the interplanetary space of the solar system with the exception of planets, satellites, asteroids, and comets. Meteors are those that are drawn by the attractive force of the earth and emit light due to the friction with the earth’s atmosphere, and meteorites are parts that remain without burning off entirely and end up

falling to the surface of the earth. Meteorites are categorized into stony meteorites, iron meteorites, and stony iron meteorites, and they provide important information that allows us to explain the age and origin of the solar system.

The Origin of the Solar System

The nebular hypothesis and the collision hypothesis have been presented as models for explaining the origin of the solar system, and ultimately the validity of these models are determined based on how well they are able to explain the information that we currently know about our solar system. Currently, the models accepted to be the most plausible are the proto-nebular hypothesis or the planetesimal hypothesis, which claims that planetesimals are created through an accretion process. The sun was created through the process of star formation, and many hypotheses have also been presented regarding the origin of the moon, including the fission hypothesis, the capture hypothesis and the binary accretion model, but currently we have obtained calculation results of quantitative simulations based on the giant impact model.

Galaxies

A galaxy is the most basic of the celestial bodies that compose the universe,

and our own galaxy is one among numerous galaxies that exist in the cosmo

In English, our own is written with a capital G as “Galaxy,” to distinguish it

from a “galaxy” which refers to other ordinary external galaxies. The sun is

ocated around 8.5 kpc away from the core of the Galaxy, and is rotating at a

velocity of 220 km per second.

The Components of Our Galaxy

The major components of the Galaxy are stars, interstellar matter, and dark matter. Interstellar matter are categorized into gases an dust, and the dust occupies around 0.6% of the total mass of interstellar matter, exercising a very significant impact on our observations despite being very small in quantity. The identity of dark matter cannot be directly observed, but they are known to exist based on gravitational effects. It is estimated that around 90% of the total mass of our galaxy is composed of dark matter, indicating that the majority of the mass exists in the form of dark matter. In addition, there are magnetic fields in our galaxy, and though these are not matter, they do affect the dynamics of gases. Also, cosmic rays which move at an extremely high velocity are also an important factor that determines the balance of interstellar matter.

Interstellar Matter and Interstellar Clouds

Interstellar matter does not exist consistently dispersed through space and instead exist mostly in cloud formations that are referred to as interstellar clouds. There are many types of interstellar clouds, ranging from enormous molecule clouds with high density, mass, and size, to clouds with relatively small density and mass. The volume of interstellar clouds occupies only a few percentage of the total volume of our Galaxy, and the remaining space is filled with thin gases with low density but very high temperature. It is believed that stars are created within interstellar clouds with high density, and there are many clouds in which we can directly observe the actual activities of star creation.

Observation of Interstellar Clouds

The existence of gas is difficult to detect since gas absorbs almost no light in the range of visible rays. Hydrogen, which is the most common element in the universe, emits radio waves with a wave length of 21cm when in a neutral state. Therefore, with the development of radio telescopes, we came to know

of the existence of interstellar gas. Interstellar clouds also contain many

molecules such as hydrogen molecules, carbon monoxide, water vapor, etc.? The

majority of these molecules also generate emission lines in the radio wave zone

and therefore we observe them using radio telescopes. Based on the observation

of emission lines, we are able to measure the motion, temperature, density, etc. of

the interstellar clouds. However, because hydrogen, the most common molecule,

does not give out any radio emission lines, it is difficult to observe directly.

Recently, we have been able to use emission or absorption lines from hydrogen

molecules that appear in the infrared zone.

Interstellar Dust

Interstellar dust comprises a very small portion of the total of interstellar matter, but they have the function of absorbing or dispersing stellar light. Interstellar dust is generally known to be composed of silicate compounds and carbon, and some heavy molecules that exist within the galaxy, such as calcium, aluminum, and silicon, are mostly captured within the dust and therefore almost none of these remain in the interstellar gas. The size of interstellar dust is approximately less than 0.1 microns, and since light with shorter wavelengths are more easily absorbed, light that has passed through clouds including interstellar dust changes in color to red. This phenomenon is called interstellar reddening. Due to interstellar reddening, the existence of dust has been known to us far earlier than the existence of gas. Dust is thought to be created by stellar wind coming from the surface of late type stars or by substances emitted at the time of a supernova explosion.

The Distribution of Stars and Interstellar Matter in the Galaxy

Our Galaxy is a spiral galaxy, and the majority of our stars and interstellar

clouds are located in the very thin circular disk. Among the stars, early type

stars that are very young in age have are very thin in their distribution along

with interstellar matter. By contrast, very old stars form much thicker disks.

Many of the stars are included in stellar clusters, which are groups of numerous

stars. Stellar clusters that exist in our Galaxy can be broadly categorized into

globular clusters, open clusters and stellar associations. Globular clusters are

groups in the shape of spheres composed of hundreds of

thousands of stars, aged 10 billion years or more. Globular clusters are not limited to the disk of the Galaxy, and are found distributed evenly across the entire spherical galaxy. In the early 20th century, the American astronomer Harlow Shapley observed that the distribution of globular clusters tended to be concentrated toward the Sagittarius in the celestial sphere, and thus first identified that the sun was far away from the core of the Galaxy. By contrast, open clusters are composed of a far fewer number of stars and their shapes are also relatively irregular, mostly being located on the disk of the Galaxy. The age of open clusters are far younger than the age of globular clusters, ranging from tens of millions of years to billions of years. Stellar associations are groups of stars comparatively small in scale ad composed of very young stars, and are also distributed on the Galaxy’s plane. Since the stars of stellar associations were created not long ago, they can usually be found in the regions where stars are being created. The core of the Galaxy has a nuclear bulge that is mostly composed of old stars.

The Core of Galaxies

Our Galaxy is very difficult to observe using visible light since there is much gas and dust in the direction of the nucleus. By measuring the distribution of gas using radio telescopes, we were able to learn the existence of molecular clouds surrounding the core of the Galaxy. Also, based on the movement of gas and stars very close to the core of the Galaxy, we came to know of the existence of a heavy black hole that is more than 2 million times the mass of the sun. This type of black hole in the center of a galaxy is commonly found not only in our own Galaxy but also in many external galaxies. The black hole with immense mass in the center of a galaxy is thought to be the cause of the powerful energy emitted from active galaxies or Quasars.

The Death and Birth of Stars

Stars have a limited life span. The stars that exist in our Galaxy are diverse in

age. This indicates that the birth of stars has continued to occur. In actuality,

among the interstellar clouds with large mass, there are many locations where

stars continue to be created. By contrast, some stars are entering into the last

phase of their evolution, having ended their life span. Stars with large mass

experience a supernova explosion at the final stage of their evolution. In our

Galaxy, there exist multiple supernova remnants, which are gases that have

spread out after the explosion of a supernova. In this manner, a star is created

by the contraction of an interstellar cloud but once it has completed its

evolution, it returns the majority of its mass back into the interstellar cloud. Our

Galaxy is thus a kind of ecosystem in which stars and gases circulate.

Large Scale Structure- Galaxies

Studying the distribution of matter on all scales may give clues as to what the distribution of matter was like at earlier times -- especially on the largest scales as the Universe isn't old enough for the largest scale distributions to have changed much.

this is a relatively new area in astronomy (such issues didn't arise when galaxies were still thought to be part of the Milky Way!).

Concept of hierarchical structures meaning small objects group together to form larger entities which group together to form yet larger entities and so on has been one theme for studying structures in the Universe.

Galaxies => Groups => Clusters => Super clusters

Milky Way is a member of the Local Group which lies on the outskirts of the Virgo Super cluster. The Virgo Cluster is the nearest cluster. The Local Group consists of two large spirals (Milky Way and M31), a small spiral (M33), and a number of irregulars and small elliptical for a total of about 20 members.

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Stars

A fixed star (or star) is a mass of gases gathered together had having energy sources (nuclear fusion energy) that self-generate light and that maintains equilibrium of gravity and pressure (statics equilibrium) in space. Rather than identifying individually differentiated features of each star, we systematically categorize the stars according to criteria based on specific physical quantities. Physical quantities that can distinguish stars include the star’s age, magnitude, mass, radius, surface temperature, luminosity and chemical components, etc. and these physical quantities can be identified through observations and theoretical methods based on the observational data.

Star Populations

Stars can be categorized into two distinct populations. In astronomy, elements that are heavier than hydrogen and helium are collectively referred to as metals, and stars that have an abundance of metals and are young in age is categorized as Population I stars. By contrast, old stars with a deficiency in metals are referred to as Population II stars.

Star Clusters

Based on much observation, astronomers have determined that the majority of observed stars form a binary system or a multiple star system,

and a large number of stars compose a star cluster. A star cluster refers to a group of stars that have been created at nearly the same time period and exercise gravitational force on one another. Such clusters can be divided into two categories, namely open clusters where stars are gathered together but are dispersed without any specific form, and globular clusters where stars are gathered into a spherical form. If we assume that the distances to all stars within the cluster are the same, we are able to compose an H-R diagram using the color and apparent magnitude of each star within the cluster. Using the H-R diagram, it has been identified that in an open cluster, the majority of stars are young and bright, while by contrast in a globular cluster, the majority of stars are old and dark. Also, we use the term OB stellar association to refer to regions where, though the stars are not as densely gathered as in a star cluster, there is a concentration of stars with O and B spectral types. The stars that exist in the OB stellar association are very young astronomical objects that have been created a short period ago. By this observing, researching and understanding the observable stars, we gain the foundation for comprehending the structure and history of our galaxy.

The Sun

The Sun dominates the Solar System in many respects (e.g., mass, energy production), but luckily for astronomers, the Sun is a very average star and therefore useful as a basis for understanding all stars. The output characteristics of the Sun define the habitable zone in the Solar System. It is the only star whose surface we can study in any kind of detail.

The sun is the fixed star that is closest in distance from the earth, and is the

most important celestial body available for the study of stars. The

appearance of the sun differs depending on the wavelength used in the

observation. By observing the visible rays, we can clearly identify the

photosphere emitting bright light and observe the sunspots on the surface.

When we observe using X-rays, the photosphere appears relatively dark

while the corona, composed of extremely hot gas, or the areas near the

sunspots with high activity appear very bright. The corona

cannot be seen by the visible rays under ordinary circumstances due to the bright light emitted from the photosphere, but during a total solar eclipse, the corona can be seen shining brightly.

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The Structure of the Sun

The interior of the sun is composed of the core that generates the energy, the radiation layer that conveys this energy outwards, and the convection layer. The sun’s surface consists of the atmospheric layer composed of the photosphere, the chromosphere, and the corona. The visible rays that our eyes can observe are emitted from the photosphere with structure including sunspots and granulations. The granulations are created by convective phenomena on the inside of the photosphere, while the sunspots appear dark because of their low temperature with the existence of a strong magnetic field. There are variations in the time period when the sunspot population reaches its peak on a cycle of 11 years. The chromatic layer is the region that appears pink during a total solar eclipse, and this is where we observe phenomena such as spicules, prominence and flares. The border region between the chromatic layer and the corona is referred to as the transition region, where a mere increase of around 300 km is accompanied by a temperature increase of 1 million degrees and where can be found the cause of various phenomena that occur on the sun or of those phenomena that we refer to as solar activities. The corona remains in high temperature of around 1 million degrees, and appears silvery white during a total solar eclipse. This is the region where the solar wind emitted from the coronal hole is dispersed. It has not yet been accurately explained how the corona is able to maintain such a high temperature.

The Energy Source of the Sun

The sun emits an enormous quantity of energy amounting to

approximately 4x1033 erg per second. This energy is generated by the fusion of hydrogen near the sun’s core. The fusion of 1 g of hydrogen transforming into helium results in converting approximately 0.007g of the mass in to energy. This is the means by which the sun is able to stably emit energy for around 10 billion years. This generated energy passes through the radiation layer in the core region and the convection layer in the outer region during its movement to the surface and is then emitted into outer space. The earth maintains its current temperature by receiving the light emitted by the sun.

Solar Wind

Solar wind refers to the rarefied gas that is emitted from the sun’s surface and flies out into the empty space between planets. The emission of solar wind is particularly increased during the time period when the population of sunspots is on the rise, and in some cases the solar wind affects the magnetosphere surrounding’ the earth’s atmosphere, resulting in disruptions of communications here on earth.

Solar Magnetic Field and Sunspots

We knew that the Sun had a strong magnetic field and that sunspots have even stronger fields than in the quiescent Sun without sending any space probes to measure the field.

How? -- By taking advantage of the Zeeman effect the magnetic field in a star can be measured. The Zeeman Effect arises because an electron orbiting an atomic nucleus is a moving electrical charge which generates a magnetic field.

So the electron's energy levels are slightly altered by an external field and hence the emitted or absorbed wavelengths are slightly changed. Note that a spectrograph has to have good performance to detect Zeeman splitting as the wavelength shifts are rather small!

Cosmology

Cosmology is a field of astronomy that deals with the universe as a whole, an academic field that addresses questions such as the following: what is the universe composed of, and what its structure is. How was the universe created and how has it evolved. What is the ultimate fate of the universe These are some of the most fundamental questions that have also been the subject of religion and philosophy for the past millennia. However, it was only the past few centuries that cosmology became accepted as a topic and object of scientific inquiry, and currently an abundance of research in this field has brought us to a stage where we can now expect to find substantive answers. The scope of cosmology? is immense in both time and space since it studies the universe itself. Modern cosmology surprising simultaneously encompasses both the microcosmic world of particles as well as the macrocosmic universe. By integrating both microcosmic and macrocosmic worlds in its range of study, cosmology has shown us the features of the early universe, and presented us with significant answers regarding the origin of substance. Up to recent times, cosmology lacked sufficient comparative observational data and relied mostly on theoretical research based on the theory of relativity. However, energized by contemporary astronomy’s astounding new developments in observatory technology, cosmology has achieved remarkable developments in the past two decades. Observation has contributed to the establishment of the Big Bang theory which widely accepted today.

Cosmic Background Radiation (CBR)

After Hubble’s law, the next astronomical observation important to cosmology was the discovery of cosmic background radiation in 1965. Based on the theoretical research regarding the Big Bang theory, it anticipated that the current universe would be full of black body radiation with a temperature of around 3K, and such background radiation was indeed verified through actual observation. Such cosmic background radiation is nearly consistently distributed throughout the universe, not only supporting the theory that the universe was created by a Big Bang but also evidencing the isotropy and consistency of the universe. This coincides with the Cosmological Principle, the basic working assumption behind attempts to establish a model of the evolving universe.

The Geometrical Structure of the Universe

Before the discovery of Hubble’s law, Einstein proposed a static model of the universe based on his own theory of relativity, but once Hubble’s law was discovered, it was necessary to revise this into a model of an expanding universe. Thereafter, Friedman also presented a model based on the theory of relativity and corresponding to Hubble’s law. According to Friedman’s model, it is possible to envision an open universe, a closed universe, and a flat universe depending on the curvature of the universe. Another major challenge for modern cosmology is to use observational astronomy to determine which of these three models would be an accurate reflection of the current universe. Although this is an extremely difficult project, several methods have been proposed. ?If the density of the universe is larger than the critical density, it is a closed universe, and if the density is less, it is an open universe. Accordingly, we can reach a conclusion if we can determine the density of the current universe, but to do so, we must first know the material content of the whole universe . The results of up to the present indicate that the observed density of the

universe does not exceed a few percentages of the critical mass and therefore it seems to be an open universe. However, since this density is only the lower limit value and since it has been discovered that there is an immense amount of dark mass that is not actually visible, it is difficult to reach a conclusion.

The Early Universe

It is believed that the universe was created by a great, hot explosion called the Big Bang. In the first moments, the density and temperature must have been so high that we do not have a theory capable of explaining the physical phenomena under such conditions. However, regarding the process of evolution from the Big Bang to the present, we do know that between the first 10-45to 10-30seconds, the universe underwent an epoch of rapid inflation in which it expanded more than 1050 times, then passed through a hadron epoch, a lepton epoch, a radiation dominated epoch, and a matter dominated epoch before reaching the present time.

External Galaxies :

The universe contains numerous galaxies. Even up to the early 20th century, we had almost no knowledge of the existence of external galaxies, but once we were able to measure distances through Cepheid, etc. it became known that many of what we had considered nebulae were actually external galaxies. External galaxies are very diverse in all aspects, including their shapes, sizes, and masses, etc. Many galaxies are gathered together in our universe.

Types of Galaxies and their Categorization

According to their external appearance, galaxies are broadly categorized

into spiral galaxies, elliptical galaxies, and irregular galaxies. Spiral

galaxies are in the structure of a very thin disk with spiral arms. Elliptical

galaxies appear in the shape of an ellipse and are far more

gently sloping compared to spiral galaxies. Irregular galaxies refer to those that are irregular in shape unlike spiral galaxies or elliptical galaxies. Spiral galaxies are more specifically categorized according to the degree of looseness or tightness of the spiral arms, while elliptical galaxies are subdivided according to the degree of contortion. In general, elliptical galaxies are composed of stars of old age, the movements of the stars are relatively irregular, and it does not contain a lot of cold interstellar matter that are capable of forming new stars. By contrast, old and young stars coexist in spiral galaxies, indicating that the activity of star birth continues to occur today in these galaxies. Spiral galaxies contain a lot of gases capable of creating stars, and the stars move on a circular orbit on the disk. While elliptical galaxies have a very wide range of mass, spiral galaxies have a relatively narrow range of mass. The spiral arms of the spiral galaxies are formed by spiral density waves and rotate at a constant velocity unlike the stars.

Galaxy Clusters

Groups consisting of hundreds to ten thousands of galaxies are referred to as galaxy clusters. In particular, clusters with a high number of clusters are called rich galaxy clusters. The Virgo galaxy cluster is the closest to our own galaxy, being around 178 Mpc away. Also, the Coma Berenices cluster is located around? 90 Mpc away, and this galaxy cluster is estimated to be composed of ten thousands of galaxies. The diameters of galaxy clusters are within the range of several Mpc. Galaxy clusters are organically interrelated and thereby form a far larger structure that we refer to as a super cluster of galaxies. The length of a super cluster of galaxies occupies around 10% of the size of the observable universe. In the central region of the majority of rich galaxy clusters, there is an enormous elliptical galaxy with great mass.

Hubble’s Law

Galaxies are moving away from one another at a velocity proportional to their distance, and this is referred to as Hubble’s Law. Hubble’s Law is evidence that the universe is expanding. Using Hubble’s Law, we are able to estimate the distance to a very far galaxy. Hubble’s Law and

Cosmic Background Radiation are important observed data that support the Big Bang theory of cosmology. The velocity of galaxies’ receding movements is observed by red shifts in the spectrum. A red shift indicates the degree to which a wavelength has lengthened, and in cases where the value is much smaller than 1, the receding velocity is the quantity obtained by multiplying the velocity of light to the red shift. However, in cases where galaxies recede at a velocity close to the velocity of light, the red shift can have a value much greater than 1. According to the Big Bang theory, a celestial body with a red shift of z exhibits a light that started off in a past when the size of the universe was 1/(1+z) times its current size. The distance to a far galaxy is expressed simply using the red shift. Among the celestial bodies that have been hitherto discovered, the largest red shift is around z~6, and these show us the state of the universe when its age was around a billion years old.

The Birth and Evolution of Galaxies

When the universe was first created, the distribution of mass was very consistent, but there was a very small degree of density fluctuation. It is thought that as time passed, regions with high density contracted to create galaxies or galaxy groups, and the regions with low density became voids. A large amount of dark matter is required to form a galaxy. Depending on the properties of the dark matter, the formation of the galaxy and its evolution varies greatly. According to the cold dark matter theory that is favored by many scholars today, after galaxies relatively small in size were created in the universe, these collide, combine and grow into a larger galaxy. However, no observed data has been able to verify the existence of this process. However, it appears indisputable that the collision and merger between galaxies is an important factor that determines evolution.

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