Wednesday 26 September 2018

EVOLUTION OF MAN.


As a species we are known as Homo Sapiens about which you would be aware of. But very few of us are aware how Homo Sapiens have evolved. This is a short note on the evolution of Homo Sapiens.

In Homo sapiens Homo is our Genus and Sapiens is our species. Today we are the only species in the Genus Homo.

Earlier, apart from us another species existed and that was Neanderthal man who later became extinct. The Neanderthal had a bigger cranial capacity than humans which means he had a bigger brain and is therefore smarter than us. The Neanderthal man originated before our species and he became extinct about 40,000 years ago.

The Genus Homo evolved about 1.8 million years ago and our species is a mere 300,000 years old. Of this the Cro Magnan man who is considered our real ancestor evolved around 40,000 years ago.
In the evolutionary cycle apart from man, apes are the highest evolved. They are related the closest to us.

As per zoological nomenclature Man along with Apes belongs to an ORDER called the “PRIMATES”.

On earth, the “CENOZOIC ERA” started about 7.5 crore years ago. It is divided into periods and the first period of this era is known as the “TERTIARY PERIOD”.

The first part of the Tertiary Period is known as the “PALEOCENE EPOCH” which lasted from 7.5 crore years to 5.8 crore years ago. During this era the order “PRIMATES” has originated.
By the first half of the Paleocene Epoch “PRIMATES” separated from the order of “INSECTIVORA”

What are the qualities of PRIMATES? They acquired the characteristic of catching things with both hands and feet. Their eyes were located in front of the face enabling them to see the same thing with both the eyes. Their brain size also grew bigger.

The order “PRIMATES” has 2 sub orders. 1. PROSIMEA and 2. ANTHROPOIDEA.
PROSIMEA sub order in turn has 4 “INFRA ORDERS”

1.       TREE SHREWS-They are like small squirrels. They are now found in China and South East Asia.
2.       TORSIERS-They are in the size of cats but the tail is very long. They are now found in South East Asian countries.
3.       LEMURIFORMES- They too are in the size of cats and have a special set of teeth in the front lower part of the mouth for combing the fur for grooming. They are now found only on the island of Madagascar.
4.       LORISIFORMS- Some of them are in the size of rats and some are in the size of monkeys. They are found in Africa and Asia.

ANTHROPOIDEA sub order in turn has 3 “SUPER FAMILIES”

1.       PLATERINE MONKEYS- They have broad noses and have the power to catch objects with their tail. They are found in Central and South America.
2.       CATERINE MONKEYS- Their noses are triangular and they are found from east in Africa to Japan in the West. All the monkeys known to us are in this category.

3.       HOMINOIDEA-This SUPER FAMILY in turn has 2 “FAMILIES”

1.    PONGIDAE-All the tail less apes come into this category. They are     Gibbon, Siamang, Orangutan, Gorilla and Chimpanjee.
2.       HOMINIDAE- Presently only man is left in this family.

Thus man belongs to the ANIMAL KINGDOM, to the PHYLUM Chordata, to the SUB PHYLUM Vertebrata, CLASS Mammalia, ORDER Primates, SUB ORDER Anthropoidea, SUPER FAMILY Hominoidea, FAMILY  Hominidae, GENUS Homo and SPECIES Sapiens.

It is surprising to know that order PRIMATES and the Order INSECTIVORA are related and got separated only about 6 crore years ago.

THE 6 HINDU SYSTEMS AND SANKHYA.


There are 6 systems of Hindu philosophy some of which even predates the Upanishads. Their thought and the Upansihadic thought have mutually influenced each other. They are

1.     Sankhya
2.     Yoga
3.     Vaiseshika
4.     Nyaya
5.     Poorva Mimamsa
6.     Uttara Mimamsa also known as Vedanta or Advaita.

Let us have a brief look at what they say.

Tradition regards Kapila as the founder of this system. This is very ancient and perhaps even predates Vedas themselves. The book Sankhya Karika of 5th century AD is the earliest available work on this system. Sankhya recognizes 2 entities, Purusha and Prakriti. Sankhya means number as well as right knowledge.

Right knowledge is the separation of the Purusha from the Prakriti.

Yoga means action or practice and tells us how the theoretical teachings of Sankhya may be realized an actual practice.

Thus Sankhya-Yoga forms a complete system. While Sankhya supplies the philosophy Yoga supplies the means to reach it.  

Sankhya is an intellectual system and it maintains a clear cut dualism between Purusha and Prakriti and further maintains the plurality of the Purushas and is silent on God.

All material effects are the modifications of Prakriti. They pre exist within it and come out of it at the time of creation and return to it at the time of dissolution.

Purusha by itself is pure and transcendental consciousness. It is the ultimate knower and is the foundation of all knowledge. It is the pure subject and it can never become the object of knowledge. It is uncaused eternal and all pervading.  

The selves are all alike, only numerically they are different. 

PRAKRITI is the enjoyed and PURUSHA is the enjoyer. Purusha needs Prakriti for enjoyment as well as for liberation. For samsara as well as kaivalya.

Purusha is above bondage and liberation, merit and demerit. It mistakes itself with the ego and the mind and feels it is bound. When Purusha realizes its own pure nature it gets liberated. Good and bad actions may lead to Heaven and Hell but it is only knowledge that leads to liberation. In Sankhya liberation there is neither pain nor pleasure.  

Bondage of the Purusha is fiction. It is Prakriti that is bound and Prakriti that is liberated.

Sankhya does not talk about God because as per it Parkriti and Purushas are sufficient to explain away the Universe. 

Wednesday 12 September 2018

CIVILIZATIONS ON OTHER PLANETS.


There may be many science fiction novels and movies depicting aliens from other planets. But is that a reality or is it simply fertile imagination?

The first scientific approach to this was done by the Astronomer Dr Francis Drake. He knew that there are a number of variables that affect the birth of life on a planet. Taking all those parameters into consideration he brought out an equation that predicts the number of planets in our galaxy with intelligent life that can transmit into space. This is known as the Drake equation.

He took the following into consideration:

Number of intelligent civilizations in our galaxy

Average rate of star formation in our galaxy

Fraction of those stars that have planets

When the star has planets then those planets that could support life.

Fraction of planets where life actually develops

Fraction of planets with life that develops intelligence

Fraction of planets that are advanced enough to transmit into space.   
          
Length of time such civilizations transmit into space

But the problem with this equation is that the last 4 parameters are very difficult to estimate.

As per the Drake equation there should be millions of planets that should support intelligent life in our Galaxy itself.

But the Drake equation is inexact, and we cannot assess the parameters of the equation correctly. Thus it is difficult to arrive at any logical conclusion based on this.

Despite the SETI experiment for 50 years no signs of intelligent life in our galaxy other than us have been discovered till date.

This also puts forth another problem before us. Is there really other intelligent life other than us in our galaxy at all?

Logic points out that if there is other intelligent life in our galaxy, and then at least some of them should be as intelligent as us to develop radio transmission as the Drake equation itself predicts.

Then certainly some of them should be more advanced than us and would have mastered inter planetary space travel. That being the case then at least some of them should have contacted us. None have done that so far. On top of that no one has even intercepted our SETI transmission into space. So it appears either we are alone in this galaxy or else the light barrier cannot be surpassed ever, however much a civilization develops.

Otherwise, life may be rarer in the Universe than we perceive and none of the nearer planets to the us support life. In 50 years our SETI radio transmission would have just traveled 50 light years. And if anyone 50 light years away is intelligent enough their reply would take another 50 years to reach us because the light barrier cannot be breached.  Just supposing we are alone in the galaxy then why this special status to earth and not to other planets in the Galaxy?

Of course all this is conjecture and unless science progresses far more and we can speed our rockets to the speed of light we will never know what the reality is.
It is a terrible thought to think that we are alone in the Universe.

Monday 10 September 2018

MUSNURI KAPANAYAKA


In the year 1323 the Kakatiya kIngdom fell on account fo Muslim invasion from the North.  This victory was won by Mohammed Bin Tughlak himslef who was also know as Ulugh Khan. When Ulugh Khan returned back to Delhi he left the area under his wazir Malik Burhanuddin stationed at Daulatabad and an adimisntrator was appointed at Orugallu.

In the war with Ulugh Khan most of the Kakatiya commanders perished. Only 3 important commanders remained. They are the minister Bendapudu Annayya who was the commander of the elephants of the Kakatiay forces, Kolani Rudradeva also known as Prataparudra (Not to be confused with Kakatiya Prataprudra) and Recherla Singamanayaka.

The name of Musunuri Prolayanayaka was not heard of before the war with Ulugh Khan but he must be an influential king with a good name because under the guidance of Bendapudi Annaya all the remaining kings of the Andhra area united under Musnuri Prolaya Nayaka.

Prolayanayaka ( 1325-1333 AD) was the son of Pochinayaka of Vengi and Kapanayaka was his first cousin on the father’s side. The commanders that supported Prolayanayaka include Addanki Vemareddi, Koppula Prolayanayaka, Recherla Singamanayaka, Manchkonda Ganapatinayaka and Undi Venga Bhupati. As per sasans the Andhra area was released frothe power of Muslims in about 3-4 years time. Prolaya nayaka ruled with his capital at Rekapalli in Bhadarachalam Taluk.

After Proalaya Nayakas short reign, his paternal cousin Kapa Nayaka (1332-1367/68 AD) came in possession of the Kingdom. He extended the kingdom to include the whole of Andhra pradesh after capturing the Orugallu fort form the Muslims.

In 1368 AD Kapa Nayaka was attacked by Anapota Nayaka and Mada Nayaka, the sons of Recherla Singama Nayaka. In the Bhimavaram battle between the two forces Kapa Nayaka was killed and his Kingdom was taken over by Anapota Nayaka.  

HANNIBAL THE MIGHTY CARTHAGINIAN COMMANDER.

The world had some extraordinary generals who by their thinking had made a great difference to the history of the world. Hannibal is one such.

His life also shows how brutal and uncertain life was in those times. In one battle a Roman army of 86000 was sent against him. In that Hannibal's army slaughtered 55000 Romans and took 19000 as prisoner in a single day. How terrible it is for Rome to lose so many men in a single day and what would have been the grief of those numerous families. War is a dirty game but it could not be avoided in the olden times and more often the circumstances were compelling.

 The Roman army was then known as a mighty fighting force yet it had to meekly bow down to this mighty general.

 But to its credit it never gave up and fought back till he is finally defeated much later and that is  great fighting spirit. Down but never out. 

There are a few men in the world who have changed history of our times. The Carthaginian general Hannibal (247-181 BC) was one of them. That makes him a contemporary of King Asoka who ruled between 273-232 BC. Hannibal is one of the mightiest thinking generals the world has ever seen and managed to shake the then all powerful Roman Empire. But for lack of support from his home country he would have defeated the Roman Empire itself. 

The Roman army was then an efficient war machine and no one before or after Hannibal could defeat Roman armies with such utter contempt.

 Hannibal posed a big challenge to the Roman Empire and gave the Roman commander Scipio Africanus lessons on war strategy which finally led to his own defeat at the hands of Scipio in Africa.

 The tug of war with Hannibal resulted in Rome learning new techniques of battle that helped it greatly in its further expansion and final domination of the vast area surrounding the Mediterranean and into most of Europe and also to the east.    

The Carthaginian Empire stretched across the northern shores of Africa in the Mediterranean Sea. Its capital city was Carthage located in Tunisia. The empire stretched from Egypt  in the East and then west to Libya, Tunisia, Algeria and Morocco. This empire only included thin stretches of land in the mentioned countries adjacent to the sea because Carthage was essentially a sea trading civilization.

 Both Carthage and Rome were founded in about 800 BC. 

 It also included the south eastern tip of Spain and the islands of Sicily, Corsica and Sardinia in the Mediterranean Sea. The Roman Empire was then just confined to Italy and was flexing its muscles and the inevitable war between the two Empires known as the Punic wars started in 264 BC. Rome won the first Punic war and wrested the control of the sea from the Carthaginians and also annexed Sicily. The war gave Carthage a foothold in Spain which was a great resource because of its silver mines.  

Among the two, Rome is a militarized nation depending on farmers tilling their soil while Carthage was a sea faring trading civilization. Being a trading civilization Carthage was against war but the slow Roman expansion alarmed them and goaded them into the Punic wars. 

Hannibal was from the Aristocratic house of “Barca” which gave many commanders to the Carthaginian army. Hannibal’s father Hamilcar was a general in the army. He took Hannibal to Spain when he was 9 years old and trained him in the art of war and died when he was just 18 years old. Hannibal learnt well from his father. He had taken an oath that he would suppress the power of Rome at that tender age and never relaxed on that till his death much later. After his father’s death the command of Hannibal’s father’s army passed to Hasdrubal (Not to be confused with Hannibal’s brother with the same name) his son in law. Eight years later, when Hasdrubal was murdered Hannibal was elected as commander of his troops when he was just 26. 

Hannibal started his campaign with an attack on the Iberian tribes in Spain. Theirs was a much larger army, but Hannibal crossed the river in the night, surprised the Iberains and emerged victorious by lunch time with hardly any losses. His elephants had done the maximum damage to the enemy. Elephants were the Carthaginian special weapon.

The news of this victory reached Rome. Later Hannibal laid seize to Saguntum  in Spain knowing that the Romans who were busy defending against Gauls and were too busy to come to Saguntum’s aid. After 8 months the city fell and the inhabitants were raped and murdered and their possessions looted.

This was too much for the Romans and they sent ambassadors to Carthage and demanded them to hand over Hannibal to face justice. Carthage refused. 

Hannibal felt instead of waiting for the Romans to attack him, he should surprise the Romans from their backyard by passing through the Alps. Now this was simply unthinkable at that time because no man had even attempted crossing the Alps with an army before. And the Hannibal’s army had war elephants which he felt would give him a psychological edge in the battle with the Romans. Hannibal made his preparations for his idea. There was hardly any help from his home country Carthage to the idea. He then raised a mercenary army of 46000 troops and commenced his crossing the Alps in October just before the onset of winter. 

The Alps are treacherous to cross during that time. Moreover, some of its areas were peopled by tribes of fierce Gaul’s who do not have any allegiance to anyone and are independent. Moreover, at that time armies like that of Hannibal had no supplies and lived off the loot made from the lands they crossed. This resulted in loss of food to the people wherever the armies passed. Hannibal’s army was repeatedly attacked by Gauls who reduced its numbers. Then while crossing a snowstorm ensued and many brave men lay dead on account of frostbite and snow along with the elephants. Nevertheless Hannibal had no intention of turning back. He repeatedly exhorted his men not to lose hope and with an iron will finally achieved the impossible. He crossed the Alps with his army and marched into Northern Italy along with his few elephants that were left.  

Hannibal commenced his march with 46000 men but only 26000 managed to cross the Alps. But these men are the best and the toughest who had survived the ordeal of crossing the Alps. When a Roman commander at the vicinity of crossing was told by his scout that an army along with elephants is arriving, the commander told him he was dreaming. Such was the improbability of the task Hannibal had accomplished.    

With just those 26000 troops, later joined by 15000 Gauls, Hannibal played havoc with Roman armies sent against him. He is a thinking commander who always took his enemy troops by surprise. He defeated one Roman army after another and marched forward and penetrated deep into Italy. 

The battle Hannibal fought with the Romans at Cannae was a masterpiece in war strategy. Hannibal just had his 41000 men while the Roman army was 85000 strong. But by superior strategy Hannibal won the battle and 55000 Roman soldiers were slaughtered on the battlefield and 19000 taken prisoner. Hannibal was in the thick of the battle and led the army from the front. This battle shook the Romans and they could never forget this defeat. 

They sent one army after another against Hannibal which was defeated by him.  Now Hannibal threatened Rome itself  but because of its size he needed more troops to attack and lay seize to the city. He therefore sent his brother Mago to Carthage requesting for reinforcements. But his home country refused any help and left him to his own devices. Hannibal went on fighting continuing his victories but he could not take Rome itself. In all this war Carthage did nothing to help Hannibal and did not send him a single solider. He was fighting the war with mercenaries for the sake of Carthage along with some Carthaginian men he already had.

 In the meantime Rome made Scipio Africanus (though the title Africanus was got by him after defeating Hannibal in Africa) as the commander of the Roman armies. Scipio had a good knowledge of the war strategy of Hannibal. Scipio senior was killed in the battles with Hannibal where Scipio Africanus too accompanied him. Thus Scipio knew Hannibal well. 

Now Scipio and Rome refused to give a direct battle to Hannibal while he sat and waited for them to attack him so that he can defeat them. But Scipio did nothing of the sort. He then planned to invade the Carthaginian territories in Spain which were the powerbase of Hannibal while Hannibal himself is now in Italy. Finally he planned to attack Carthage itself instead of fighting with Hannibal.         

Scipio finally conquered Spain and then attacked Carthage itself. The Carthaginian council in panic sent a message asking Hannibal to come back to fight the Romans. His home city never helped him in the war and Hannibal could have simply refused, but he sailed to Africa instead to protect his home city. Hannibal joined battle with Scipio’s army at Zama. Scipio has learnt well from Hannibal and used the tactics which he learnt from Hannibal and defeated him. This is the only battle that Hannibal ever lost in his life. But even after his defeat he went on fighting the Romans. 

Hannibal helped those kings who were fighting the Romans like Antiochus of Syria and others. Ultimately Romans could not forget Cannae and sent Roman assassins to kill him. Hannibal did not want to die in Roman hands and committed suicide in a Turkish town in 181 BC when he was 66 years old. So from the time he became the commander when he was 26, he fought the Romans for 40 years before he died. To his last he had that principle of opposing Rome etched on his mind and never wavered from it.


ASIAN GAMES 2018-ASSESSMENT OF PERFORMANCE

The Asian Games are concluding today. These are the Asian games to be remembered for the Indians. It is not just a case of winning more medals and equalling the highest number of gold’s ever won. It is the performance of our athletics team that gives us great satisfaction. At either the Asian Games or the Olympics, the maximum number of medals is allocated for athletics. If our team is good in athletics that would improve the chances of India winning medals at the Olympics.  

Of course, in wrestling India had been traditionally strong and our shooters too shot into the word level after the current sports minister Rajayavardhan Singh Rathore won a silver at the 2004 Olympics.

In athletics India had been traditionally weak and even the legendary PT Usha who was unchallenged at the Asian level was not good enough for the Olympics. At the Los Angeles games she made it to the final only because the entire soviet bloc countries who have the best athletes in 400 mtrs hurdles, the event of PT Usha boycotted the games. Of course, this is no discredit to her as she dominated the Asian athletics completely and got the top honors.

 As far as athletics are concerned except for Milkha Singh and Gurbacahan Singh Randhawa way back in 1960 and 1964 respectively we had no athletes who can be called Olympic medal-winning class. Unfortunately, both of them could only finish 4th in their event at the Olympics and could not get India any medals.

Our athletics team has done exceptionally well at the games. But all of these performances are not World class except for those of Neeraj Chopra and Hima Das.

 In Javelin at the 2016 Olympics a throw of 90.30 got a Gold. Neeraj Chopra threw 88.06 which is pretty close. He is young and would certainly improve by the time of 2020 Olympics and he is certainly a gold medal prospect for India.     

In the 400 meters Hima Das did as well as Neeraj Chopra did in javelin. Despite getting a silver she did 50.59 seconds which is very close to the very best in the world. In the last Olympics Shaune Miller of Bahamas won a gold in this event with a timing of  49.44, silver to Allyson Felix of the US at 49.51and bronze to Jamaica at 49.85. See how close these times are to the record of Hima Das.  Despite winning a silver here she too is a gold medal prospect for the 2020 Olympics.

Both these athletes are great finds for India and their performance in the next Olympics turn would spur a generation of athletes in the same way the performance of Rajyavardhan Singh Rathore did in shooting. 

In boxing Amit Panghal has shown absolute class by defeating the Olympic champion and the world championship silver medallist in the final. He is another gold medal prospect for India at the next Olympics.

Looking to these performances, and our shooters and wrestlers we have every right to be optimistic about the medal tally at the next Olympics. Gone are those days when we drew a blank in the years 1976, 1984, 1988 & 1992.
 

STELLAR EVOLUTION-PART 2


Higher brightness of a star means it is using up more of its matter and is rapidly converting it into energy. Now why do stars shine with different brightness? That depends on the amount of matter they possess.

The rate of fusion at the stars core depends on its temperature and the temperature in turn depends on the mass of the star. Although large stars have more fuel they burn it much faster and hence their energy generating life is lesser than a star with lower mass.

A star with a mass of just 0.4 times the sun has a lifetime of 200 billion years, that of 0.8 times the sun 14 billion years, that of sun 9 billion years and that of 40 times the sun just 1 million years. See how rapidly the life span decreases as the mass of the star increases. Life evolves over billions of years, therefore only those stars which have a mass around that of the sun have ample time to evolve life.

Stars are classified as per their spectra and their temperature. The classifications are O B A F G K and M. to make one remember this is the sentence “Oh be a fine girl kiss me”. Sun belongs to the spectral class G and these are the stars that are most likely where life can evolve.   

For knowing the way the stars evolve an American called Russel and a Russian called Hertzsprung made a diagram known as the “Hertzsprung Russel Diagram”. or HR diagram.  In this diagram the X axis denotes absolute magnitude of the stars and the Y axis denotes temperature of the stars.

On the HR diagram a star that follows a specific pattern meaning the higher the temperature the higher the mass then those stars are known as main sequence stars. On the HR diagram they follow a slope from the top left corner of the diagram to the bottom right corner. If we take a main sequence star its central part can be considered as a large nuclear factory. On top of that is the convective zone where energy is transported. The temperature at which the fission reaction takes place is from about 1 crore centigrade onwards. Our sun has a core temperature of 1.40 crore degree Celsius.

Initially all the Hydrogen at the central part of the star gets used up and all of it is converted into Helium and the fusion reactions pass to the higher layers till all the hydrogen reserves of the star get exhausted. The fusion reactions in the star then stop and gravitational forces take over. As the star condenses on account of gravitation it reaches a temperature of 10 crore degrees Celsius where the fusion reaction start with Helium and Neon is produced. When the Neon is exhausted it passes onto the higher element of Magnesium and so on till Nickel. After that the fusion reactions stop.

Scientists assume that stars known as red giants with large surface areas and low temperatures are at this stage. Our Sun still has about 81.6% Hydrogen and for it to turn into a red giant it would take 500 crore years. As the size of the star expands when it reaches the red giant stage the temperature of the star cools down which is the reason why the star appears red. Compared to the surface temperature of the sun which si 6000 degrees, the red giants have a surface temperature of 3000 degrees. The star therefore leaves the main sequence and travels upwards and to the right of the HR diagram.

Some of the red giants are enormous in volume compared to the sun. For example the bright star Betelgeuse in the constellation of Orion has a diameter of 100 crore KM compared to just 14 lac KM for our Sun. However, the density of this star is almost negligible enough to be zero compared to 1.4 for our sun and this star weighs just about 16 times our sun.

As already said earlier, as the star is much bigger than the sun it loses its matter much faster and outshines the sun by far. Even in its red giant phase this star is 46,000 times more luminous than the sun. The result is while the sun is already 450 crore years old and would take another 500 crore years to reach the red giant stage, this star has splurged off its energy in just 1 crore years due to its heavier mass.

The stars have been categorized into different names depending on their size.

All those stars that are up to 20 times brighter than the sun are called Dwarf Stars. Our sun is a yellow dwarf. We consider the sun supreme but it just happens to be a dwarf star in the Universe.     

Super giant stars are the largest known stars in the Universe but they are rare. The star Betelgeuse mentioned above is a super giant. When these super giant stars die they become Super Novae and then form Black Holes.

When giant stars die they turn into Novae. In both Novae and Super Novae a single massive explosion would blow apart the matter in them. A star shines tens of thousands and sometimes 100,000 times brighter on turning into a Nova.

A Nova reaches maximum luminosity in a few hours after the explosion and return to its normal luminosity in days or a few weeks.

What happens after that? The star becomes a White Dwarf. Very hot and dense and full of carbon. With time it loses its heat and turns into a black dwarf and that can be called a dead star.  

A Super Nova explosion unlike that of the Nova is a massive event and is much more violent and it ends the life of a star. The Super Nova explosion would blast massive amounts of matter with a mass of several times the sun into space and at that time it outshines an entire galaxy consisting of 10,000 crore stars.

What happens after the Super Nova explosion? Bigger Super nova explosions turn into what we know as Black Holes. A black hole is so dense that it would not even let light escape form it. That is why a black hole cannot be seen.

Some black holes are very minute. These are just as big as an atom but contain the mass of a mountain. Another type of black holes known as Stellar black holes have a mass of up to 20 times the mass of the sun but the mass is concentrated in an extremely small area that gives it an immense gravitational attraction. Then there are the super massive black holes that have a mass of some 1 million times that of the sun. Scientists have postulated that all the galaxies have a super massive black hole at its center.   

However, not all super novae explosions give rise to black holes. Stars with masses up to 29 times the sun turn into Neutron stars. The Neutron stars have a diameter of about only 10 Km but have a mass that is up to 2 times that of the sun. Matter exists in them only in the form of Neutrons and that is why the name Neutron Star.

STELLAR EVOLUTION PART-1




Just like people aging and then dying all the stars in the Universe too age and die. The only difference being the death of star does not mean the end of its matter but the end of its self luminosity and the thermonuclear reactions taking place in its core.

As I have written in my earlier note there are about 100,000 crore stars in our Galaxy. The average galaxy size in the Universe is 10,000 crore stars and there are 10,000 crore such galaxies in the Universe. Thus the Universe consists of 1011*1011 or 1022 stars.

Before going into the evolution of stars, there are other aspects of stars that have to be considered.

Of the stars some are small, some are big and some are massive. Stars emit energy on account of the innumerable fusion reactions taking place in their core. The energy produced in a second in a star is enormous. For example  our Sun loses about 43 lac tons of mass each second and this mass is fully converted into energy as per the equation E=mc2. If we can bring a pinhead of matter from the Sun to the earth it can turn some populated cities on the earth to ashes.

Depending on the mass and brightness of the star its evolution varies. Thus it is important to know the variety of stars in the Universe. On an average night one can see just about 3000 stars with the naked eye. But instruments enhance our vision. With binoculars one can see 50,000 stars. If we view through a 2 inch telescope the figure rises to 3 lakh stars. The largest reflecting telescope in the world, the Gran Telescopio Canarias in Spain has a diameter of 410 inches and can virtually show us enormous number of stars. Of course there are also refracting telescopes as well as radio telescopes that enable us to see further and further.  

For measuring the distance of the stars we have to use the unit Light Year which is the distance light travels in a period of 1 year. Light travels at a speed of approximately 300,000 Km/Sec. In a year this distance becomes approximately 9.5 lakh crore Km.

The nearest star to the sun is Proxima Centauri which is located at a distance of 4.2 light years away from us. It is in the star system Alpha Centauri which is a triple star. The 3 stars rotate against a common centre of gravity. The next star is Barnards which is 6 light years away and after that Wolf 359 which is 7.7 light years away. The brightest star visible to us in the sky with the naked eye is Sirius and it is at a distance of 8.6 light years from us.  

Stars are classified into magnitudes depending on their luminosity. Stars that are visible to the naked eye are classified into 6 magnitudes. This classification was done by Greek astronomers. The brightest stars are classified as magnitude 1. Those with a little less luminosity are classified as magnitude 2, then 3 and so on till 6. A magnitude 6 star is so faint that it is barely visible to the naked eye. After the arrival of the telescopes we have been able to see much higher magnitudes of stars. With the largest telescope stars up to magnitude 30 are visible to us.  

A 1st magnitude star is 2.5 times brighter than the 2nd magnitude star. A 3rd magnitude star is 2.5 times brighter than the 2nd magnitude star and so on. The brightest star visible to the naked eye is Sirius and it has a magnitude of -1.6. The minus sign indicates higher brightness. A 0 magnitude star is 2.5 times brighter than a star of magnitude 1. Similarly a -1 magnitude star is 2.5 times brighter than the 0 magnitude star. As per this a magnitude 1 star is 100 times brighter than the 6th magnitude star.

On this magnitude scale the brightness of our moon is -12.6 and that of the sun is -26.7. What is visible to the naked eye is the apparent brightness of a star and not its real brightness as there is a tremendous variation in distances to different stars. To evaluate the actual luminosity of a star scientists have devised a mathematical model by which the stars are brought to distance of 10 parsecs (1 parsec is 3.26 light years) or about 33 light years away from us and then evaluate their brightness. This is known as the absolute magnitude of that star.

If our sun is taken to that distance it would shine as a star of magnitude 4.8.  The brightest star visible to the naked eye is Sirius and it shines with a magnitude of -1.6. Its absolute magnitude however is 1.3.

There is one galaxy called the Larger Magellanic cloud near to the Milky Way. In it is a star called S Doradus which has an absolute magnitude of -10. In the same galaxy the star R136a1 has an absolute brightness of -12.5 which means if it is brought to a distance of 10 parsecs (33 light years) it would shine as bright as the moon itself while at the same distance our sun at a magnitude of 4.8 is barely visible to the naked eye.