MAHATMA GANDHI MISSION’S COLLEGE OF ENGINEERING AND TECHNOLOGY

KAMOTHE, NAVI MUMBAI - 410209.

Electronics & Telecommunication Department T.E. / A

GROUP 1

A Report on ANCIENT AND MODERN ASTRONOMY

SUBMITTED TO

PROF. SRIDEVI NAIR.

DATE OF SUBMISSION: 10 September 2014.

A PROJECT REPORT ON

ANCIENT AND MODERN

ASTRONOMY:

A Quest To Understand The Universe

PREPARED BY:

1. Madhuri Aldar

2. Amrut Anantwar

3. Anjali Ayambara

4. Nimish Bagwe

5. Aditya Bali

6. Kshitij Bane (Group Leader)

7. Lalita Bhondivale

MGM’s College of Engineering and Technology

Kamothe, Navi Mumbai-410209

Electronics And Telecommunication Engineering Department

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PREFACE

The report “Ancient & Modern Astronomy” refers to

the study of celestial objects outside the boundaries of our

Earth, how ancient civilizations made great discoveries

through observations & how modern means have made us

able to understand the universe.

We have made sincere attempts and take every care to

present this matter in precise and compact form, the language

being as simple as possible.

We are sure that the information contained in this report

would certainly prove useful for better insight of this topic

which most of the common people find complicated.

The task completion of the report though being difficult

was made quite simple, interesting and successful due to deep

involvement and complete dedication of our group members.

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ACKNOWLEDGEMENT

It’s been a privilege working under Sridevi Madam for

developing this report. Taking this opportunity to express

our deep sense of gratitude and thankfulness to our guide Ms.

Sridevi Nair for timely and valuable guidance which help us

to complete our report.

Thanks to our respected principal Dr. S. K. Narayankhedkar

and our HoD Dr. B. Dubey sir for this support and facilities

provided to us for the report and Sridevi madam your

incorporable measure of the knowledge has really helped us to

bestow our report.

Lastly thanks to our group members who helped us to

make this project work of great appraisal to be recognized as

one of our identity.

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TABLE OF CONTENTS

A) PREFACE I

B) ACKNOWLEDGEMENT II

C) ABSTRACT IV

1) INTRODUCTION 1

2) ANCIENT ASTRONOMY 3

2.1 Early Astronomy 4

2.2 Ancient Indian Astronomy 8

2.3 The Copernican Revolution 11

3) THE SPACE AGE 16

4) THE SOLAR SYSTEM 18

5) THE UNIVERSE 30

5.1 Galaxies 31

5.2 Stars 35

5.3 Nebulae 38

6) UNSOLVED MYSTERIES 40

6.1 The Big Bang Theory 40

6.2 Dark Matter & Dark Energy 42

6.3 Quasars & Wormholes 44

6.4 End of the Universe 45

CONCLUSION 46

BIBLIOGRAPHY 47

IV

ABSTRACT

Astronomy studies the universe beyond Earth, including the

formation, development & evolution along with the physics

& chemistry of celestial objects such as Stars, Planets,

Galaxies & awe inspiring phenomena like Nebulae,

Supernovas, Black Holes & Quasars.

Astronomy was an integral part of many early civilizations. It

was connected to the religious & spiritual outlook of the

world. It was believed that the heavenly bodies have

powerful influence upon human life.

Throughout these years we have made great discoveries

regarding the celestial bodies. We have developed many

theories explaining how & why we are here. Our knowledge

of what lies beyond the boundaries of earth may be

considerable, yet we are still fascinated about the space.

There is still a sense of awe towards the universe.

This report will take us on a journey of discoveries, a voyage

through the time, a quest to understand the universe.......

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1. INTRODUCTION

Astronomy is arguably the oldest science. The night skies &

astronomical bodies have been a source of wonder & speculation

since the development of early civilizations. The term ‘Astronomy’

derives from an ancient Greek phrase meaning the laws or science

governing the stars. However, Astronomy is not just the study of

stars; rather it is the study of all the celestial phenomena.

Today we might say that astronomy is our attempt to study and understand celestial phenomena, part of the never-ending urge to discover order in nature. We do not know who were the first astronomers—what we do know is that the science of astronomy was well advanced in parts of Europe by the middle of the third millennium BC and that the Chinese people had astronomical schools as early as 2000 BC. In all ages, from the burgeoning of man’s intelligence, there have been people fascinated by the heavens and their changing aspect and these people, as far as their cultural environment has allowed them, have tried to formulate cosmologies. We are no different today. The Sun, with its life giving energy, was deified, its daily journey across the skies imbued with religious significance. The ancient Egyptian were the first to calculate the length of a solar year, adding five days to their original 360-days calendar, a margin of error of just six hours. Where myth & mysticism led, scientific discovery was quickly followed. 5000 years on, our knowledge of the Solar system and what lies beyond may be considerable, yet the sense of awe is hardly less than that experienced by the earliest observers.

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If our current theories of the Universe are nearer the truth, it is probably not that our intelligence has increased in the past six millennia. It is more likely that the main factor has been the discovery and development of the ‘scientific method’, which has led to our present civilization based on the flood of technological advantages provided by this method. This has enabled scientists in far greater numbers than ever before to devote their lives to the study of the heavens, assisted by telescopes, computers, space vehicles and a multitude of other equipment. Their attempts to interpret and understand the wealth of new information provided by these new instruments have been aided by allied sciences such as physics, chemistry, geology, mathematics and so on... The canvas of space & time is vast; 15 billion years since the Big Bang, when the entire universe occupied the space of a sub-atomic particle; 4.5 billion years since a cloud of gas & dust collapsed to form the star which sustains life on Earth. To study an object in deep space is to see hundreds of millions of years into the past.

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2. ANCIENT ASTRONOMY

Astronomy is the science of understanding everything that goes on beyond Earth’s boundaries. It is one of the oldest of sciences. Every civilization, through antiquity to the recent past, had stunning views of stars night after night, as sightings of the cosmos would not have been hampered by the light pollution and an indoor life style, both of which hide much of the heavens from observers today. All over the world some sort of the understanding of the celestial sphere was an integral part of civilization, whether or not they opted for scientific explanations of the observed phenomena. We must remember, however, that for more than nine-tenths of the last five thousand years of our study of the heavens, we have had to rely on the unaided eye. The Mediterranean people who set the constellations in the sky, the Babylonians, Egyptians and Greeks, the Arabian astronomers who flourished during the Dark Ages of Post-Roman Europe, the Chinese, the Mayan, the Indians and other early American astronomers, all built their theories of the Universe on naked eye observations.

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2.1 EARLY ASTRONOMY Ancient China Ancient Chinese civilizations paid close attention to the night sky because an important part of the culture’s philosophy was the idea of harmony between man and nature.

Oldest established culture with recorded astronomical observations.

First people to record solar eclipse, Super Nova, Stellar positions in a catalogue.

Chinese mythology held that an eclipse occurred when a dragon was eating the sun and that only way to defeat the dragon was to make as much noise as possible. In the event of an eclipse, people would make a mighty racket, which would scare the dragon off, & (naturally) the Sun would return.

Ancient Egypt

Pyramids are thought to have been aligned with the stars in Orion Belt to help facilitate the passage of the ‘Pharaohs’ into the afterlife.

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Used the star Isis (Sirius) to predict the flooding of the Nile for planting the crops & keep track of their year.

Many temples & structures built to honour Gods & keep track of heavenly movements.

Ancient Babylonians The Babylonians, an ancient Mesopotamian people who flourished between the Tigris & Euphrates rivers, in the area of modern day Iraq, were one of the earliest civilizations know to have adopted a scientific outlook towards the stars & planets.

Created the first recorded constellations

Created Zodiac (12 constellations, the Sun passes through each year)

Invented degree system used for positions in the sky

The Mayans

Built many structures to keep track of solstices & equinoxes.

Astronomy was an integral part of their culture & day to day life.

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Seriously obsessed with Venus- conducted wars based on the planet’s position & brightness.

The Ancient Greek The Ancient Greeks greatly advanced the scientific study of astronomy by placing an emphasis upon observations and data collections. Greece was hotbed for astronomical theories & observations as well as philosophy, mathematics, ethics, drama, politics & other scholastic pursuits.

Aristotle (384-322 BC, Greek)

Proved the earth is sphere using sailing ships & eclipse shadows

Geocentric view (the idea that the Earth lies at the centre of the universe)

Aristarchus (310-230 BC, Greek)

First suggested the Heliocentric model

Used simple geometry to calculate distance to Sun from the Earth

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Eratosthenes (276-195 BC, Greek)

Calculated the Earth’s circumference with almost

exact accuracy

Hipparchus (190-120 BC, Greek)

Created the first star catalogue

Calculated the accurate distance to the Moon

Invented trigonometry

Islamic Astronomers During the middle ages, in Western Europe the scientific development of astronomy stagnated. Most scientists, thinkers and ordinary people were content to support many of the ideas propounded by the Greeks, especially as it usually had the firm backing of the Church, with the result that to question the orthodox view was considered heresy. While the advance of astronomy lost momentum in Western Europe, it accelerated in the Islamic empire which spanned a wide area & population, from the Middle East, through North Africa and into Spain. Many of the works by Greek astronomers were translated into Arabic Knowledge of astronomy was useful in Islamic rituals, which interpreted the heavens as a guide to ensure prayers five times a day, to date religious festivals correctly & also to accurately locate Mecca.

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2.2 Ancient Indian Astronomy

Indian astronomy was heavily tied to their religious and spiritual outlook of the world, but it contained many accurate observations of phenomena. This acted as a catalyst for the growth of mathematics in the subcontinent, one of the greatest legacies passed on by India to the western world.

Ancient India's contributions in the field of astronomy are well known and well documented. The earliest references to astronomy are found in the Rig Veda, which are dated 2000 BC. During next 2500 years, by 500 AD, ancient Indian astronomy has emerged as an important part of Indian studies and its affect is also seen in several treatises of that period. In some instances, astronomical principles were borrowed to explain matters, pertaining to astrology, like casting of a horoscope. Apart from this linkage of astronomy with astrology in ancient India, science of astronomy continued to develop independently, and culminated into original findings, like:

The calculation of occurrences of eclipses Determination of Earth's circumference Theorizing about the theory of gravitation Determining that sun was a star and determination of number

of planets under our solar system

The Jyotish Vedanga, the first Vedic text to mention astronomical data, records events going back as far as 4000 BC. This period saw many advances in measuring time and the procession of the heavens, with a few proto-theories about the structure of the universe. More importantly, this period saw the transmission of

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ideas between the Indians, Babylonians, Greeks, and Persians. This exchange of theories and philosophy was extremely important to the development of astronomy.

Aryabhata (500 CE)

In this period, a new branch of astronomy, diverging from the Vedas began. Called the Siddhantic Era, it began with a series of books called the Siddhanta, which charted the solar year, including solstices, equinoxes, lunar periods, solar and lunar eclipses, and planetary movements.

The first properly recorded Siddhantic astronomy began in the 5th Century CE, where Indian astronomers such as Aryabhata began to adopt a more rigorous, mathematical approach to astronomy, directing it away from mysticism and its emphasis on the calendar. Aryabhata added to the heliocentric theory, proposing the idea that the moon reflects the light of the sun, a theory also proposed by some Greeks but not widely adopted. He also proposed that the earth rotated rather than the skies, although this theory lay undiscovered until the European Renaissance and Copernicus.

His idea, which included mathematical models about how to forecast eclipses, eventually found its way into Europe and influenced Renaissance thought. His book, the ‘Aryabhatia,’ was translated into Latin in the 13th Century. This work gave the Europeans some methods for measuring the volume of spheres and the area of triangles, as well as methods for calculating square roots and cube roots.

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Varahmihir (505 CE)

In the 6th Century, Indian astronomers proposed that the same force holding objects to the Earth also held the celestial bodies in place. This was an advance upon Anaximander’s idea of equilibrium and the recognition of a proto-gravitational theory, long before Newton. Varahamihira proposed that there must be some type of attractive force keeping objects stationary.

Brahmagupta (591 CE)

The Siddhantic astronomers also understood that the earth was spherical and attempted to calculate the circumference of the planet. In the 7th Century CE, the astronomer Brahmagupta arrived at a figure of 36 000 kilometers for the circumference of the earth, which is very close to the actual figure.

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2.3 The Copernican Revolution

The Ancient Greek philosopher, Aristotle, believed that the Earth was at the centre of the universe & all the bodies in the sky orbited the Earth. This is known as the ‘Geocentric Theory’.

However upon closer inspections, Aristotle’s idea of ‘perfect circles’ seemed to be flawed. Some planets, Mars in particular, seemed to switch briefly in retrograde orbits- as if they were temporarily doubling back upon themselves. Also the brightness of the planets appeared to vary as they orbited the earth. This all seemed to contradict Aristotle’s theory.

An answer, proposed by Claudius Ptolemy, was held as truth for centuries; he continued to advocate a geocentric system, arguing that the varying brightness & brief retrograde motion were result of epicycles.

All the theories & discoveries in that era were made with the background assumption that the Earth was the centre of universe. In Western Europe too, Ptolemaic theory was unchallenged & backed by the Church as it placed humanity as the central fact in the universe. Shortly after Aristotle’s death, Aristarchus proposed a heliocentric theory, but this was unpopular at that times.

Nicolaus Copernicus (1473-1543, Polish)

Copernicus was born in the Renaissance era, which saw an emphasis placed upon careful, scientific observations is Astronomy. Copernicus believed that the Ptolemaic system did not properly account for

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what he observed in the heavens. He explained the Mars’s retrograde motion as an optical illusion, caused by the fact that the Earth is orbiting the Sun faster than Mars.

Copernicus became the first realize the true order of the planets in the solar system; Earth was demoted from the centre of the universe to the third rock from the Sun. He published his findings in the book De Revolutionibus Orbium Coelestium, in 1543, the year of his death. The Church was not too bothered by such heresy. Copernicus died before he could be challenged and, moreover, he had asserted that the planets orbited the Sun in perfect circles. However observational evidence suggested this was not the case. It fell to another scientist Johannes Kepler, to make sense of this problem.

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Johannes Kepler (1571-1630, Germen) Using the observational data compiled by Danish astronomer, Tycho Brahe, Kepler first suggested that the orbits of the planets were ellipses rather than circles. When Brahe moved to Prague, Kepler became his assistant. The men were great rivals, but Brahe’s observations & Kepler’s theory made for a fruitful collaboration as Kepler was able to prove the elliptical orbits of the planets. Kepler’s laws of planetary motion:

1. The orbit of a planet is an ellipse with the Sun at one of the two foci.

2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

3. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Galileo Galilei (1564-1642, Italian)

This new wave of astronomical thinking did not arouse the interest of the Church until it reached Italy at the beginning of 17th century. Galileo was unwilling to commit to a heliocentric model until there was sufficient observational evidence. To gather such evidence, Galileo pioneered the use of Telescope in astronomy by advancing the new Dutch invention for studying the heavens.

Many of the things he saw through his telescope seemed to rule against the geocentric model. He identified four moons (Ganymeda, Callisto, Europa & Io) orbiting Jupiter. He also observed the sunspots.

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Sir Isaac Newton (1643-1727, English)

Although Kepler had described how planets orbit the sun, he never managed to explain why they do so in such fashion. That was an unknown for over half a century until the English physicist, Isaac Newton, established his three laws of motion & a law of Universal Gravitation in his book Principia published in 1678.

Newton’s law of Universal Gravitation:

Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them

Newton’s ideas were groundbreaking. They explained why an apple fell to the ground as well as why the planets were held in orbits around the Sun. However Newton’s theory of gravity did not account for every eventuality. It was unable to explain the perihelion (closest point to the Sun) shift of Mercury. It was calculated that the gravitational pull of the sun & other seven known planets was not sufficient to explain the advancing perihelion of Mercury. The puzzle was not solved until a young Germen-born physicist, Albert Einstein, established a new theory of Gravity.

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Albert Einstein (1879-1955, Germen)

In 1905, while working as a desk clerk for a Swiss patent office, Einstein published his ‘Special theory of Relativity’. Essentially, Einstein had proved that, in a vacuum, light always travels at a constant speed of 300,000 km/s, relative to an observer. His theory also states that the velocity of light in vacuum is the fastest speed attainable in the universe. The special relativity had shown that distance as well as time was variable.

In General relativity (published in 1915), Einstein adopted the view that space & time are linked in a four-dimensional unit called ‘spacetime’. General theory of Relativity holds that the mass distorts spacetime. It is the distortion of the spacetime by mass rather than the mass itself that is responsible for the gravitational attraction.

Einstein had worked out the mathematics behind General Relativity & it even accounted for advancing perihelion of Mercury. The scientific community was understandably sceptical; Einstein needed a proof that his theory worked in practice. The result of observations of eclipse of May 1919 showed that the actual position of stars behind the sun did not match their apparent position. Such an occurrence could only be explained by General Relativity; the Sun was distorting the fabric of spacetime & the light from the stars was being bent. Einstein turned into an overnight celebrity & became the most prominent scientist of the 20th century.

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3. THE SPACE AGE

The Space Age was an entirely new era ushered in by the end of the Second World War and emerging nuclear power as well as the beginning of the Cold War. The Space Age began in October of 1957 when the Soviets launched Sputnik 1, the first satellite, into space. This was when space exploration first became possible. The Space Age came about as the Soviet Union and the United States started competing in arms and technology as well as to see which country would make it into space first. Thus the Space Race between the Soviets and America was a vital part of the Space Age. About a month after the Soviets sent Sputnik 1 into space, they sent the space dog Laika up into orbit in Sputnik 2.

On 12 April 1961, the Soviet Union successfully put a man in space. Cosmonaut Yuri Gagarin spent 108 minutes orbiting the Earth once in the Vostok 1 probe. Less than a month later, On 5 May, Alan Shepard became the first American in space. It was not until February 1962, that an American successfully orbited the earth; John Glenn, aboard Friendship 7 circled the Earth 3 times.

Yuri Gagarin

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One of the highlights of the Space Age was the Apollo program. NASA’s Apollo 8 astronauts became the first men to leave Earth’s gravity & orbit the Moon. The most famous of the Apollo aircraft is Apollo 11, which was the craft carrying Commander Neil Armstrong and his fellow astronauts Michael Collins and Buzz Aldrin to the Moon. On that mission, Armstrong and Aldrin were the first humans to land and walk on the Moon. They were later followed by a number of other astronauts. Apollo 11 astronaut Buzz Aldrin

Probes were sent out to study many planets and their satellites,

including the Voyager probes and the Viking probes. These probes

are to thank for much of what we know about some of the other

planets in our Solar System. One recent historic event was the

creation of the Hubble Space Telescope in the early 1990’s. This

enormous project cost $1.5 billion and has allowed scientists to learn

much more about our Solar System as well as others.

Launch of Space Shuttle Discovery Hubble Space Telescope

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4. THE SOLAR SYSTEM

‘The Solar System’ is the name given to the planetary system of

which the Earth is part. It comprises 8 planets, moons, comets,

meteors, asteroids & dwarf planets which are all held together by

the gravitational pull of a star, named either the Sun or ‘Sol’.

Formation of the solar system:

The formation of the Solar System is estimated to have begun 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a proto planetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.

The Planets:

The known planets in the solar system can be divided into two

groups. The four planets closest to the sun: Mercury, Venus, Earth &

Mars are called the ‘terrestrial planets’. The outer four planets are

called the ‘gaseous giants’ or ‘Jovian planets’. The terrestrial & Jovian

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planets are divided by a belt of asteroids between Mars & Jupiter.

Pluto was demoted to the status of ‘Dwarf planet’ giving it home

among similar sized objects & asteroids which make up the Kuiper

Belt.

End of the solar system:

It is difficult to calculate exactly where our solar system ends. It ends

at a point at which objects are no longer affected by the sun’s

gravitational pull. The farthest reaches of the solar system are

thought to be surrounded by a great halo: Oort cloud; home to

millions of comet nuclei & small icy rocks.

Voyager 1 & 2 are the farthest reaching man-made objects in the

solar system. In 2004, Voyager 1 cleared the termination shock, the

area where solar winds begin to slow down & increase in

temperature as they come up against interstellar winds. Voyager

probes will continue transmitting data for several more decades, but

it would take thousands of years for them to reach the nearest star,

Alpha Centauri.

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4.1 THE SUN:

In the grand scheme of the universe, the sun in just another middle

aged star. Its stellar classification, G2, denoting its yellowish

colouring & its surface temperature (5000°-6000° kelvin) is not

extraordinary either; there are countless G2-type stars.

Fusion:

In the sun, Hydrogen nuclei collide with one another to form Helium

atoms. In this process, called ‘fusion’, mass is transferred into

energy, which is explained by Einstein’s famous equation: 𝐸 = 𝑚𝑐2.

The period during which sun generates energy through fusion is

called ‘Main sequence’. Our sun is estimated to be 5 billion years old

& its main sequence will last another 5 billion years.

Solar Layers:

The atmosphere of the sun is

composed of several layers, mainly

the photosphere, the chromosphere

and the corona. It's in these outer

layers that the sun's energy, which

has bubbled up from the sun's

interior layers, is detected as

sunlight.

Sunspots:

These are minor regions where the temperature of the photosphere

is cooler than its surroundings. Sunspots are the result of string

localised magnetic field & follow a cycle of 11 years.

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4.2 MERCURY

Mercury is the smallest and closest to

the Sun of the eight planets in the Solar

System, with an orbital period of about

88 Earth days. Seen from Earth, it

appears to move around its orbit in

about 116 days, which is much faster

than any other planet. It has no

known natural satellites. The planet is

named after the Roman deity Mercury;

the messenger to the gods

Mercury has almost no atmosphere. Its surface is heavily cratered

due to impacts from meteorites.

4.3 VENUS

Venus is the second planet from

the Sun, orbiting it every

224.7 Earth days. It has no natural

satellite. It is named after the Roman

goddess of love and beauty. After

the Moon, it is the brightest natural

object in the night sky, bright enough to

cast shadows. Venus is a terrestrial

planet and is sometimes called Earth's

"sister planet" because of their similar

size, gravity, and bulk composition.

It is the hottest planet in solar system. It rotates on its axis from east to west. Therefore, on Venus the sun rises in west & sets in east.

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4.4 EARTH Earth, also known as Terra, is the

third planet from the Sun,

the densest planet in the solar system,

the largest of the Solar System's for

terrestrial planets, and the only celestial

body to accommodate life. It is home to

millions of species, including billions of

humans.

The Earth takes 365.26 days to orbit the sun & 23.93 hours revolve

once around its axis which is tilted 23.5° to the planet’s orbit.

4.5 THE MOON

The Moon (Latin: Luna) is the Earth's

only natural satellite. Although not the

largest natural satellite in the Solar System,

it is, among the satellites of major planets,

the largest relative to the size of the object

it orbits and, after Jupiter's satellite Io, it is

the second densest satellite among those

whose densities are known.

The Moon is in synchronous rotation with Earth, always showing the

same face with its near side marked by dark volcanic maria that fill

between the bright ancient crustal highlands and the prominent

impact craters . It is the most luminous object in the sky after

the Sun. It takes moon 27.3 days to revolve around earth.

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4.6 MARS

Mars is the fourth planet from the Sun

and the second smallest planet in the

solar system, after Mercury. Named

after the Roman god of war, it is often

described as the "Red Planet" because

the iron oxide prevalent on its surface

gives it a reddish appearance.

Mars’s atmosphere is consists of 95%

of carbon dioxide & remaining 5% of Argon & Nitrogen. Average

surface temperature is 60° Celsius. Because of this water exist on

mars in frozen & vapour form.

4.7 JUPITER

Jupiter is the fifth planet from the

sun and the largest planet in the solar

system. It is a gas giant with mass one

thousandth of that of the sun but is

two and a half times the mass of all

the other planets in the Solar System

combined.

Jupiter is primarily composed

of hydrogen with a quarter of its mass being helium. There are also

at least 67 moons, including the four large moons called the Galilean

moons that were first discovered by Galileo Galilei in

1610. Ganymede, the largest of these moons, has a diameter greater

than that of the planet Mercury.

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The Giant Red Spot is its most notable feature. It is a giant storm

which flows anti-clockwise across in area of 24,000 km in length &

12,000 km in width.

4.8 SATURN

Saturn is the sixth planet from the

sun and the second largest planet in

the Solar System, after Jupiter. It is

named after the Roman god of

agriculture. Saturn is gas giant with

an average radius about nine times

that of Earth. While only one-eighth

the average density of Earth, with its

larger volume Saturn is just over 95 times more massive.

One of the greatest fascinations of the solar system is the Rings of

Saturn. They have often earned Saturn the title of the most attractive

planet in solar system.

Titan, Saturn's largest and the Solar System's second largest moon, is

larger than the planet Mercury and is the only moon in the Solar

System to retain a substantial atmosphere.

4.9 URANUS

Uranus is the seventh planet from the Sun. It

has the third-largest planetary radius and

fourth-largest planetary mass in the Solar

System. Uranus is similar in composition

to Neptune, and both are of different

chemical composition to the larger gas

giants Jupiter and Saturn. For this reason,

astronomers sometimes place them in a

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separate category called "ice giants".

It is the coldest planetary atmosphere in the Solar System, with a

minimum temperature of −224.2 °C and has a complex, layered cloud

structure, with water thought to make up the lowest clouds, and

methane the uppermost layer of clouds. In contrast, the interior of

Uranus is mainly composed of ices and rock.

4.10 NEPTUNE

Neptune is the eighth and farthest

planet from the sun in Solar System.

It is the fourth-largest planet by

diameter and the third-largest by

mass. Among the gaseous planets,

Neptune is the densest. Neptune is

17 times the mass of Earth and is

slightly more massive than its near-

twin Uranus, which is 15 times the

mass of Earth but not as dense.

Neptune orbits the Sun at an average distance of 30.1 astronomical

units. It is named after the Roman god of the sea.

Neptune's atmosphere is notable for its active and visible weather

patterns. For example, at the time of the 1989 Voyager 2 flyby, the

planet's southern hemisphere possessed a Great Dark Spot

comparable to the Great Red Spot on Jupiter.

4.11 PLUTO & THE KUIPER BELT

Discovered in 1930, Pluto was originally classified as the ninth planet

from the Sun. Its status as a major planet fell into question following

further study of it and the outer Solar System over the ensuing 75

years. Starting in 1977 with the discovery of the minor planet 2060

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Chiron, numerous icy objects similar to Pluto with eccentric orbits

were found. The most notable of these was thes cattered disc

object Eris, discovered in 2005, which

is 27% more massive than Pluto.

Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Nix, Hydra, Kerberos & Styx.

On July 14, 2015, the Pluto system is due to be visited by spacecraft for the first time. The New Horizons probe will perform a flyby during which it will attempt to take detailed measurements and images of the plutoid and its moons.

KUIPER BELT:

Kuiper Belt is a region of the Solar System beyond the planets,

extending from the orbit of Neptune (at 30 AU) to approximately

50 AU from the Sun. It is similar to the asteroid belt, but it is far

larger—20 times as wide and 20 to 200 times as massive. Like the

asteroid belt, it consists mainly of small bodies, or remnants from the

Solar System's formation. Although most asteroids are composed

primarily of rock and metal, most Kuiper belt objects are composed

largely of frozen volatiles (termed "ices"), such as methane,

ammonia & water. The Kuiper belt is home to at least three dwarf

planets: Pluto, Haumea, and Makemake. Some of the Solar System’s

moons, such as Neptune's Triton and Saturn's Phoebe, are also

believed to have originated in the region.

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4.12 MINOR BODIES IN SOLAR SYSTEM

4.12.1 ASTEROIDS

Asteroids are fragments of rock & metal which are greater than 50m

in diameter. On New Year’s Day 1801, the Italian astronomer,

Giuseppe Piazzi, discovered the first asteroid Ceres. Initially he

thought it was a comet, but its orbit was too slow & uniform. Some

scientists suggested it might be a planet between Mars & Jupiter. But

in 1802, second asteroid was discovered, named Pallas. This 2nd find

led William Herschel, the discoverer of Uranus, to offer a collective

name ‘asteroids’, meaning ‘Star-like’.

Many of the asteroids in the solar system are located in a band

between Mars & Jupiter called the ‘Asteroid Belt’. It is believed that

the belt is failed planet- the chunks of rock & metal were unable to

group together & form 5th terrestrial planet because of the strong

gravitational pull of Jupiter.

4.12.2 METEOROIDS

Meteoroids can be found throughout the solar system. They are

small fragments of rock & minerals, often the size of a grain of sand.

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Meteoroids are either the chipped away parts of grater bodies or are

remnants from the creation of the solar system.

SHOOTING STAR

When meteoroids collide with the Earth they burn up in the upper

atmosphere, creating a striking spectacle called Meteor.

METEOR SHOWERS

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4.12.3 COMETS

A comet is an icy small Solar System body that, when passing close to

the Sun, heats up and begins to outgas, displaying a visible

atmosphere or coma, and sometimes also a tail. These phenomena

are due to the effects of solar radiation and the solar wind upon the

nucleus of the comet. Comet nuclei range from a few hundred

metres to tens of kilometres across and are composed of loose

collections of ice, dust, and small rocky particles. The coma and tail

are much larger and, if sufficiently bright, may be seen from the

Earth without the aid of a telescope. Comets have been observed

and recorded since ancient times by many different cultures. Comets

are known as the ‘dirty snowballs’.

Comets have a wide range of orbital periods, ranging from several

years to several millions of years. Short-period comets originate in

the Kuiper belt or its associated scattered disc, which lie beyond the

orbit of Neptune. Longer-period comets are thought to originate in

the Oort cloud, a spherical cloud of icy bodies extending from

outside of the Kuiper belt to halfway to the next nearest star.

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5. THE UNIVERSE

The Universe is all of spacetime and everything that exists therein, including all planets, stars, galaxies & the contents of intergalactic space, the smallest subatomic particles, and all matter & energy.

The observable universe is about 46 billion light years in radius. Scientific observation of the Universe has led to inferences of its earlier stages. These observations suggest that the Universe has been governed by the same physical laws and constants throughout most of its extent and history. The Big Bang theory is the prevailing cosmological model that describes the early development of the Universe, which is calculated to have begun 13.798 ± 0.037 billion years ago. Observations of supernovae have shown that the Universe is expanding at an accelerating rate.

There are many competing theories about the ultimate fate of the universe. Physicists remain unsure about what, if anything, preceded the Big Bang. Many refuse to speculate, doubting that any information from any such prior state could ever be accessible. There are various multiverse hypotheses, in which some physicists have suggested that the Universe might be one among many, or even an infinite number, of universes that likewise exist

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5.1 GALAXIES

In the early 1920s, studies by the renowned American astronomer, Edwin Hubble, showed that our galaxy, the Milky Way, was not the only galaxy in the universe. For a long time it had been believed that the Universe & the Milky Way were one & the same thing, but the discovery of other galaxies, outside our own, greatly expanded the size of the known universe.

Galaxies contain varying numbers of planets, star systems, star clusters, dark matter & interstellar clouds. In between these objects is a sparse interstellar medium of gas, dust, and cosmic rays. Supermassive black holes reside at the centre of most galaxies.

Galaxies have been historically categorized according to their apparent shape, usually referred to as their visual morphology. A common form is the ‘Elliptical galaxy’ which has an ellipse-shaped light profile. ‘Spiral Galaxies’ are disk-shaped with dusty, curving arms. Those with irregular or unusual shapes are known as ‘Irregular galaxies’.

M110 (Elliptical Galaxy)

NGC 4414 (Spiral Galaxy)

The Bird Galaxy

(Irregular galaxy)

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THE MILKY WAY

The Milky Way is the name given to our own galaxy, as it is seen from

the Earth, it appears to be a milky-coloured brushstroke sweeping

across the night sky. The fact that this whitish band is actually

millions of stars was not discovered until Galileo become the first

person known to observe the phenomenon through his telescope.

It is impossible to know

exactly what the Milky

Way looks like because

we do not have an

objective viewpoint of

our galaxy. Nevertheless,

observations of other

galaxies, as well as the

subjective view from

Earth & conscientious telescopic studies, have shown the Milky Way

to be a large barred-spiral galaxy.

Origin of our galaxy:

Much remains unknown about the formation of our galaxy; it is

thought that a great cloud of gas collapsed under the weight of its

own gravity between 10 and 15 billion years ago to form the Milky

Way.

Our location in the Milky Way

Our solar system is found on the inner rim of the 0rion arm; a minor

arm found towards the edge of our galaxy. From its position on the

outskirt of the Milky Way, it takes the Solar System 220 million years

to complete one revolution of the core.

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THE LOCAL GROUP

Most galaxies in our observable universe are moving away from us

as a result of the great explosion which created the Universe, the Big

Bang. This concept has been proved because the stars travelling

away from us emit a longer, redder wavelength. This phenomenon is

known as the ‘red shift’. However the closest galaxies to us emit a

shorter wavelength, which appears bluer on the visible spectrum,

which indicates that they are moving towards us. This occurs

because the force of gravity has overcome

the force of the explosion, a process which

results in the creation of galaxy Clusters

The galaxy cluster to which the Milky Way

belongs is called ‘the Local Group’, which

consists of around thirty galaxies.

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The Milky Way is the 2nd largest galaxy in the Local Group, the

largest being Andromeda.

ANDROMEDA

Andromeda is the nearest major galaxy to our Milky Way. It is

approximately 2.5 million light years away, making it the most

distant object we can see through our naked eyes. The Andromeda

galaxy is one of 110 objects visible in the night sky in the northern

hemisphere which were catalogued by French astronomer, Charles

Messier. Catalogued as the 31st Messier object, Andromeda is often

referred as M31.

The 2006 observations by the Spitzer Space Telescope revealed that

M31 contains one trillion (1012) stars: at least twice the number of

stars in the Milky Way.

Andromeda is slowly moving toward our Milky Way galaxy. It is

predicted that in about 4 billion years, the two galaxies will collide,

forming an elliptical galaxy.

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5.2 STARS

A star is a massive, luminous sphere of plasma held together by its

own gravity. The nearest star to Earth is the Sun, which is the source

of most of the planet's energy. Some other stars are visible from

Earth during the night, appearing as a multitude of fixed luminous

points due to their immense distance. Historically, the most

prominent stars were grouped into constellations and asterisms, and

the brightest stars gained proper names. Extensive catalogues of

stars have been assembled by astronomers, which provide

standardized star designations.

STAR FORMATION:

Stars are born within the clouds of dust and scattered throughout most galaxies. A familiar example of such as a dust cloud is the Orion Nebula. Turbulence deep within these clouds gives rise to knots with sufficient mass that the gas and dust can begin to collapse under its own gravitational attraction. As the cloud collapses, the material at the centre begins to heat up. Known as a protostar, it is this hot core at the heart of the collapsing cloud that will one day become a star. As the cloud collapses, a dense, hot core forms and begins gathering dust and gas. Orion Nebula

Not all of this material ends up as part of a star -the remaining dust can become planets, asteroids, or comets or may remain as dust. Once temperature inside the core is hot enough, hydrogen fusion begins. In this process hydrogen nuclei are fused together to make helium atoms. In stellar core, this occurs millions of times each second, generating incredible amount of energy.

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STELLAR EVOLUTION: Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years for the most massive to trillions of years for the least massive. The table shows the lifetimes of stars as a function of their masses

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Supernovas:

A supernova is stellar explosion which is so bright & intense that it is

visible from the Earth. One that appeared in 1572 was said to be as

bright as Venus. A supernova was recorded in 1054 by Chinese

astronomers in the constellation Cassiopeia & its remains can be still

seen today in the form of Crab Nebula.

Black Holes:

If a star undergoing a gravitational collapse is three or more times as

massive as the Sun, gravity is so strong that the collapse is

unstoppable, even the neutrons are crushed. The result is a black

hole. The gravitational force of a black hole is so strong that even

light is not able to escape its gravitational field.

STELLAR CLASSIFICATION

Stellar classification is the classification of stars based on their

spectral characteristics

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5.3 NEBULAE

The term Nebula, meaning ‘mist’ in Latin, was once applied to any

fuzzy patch of light in the night sky. Many of the objects thought to

be nebulae were later discovered to be galaxies outside our own.

However, Messier had catalogued a number of genuine nebulae

including the Crab nebula, which was his Messier Object Number 1.

He also indexed Eagle, Triffid, Omega & Orion nebulae.

Crab Nebula

Nebulae are known to be interstellar clouds of gas & dust within our

own galaxy. This interstellar material is not spread evenly throughout

the galaxy; instead vast areas dense in gas & dust can be found,

having clumped together as a result of gravity. Nebulae are factories

of star formation. Our own planetary system is thought to have

formed from one, The Solar Nebula.

Types of Nebulae

Emission Nebulae

Reflection Nebulae

Dark Nebulae

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HUBBLE SPACE TELESCOPE

The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. With a 2.4-meter mirror, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra. The telescope is named after the astronomer Edwin Hubble.

Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely high-resolution images with almost no background light. Hubble's Deep Field has recorded some of the most detailed visible-light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.

Eagle Nebula captured by Hubble Space Telescope

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6. UNSOLVED MYSTERIES

Despite spectacular recent progress, there is still a lot we don't know

about our universe. We don't know why the Big Bang happened. We

don't know what most of the universe is made of. We don't know

whether there is life in space. We don't know how black holes get so

big, or where the first stars have gone. There are still some unsolved

mysteries about our universe.

Let’s start with the biggest question of them all. How did we get

here? How did the universe get started? Why is the universe here at

all?

6.1 THE BIG BANG THEORY

The Big Bang theory is the prevailing cosmological model for the

early development of the universe. The key idea is that the universe

is expanding. Consequently, the universe was denser and hotter in

the past. Moreover, the Big Bang model suggests that at some

moment all matter in the universe was contained in a single point,

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which is considered the beginning of the universe. Modern

measurements place this moment at approximately 13.8 billion years

ago, which is thus considered the age of the universe. After the initial

expansion, the universe cooled sufficiently to allow the formation

of subatomic particles, including protons, neutrons, and electrons.

Though simple atomic nuclei formed within the first three minutes

after the Big Bang, thousands of years passed before the first

electrically neutral atom formed. The majority of atoms that were

produced by the Big Bang are hydrogen, along with helium and

traces of lithium. Giant clouds of these primordial elements later

coalesced through gravity to form stars and galaxies, and the heavier

elements were synthesized either within stars or during supernovae.

Extrapolation of the expansion of the

universe backwards in time using

general relativity yields an infinite

density and temperature at a finite

time in the past. This ‘singularity’

signals the breakdown of general

relativity. How closely we can

extrapolate towards the singularity is

debated-certainly no closer than the

end of the Planck epoch (from 0 to 10−43 seconds). This singularity is

sometimes called "the Big Bang", but the term can also refer to the

early hot, dense phase itself, which can be considered the "birth" of

our universe. Based on measurements of the expansion using Type a

supernovae, measurements of temperature fluctuations in

the cosmic microwave background, and measurements of

the correlation function of galaxies, the universe has a calculated age

of 13.798 ± 0.037 billion years.

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The Big Bang theory does not provide any explanation for the initial

conditions of the universe; rather, it describes and explains the

general evolution of the universe going forward from that point on.

6.2 DARK MATTER

We actually don’t know what most of the universe is made of.

Astrophysicists hypothesized dark matter because of discrepancies

between the mass of large astronomical objects determined from

their gravitational effects and the mass calculated from the

"luminous matter" they contain. It was first postulated by Jan Oort in

1932

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Dark matter is a kind of matter hypothesized in astronomy to

account for gravitational effects that appear to be the result of

invisible mass. Dark matter cannot be seen directly with telescopes;

evidently it neither emits nor absorbs light or other electromagnetic

radiation at any significant level. It is otherwise hypothesized to

simply be matter that is not reactant to light. Instead, the existence

and properties of dark matter are inferred from its gravitational

effects on visible matter, radiation, and the large-scale structure of

the universe. According to the Planck mission team, and based on

the standard model of cosmology, the total mass-energy of

the known universe contains 4.9% ordinary matter, 26.8% dark

matter and 68.3% dark energy. Thus, dark matter is estimated to

constitute 84.5% of the total matter in the universe, while dark

energy plus dark matter constitute 95.1% of the total content of the

universe.

DARK ENERGY

In physical cosmology and astronomy, dark energy is a hypothetical

form of energy which permeates all of space and tends to accelerate

the expansion of the universe. Dark energy is the most accepted

hypothesis to explain the observations since the 1990s indicating

that the universe is expanding at an accelerating rate.

High-precision measurements of the expansion of the universe are

required to understand how the expansion rate changes over time.

In general relativity, the evolution of the expansion rate is

parameterized by the equation of state (the relationship between

temperature, pressure, and combined matter, energy, and vacuum

energy density for any region of space). Measuring the equation of

state for dark energy is one of the biggest efforts in observational

cosmology today.

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6.3 QUASARS

Super massive black holes are known as Quasars. Quasars or quasi-

stellar radio sources are the most energetic and distant members of

a class of objects called active galactic nuclei (AGN). Quasars are

extremely luminous and were first identified as being high redshift

sources of electromagnetic energy, including radio waves and visible

light, that appeared to be similar to stars, rather than extended

sources similar to galaxies. Their spectra contain very broad emission

lines, unlike any known from stars, hence the name "quasi-stellar".

Their luminosity can be 100 times greater than that of the Milky Way

Half a century after first getting a bead on quasars, astronomers still

lack a basic understanding of how the most luminous objects in the

universe work.

WORMHOLES

A wormhole, also known as an Einstein-Rosen bridge, is a

hypothetical topological feature of spacetime that would

fundamentally be a "shortcut" through spacetime. A wormhole is

much like a tunnel with two ends each in separate points in

spacetime.

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Researchers have no observational evidence for wormholes, but the

equations of the theory of general relativity have valid solutions that

contain wormholes.

Wormholes may not only connect two separate regions within the

universe, they could also connect two

different universes. Similarly, some

scientists have conjectured that if one

mouth of a wormhole is moved in a specific

manner, it could allow for time travel.

However, British cosmologist Stephen

Hawking has argued that such use is not

possible.

6.4 END OF THE UNIVERSE

Red shifts have shown that our universe is expanding. But some of

the galaxies closer to the Earth emit blue shift, indicating that they

are moving towards us. The reason these galaxies are moving

towards us is that the gravity is sufficiently strong to overcome the

recession of nearby galaxies.

Some Big Bang theorists have suggested that this blue shift indicates

that the universe will end in a ‘Big Crunch’, when the expansion of

the universe is halted and reversed until all matter in the universe

contracts back into the gravitational singularity from which it came-

at which point time would come to an END.

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CONCLUSION

Let’s conclude what we have learnt through this report

What is Astronomy

How early civilizations observed night sky through naked eyes

How astronomical theories developed from ancient era, which

formed the basis of our knowledge of heavenly bodies today

The space age & how it revolutionized the astronomical

thinking

We learnt about the Solar system, galaxies & our position in the

universe

How big the universe is in space & times

Some spectacular cosmic phenomena like Nebulae, Supernovas

& Quasars

We also had a brief look on some of the unsolved mysteries of

the modern astronomical era.

Now that we have expanded our knowledge about the vast universe

& world beyond Earth, we are ready to look even further.

There are two ways to look at the universe: Philosophical way & the

Physical way. Both ways have their significance in our quest to

understand the universe.

Astronomy can not be learned through theories only, significant

practice & observations are required to completely understand what

lies beyond the boundaries of our world.

Let’s enjoy & continue learning more about what makes our universe

so great!

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BIBLIOGRAPHY

Following books & internet websites were referred while working on

this report.

Books

1) Astronomy by Duncan John

2) A Text Book of General Astronomy by Charles Young

3) Astronomy: Principles and Practice by Roy & Clarke

4) Astronomical Calculations by Mohan Apte

Websites

www.space.com

www.universetoday.com

www.wikipedia.com

www.nasa.gov