Star birth and how are stars formed step by step, Starbirth nebulas - by Encyclopedia

 Stars have been forming throughout the Universe for more of its life. They take shape in vast clouds where thousands of starts are born at a time. 

The clouds that give birth to the stars are cold and dense and consist mainly of hydrogen gas. The newly formed stars are huge spinning globes of hot, glowing gas - mainly hydrogen, with helium and small amounts of other elements. Much of this material is packed tightly into the stars' cores, and it is here that nuclear reactions release energy in the form of heat and light. 

How new stars from

The star-forming process begins when the cloud becomes unstable and breaks up into fragments. Gravity pulls the material in a fragment into an ever-tighter clump, and the clump slowly forms a sphere as it shrinks. Now a protostar, this star-to-be carries on shrinking, its core getting denser and hotter. Eventually the pressure and temperature are so high that nuclear reactions begin, and the star starts to shine. 

1. Interstellar cloud

Stars are born within enormous, cold, dense clouds of gas and dust. The process of star formation may be triggered if something disturbs the cloud, such as a collision with another cloud or a shockwave from a supernova explosion. 

2. Fragments form

Now unstable, the cloud breaks up into fragments of different size and mass. The most massive and dense of these fragments are gradually pulled by their own gravity into tighter clumps. These shrinking fragments will eventually turn into protostars. 

3. Protostar

A protostar forms. Gravity pulls material into its core, where the density, pressure, and temperature build up. The more matter the original cloud fragment contained, the greater the temperature and pressure rise as the protostar develops.

4. Spinning disc

The growing mass at the centre creates a gravitational pull, drawing ever more gas and dust inwards. A bit like water going down a plughole, the material being pulled in starts to spin round. Powerful winds develop, blowing jets of gas out from the centre. 

5. A star is born

Squeezed by the force of gravity, the protostar's core becomes so hot and dense that nuclear reactions occur, and the star begins to shine. The glowing core produces an outward pressure that balances the inward pull of gravity, making the star stable. It is now a "main sequence star". 

6. Planets form

Not all the material from the gas cloud has been used to make the star. The leftovers form a spinning disc of gas and dust around the star. This debris may be lost into space, or it may clump together to form planets, moons, comets, and asteroids. 

Types of star

A star begins to shine when nuclear reactions in its core convert hydrogen into helium and release energy. It is then called a "main sequence star". Not all main sequence stars are the same - they differ in size, temperature, colour, brightness, and the amount of matter they contain. When stars begin to run out of fuel and near the end of their lives, they stop being main sequence stars and may swell up and turn into red giants or shrink to become white dwarfs.

Classifying stars

The Hertzsprung-Russell diagram is a famous graph that astronomers use to classify stars. The graph plots brightness against temperature and reveals that there are distinct groupings of stars, such as red giants (dying stars) and main sequence stars (ordinary stars). Astronomers also classify stars by colour, which is linked to their temperature: hot stars are blue; cooler stars are orange or red. 

Starbirth nebulas

Clouds of gas and dust in space are called nebulas. Much of the gas and dust in a nebula is debris from old stars that exploded when they ran out of fuel. Over millions of years, this material is recycled to make new stars. Starbirth nebulas are among the most beautiful objects in space, their colourful clouds illuminated from within by the blue light of newborn stars. 

Orion Nebula

The Orion Nebula is one of the closest star-forming regions to Earth. In the night sky it looks like a fuzzy star in the sword of Orion. In reality, it is a vast cloud of gas and dust thousands of times bigger than the Solar System. 

Star clusters

Stars are not formed singly - they are born in clusters from the same cloud of material at roughly the same time. Eventually, the stars of a cluster will drift apart and exist alone in space, or with a close companion or two. Our Sun, like about half of the stars nearest to us, is alone. About a third of the stars in the night sky are in pairs,bound together by gravity. 

Pleiades cluster

A handful of the 5,000 or so stars that make up the Pleiades cluster can be seen with the naked eye. In about 250 million years time, the stars will have dispersed and the cluster will no longer exist. 

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The largest stars

in the night sky are big enough to swallow our sun a big billion times. 

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Fighting germs

 Your body is under constant attack. Tiny organisms are continually trying to get inside you and multiply, which can make you ill. Fortunately, your body has a powerful immune system to repel the Invaders. 

The first line of defence against germs is your body's surface, which acts as a barrier. The surface includes not only your skin but also the surface of your eyes and the soft tissues lining your mouth, nose, throat, and stomach. If germs find a break in any part of your body - such as a cut - the damaged tissue reacts immediately by becoming inflamed: it swells and fills with germ-destroying blood cells. Many parts of the immune system work to block all kinds of germs, but others are more specific. Your adaptive immune system identifies new germs and then targets them specifically. It also remembers them for the future, giving you immunity to the diseases they cause. 

Filtering germs

Germs that break through the body's barriers and invade internal tissues do not usually survive for long. The human body contains a network of tiny vessels that collect fluid from every organ and carefully filter it for germs, which are swiftly destroyed. This network of vessels is called the lymphatic system. Dotted along it's vessels are small filtering units called lymph nodes, which are packed with germ-destroying cells. 

Tears

With every blink, watery tears wash dirt and bacteria off the surface of your eyes. Tears also contain lysozyme,a chemical that destroys the cell walls of bacteria. 

Saliva

Continually produced by glands in your cheeks and under your tongue, saliva flushes germs out of your mouth and into your stomach, where acid destroys them. Saliva also contains a range of antibacterial chemicals that germs. 

Tonsils

These soft red areas at the back of the month are packed with white blood cells that destroys germs from food or the air. When you have a sore throat caused by viruses or bacteria, your tonsils swell up as they help fight the germs. 

Skin

Your skin forms a thick, protective barrier that germs cannot cross, unless the skin gets cut. Glands in the skin secrete sweat and an oily fluid called sebum, both of which contain chemicals that repel germs. 

Stomach acid

The lining of the stomach makes powerful hydrochloric acid, which destroys germs in food. It also kills the germs in mucus from the throat, which we swallow regularly to help keep the airways clean. 

Lymph node

As body fluids flow through the vessels of the lymphatic system, they are filtered through swellings called lymph nodes, which vary from the size of a full stop to the size of a grape. They are packed with white blood cells that s screen the passing fluid for germs and destroy them. 

An allergy

occurs when the

immune system

attacks something

harmless, like pollen

or household dust. 

Germs

Whenever you touch something or breathe in, you pick up tiny organisms too small to see. Most do no harm, but some try to invade your body and feed on you. Harmful microorganisms are called germs. The most common types are viruses and bacteria. Viruses cause colds, warts, and many diseases. Bacteria make wounds swell up and can also cause various diseases. 

Bacteria

Bacteria are single-celled organisms. They are so tiny that hundreds could fit on the point of needle. 

Defence force

The human body contains about 50 billion white blood cells. These are the body's defenders. They seek out germs and kill them, using a variety of different methods. White blood cells called macrophages kill by swallowing germs whole and digesting them. 

How antibodies work

Antibodies are chemicals that stick to specific kinds of germs, flagging them for destruction. There are millions of different germs, but the human body can manufacture 10 billion different antibodies, ensuring there's one for any germ you encounter. Once an antibody cell has been activated by meeting a matching germ, it makes copies of itself and makes the body immune. 

1. Infect

A new germ invades the body and multiplies. It gets carried by body fluids to a lymph node, where many different white blood cells examine it. 

2. Detect

Antibody cells touch the germ to see if it matches molecules on their surface. Eventually, an antibody cell with matching molecules sticks to the germ. 

3. Activate

Now activated, the matching cell makes an army of clones. It also makes memory cells, which will stay in the body for years in case the germ returns. 

4. Seek

The clones make antibodies and release them into the blood. When they find germs, they stick to them. 

5. Destroy

The antibodies act as signposts to cells called macrophages, which swallow and destroy the germs. 

A vaccine

triggers your body

into producing

antibodies, making

you immune to a

 disease without

having to suffer it. 

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World religions

 Millions of people around the world worship a greater power that gives meaning to their lives. For many, religion is an intrinsic part of their very existence. 

A religion is a set of beliefs that deal with every aspect of life, from birth to death,joy and sorrow, good and evil. Some people worship a god or gods, others follow a religious teacher. Religion includes not just beliefs themselves, but the religious rituals and ceremonies that are the outward expression of those beliefs. Religion can bind a small community, or offer people membership of a huge global organization. There are six major religions in the world: Christianity, Judaism, Islam, Hinduism, Buddhism, and Sikhism. These account for 85 per cent of all the world's believers. Millions of others belong to religions old and new, making religion a rich, diverse, and sometimes controversial aspect of human history. 

World religions

Apart from the followers of the six largest religions, about 12 per cent of people belong to other faiths, sects, and cults. Pagans, for example, including witches and druids, revere nature. All religions share a quest to understand the world and make sense of our existence. 

Judaism

The religion of Jewish people, Judaism centres on the first Jew, Abraham, who taught Jews to worship one God. There are more than 14 million believers today, but there are different forms of Judaism, including Orthodox and Liberal. Jews worship in synagogues, observe many rites of passage, and have a day of rest, called the Shabbat (Sabbath). They have struggled against hatred - in World War ll, more than 6 million Jews were killed in the Holocaust. Most Jews now live in the United States and Israel. 

Torah scroll

The most holy Jewish book is the Torah, which contains the rules for everyday life. In the synagogue, the Torah is read from precious scrolls. 

Islam

Followers of Islam are called Muslims. There are more than 1.5 billion Muslims in the world, divided into Sunni and Shi'a. Their faith is based upon the Five Pillars: belief, worship, fasting, alms-giving, and pilgrimage. They follow a Holy Scripture known as the Qur'an, the word of God as told to the Prophet Muhammad. 

Mosque

Many Muslims visit a mosque daily to say their prayers, but on Fridays all attend to listen to the Imam (teacher). Larger mosques have libraries and classrooms. 

Christianity

Christians follow the teachings of Jesus Christ, believing he was the Son of God. There are more than 2.1 billion Christians worldwide, and they are united in the belief in one God, the Bible as a holy text, and the use of prayer in worship. However, different branches of Christianity - Protestant, Catholic, and Orthodox - have different ideas about how their faith should be practised. 

Protestant	Catholic	Orthodox
No official leader	Led by the Pope in Vatican City	Led by Patriarchs
Began with Martin Luther, a 16th century scholar who rejected Catholic teaching	Believe that popes inherit their authority from Saint Peter, one of the 12 apostles of Jesus	Formed in 451 CE after Christians in Rome and Constantinople disagreed over the Church's teachings
Found across the world, but chiefly in Northern Europe, North America, New Zealand, Australia, and parts of Africa	Found across the world, but especially in Southern Europe, Eastern Europe, and South America	Found mainly in Greece, the Balkans, Russia, the Middle East, and North Africa
Emphasize simple worship in language everyone can understand	Use elaborate ceremonies, sometimes in Latin, to glorify God	Use elaborate ceremonies in different languages, including Greek and Syriac, to glorify God
Do not generally have monasteries, but use churches or cathedrals	Have monasteries for men and women	Have monasteries for men and women
Believe everyone can speak directly to God through prayer	Believe most people can speak to God only through the help of a priest or saints	Believe most people can speak to God only through the help of a priest or saints

Hinduism

To the 1 billion Hindus worldwide, Hinduism is a very varied religion. Hindus believe in a great spirit called Brahman who cannot be seen, but is present everywhere. They worship a wide range of gods and goddesses, each depicting a different aspect of Brahman's power. The three most important gods are Brahma, the creator; Shiva, the destroyer; and Vishnu, the protector. According to Hinduism, every person has a soul, which lives on after a person dies. The soul takes on a new form and begins a new life and this cycle continues. This is known as "reincarnation". For Hindus, the aim is to escape this cycle and gain freedom to be with Brahman. Each good deed takes them a step closer. A bad deed takes them further away. This is the law of karma. 

Brahma

The creative aspect of Brahman, Brahma is depicted with four arms, and four faces each reciting one of four holy texts. 

Shiva

The force of destruction and transformation, Shiva can be both kindly and fearsome. As Nataraja, he dances inside a ring of flames. 

Vishnu

Blue-skinned Vishnu is charged with upholding the Dharma - the law that maintains the Universe. 

Lakshmi

The goddess of luck and wealth, Lakshmi is one of the most widely worshipped Hindu deities. She is often seen sitting on a lotus. 

Hanuman

A monkey-like being (or vanara), Hanuman is best known for aiding the hero Rama in his war against the demons. 

Ganesh

Elephant-headed Ganesh is the patron of wisdom, writing, art and science, and new endeavours. 

Buddhism

Buddhism originated in India 2,500 years ago when a man called Siddhartha Gautama gained enlightenment and became the Buddha ("the Enlightened one"). Buddhism gradually spread from India to other countries. Today, more than 376 million people across the world follow the teachings of the Buddha - the dharma, which seeks to end suffering (dukkha) and find answers to the true meaning of life. By respecting the Eightfold Path, including right thoughts and deeds, keeping Five Promises, and repeating three prayers (Three Jewels), Buddhists hope to attain a state of peaceful enlightenment called nirvana. 

Statue of Buddha meditating

Buddhists worship by meditation (dhyana), trying to clear their minds of earthly distractions in order to perceive the Universe more clearly. 

"WE ARE WHAT WE 

THINK. ALL THAT WE ARE

ARISES WITH OUR THOUGHTS. 

WITH OUR THOUGHTS, WE MAKE

THE WORLD."

      

                 BUDDHA

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The 21st century

 At the end of the 20th century, the world got ready to party. Huge celebrations took place across the globe to greet the year 2000, the start of the new millennium. The new century brought grave new challenges, but also amazing opportunities. 

With the world's population expanding, humanity's demands on the planet are growing rapidly. As the 21st century goes on, scientists have become increasingly concerned that we may run out of some natural resources, and that human activity is causing dangerous changes to our environment. Many countries have also had to contend with devastating natural disasters. Terrorist attacks brought fear and conflict to many cities, and a global financial collapse increased the hardship for millions. At the same time, the 21st century has seen astonishing new advances in technology. Smartphones and tablets have transformed the way we communicate, and the internet has expanded hugely to give voices to users across the globe. 

Digital revolution

The digital revolution began in the 1980s, when computers became cheap enough for people to buy and use at home. At first computers were big metal boxes, but today, MP3 player, and cameras. The internet is rapidly evolving to play a central role in society, transforming cultural, economic, and political landscapes. There are thought to be more than 2 billion internet users worldwide, all of whom can exchange information in an instant. 

Web use

During the 1990s, most people only used the internet to look up information. In the 21st century, the amount of user-generated content has hugely increased, with blogs and social networking sites allowing people to share their ideas and experiences. 

IN 2001, GOOGLE INDEXED

 250 MILLION IMAGES.

 IN 2010, IT INDEXED 

MORE THAN 10 BILLION. 

The War on Terror

In 2001, a group of islamist terrorists named al-Qaeda launched a series of attacks on targets in the USA. A decade of conflict followed. The USA and it's allies launched a "War on Terror", invading Afghanistan to capture the terrorists and prevent further attacks. Meanwhile, al-Qaeda and their allies plotted to cause more deaths and destruction in other countries across the world. 

Sept 2001

9/11 

On 11 September 2001, the USA suffered devastating terrorist attacks. Members of al-Qaeda, a global terrorist network of radical Muslims, hijacked four aircraft. They flew two into the World Trade Center in New York (pictured) and one into the Pentagon. The fourth crashed in Pennsylvania. Almost 3,000 people were killed in the attacks, which shocked the world. 

Oct 2001

Invasion of Afghanistan

The USA and its NATO allies launched Operation Enduring Freedom after the 9/11 attacks, in an effort to track down Osama bin Laden. The terrorist leader was thought to be in Afghanistan, where the Taliban government was allied with al-Qaeda. The invasion succeeded in overthrowing the Taliban, but violence continued in Afghanistan for years. 

March 2004

Madrid bombings

On the eve of Spanish political elections, members of al-Qaeda exploded bombs on four trains in Madrid, killing 191 people and wounding 1,841. The Spanish government had supported the 2003 US-led invasion of Iraq. The Spanish public promptly voted that political party out of office and installed a party that withdrew Spanish troops from Iraq. 

July 2005

London bombings

Britain experienced attacks on 7 July 2005, when terrorists carried out a series of suicide bombings on London's transport system. Three bombs exploded on underground trains, and one on a double-decker bus. An al-Qaeda website claimed that they had launched these attacks in retaliation for Britain's involvement in the wars in Iraq and Afghanistan. 

May 2011

Death of Bin Laden

US President Barack Obama received intelligence that Osama bin Laden, the head of al-Qaeda, was hiding out in a compound in Abbottabad, Pakistan. In a daring night raid named Operation Neptune Spear, a US Navy Seal team shot dead bin Laden and four others. It was an important milestone in the War on Terror, but not an end to Islamist extremist terror attacks. 

The War in Iraq

In 1991, Saddam Hussein, leader of Iraq, ordered an invasion of neighbouring Kuwait. His armies were driven out by an international force led by USA, but tensions remained high. In 2001, the international community suspected that Saddam Hussein possessed weapons of mass destruction capable of causing huge civilian casualties. As the War on Terror heightened tensions across the Middle East, the USA and UK led an invasion of Iraq in 2003, toppling Saddam Hussein from power. Although the invasion lasted only a few weeks, violence would continue in Iraq for many years. 

Saddam Hussein's statue is toppled

US tanks rolled into the Iraqi capital, Baghdad, in April 2003, signalling the end of the dictatorship of Saddam Hussein. Jubilant Iraqis toppled a massive statue of the former leader in a symbolic gesture of contempt. 

The Arab Spring

In 2010, a Tunisian man set fire to himself in protest at ill-treatment by the Tunisian police. His rebellion sparked a wave of unrest that spread across the Arab world, in countries ruled by dictators or corrupt and oppressive governments. First, the Tunisian leader, Zine al-Abidine Ben Ali, was forced from power. Then dissent spread to Egypt, where President Hosni Mubarak resigned after massive popular protests. In 2011, there were uprisings in Yemen, Bahrain, Libya, and Syria. Libya's leader, Colonel Muammar Gaddafi, was overthrown by rebel fighters. Free elections took place in some Arab countries, but others such as Syria were thrown into civil war. 

Wave of protest

Demonstrations in Tunisia spread to countries across the Middle East and North Africa. 

Natural disasters

The first years of the 21st century were beset by natural disasters and extreme weather. In 2003, more than 40,000 people died in heat waves across Europe. In 2004, a huge tsunami caused devastation around the Indian Ocean, killing almost 230,000 people in 14 countries. The following year, a powerful storm, Hurricane Katrina, laid waste to the US city of New Orleans, with wind speeds of 200 kph (125 mph). A massive earthquake devastated the island of Haiti in the Caribbean in 2010, killing more than 300,000 people and leaving millions homeless. In 2011, another earthquake triggered a tsunami in Japan, wrecking homes and causing radioactive material to leak from the Fukushima nuclear power plant. 

Global dangers

Countries all across the world experienced devastating natural disasters in the early years of the 21st century. Some were freak chance events, while others have been linked to changes in the world's climate. 

Global financial crisis

In 2007, US banks realized that they had lent money for house mortgages to hundreds of thousands of customers who could not afford to pay them back. To make matters worse, the banks had bundled up the mortgages with other investments, worth billions of dollars. These suddenly lost value, threatening financial systems across the world. The value of investments plummeted, and huge banks collapsed in the USA and Europe. The crisis brought poverty and unemployment to many countries across the globe. 

Losses and bailouts

The crisis wiped 33 per cent off the value of the world's companies. Governments were forced to pay out huge sums of money to keep their economies afloat. 

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Shakespeare's theatre

 Painting and sculpture were not the only arts to be revolutionized by the Renaissance. Theatre also changed, not least with the arrival of the period's most famous playwright, William Shakespeare. 

In Europe, medieval theatre was mostly morality plays and stories from the Bible, which followed a fixed formula. Around the middle of the 16th century, new plays began to present stories of romance, tragedy, and adventure based on Classical myths, history, and even current events. The new plays were extremely popular. Everyone from poor labourers to rich merchants and nobles flocked to the new theatres, and the most famous actors were even invited to court to perform for royalty. 

Stories on stage

For thousands of years, human beings have used theatre to share stories and ideas. The Ancient Greeks built some of the earliest theatres. They divided plays into two types. 

Tragedy

Serious stories in which the heroes and heroines suffer and often die at the end are called tragedies. They often explore the way honour, justice, or fate can force us to go against our personal feelings. 

Comedy

These plays use humour to tell a story, although not always a happy one. Some versions, known as satire, use comedy to point out weakness or bad behaviour, especially in those in power. 

Theatre design

Plays can be performed almost anywhere, from open streets to tiny studios. Most take place in buildings to see and hear the actors, and to make the scene seem as realistic as possible. 

Ancient Greek theatre

This design uses a curve of seats to reflect sound. Even a whisper from the stage can be heard by the whole audience. 

In the round

Travelling actors in medieval Europe often set up a stage surrounded by the audience on three or even four sides. 

Proscenium arch

Modern theatres often have an arch to frame the action on stage and keep the audience separate. 

Shakespeare's Globe Theatre

The late 16th and early 17th centuries saw many great playwrights emerge. By far the most famous is English writer William Shakespeare. His plays were so successful that, in 1599, his theatre company was able to build a permanent playhouse in London: the Globe Theatre. A copy of his theatre stands near the original site today. 

The stage

Three doors led from the tiring house on to the stage. Actors could also arrive through the audience, or through trapdoors in the stage floor. The roof was painted with stars, to represent the heavens. 

The hut

A hidden space above the stage was used for special effects such as heavenly music. 

Lords' boxes

Noble visitors to the theatre sat here, away from the crowds. 

Roof

Roof thatched with straw

Tiring house

These rooms were used for storage, and for the actors to change their clothes (or "attire"). 

Back stage

Actors could wait here without being seen by the audience. Each actor might play several roles in a single play. 

Stage door

Actors could enter through three doors in the back wall. 

Stage

Stage was hollow, so actors could emerge from underneath. 

Floor

Floor of mud covered in straw

Groundlings

It cost only a penny to watch a performance if you didn't mind standing in the yard. 

Staircase

Staircase access to upper levels

Outer walls

Outer walls plastered with a mixture of lime, sand, and goat hair   

Seated spectators

Those who could afford it bought seats in the galleries, so they could watch in comfort. 

Entranceway

Three entrances led under the galleries to the street outside. 

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"All the world's a stage, And all the men and women merely players". As you like it by

William Shakespeare

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