The Universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies, and the contents of intergalactic space, although this usage may differ with the context (see definitions, below). The term universe may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world, or nature.

• Our nearest star- millions kilometer out in the space there is a ball of hot, glowing gas. We call this the sun. the sun is actually a star•Its official name is sol•It was after the Ancient Roman Sun God•It is enormous! At least 1,300,000 planets the size of earth could be packed into it.•It is about 150 million kilometer from the earth.•Light travels at the amazing speed of 300,000 kilometers per second. But it still takes light from the sun about eight minutes and 20 seconds to reach us •The sun glows so fiercely that we can’t look straight at it, even though it is so far away.•But is the sun actually burning is it a ball of fire?

Ans – No, it’s a ball of gas squeezed together so tightly that its centre becomes extremely hot

•Mercury is the smallest planet of our solar system and is one nearest to the sun.•It is also known as the speedy messenger.•That is why we cannot see it easily.•However, it can be seen at sunrise or sunset on the horizon. •Diameter -3029 miles (4878 km). •year that means one orbit around the sun in Earth time is 88 days.•The day that means one rotation on its axis in Earth time is 59 days. •The main gases in atmosphere- Traces of Argon, Neon, Helium.•Moon - 0 •Weight -41.0lb ( 18.5 kg) •The Claim to Fame- daytime temperature - 880oF or 470oC and night time temperature– 300oF or -183oC.

•The planet nearest to the Earth is Venus.•It is also called the morning and the evening star.•It looks very bright early in the morning and in the evening.•Venus, too, has phases like the phases of our moon.•The diameter of this planet is 7515 miles (12102 km).•The year that is one round around the sun in Earth time is 224 days.•The day that means one rotation on it’s axis in Earth time is 243 days.•The main gas in it’s atmosphere is Carbon Dioxide (very thick).•Venus, too, like mercury does not have any moon. •The weight of this planet according to kilograms is 44.0 kg.•The Claim to Fame of this planet is that the planet rotates east to west instead of west to east, as other planets do.

•The factors necessary for life such as the right temperature, water, air, atmosphere, protection of ozone layer, etc. are found only on Earth. •Of all the planets of our solar system, only earth has a living world.•The axis around which earth rotates is not perpendicular to it’s orbit but slightly inclined. Because of this, Earth has seasons like summer and winter.•The diameter of this planet is 7921 miles or 12756 km.•It takes 365 days for earth to complete one revolution i.e. one orbit around the sun.•It takes 1 day i.e. is 23 hours i.e. is 56 minutes for earth to complete one rotation on its axis. •The main gas found in this planet is nitrogen and oxygen.•Earth has one natural satellite that is the moon.•The weight of this planet is 50.0 kg.•Only body known to have life ; mild climate , water and solid , liquid , gas.

•Mercury and Venus are called the inferior planets as their orbits are inside Earth’s orbit.•Those outside Earth’s orbit are called the superior planets.•Mars is the first superior planet.•The soil on Mars is rich in iron, which makes the planet appear red. That is why it is also called the Red Planet.•The diameter of this planet is 4218 miles or 6792 km.•It takes 687 days for it to complete one revolution i.e. is one orbit around the sun in Earth’s time.•It takes 24 hours i.e. is 37 for it to complete one rotation around itself.•The main gas in it’s atmosphere ids Carbon Dioxide (thin).•It has two moons.•The weight of this planet is 19.0 kg.•The claim to fame of this planet is that is Ice- Capped poles, Four Seasons, Global dust storms.

• The largest planet in the solar system is Jupiter.

• it is big enough to hold 1397 Earths within itself but its mass is only 318 times that of Earth.

• In spite of its size, Jupiter rotates very fast, completing one turn around itself in just 10 hours.

• The diameter -88793miles or 142984 km.

• The time taken by it to complete one revolution in earth’s time is 11 years.

• It takes 10 hours i.e. is 56 minutes for Jupiter to complete one rotation on it’s axis.

• The main gas in it’s atmosphere are Hydrogen and Helium.

• Jupiter has 63 satellites but we can see only four of them by means of a telescope.

• The weight of this planet is 125.5 kg.• The claim of fame of this planet 9is that

it has colorful bands of gas, marked by lightning, with auroras near poles; Great Red Spot is storm bigger than earth.

•After Jupiter, the next planet is Saturn.•Saturn has some unique characteristics.•It has rings around it, although they cannot be seen by the unaided eyes.•Another of Saturn’s special features is its density which is less than that of water. If there were a large enough ocean of water this huge planet would float in it!• Diameter – 74,853 miles ( 120,536 km).•Year (one orbit around sun) In Earth Time – 29 years•Day (one Rotation on axis) In Earth Time – 10 hours ,39 minutes.•Main Gas In Atmosphere – Hydrogen, Helium.•Number of moons – more than 60.•Weight of 110-LB.(50 KG) kid – 118.0lb (53.5kg).•Claim To Fame – Circled with colorful ice rings ranging in width from fingernails to houses.

The Planet Uranus is the third largest planet in the solar system, is a Gas Giant and is the seventh planet from the sun. Planet Uranus has rings like Planet Jupiter, Saturn and Neptune.It was discovered by William Herschel on March 13, 1781 and was the first planet discovered in modern times. It is also the first planet discovered with a telescope as opposed to the naked eye. The Planet Uranus has been visited by the Voyager 2 spacecraft Facts about Planet Uranus* Diameter: 51,500 km (32,000 miles)* Temperature: -197.15 C (-322.87° F)* Orbit: Takes 84 years to complete an orbit.* Average Distance: 2,870,972,200 km (1,783,939,400 miles - 19.2 AU) from Sun

* Mass: 8.6849 x 1025 kg * Moons: 27* Period of Rotation: 17.24 hours (retrograde: spins backwards compared to most other planets)

•The Planet Neptune is the eighth planet from the sun. It is also known as the Blue Giant. Neptune is the fourth and outermost of the gas giant planets and also has rings. Its atmosphere is mostly hydrogen and helium. In Roman mythology Neptune was the god of the Sea. •Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. It was the last stop in 1989 for the Voyager 2 spacecraft on its grand tour of the solar system. •Recent knowledge has been gained by ground-based telescopes and the Hubble Space Telepscope. •Due to Pluto's eccentric orbit, Neptune at times becomes the most distant planet from the Sun for a few years. •Planet Neptune Facts:•Mass: 17.15 Earth-masses•Number of known satellites: 8•Length of Year: 164.8 Earth-years•Mean Distance from the Sun: 4,500 million kilometers

Mean Orbital Velocity: 5.4 kilometers per second

Length of Day: 16.11 hours, 0.67 Earth-day

Equatorial diameter: 49,500 kilometers •Atmospheric components: 74% hydrogen, 25% helium, 1% methan.

The Moon is a large ball of rock that doesn’t change shape – it just looks as though it does. The shape we see in the sky today depends on how much of the Moon’s face is lit up. Sometimes we observe a thin crescent, and at other times we see half or three quarters of the Moon, and then a fully lit face- a Full Moon. Moon is Earth's only natural satellite and the only astronomical body other than Earth ever visited by human beings. The moon is the brightest object in the night sky but gives off no light of its own. Instead, it reflects light from the sun. Like Earth and the rest of the solar system, the moon is about 4.6 billion years old. The moon is much smaller than Earth. The moon's average radius (distance from its center to its surface) is 1,079.6 miles (1,737.4 kilometers), about 27 percent of the radius of Earth

Stars•A star is a huge, shining ball in

space that produces a tremendous amount of light and other forms of energy. The sun is a star, and it supplies Earth with light and heat energy. The stars look like twinkling points of light -- except for the sun. The sun looks like a ball because it is much closer to Earth than any other star.

It contains irregularly shaped chunks of debris called asteroids. Scientists believe the asteroids

are the pieces of a planet that never formed. One possible theory is the ongoing gravitational tug-of-war between Jupiter and Mars has prevented the pieces from bonding together, hence, this

planet was never created.The Space Asteroids are made of rock and metal,

mostly nickel and iron. 

The first flybys of asteroids were performed in 1991 and 1993 by NASA's Galileo spacecraft and in 1996 by the Near Earth Asteroid Rendezvous

(NEAR) spacecraft. In the 1980's, the Soviet Union was planning to send a probe to Vesta. No information available

on its status. The Asteroid Belt is a region between the inner planets and outer planets where thousands of asteroids are found orbiting around the Sun.

• A comet (KOM iht) is an icy body that releases gas or dust. Most of the comets that can be seen from Earth travel around the sun in long, oval orbits. A comet consists of a solid nucleus (core) surrounded by a cloudy atmosphere called the coma and one or two tails. Most comets are too small or too faint to be seen without a telescope. Some comets, however, become visible to the unaided eye for several weeks as they pass close to the sun. We can see comets because the gas and dust in their comas and tails reflect sunlight. Also, the gases release energy absorbed from the sun, causing them to glow.

• Astronomers classify comets according to how long they take to orbit the sun. Short-period comets need less than 200 years to complete one orbit, while long-period comets take 200 years or longer.

• An eclipse is the darkening of a planet, moon, or star. This darkening is caused in one of two ways. It can be caused when the shadow of one planet or moon falls on another planet or moon. Or, it can be caused when one planet or moon moves in front of another to block its light. The light of the sun causes both Earth and the moon to throw shadows into space. This causes two kinds of eclipses, a lunar eclipse and a solar eclipse.

• A lunar eclipse takes place when the moon gets dark as it passes through Earth's shadow. The moon does not become completely dark during most lunar eclipses. In many cases, it becomes reddish.

• A solar eclipse takes place when the moon blocks the light of the sun. This makes the shadow of the moon pass across Earth. The moon may darken all or part of the sun.

A meteor is a bright streak of light that appears briefly in the sky. Observers often call meteors shooting stars or falling stars because they look like stars falling from the sky. People sometimes call the brightest meteors fireballs. A meteor appears when a particle or chunk of metallic or stony matter called a meteoroid enters the earth's atmosphere from outer space. Air friction heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles. The gases include vaporized meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere. Most meteors glow for about a second.

A meteorite is a natural object originating in outer space that survives impact with the Earth's

surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids

, but they are also sometimes produced by impacts of asteroids. When it enters the atmosphere,

impact pressure causes the body to heat up and emit light, thus forming a fireball, also known as a meteor or

shooting/falling star. The term bolide refers to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of

whether it ultimately impacts the surface.

MeteoriodA meteoroid is a piece of stone-like or metal-like

debris which travels in outer space. Most meteoroids are no bigger than a pebble. Large meteoroids are believed to come from the asteroid belt. Some of the smaller meteoroids may have come from the Moon or Mars. If a meteoroid falls into the Earth's atmosphere, it will begin to heat up and start to glow. This is called a meteor. If you have ever seen a "falling star", you were actually seeing a meteor. Most of the original object burns up before it strikes the surface of the Earth. Any leftover part that does strike the Earth is called a meteorite. A meteorite can make a hole, or crater, in the ground when it hits it. The larger the meteorite, the bigger the hole.

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Constellations

A constellation is a group of stars visible within a particular region of the night sky. The word constellation also refers to the region in which a specific group of stars appears. Astronomers have divided the sky into 88 areas, or constellations.

Artificial satellite

An artificial satellite is a manufactured object that continuously orbits Earth or some other body

in space. Most artificial satellites orbit Earth. People use them to study the universe, help

forecast the weather, transfer telephone calls over the oceans, assist in the navigation of ships and aircraft, monitor crops and other resources,

and support military activities. Artificial satellites also have orbited the moon,

the sun, asteroids, and the planets Venus, Mars, and Jupiter. Such satellites mainly gather information about the bodies they orbit.

Dwarf PlanetWhen the final vote on the definition of "planet" was made, and the eight dominant bodies in the solar system were declared (quite rationally) a class separate from the others, a new class of objects was defined. The "dwarf planets" are all of those objects which are not one of the eight dominant bodies (Mercury through Neptune) yet still, at least in one way, resemble a planet. The best definition heard so far is that a dwarf planet is something that looks like a planet, but is not a planet. The dwarf planets are bodies in the solar system which are large enough to become round due to their own gravitational attraction. Why do astronomers care about round? If you place a boulder in space it will just stay whatever irregular shape it is. If you add more boulders to it you can still have an irregular pile. But if you add enough boulders to the pile they will eventually pull themselves into a round shape. This transition from irregularly shaped to round objects is important in the solar system, and, in some ways, marks the transition from an object without and with interesting geological and planetary processes occuring (there are many many other transitions that are equally important, however, a fact that tends to be ignored in these discussions).

• A galaxy is a cluster of stars, dust, and gas which is held together by gravity. Galaxies are scattered throughout the universe and they vary greatly in size. A galaxy may be alone or it may be in a large group of galaxies called a "supercluster". Galaxies are classified by scientists according to their shape and appearance. An irregular galaxy has an undefined shape and is full of young stars, dust, and gas. A spiral galaxy is shaped like a disk. The disk tends to resemble a pinwheel with arms which spiral outward as it rotates. Spiral galaxies tend to contain more middle-aged stars along with clouds of gas and dust. The next galaxy classification is an elliptical galaxy. The elliptical galaxies contain older stars and very little gas and dust. Elliptical galaxies vary in their shape from round to flattened, elongated sphere