The quark model

In 1964, American physicist Murray Gell-Mann (1929– ) and Swiss physicist George Zweig (1937– ) independently suggested a way out of the particle zoo. They suggested that the nearly 100 subatomic particles that had been discovered so far were not really elementary (fundamental) particles. Instead, they suggested that only a relatively few elementary particles existed, and the other subatomic particles that had been discovered were composed of various combinations of these truly elementary particles.

Words to Know

Antiparticles: Subatomic particles similar to the proton, neutron, electron, and other subatomic particles, but having one property (such as electric charge) opposite them.

Atomic mass unit (amu): A unit of mass measurement for small particles.

Atomic number: The number of protons in the nucleus of an atom.

Elementary particle: A subatomic particle that cannot be broken down into any simpler particle.

Energy levels: The regions in an atom in which electrons are most likely to be found.

Gluon: The elementary particle thought to be responsible for carrying the strong force (which binds together neutrons and protons in the atomic nucleus).

Graviton: The elementary particle thought to be responsible for carrying the gravitational force.

Isotopes: Forms of an element in which atoms have the same number of protons but different numbers of neutrons.

Lepton: A type of elementary particle.

Photon: An elementary particle that carries electromagnetic force.

Quark: A type of elementary particle

Spin: A fundamental property of all subatomic particles corresponding to their rotation on their axes.
The truly elementary particles were given the names quarks and leptons. Each group of particles, in turn, consists of six different types of particles. The six quarks, for example, were given the rather fanciful names of up, down, charm, strange, top (or truth), and bottom (or beauty). These six quarks could be combined, according to Gell-Mann and Zweig, to produce particles such as the proton (two up quarks and one down quark) and the neutron (one up quark and two down quarks).
In addition to quarks and leptons, scientists hypothesized the existence of certain particles that "carry" various kinds of forces. One of those particles was already well known, the photon. The photon is a strange type of particle with no mass that apparently is responsible for the transmission of electromagnetic energy from one place to another.
In the 1980s, three other force-carrying particles were also discovered: the W ⁺ , W ⁻ , and Z ⁰ bosons. These particles carry certain forces that can be observed during the radioactive decay of matter. (Radioactive elements spontaneously emit energy in the form of particles or waves by disintegration of their atomic nuclei.) Scientists have hypothesized the existence of two other force-carrying particles, one that carries the strong force, the gluon (which binds together protons and neutrons in the nucleus), and one that carries gravitational force, the graviton.

Five important subatomic particles

For most beginning science students, the five most important sub-atomic particles are the PROTON, NEUTRON, ELECTRON, NEUTRINO, and POSITRON. Each of these particles can be described completely by its mass, electric charge, and spin. Because the mass of subatomic particles is so small, it is usually not measured in ounces or grams but in atomic mass units (label: amu) or electron volts (label: eV). An atomic mass unit is approximately equal to the mass of a proton or neutron. An electron volt is actually a unit of energy but can be used to measure mass because of the relationship between mass and energy (E = mc ² ).

All subatomic particles (indeed, all particles) can have one of three electric charges: positive, negative, or none (neutral). All subatomic particles also have a property known as spin, meaning that they rotate on their axes in much the same way that planets such as Earth do. In general, the spin of a subatomic particle can be clockwise or counterclockwise, although the details of particle spin can become quite complex.

PROTON:The proton is a positively charged subatomic particle with an atomic mass of about 1 amu. Protons are one of the fundamental constituents of all atoms. Along with neutrons, they are found in a very concentrated region of space within atoms referred to as the nucleus.The number of protons determines the chemical identity of an atom. This property is so important that it is given a special name: the atomic number. Each element in the periodic table has a unique number of protons in its nucleus and, hence, a unique atomic number.

NEUTRON. A neutron has a mass of about 1 amu and no electric charge. It is found in the nuclei of atoms along with protons. The neutron is normally a stable particle in that it can remain unchanged within the nucleus for an infinite period of time. Under some circumstances, however, a neutron can undergo spontaneous decay, breaking apart into a proton and an electron. When not contained with an atomic nucleus, the half-life for this change—the time required for half of any sample of neutrons to undergo decay—is about 11 minutes.
The nuclei of all atoms with the exception of the hydrogen-1 isotope contain neutrons. The nuclei of atoms of any one element may contain different numbers of neutrons. For example, the element carbon is made of at least three different kinds of atoms. The nuclei of all three kinds of atoms contain six protons. But some nuclei contain six neutrons, others contain seven neutrons, and still others contain eight neutrons. These forms of an element that contain the same number of protons but different numbers of neutrons are known as isotopes of the element.
Electron. Electrons are particles carrying a single unit of negative electricity with a mass of about 1/1800 amu, or 0.0055 amu. All atoms contain one or more electrons located in the space outside the atomic nucleus. Electrons are arranged in specific regions of the atom known as energy levels. Each energy level in an atom may contain some maximum number of electrons, ranging from a minimum of two to a maximum of eight.

ELECTRONS AND LEPTONS: Unlike protons and neutrons, they are not thought to consist of any smaller particles but are regarded themselves as elementary particles that cannot be broken down into anything simpler.
All electrical phenomena are caused by the existence or absence of electrons or by their movement through a material.

Properties of the Leptons

Particle	Symbol	Anti- particle	Rest mass MeV/c²	L(e)	L(muon)	L(tau)	Lifetime (seconds)
Electron	e^-	e⁺	0.511	+1	0	0	Stable
Neutrino (Electron)	ν_e	ν_e	0(<7 x 10^-6)	+1	0	0	Stable
Muon	μ^-	μ⁺	105.7	0	+1	0	2.20x10^-6
Neutrino (Muon)	ν_μ	ν_μ	0(<0.27)	0	+1	0	Stable
Tau	τ^-	τ⁺	1777	0	0	+1	2.96x10^-13
Neutrino (Tau)	ν_τ	ν_τ	0(<31)	0	0	+1	Stable

NEUTRINO. Neutrinos are elusive subatomic particles that are created by some of the most basic physical processes of the universe, like decay of radioactive elements and fusion reactions that power the Sun. They were originally hypothesized in 1930 by Swiss physicist Wolfgang Pauli (1900–1958). Pauli was trying to find a way to explain the apparent loss of energy that occurs during certain nuclear reactions.
Neutrinos ("little neutrons") proved very difficult to actually find in nature, however. They have no electrical charge and possibly no mass. They rarely interact with other matter. They can penetrate nearly any form of matter by sliding through the spaces between atoms. Because of these properties, neutrinos escaped detection for 25 years after Pauli's prediction.
Then, in 1956, American physicists Frederick Reines and Clyde Cowan succeeded in detecting neutrinos produced by the nuclear reactors at the Savannah River Reactor. By 1962, the particle accelerator at Brookhaven National Laboratory was generating enough neutrinos to conduct an experiment on their properties. Later, physicists discovered a second type of neutrino, the muon neutrino.
Traditionally, scientists have thought that neutrinos have zero mass because no experiment has ever detected mass. If neutrinos do have a mass, it must be less than about one hundred-millionth the mass of the proton, the sensitivity limit of the experiments. Experiments conducted during late 1994 at Los Alamos National Laboratory hinted at the possibility that neutrinos do have a very small, but nonzero, mass. Then in 1998, Japanese researchers found evidence that neutrinos have at least a small mass, but their experiments did not allow them to determine the exact value for the mass.
In 2000, at the Fermi National Accelerator Laboratory near Chicago, a team of 54 physicists from the United States, Japan, South Korea, and

Electronic display of energies from subatomic particles. (Reproduced by permission of
Photo Researchers, Inc.
)

Greece detected a third type of neutrino, the tau neutrino, considered to be the most elusive member of the neutrino family.

POSITRON. A positron is a subatomic particle identical in every way to an electron except for its electric charge. It carries a single unit of positive electricity rather than a single unit of negative electricity.
The positron was hypothesized in the late 1900s by English physicist Paul Dirac (1902–1984) and was first observed by American physicist Carl Anderson (1905–1991) in a cosmic ray shower. The positron was the first antiparticle discovered—the first particle that has properties similar to protons, neutrons, and electrons, but with one property exactly the opposite of them.

ARE THERE OTHER UNIVERSES OUT THERE?

According to "STRING THEORY" - a relatively new theory which attempts to combine all the forces known to physics in a single unified WHOLE - there may be any number of universes in existence. However, each of them might be governed by different natural laws. For this reason most of these universes could not sustain life, since to find a combination of natural laws that would allow life to exist would be exceptional.

However rare such a combination may be, any universe containing an intelligent observer would inevitably be an exceptional universe of this kind. Some scientists this is one way of explaining why it is that the natural laws in our universe seem designed to allow life to exist - because we are here to observe it. Or it may be merely a matter of chance that this is how it is.

HOW DO NEWLY DISCOVERED CELESTIAL BODIES GET THEIR NAMES?

Only the astronomer's professional organization, the "INTERNATIONAL ASTRONOMICAL UNION"(IAU) can decide on names, & there are strict rules surrounding the naming of celestial bodies.For example, comets are always named after their discoverer.In the case of asteroids, the discoverer is entitled to suggest a name but it must be approved by a committee of the IAU. These days, most stars are merely given a catalogue number which usually contains a set of celestial coordinates indicating the body's position in the sky.

for more info about IAU you can check their official website..

http://www.iau.org/

WHAT PROTECTS THE EARTH FROM THE PARTICLES THAT ARE EMANATING FROM SUN?

Well it's quite simple. The answer is "MAGNETIC FIELD" of the earth..

WHY DOES THE SUN HAVE SPOTS?

Unlike earth, the sun has an extremely complicated magnetic field.A large part of this magnetic field runs beneath the surface of the sun in the form of so - called "magnetic tubes".Sometimes these tubes can break through the sun's surface, and where they do so,strong magnetic fields prevent hot matters from rising out of the sun's interior,cooling the affected areas of the surface to a temperature of 4000^o c. Because of their lower temperature, these regions aren't bright as the rest of the sun - which is about 1500^o c hotter - & thus they appear as dark spots on the sun's surface.Sunspots are between 2500 km and 50000 km wide, which means they can be several times larger than earth.The life span of individual sunspots varies from days to months.

DOES THE SUN ALWAYS HAVE THE SAME NO OF SUNSPOTS?

Sunspots numbers rise and fall in a cycle of approximately 11 years. The last sunspot maximum was in 2000,so the next one is expected in 2011.The sunspot cycle is controlled by the sun's magnetic field,which changes direction every 11 years.

DO OTHER STAR'S ALSO HAVE SPOTS?

Our sun is definitely not exceptional,and other stars also have dark spots in number's that fluctuate in accordance with a regular cycle.The magnetic processes at work appear to be very similar. These 'starspots' can be even larger than the spots on our sun.

WHAT IS CORONA?

The "CORONA" is the sun's thin external atmosphere. Sound waves & magnetic fields heat the gas in the corona to a temperature of over 1 million degrees celsius. This high temperature causes the corona to emit x-rays.However, it also emits a lot of light, which is why the corona can be seen with the naked eye when the sun's bright disc is covered,as is the case during a total eclipse of the sun. In order to observe the corona, space scientists use a special telescope,like the one aboard the solar and heliospheric observatory(SOHO) spacecraft, which has been fitted with a device to cover the disc of the sun. The corona stretches several million kilometres in to space two or three times the diametre of the sun

DO YOU KNOW THAT SCIENTISTS ARE HUNTING FOR NEUTRINOS?

Well it's a fact that scientists are hunting for neutrino's. but why? this has been our question right? so here it is......

The process of "nuclear fusion" within the sun generates a huge no of neutriono's as well as EMR( Electro Magnetic Radiations). Neutrinos are mysterious elementary particles. They have miniscule mass and are able to pass through matter almost undisturbed, which is why, in contrast to radiation, the neutrino's that originate in the core of the sun arrive at the earth in only 8 minutes. About 70 billion neutrinos strike each square centimetre of our planet every second. Physicists are developing gigantic detectors in their efforts to catch at least a few of these elusive particles to help them understand a few more of the mysteries of the sun's interior.

One such detector is The "SUPER KAMIOKANDE" detector which is 59m high and fitted with more than 11000 photomultiplier tubes which are used to detect neutrinos.

you see the tiny tiny things here in the picture these are the "photomultiplier tubes"

DOES WATER EXIST ON OTHER PLANETS?

So far scientists have found liquid water only on earth.That is the reason maybe life was first originated on earth. Some suspect that there may be frozen water in the perpetually shaded regions around Mercury's poles. Frozen water is also present near the poles on mars, and it is highly probable that there is an ocean on jupiter's moon "EUROPA"

Magnetic field measurements indicate that an ocean about 100 km deep is concealed under a 1 km thick layer of ice on jupiter's moon- europa.It may be that the giant planet's gravity heats the inside of the moon by 'squeezing' it thoroughly, maintaining any water in a liquid form.The american space agency NASA is currently working on plans to send a space probe to this moon in an attempt to find out what exactly is happening there.

DOES 'VULCANISM' OCCUR ON OTHER PLANETS?

"VULCANISM" - Well vulcanism(verb) means volcanic activity or volcanic eruption....

Astronomers have discovered old volcanoes on venus, as well as on mars. So far, no active vulcanism has been detected on any other planet, although it has been detected in jupiter's moon "IO". However, atmospheric gases on venus indicate that there may be active volcanoes on that planet as well....

there you see the small one is the "IO"

WHY ARE JUPITER & SATURN SO LARGE?

In the inner solar system, the young sun's radiation blew away any leftover gas at an early stage, but it was preserved for a longer period in the outer areas.This is why those planets that formed in the outer regions of the solar system had more time to attract the gas present in their surroundings, and so grew for much longer.

WILL WE EVER BE ABLE TO TRAVEL THROUGH WORM HOLES?

WORM HOLES:- A Wormhole is just like a space portal which acts as a shortcut for a journey to other galaxies.... it's just an assumption well there is no proof at present for the existence of "wormhole's"...

Because we are restricted to velocities below the speed of light, the kind of space travel to distant stars and galaxies we see depicted in science fiction films is impossible.The realisation that this is the case, & that humankind may never visit even a fraction of the "vast" universe, is a situation that even some physicists find unsatisfactory.This has lead to a search for loopholes in the laws of physics that may make intergalactic space travel possible. One such loophole involves the possibility of so called "wormholes" in space. These strange entities are a consequence of the theory of relativity, and the suggestion is that distant regions of the universe may be connected by a kind of space-time tunnel.However,theory predicts that wormholes will be unstable and so unsuitable for use as shortcuts by future astronauts. As soon as they have formed- if indeed they do form - they would collapse again. One suggestion is that wormholes could be stabilized by matter with "NEGATIVE ENERGY & NEGATIVE GRAVITY". Unfortunately - like wormholes themselves - this kind of matter exists only in theory so far.

WHY DOESN'T THE EARH'S ROTATION HURL US OFF THE SURFACE OF THE PLANET?

WELl you know guys.... this question got in to my mind when i was in 7th class...... :P it seems strange but when i asked someone i know who are elder to me they haven't answered to me .....

it's quite simple.... of course i would go somewhat logic wise..

The earth rotates very rapidly, it's speed at the equator being almost 1700 km/h. To keep all of the inhabitants of the earth firmly on the ground and rotating along with the planet,requires the gravitational pull of the earth's immense mass. It is "GRAVITY" that keeps our feet on the ground.In fact, there is a reduction in weight due to rotational speed that means we weigh around 0.5% more at North & South poles than we do at the Equator.If there was a planet that actually rotated so fast that it was impossible for it's inhabitants to be held down by gravity if they stood at it's equator, the planet itself would fly apart.

WHAT IS THE FAMOUS "CHANDRASEKHAR LIMIT"?

In 1928 an Indian graduate student named subrahmanyan Chandrasekhar set sail for england to study at cambridge with the british astronomer Sir Arthur Eddington.Eddington was an expert on general relativity.

During his voyage to india,Chandrasekhar worked on how big a star could be and still separate itself under it's own gravity after it had used up all it's fuel.The idea was this: when the star becomes small, the matter particles get very near to each other.But the pauli exclusion principle says that two matter particles can't have both the same position and the same velocity.The matter particles must therefore have very different velocities.

This makes them move away from each other,and so tends to make the star expand. A star can therefore maintain itself at a constant radius by a balance between the attraction of gravity and the repulsion that arises from the exclusion principle, just as earlier in it's life the gravity was balanced by the heat.

Chandrasekhar realized, however, that there is a limit to the repulsion that the exclusion principle can provide.The theory of relativity limits the max difference in the velocities of the matter particles in the star to the speed of light. That meant that when the star got sufficiently dense, the repulsion caused by the exclusion principle would be less than the attraction of gravity.Chandrasekhar calculated that a cold star of more than one and a half times the mass of the sun wouldn't be able to support itself against it's own gravity. This mass is now known as the "CHANDRASEKHAR LIMIT".

LIGHT CAN BE STOPPED?

Well before going for the question i'll quickly post some properties abt light. well "light" can travel with a speed of 3 lakh m/s where as in miles it is 6.702 * 10^8 miles/hour.

Scientists stop light completely for a record-breaking MINUTE by trapping it inside a crystal!

Scientists in Germany have succeeded in stopping light - the fastest thing in the universe - for a whole minute, smashing earlier records.

Researchers at Darmstadt Technical University achieved the remarkable feat by trapping it in a crystal.

In a paper published this month in the journal Physical Review Letters, the scientists explained how they stopped the light using a technique called electromagnetically induced transparency.

At full pelt, light would normally travel about 11 million miles in one minute – equivalent to more than 20 round trips to the moon.

'One minute is extremely, extremely long,' Thomas Krauss, Professor of optoelectronics at the University of St Andrews, UK, commented to the New Scientist. 'This is indeed a major milestone.'

The physicists, Professor Thomas Halfmann, Christian Hubrich and PhD student Georg Heinze, also used the same technique to store and then retrieve an image consisting of three stripes. 'We showed you can imprint complex information on your light beam,' said researcher Georg Heinze.

The results may further light-bas

HOW ABOUT A LIFT IN TO THE SPACE?

well, a scientist inspired by the "EIFFEL TOWER" construction had a thought in his mind.He decided to construct a tower of height 348000 km near our earth's equator.At the top of this tower if a person reaches he will be able to easily float in the space,and the tower's speed would match the earth's orbit speed.Neverthless that ain't gonna happen.But the idea is nice isn't it? An american scientist realized that the tower itself wasn't necessary.All that was needed was a rope that could tie the lift from a satellite to the earth. But the only problem is the material with which that rope would me made of. Even steal of width 90 km can't hold that much weight.Well still an american space organization has planned to launch a lift into the space by 2025.They decided to make the rope from "carbon micro nanotubes".

ARE THERE ALSO GALAXIES WHICH ARE RACING TOWARDS US?

Although the universe as a whole is expanding, there are still galaxies moving in our direction- for example the nearby "ANDROMA GALAXY" which is travelling towards us at rate of about 3000 km/sec.

To understand this apparent contradiction we have to differentiate between two phenomena: on the one other hand the motion of galaxies through space,on the other hand the expansion of the cosmos itself.Random motions of galaxies in space are typically in the order of a few hundred kilometres per sec. For galaxies that are very close to our milky way galaxy, the expansion is negligible compared to that of expansion.Hence all distant galaxies seem to be rushing away from as a result of expansion,whereas near by galaxies can be moving either towards us or away from us.

DOES THE UNIVERSE HAVE A CENTRE?

When it was discovered that nearly all galaxies are moving away from us,scientists wondered whether the milky way might be situated at the centre of the universe.Plausible as the idea may seem,it is incorrect.In reality, galaxies scarcely move, it is the space between them that stretches - just like the surface of a balloon when it is inflated. Every point moves away from every point , surface.This would also be true if the universe were not curved like the balloon's surface but infinite.Although we may find this hard to imagine, even a universe of this kind would have no centre.

HOW IS DISTANCE MEASURED IN SPACE?

Many different methods are used to measure distance in space.Apollo 11 astronauts left a laser reflector on the moon, making possible to measure the centimetre the precise distance the moon and earth.

The distances of other bodies in our solar system, such as the planets & asteroids, can be measured by RADAR,that is reflecting radio waves off them.However,this method wonn't work for stars,which are much further away.For these, astronomers use a technique that measures tiny differences in the position of a star when it is observed from opposite side of the earth's orbit,that is at intervals six months apart.Since the diameter of the earth's orbit is known, the change in angular position of a star at either side of the orbit can be used to calculate it's distance known as the "PARALLAX" method this works for objects at distances of upto about 1000 light years.

For still more distant objects,such as galaxies astronomers use indirect methods.One of these involves cepheid variables, a type of star which has the convenient property of varying in brightness at regular intervals.We know that the length of the intervals depend on a star's luminosity,which means that by measuring a cepheid variable's brightness it is possible to calculate how far away it- and the galaxy that it is a part of- is from us.

What's So Special About The Celestial Body That Shone Over Bethlehem?

There have been many attempts to explain the star of bethlehem said to have guided the three wise men to the birthplace of "JESUS" as a natural celestial phenomenon.It has been suggested that it might have been a comet or even a supernova, an exploding star.

Many researchers believe the most likely possibility to be the meeting of two or more bright planets - a celestial event known as a conjunction- and there are a number of candidates in the relevant period of time.Among the possibilities are the rare triple conjunction of jupiter and saturn in 7 BC or the conjunctions of venus & jupiter in 3 BC and again in 2 BC. However none of these hypotheses has so far been proven and none may ever be.

GALAXIES

GALAXIES are mixture of several hundred billion stars. Stars are not evenly scattered across the universe,instead they form large systems that's what i call as a galaxy. Galaxies exist in a variety of different shapes and sizes,from gigantic elliptical galaxies,through to spiral galaxies like our own "MILKY WAY", and small, irregular galaxies such as the large and small magnetic clouds.

what are clusters of galaxies?

well galaxies themselves are not distributed randomly or evenly through the cosmos.They collect in groups and clusters.For example,our milky way belongs to the local group of galaxies which comprises about 30 star systems. Other galaxies are located in the clusters which have several thousand members. One example is a cluster within the constellation VIRGO, which is made of more than 2000 galaxies.

HOW MANY GALAXIES CAN WE SEE?

Between september 2003 and jan 2004, The "HUBBLE" space telescope took the longest ever exposure of the sky in the history of astronomy - more than 270 hours.Based on the number of galaxies visible in the spectacular "HUBBLE ULTRA DEEP FIELD" scientists estimate that with the technology available today some 50 billion galaxies can be observed.

How Far Is To The Nearest Galaxy?

It is currently thought that the "CANIS" major dwarf galaxy in the constellation of the great dog is the nearest galaxy closest to us. It is only 25,000 light years away from the centre of the milky way. This small system appears to be disintegrating as the gravitational pull of the much larger milky way is tearing it apart and absorbing it's stars.

QUASARS

Quasars are among the brightest objects in the universe,radiating more energy than entire galaxies! great aren't they? After speculating for years about the mysterious nature of quasars, astronomers had known that they lie at the heart of some galaxies.They draw their energy from enormous black holes which have masses billions of times greater than of our sun.Like cosmic vacuum cleaners these gravitational "MONSTERS" suck up matter from their surroundings,releasing unimaginable quantities of energy in the process.
now if anybody asks you what are the most brightest objects in our sky? you should say "quasars" but not stars.....

well u may be thinking it's nice knowing abt quasars but how are they "DISCOVERED"

Light rays are subject to the effects of gravity. If a ray passes close to a star or galaxy its path is curved by an effect known as "GRAVITATIONAL LENSING". This can produce some interesting effects.This is how scientists can observe quasars which would otherwise be hidden from us behind a much closer galaxy. Thanks to this phenomenon, astronomers have discovered several planets orbiting other stars.

They draw their energy from enormous black holes which have masses billions of times greater than of our sun. this was my sentence in the very first paragraph. all may be amused at the first look at this sentence, wondering what exactly that sentence meant... well here i explain it clearly....
. Quasars Are So Bright, In Fact, That They Can Be Seen At Very Large Distances When The Universe Was Quite Young.

STAR'S LIFE & DEATH

Although stars seem constant to us,there is in fact a relentless cycle of life and death going on in a space.Astronomers can identify regions where new stars are being born as well as the remains of stars that have exploded. the stars appear unchanged to us only because they take an almost inconceivably long time - millions & billions of years - to develop. Spectacular and rapid events like a "SUPERNOVA"- a star exploding- are very rare.The course of a star's life and it's eventual death depend on the amount of mass it accrued during it's formation.

how are stars and planets formed?

The life of a star begins with a gigantic cloud of cool hydrogen gas with an initial temperature no more than a few degrees above absolute zero(-273.15^o c). The cloud gradually collapses under it's own gravity and clumps of material begin to form inside it,causing it to collapse at ever increasing speeds,while the temperature of the gas rises steadily.The cloud eventually starts to glow,giving off thermal radiation which can be detected by infrared telescopes.The internal density and temperature ultimately increase to a point where "nuclear fusion" takes place.in which hydrogen is converted into helium,& so a new star is "BORN"

Typically many stars of different sizes emerge from one large gas cloud.Sometimes,stars clusters made up of thousands or even millions of stars are created all at once.A rapidly rotating cloud of gas and dust( the remnants of original cloud) floats around many of the young stars, and inside this cloud there are further clumps of matter which have the potential to develop into planets and other smaller celestial bodies. It is thought that planets may be formed around most stars.

what about age of stars?

The first stars found in the cosmos were formed 400 million years after the big bang.Some stars are very frugal in using their supply of fuel,that even today we are still able to see the stars belonging to the very first generations.This is especially the case with globular clusters,where we find stars that are more than 13 billion years old,although new stars are being formed all the time. One of the best known starbirth regions is the "GREAT ORION NEBULA". which is 1600 light years away and visible with the naked eye as part of the constellation orion. The hubble and spitzer telescopes have revealed that many young stars in the orion region have discs of matter rotating around them in which planets may be forming.

how long does a star live and how do they "die"?

The duration of star's life and the manner of it's death depend on it's "MASS".This is because large,high mass stars use up their energy reserves more rapidly than smaller,low mass stars.This is the reason why large stars shine brightly for no more than a few million years,while smaller stars can live for billions of years.Stars produce their energy as a result of a process known as nuclear fusion- during which hydrogen is converted into helium.However the time inevitably comes when all the hydrogen at the core of a star has been used up.

RED GIANTS & WHITE DWARFS

Once a star's hydrogen reserves are used up, the star enters the final phase of it's life.It swells up to become what is known as "red giant".Our own sun will one day turn into a red giant,and in so doing may even devour the earth,along with several more of inner planets.further fusion processes occur in the core of the enlarged star over millions of years,during which,for example helium is converted in to carbon and oxygen.when all of a star's stock of potential nuclear fuel has benn exhausted,it collapses and turns into a "WHITE DWARF". At this stage the star is only about the same size as "EARTH" and it takes billions more years for it to cool down

SUPERNOVA

When a star has a mass of more than 8 times than that of our sun it's end is considerably more dramatic than that of most regular stars.In it's final stages the dying star hurls it's outer layers into space with a mighty explosion which is called as "SUPERNOVA".

at the same time,the star's interior's collapses to form a small,extremely dense body,which can form either of a "neutron star or a black hole".

NEUTRON STAR

The matter in a neutron star is packed as densely as the matter in an atomic nucleus.It is so tightly packed.that a tiny piece of a neutron star the size of a pinhead would weigh more than one million tonnes.The immense pressure in the interior of this kind of object pushes the electrons into the atomic nuclei's protons- leaving nothing but neutrons behind.Neutron stars have a diameter of only about 20 km but contain about the same mass as our sun.

BLACK HOLE:

If the mass of a star's collapsing interior is more than about 3 times that of our sun,it's gravity becomes so strong that even the neutrons can't halt the process. Inexorably, the star continues to collapse until it becomes a "BLACK HOLE". the name given to a region where gravity is so powerful that nothing,literally not even light, is able to escape. this is why these gravity holes are "BLACK".

STARS

what are star's?

Stars are nothing other than suns. just like our own sun, they too are huge balls of incandescent gas,inside which "NUCLEAR FUSION" transforms hydrogen into helium.This process releases enormous amounts of energy,which is why stars shine and radiate heat.It is only because stars are so far away that they appear in the night sky as no more than tiny points of light.In reality,many stars are considerably larger than our sun.

MERCURY

Mercury is the closest planet to the sun in our solar system.since it's average distance from the sun is only 58 million km(compare with 150 million km between the earth and the sun),it's position in the sky is also very close to the sun.seen from earth,mercury can't move any further from the sun than 28^o, and most of the time it is even closer than that,or even directly in front of or behind the sun.from earth the planet is nearly always obscured by the sun's brilliant light.mercury is only visible for most people when the sun is not in the sky at the same time - which is obviously at dawn and dusk.then mercury can be seen low on the horizon either rising or setting just before or just after the sun.

EARTH & MOON

well everybody loves moon. don't they? but do you know what makes our earth and the moon in our solar system special?

well as all know there are 8 planets in our solar system, and most have moons, but there is something special about the earth and it's moon.

The fact that there is life on earth is one important factor that makes it special,but there is another- astronomical reason as well.

And that is "NO" other planet has such a large moon relative to the planet's size.This is why some scientists don't consider the earth and it's moon to be a typical planet moon system,but prefer to think of it as a "DOUBLE PLANET".

HOW OLD IS THE UNIVERSE?

it's very difficult for the scientists to measure exactly the age of our universe.

coming to the question how scientists would have measured the age of our universe?

well, does anybody know about "cosmic microwave background radiation"?

cosmic microwave background radiation:- Cosmic microwave background reaches the earth from all the directions and is like an echo of the big bang.

The background pattern we see today emerged when the cosmos was only 400000 years old. by that time it's temperature had dropped to less than 2700 c. and what had been hot,opaque plasma became transparent gas through which electromagnetic radiation could travel freely.since then,the universe has expanded and cooled so that the temperature of the cosmic background radiation is now only 2.7 c above absolute zero(-273.15 c). so thanks to tiny variations in the cosmic background radiation we can hope to learn what happened at the time of big bang.

the most accurate measurement of cosmic microwave background radiation so far was made by,the US satellite "WILKINSON MICROWAVE ANISOTROPY PROBE.(WMAP). which found our universe to be "13.7" billion years old.by comparison, earth came into existence into being some "4.5" billion years ago.

is universe finite?

1) firstly how many of you know that our universe is expanding day by day?

2)if so why? according to some space scientists our present universe is expanding day by day.coming to the point why the universe is expanding? In 1929 Edwin Hubble, working at the Carnegie Observatories in Pasadena, California, measured the redshifts of a number of distant galaxies. He also measured their relative distances by measuring the apparent brightness of a class of variable stars called Cepheids in each galaxy. When he plotted redshift against relative distance, he found that the redshift of distant galaxies increased as a linear function of their distance. The only explanation for this observation is that the universe was expanding.

take a keen look at this.this would do the understanding.

DAMN FACTS

1) would you believe during the explosion of big bang the size of our universe was 10-36 m.

2)usually everyone loves moon. did anyone know that every year moon comes 3.7 cm close to earth?

3) does anybody knows a place on this earth where people can indirectly watch the earth's rotation? well there is a place named "pantheon" in paris. There people can observe the rotation of the earth indirectly by means of a "foucault" pendulum.
4)It(light ray emitted by moon) takes "8.3" seconds to reach the earth's surface. where as a sun ray takes 8.248 minutes.

well i love any thing,topic and whatever related to our universe....... i'll post some interesting.thrilling,mysterious facts about our universe.....

EVOLOUTION OF OUR UNIVERSE..

well....... as everyone know how our universe was evolved... actually nobody know's how it has evolved ... because there was nothing before the evolution of universe... after the evolution of universe came "time,matter, etc..... everything. well by the time you read this three sentences you will be getting bored.. so i'm not gonna waste time of your's by elongating the current topic..

ASSUMPTIONS...

1)BIG BANG THEORY:- as everyone know... the main theory(just an assumption) big bang was very much helpful in understanding about how our present universe has evolved..

IT states that the origin of our universe took place by a huge(literally very huge) explosion.. and thus how the name "BIG BANG" was given to it.

What would you say if anyone asks what is the least measurable part or unit of time?

The answer is "Planck's time". So what is this planck's time?

like 10th part of a "second" or still lesser than that.

here are some other small units of time,

1) Millisecond (thousandth part of a second)

2)Microsecond (millionth part of a second)

3)Nanosecond (billionth part of a second)

4)Picosecond (trillion part of a second)

5)Femtosecond (quadrillionth part of a second)

6)Attosecond (quintillionth part of a second)

7)Zeptosecod (sextillionth part of a second)\

Well to explain how fast did the big bang explosion took place , famous german scientist Mr.Max Planck had introduced what is so called "PLANCK TIME".

So coming to the point planck time can be defined as how much time a "photon" would take travelling with speed of light in vacuum to cover of a distance of one "Planck length". where as planck length is the unit of length in "Planck units".

To be much simple, the smallest unit of time is called "planck's time".

It's app value is 5.4 *10^-44 = 0.0000000000000000000000000000000000000000000054 "SECONDS".

dilaton can be described as the sister particle of the "HIGGS" particle. it almost has the similar characters as that of the "higgs" particle. Astonishingly it's properties are some what that of the "DARK ENERGY"- it is the force which is responsible for the expansion of the universe..

dilaton is also said to have a significance in type II A string theory.....