No one knows the exact number of galaxies in the universe, but it is estimated that there are more than 50 billion galaxies inthe universe!(How huge the universe is!!!)

The matter in the universe is so thinly dispersed that the universe can be compared with a building twenty miles long, twenty miles wide, and twenty miles high, containing only a single grain of sand.

While astronomers used to believe that galaxies were distributed more or less evenly through space, they have now found regions where galaxies are rare or absent. The largest of these regions is located in the direction of the constellation Bootes, and measures more than 300 million light years across.

A "light year" is a measure of distance, it is the distance that light travels in a year and is equal to about 9.5 trillion kilometres, or about 6 trillion miles.

About 25% of the universe consists of "dark matter", and about 70% consists of "dark energy", leaving only about 5% of the universe visible to us.

It is possible that many planets in the galaxy may not orbit around stars. Recent work by Kailash Sahu found six gravitational lenses in the star cluster M22 from objects smaller than brown dwarfs, the smallest type of star. Only one gravitational lensing event by a star was found in the same work.

Most scientists think that the universe began 13.7 billion years ago (that is 1,370 million years ago). But there is not much differece as other scientists say that the Universe is 10 to 20 billion years old.

According to the scientists our solar system was formed about 5 billion years ago.

The Earth was formed about 4.5 billion years ago.

Astronomers believe that the universe contains one atom for every 88 gallons of space.

At present the universe is believed to be at least 10 billion light-years in diameter.

The Sun


The Sun is a low mass star on the outer reaches of the Milky Way galaxy. The Sun is some 30,000 light years from the center of the Milky Way and lies on one of the spiral arms.



The average distance from the Earth to the Sun is 93,000,000 miles. It takes light almost eight and a half minutes to travel this distance from Sun to the Earth.

The diameter of the Sun is 870,000 miles, 109 times larger than the Earth's. Sun's volume is big enough to hold over one million Earths.

The Sun is about 4.5 billion years old.

The Sun contains more than 99.8% of the total mass of our solar system.

A person that weighs 75 pounds on Earth would weigh about a ton on the Sun.

The Sun is extremely HOT! The middle of the Sun is at least 10 million degrees. The "surface" of the Sun (what we see) is only 5800 degrees.

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Devil-may-care

THE UNIVERSE:
The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. Based on observations of the portion of the Universe that is observable, physicists attempt to describe the whole of space-time, including all matter and energy and events which occur, as a single system corresponding to a mathematical model.

The generally accepted scientific theory which describes the origin and evolution of the Universe is Big Bangcosmology, which describes the expansion of space from an extremely hot and dense state of unknown characteristics. The Universe underwent a rapid period of cosmic inflation that flattened out nearly all initial irregularities in the energy density; thereafter the universe expanded and became steadily cooler and less dense. Minor variations in the distribution of mass resulted in hierarchical segregation of the features that are found in the current universe; such as clusters and superclusters of galaxies. There are more than one hundred billion (1011) galaxies in the Universe, each containing hundreds of billions of stars, with each star containing about 1057 atoms of hydrogen.

Etymology:
The word "universe" is derived from the Old Greek univers, from Latin universa, which combines uni- (the combining form of unus, or "one") with versus (perfect passive participle of vertere, or "turn"). The word, therefore, means "all turned into one" or "revolving as one" or "orbiting as one".

Name of Universe:
As used by observational cosmologists, the Universe most frequently refers to the finite part of space-time. The Universe is directly observable by making observations using telescopes and other detectors, and by using the methods of theoretical and empirical physics for studying its components. Physical cosmologists assume that the observable part of (comoving) space (also called our universe) corresponds to a part of a model of the whole of space, and usually not to the whole space. They use the term the Universe ambiguously to mean either the observable part of space, the observable part of space-time, or the entire space-time.

In order to clarify terminology, George Ellis, U. Kirchner and W.R. Stoeger recommend using the term the Universe for the theoretical model of all of the connected space-time in which we live, universe domain for the observable universe or a similar part of the same space-time, universe for a general space-time (either our own Universe or another one disconnected from our own), multiverse for a set of disconnected space-times, and multi-domain universe to refer to a model of the whole of a single connected space-time in the sense of chaotic inflation models.

Observable portion: A majority of cosmologists believe that the observable universe is an extremely tiny part of the whole universe and that it is impossible to observe the whole of comoving space. It is presently unknown if this is correct, and remains under debate. According to studies of the shape of the Universe, it is possible that the observable universe is of nearly the same size as the whole of space. If a version of the cosmic inflation scenario is correct, then there is no known way to determine if the whole universe is finite or infinite. If it is infinite, the observable Universe is just a tiny speck of the whole universe.

Evolution:
Formation:The most important result of physical cosmology—that the universe is expanding—is derived from redshift observations and quantified by Hubble's Law. That is, astronomers observe that there is a direct relationship between the distance to a remote object (such as a galaxy) and the velocity with which it is receding. Conversely, if this expansion has continued over the entire age of the universe, then in the past, these distant, receding objects must once have been closer together.
By extrapolating this expansion back in time, one approaches a gravitational singularity where everything in the universe was compressed into an infinitesimal point; an abstract mathematical concept that may or may not correspond to reality. This idea gave rise to the Big Bang Theory, the dominant model in cosmology today.
During the earliest era of the big bang theory, the universe is believed to have formed a hot, dense plasma. As expansion proceeded, the temperature steadily dropped until a point was reached when atoms could form. At about this time the background energy (in the form of photons) became decoupled from the matter, and was free to travel through space. The left-over energy continued to cool as the universe expanded, and today it forms the cosmic microwave background radiation. This background radiation is remarkably uniform in all directions, which cosmologists have attempted to explain by an early period of inflationary expansion following the Big Bang.

Examination of small variations in the microwave background radiation provides information about the nature of the universe, including the age and composition. The age of the universe from the time of the Big Bang, according to current information provided by NASA's WMAP (Wilkinson Microwave Anisotropy Probe), is estimated to be about 13.7 billion (13.7 × 109) years, with a margin of error of about 1 % (± 200 million years). Other methods of estimation give different ages ranging from 11 billion to 20 billion. Most of the estimates cluster in the 13–15 billion year range

Pre-mattersoup:Until recently, the first hundredth of a second after the Big Bang was a mystery, leaving Weinberg and others unable to describe exactly what the universe would have been like during this period. New experiments at the Relativistic Heavy Ion Collider in Brookhaven National Laboratory have provided physicists with a glimpse through this curtain of high energy, so they can directly observe the sorts of behavior that might have been taking place in this time frame.

At these energies, the quarks that comprise protons and neutrons (ups and downs) were not yet joined together, and a dense, superhot mix of quarks and gluons, with some electrons thrown in, was all that could exist in the microseconds before it cooled enough to form into the sort of matter particles we observe today.

Protogalaxies: Moving forward to after the existence of matter, more information is coming in on the formation of galaxies. It is believed that the earliest galaxies were tiny "dwarf galaxies" that released so much radiation they stripped gas atoms of their electrons. This gas, in turn, heated up and expanded, and thus was able to obtain the mass needed to form the larger galaxies that we know today.

Current telescopes are just now beginning to have the capacity to observe the galaxies from this distant time. Studying the light from quasars, they observe how it passes through the intervening gas clouds. The ionization of these gas clouds is determined by the number of nearby bright galaxies, and if such galaxies are spread around, the ionization level should be constant. It turns out that in galaxies from the period after cosmic reionization there are large fluctuations in this ionization level. The evidence seems to confirm the pre-ionization galaxies were less common and that the post-ionization galaxies have 100 times the mass of the dwarf galaxies.
The next generation of telescopes should be able to see the dwarf galaxies directly, which will help resolve the problem that many astronomical predictions in galaxy formation theory predict more nearby small galaxies.

Ultimate fate: Depending on the average density of matter and energy in the universe, it will either keep on expanding forever or it will be gravitationally slowed down and will eventually collapse back on itself in a "Big Crunch". Currently the evidence suggests not only that there is insufficient mass/energy to cause a recollapse, but that the expansion of the universe seems to be accelerating and will accelerate for eternity (see accelerating universe). Potential consequences of this revelation lends credence to the Big Rip, the Big Freeze, and Heat death of the universe theories. For a more detailed discussion of other theories, see the ultimate fate of the universe.

Composition:
The currently observable universe appears to have a geometrically flat space-time containing the equivalent mass-energy density of 9.9 × 10-30 grams per cubic centimetre. This mass-energy appears to consist of 73% dark energy, 23% cold dark matter and 4% atoms. Thus the density of atoms is on the order of a single hydrogen nucleus (or atom) for every four cubic meters of volume. The exact nature of dark energy and cold dark matter remain a mystery.

During the early phases of the big bang, equal amounts of matter and antimatter were formed. However, through a CP-violation, physical processes resulted in an asymmetry in the amount of matter as compared to anti-matter. This asymmetry explains the amount of residual matter found in the universe today, as nearly all the matter and anti-matter would otherwise have annihilated each other when they came into contact.

Prior to the formation of the first stars, the chemical composition of the Universe consisted primarily of hydrogen (75% of total mass), with a lesser amount of helium-4 (4He) (24% of total mass) and trace amounts of the isotopesdeuterium (2H), helium-3 (3He) and lithium (7Li).[15][16] Subsequently the interstellar medium within galaxies has been steadily enriched by heavier elements. These are introduced as a result of supernova explosions, stellar winds and the expulsion of the outer envelope of evolved stars.

The big bang left behind a background flux of photons and neutrinos. The temperature of the background radiation has steadily decreased as the universe expands, and now primarily consists of microwave energy equivalent to a temperature of 2.725 K.The neutrino background is not observable with present-day technology, but is theorized to have a density of about 150 neutrinos per cubic centimetre.

Physical structure:
Size:Very little is known about the size of the universe. It may be trillions of light years across, or even infinite in size. A 2003 paper claims to establish a lower bound of 24 gigaparsecs (78 billion light years) on the size of the universe, but there is no reason to believe that this bound is anywhere near tight. See shape of the Universe for more information.

The observable (or visible) universe, consisting of all locations that could have affected us since the Big Bang given the finite speed of light, is certainly finite. The comoving distance to the edge of the visible universe is about 46.5 billion light years in all directions from the earth; thus the visible universe may be thought of as a perfect sphere with the Earth at its center and a diameter of about 93 billion light years.Note that many sources have reported a wide variety of incorrect figures for the size of the visible universe, ranging from 13.7 to 180 billion light years. See Observable universe for a list of incorrect figures published in the popular press with explanations of each.

Shape: An important open question of cosmology is the shape of the universe. Mathematically, which 3-manifold best represents the spatial part of the universe?
Firstly, whether the universe is spatially flat, i.e. whether the rules of Euclidean geometry are valid on the largest scales, is unknown. Currently, most cosmologists believe that the observable universe is very nearly spatially flat, with local wrinkles where massive objects distort spacetime, just as the surface of a lake is nearly flat. This opinion was strengthened by the latest data from WMAP, looking at "acoustic oscillations" in the cosmic microwave background radiation temperature variations.
Secondly, whether the universe is multiply connected is unknown. The universe has no spatial boundary according to the standard Big Bang model, but nevertheless may be spatially finite (compact). This can be understood using a two-dimensional analogy: the surface of a sphere has no edge, but nonetheless has a finite area. It is a two-dimensional surface with constant curvature in a third dimension. The 3-sphere is a three-dimensional equivalent in which all three dimensions are constantly curved in a fourth.

If the universe were compact and without boundary, it would be possible after traveling a sufficient distance to arrive back where one began. Hence, the light from stars and galaxies could pass through the observable universe more than once. If the universe were multiply-connected and sufficiently small (and of an appropriate, perhaps complex, shape) then conceivably one might be able to see once or several times around it in some (or all) directions. Although this possibility has not been ruled out, the results of the latest cosmic microwave background research make this appear very unlikely.

Homogeneity and isotropy:While there is considerable fractalized structure at the local level (arranged in a hierarchy of clustering), on the highest orders of distance the universe is very homogeneous. On these scales the density of the universe is very uniform, and there is no preferred direction or significant asymmetry to the universe. This homogeneity is a requirement of the Friedmann-Lemaître-Robertson-Walker metric employed in modern cosmological models.

The question of anisotropy in the early universe was significantly answered by the Wilkinson Microwave Anisotropy Probe, which looked for fluctuations in the microwave background intensity.The measurements of this anisotropy have provided useful information and constraints about the evolution of the universe.

To the limit of the observing power of astronomical instruments, objects radiate and absorb energy according to the same physical laws as they do within our own galaxy.Based on this, it is believed that the same physical laws and constants are universally applicable throughout the observable universe. No confirmed evidence has yet been found to show that physical constants have varied since the big bang, and the possible variation is becoming well constrained.

Other terms:
Different words have been used throughout history to denote "all of space", including the equivalents and variants in various languages of "heavens", "cosmos", and "world". Macrocosm has also been used to this effect, although it is more specifically defined as a system that reflects in large scale one, some, or all of its component systems or parts. (Similarly, a microcosm is a system that reflects in small scale a much larger system of which it is a part.)

Although words like world and its equivalents in other languages now almost always refer to the planet Earth, they previously referred to everything that exists—see Copernicus, for example—and still sometimes do (as in "the whole wide world"). Some languages use the word for "world" as part of the word for Outer space, e.g. in the German word "Weltraum".

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"A man can be as great as he wants to be. If you believe in yourself and have the courage, the determination, the dedication, the competitive drive and if you are willing to sacrifice the little things in life and pay the price for the things that are worthwhile, it can be done."

Mercury


Mercury is the fastest planet in our solar system.
It zips around our Sun at a speed of about 172,000 kilometers per hour (107,000 miles per hour).



Average temperature of mercury at day time is 840 degrees F( 450 degrees C), contrary to this at nights mercury is very cold, average temperature at night time is about -275 degrees F( -170 degrees C).

In Mercury's poles there are places where sunlight never reaches, this means that it is very cold there at all times.

The planet is named for Mercury, the Roman messenger of the gods.

Mercury may be seen as an evening "star" near where the sun has set, or as a morning "star" near where the sun will rise.

Mercury was believed by the Greeks to be two different stars. Mercury's appearance in the morning was called Apollo, and its evening appearance was referred to as Hermes.

Mercury has no atmosphere and no known satellites.

Mercury is a heavily cratered planet, composed of rock with a central iron core that is three-quarters of the diameter of the planet (3,600 km). Following the Earth, Mercury is the second densest planet in the Solar System.

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Venus


Did you know that a day on Venus is equal to 343 Earth days and a year on Venus is equal to 224.7 Earth days. So a day on Venus is longer than a Venus year. This is because it rotates very slow!



The rotation on Venus is opposite to that of Earth with the sun rising from the west.

Venus is named after the Roman goddess of love and beauty.

The first evervisit on Venus by a space craft was made by Mariner 2 in 1962.

The interior of Venus is composed of a central iron core and a molten rocky mantle, similar to the composition of Earth.

The surface of Venus is very dry with flat plains, highland regions, and depressions.

The atmospheric pressure on the surface of Venus is that 90 times the pressure on Earth.

The clouds in Venus' atmosphere are composed of sulfuric acid which causes the planet to reflect 65% of the sunlight that reaches it. Thus, Venus the third brightest object in the sky (third only to the Sun and the Moon).

Similar in size, density, and mass, Venus and Earth often referred to as sister planets. However the surface and atmosphere of the two planets are drastically different.

Venus and Earth are closer than any two planets.

Venus is so hot that it can melt Lead.

Though Murcury is closest to the Sun but still it is not the hottest.
It is Venus that is hottest. The gases around Venus trap un's heat.

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MARS


Mars's moons Phobos and Deimos go around Mars the opposite way thet most other moons in the Solar System do.



Phobos orbits Mars three times a day (Mars day), it is so far the only moon to be discovered that goes around a planet faster than that planet turns.

You could launch yourself off Deimos by running, because the escape velocity is only 7 mph (11 km/hr).

Phobos is only 6000 km off the surface of Mars, the closest moon to its planet in the Solar System.

Mars has the biggest mountain in the Solar System (Olympus Mons).

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JupiterJupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus). It has been known since prehistoric times as a bright "wandering star". But in 1610 when Galileo first pointed a telescope at the sky he discovered Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) and recorded their motions back and forth around Jupiter. This was the first discovery of a center of motion not apparently centered on the Earth. It was a major point in favor of Copernicus's heliocentric theory of the motions of the planets (along with other new evidence from his telescope: the phases of Venus and the mountains on the Moon). Galileo's outspoken support of the Copernican theory got him in trouble with the Inquisition. Today anyone can repeat Galileo's observations (without fear of retribution :-) using binoculars or an inexpensive telescope.

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† ºº»«ºº """Be Just and fear not""".† ºº»«ºº

Saturn


You cannot stand on Saturn. It is quite a bit different Earth.
Saturn is made mostly of gases. It has a lot of helium. This Helium is the same kind of gas that you put in balloons.



Saturn is huge. Its the second largest planet of our Solar-System.
It is so big that Earth can fit across it nine times!

Its beautiful rings are not solid. They are made up of bits of ice, dust and rock.

Some of these bits are as small as grains of sand. Some are much larger than tall buildings. Some are up to a kilometer (more than half-a-mile) across.

The rings are huge but thin. The main rings could almost go from Earth to the moon. Yet, they are less than a kilometer thick.

Other planets have rings. Saturn's rings are the only ones that can be seen from Earth. All you need is a small telescope.

If you drop Saturn in water, it wont sink, it will float.

Saturn can float on water because it is mostly made of gas.

The planet is named after Saturn who was the Roman god of farming and agriculture.

It is very windy on Saturn. Winds around the equator can be 1,800 kilometers per hour. That's 1,118 miles per hour! On Earth, the fastest winds "only" get to about 400 kilometers per hour. That's only about 250 miles per hour.

Saturn goes around the Sun very slowly. A year on Saturn is more than 29 Earth years.

Saturn spins on its axis very fast. A day on Saturn is 10 hours and 14 minutes.

The Ringed Planet is so far away from the Sun that it receives much less sunlight than we do here on Earth. Yes, the Sun looks smaller from there.

The day Saturday was named after Saturn.

Saturn's rings reflect 70% of sunlight and are sometimes brighter than the planet.

Saturn gives away more energy than it recives

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Solar System


The Solar System is comprised of one star-the Sun, eight known planets, the newly classified "dwarf planets", thousands of asteroids, comets, and meteoroids. There are many web sites that will provide you with very detailed information concerning all of these subjects. Here we provide you with some basic statistics to get you started.

Under the new guidelines of International Astronomical Union pulished in August 2006, Pluto is no longer a planet, instead it falls into the category of being a Dwarf Planet because it lies within the Kuiper Belt of thousands of icy asteroid like objects.

Sun comprises of 99% mass of the total Solar System.

Jupiter is the largest planet of our Solar System.

One hundred and nine Earths would be required to fit across the Sun's disk, and its interior could hold over 1.3 million Earths.

Astronomers believe that the Solar System more than almost 4.5 billion years old.

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Jupiter

Jupiter is heavier than all the other planets put together.

Jupiter is the largest of the planets. More than one thousand Earths could fit inside Jupiter, if it were empty. All of the other planets could fit inside Jupiter at the same time.

The Great Red Spot on Jupiter is a storm. It is so big that almost three Earths could fit across it.

There are more than 60 moons around Jupiter.

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