THE UNIVERSE Akshatha V Gopal BSc Student GFGC, Tumkur ANOTOMY OF THE UNIVERSE The universe is the whole of space and all the stars,planets,and other forms of matter and energy in it.Nobody knows how big the universe is,but astronomer estimate that it contains at least 125 bilion stars. The most widely accepted theory about the origin of the universe is the Big bang theory,this theory was born of yhe observation that other galaxies are moving away from own at great speed ,in all direction .AS if they had all been propelled by an ancient explosive force. The Big bang theory ststes that the universe come into being in a huge explosion the Big bang that took place between 10 to 20 billion years ago . The universe initiallycponsists of a very hot , dense fire ball of expanding , cooling gas after about one million years ,that began to condense into localized clumps called proto galaxies contineued expanding forever . GALAXIES A galaxies is a huge mass of stars ,nebulae ,and interstellar meterial.The smallest galaxies contains about 100,000 stars ,while the largest containes upto 3,000 billion star . There are three main types of galaxies , classified according to their shape : elliptical ,spiral and irregular . Some times , the shape of a galaxy is distorted by a collision with another galaxy .Quasars are thought to be galastic nuclei but are so far away that their exact is still uncertain. They are compact, highly luminous objects in the outer reaches of the universe. THE MILKY WAY The milky way is the name given to the faint land of light that stretches across the night sky this light comes from stars and nebulae in our galaxy . The galaxy is beleived to be a barred spiral.with a dense central bar of stars encircled by four arms spiralling outwards and surrounded by a less dense halo. we cannot see the spiral shape because the solar system is in one of the spiral arms,"the orion arm "also called "local arm "The central part of the galaxy is relatively small and dense and comtains mainly older red and yellow stars . The halo is a less dense region in which the oldest stars are situated ;some of there stars are as old as the galaxy itself (possibility 13billion years ago ).The spiral arms contains main sequence stars and hot , young,blue stars ,as well as nebulae. The galaxy is vast ,about 100,000 light years across (a light years about 9,460 billion kilometers );The entire galaxy is rotating in space .although the inner travel faster than those further out the sun .which is about two thirds out from centre ,completes one lap of the galaxy about every 220million years. NEBULAE AND STAR CLUSTER A nebulae is a cloud of dust and gas inside a galaxy .nebulae becomes visible if the gas glows,or if the cloud reflects starlight from more distant objects . Emission nebulae shine because their gas emitts light. when it is stimulated by radiation from hot young stars . Reflection nebulae shine because their dust reflects light from stars in or around the nebulae . Dark nebulae appears as sillhouetters because they block out light from shining nebulae or stars behind them. Two types of nebulae are associated with dying stars ;planetary nebulae and supernova remnants . both consists of expanding shells of gas that were once.the outer layers of a stars . A planetary nebulae is a gas shell drifting away from a dying stellar core . A supernova remnant is a gas shell moving away from a stellar core at great speed following a violent explosion called a supernova . Stars are often found in groups known as clusters . open clusters are loose groups of a few thousand young stars that were born from the same cloud and are drifting apart . globular clusters are densely packed. soughly spherical groups of hundreds of thousands of older stars . STARS Stars are bodies of heat .glowing gas that are born in nebulae .they enourmously in size,mass and temperature . Diameters range from about 450times smaller to over 1,000 times bigger.than that of the sun ; masses range from about a twentieth to over 50 solar masses .and surface temperature ranges from about 5,000 c to over 50,000 c . the colour of stars is determined by its temperature . The hottest stars are blue and the coolest are red The energy emitted by a shining star is usually produced by nuclear fusion in the stars core .The brightness of a star is measured in magnitudes -the brighter the stars , the lower its,magnitude the light emitted by a star may be split to form a spectrum .containing a series of dark lines . the patterns of lines indicates the presence of particular chemical elements ,enabling astronomers to deduce the composition of the stars atmosphere. THE SOLAR SYSTEM The solar system consists of a central star (the sun )and the bodies that orbit it.there bodies include eight planets and their more than 160 known moons , dwarf planets keriper but objects auteroids ,comets ,and meteroids it also contains interplanetary gas and dust .The planets fall into two group ; four small rocky planets near the sun (mercury,venus,earth,mass)and four planets further out ,the gaints (jupiter,saturn,uranus and neptune ). Between the rocky planets and gaints is the asteroid belf,which contains and thousand of chunks of rock orbiting the sun.Beyond neptune is the -keeiper belt and ,more distant ,the oort cloud .most of the bodies in the planetary part of the solar system move around the sun in elliptrical orbits located in a thin dise around the suns equator .all the planets orbit the sun in the same direction and all but venus and aranus also spin about their axes in this direction .moons also spins as they ,in turn ,orbit their planets the entire solar system orbits the centre of our galaxy . THE SUN THE SUN IS THE STAR AT THE CENTRE of the solar system .It is about five billion years old and will continue to shine as it does now for about another five billion years .The sun is a yellow main sequence star about 1.4 million kilometers in diameter . it consists almost entirely of hydrogen and helium .in the sun'score,hydrogen is converted to helium by nuclear fusion,releasing energy in the process. Beyond the photosphere is the chromosphere (inner atmosphere) and the extremely rarified corona (outer atmosphere),which extends millions of kilometersinto space .Tiny particles that escape from the corona give rise to the solar wind, which streams through space at hundreds of kilometers per second .The chromosphere and corona can be seen from earth when the sun is totally eclipsed by the Moon. MERCURY Mercury is the smallest planet of our solar system and it is near of planet to the sun , orbiting at an average distance of about 50million kilometers .mercury is doesnt planet to the sun ,it moves faster than any other planet , travelling at an average speed of nearly 48kilometers per second and completing an orbit unche 88days. Although it is the closut to the sun it is not hottest planet .its thin atmosphere cannot trap heat .so,at night when thus is no sun the temperature can fall to as lowar - 180 degree C .You can see mercury near the eastern horizon before sunrise at certain times of the years .and at certain other times ,you can see it near the western horizon after sunset. VENUS The thick atmosphere of venus makes it the brightest and the hottest planet of the solar system ,its atmosphere has mainly carbondioxide gas ,which syluts a lot of sunlight .but it also traps so much heat that average temperature on venus is about 450degree C . Venus takes 243 days to complete one rotation making its day the longest in the solar system as a matter of fact , a day on venus is longest than its year ;it is easy to spot venus because it is so bright .when it is visible in the east before sunrise,it is called a morning star.and when it is visible in the west in the evening, it is called an evening star. EARTH The earth is not the fastest ,slowest ,hottest,coldest,largest or smallest planet but it is the only planet on which life is known to exist.about 70% of the earth's surface is covered by water,which is not found in liquid form on the surface of anyother planet. there are 4 main layer they are Thinner core,The outer core,The mantole,and the crust. Were it nearer the sun,the waters on it would have evaporated . were it further away,all our oceans , rivers and lakes would have frozen . the carbon dioxide in the earth's atmosphere plays two important rule .planets it to make food which feeds,directly or indirectly, all animals .it also traps furt enough heat to ensure that the nights on earth donot become freezing cold. MARS No other palnets evokes so much interact as mars does.this because scientists have found evidence that liquid water once flowed through the channels visible on its surface . so it is possible that some form of life once erxisted on this planet .the coloured soil of mass gives it is red colour so,it is called the red planet. When visible ,mars look like a red sphere during its two years orbit .it looks the brighter when the earth is between the sun and mars.during this time ,you can see it rises in the east as the sunsets in the west. JUPITER It is the largest and heaviest planet of our solar system it also has the largest number of moons . the strong winds blowing on it .and on the other gas gaints ,create light and dark areas ,giving them a striped look. If you look through a powerfultelescope,you will see a big spot on jupiter's surface.this spot is actually a huge storm,which has been raging on jupiter for more than 300years.In 1979,vogager 1 spare cryst discovered paint rings around jupiter .there rings are not visible even through the most powerful earth based telescope .jupiter is also visible to the naked eye .it looks like abright spot in the sky. SATURN We can easily seeognies a picture of saturn because of the planets prominent rings . there rings are actually particles if dust and the revolving around the saturn .saturn is taught to consists of a small core of rock and the surrounde by an inner mantle of metallic hydrogen. Saturn has an extremely thin but wide system of rings that is lue than one kilometers thick but extends outwards to about 420,000kilogram from the planets surface the main ring comprises the thousands of narrow ringlets .Macleay icy rock lumps that range in size from qtiny particles to chunks several meters aeroes. Saturn has more than 60 moons URANUS It is the seventh planets from the sun and the third largest. with a diameter of about 51,000 kilometers . it is thought to consist of a dense mixture of different types cyke and gas around a solid core .Uranus is the most feature less planet to have been closely observed . Miranda has the most varied surface ,with cratered areas broken up by huge ridges and cliffs 20kilometers high. Beyond these are more distant moons with diameters less than 150km. NEPTUNE Neptune is the furthest planet from the sun , at an average distance of about 4,500 million kilometers. Neptune is the smallest of the giant planets and is thought to consist of a small rocky core surrounded by a mixture of liquids and gases. The great and small dark spots were huge storms that were swept around the planet by winds of about 2,00kilometers per hour the larger dwarf planets which include Pluto, are almost round bodies .Pluto was the first object discovered beyond Neptune and was considered a planet until the dwarf planet category was introduced in 2006 .it is made of rock and ice and is 2,274kilometers across . it has there known moons. The largest , charon,is about half piuto's size and the two probably had a common origin. THE MOON THE MOON IS THE EARTH'S only natural satellite. It is relatively large for a moon, with a diameter of about 3,470kilometers-just over a quarter that of the earth. The moon takes the same time to rotate on its axis as it takes to orbit the earth (27.3days),and so the same side (near side) always faces us. However, the amount of the surface we can see-the phase of the Moon -depends on how much of the near side is in sunlight. The Moon is dry and barren, with negligible atmosphere and water .It consists mainly of solid rock, although its core may contain molten rock or iron. The surface is dusty, with highlands covered in creators caused by meteorite impacts , and lowlands in which large creaters have been filled by solidified lava to form dark areas called Maria or "seas".Mariaoccur mainly on the near side , which has a thinner crust than the far side .many of the creators are rimmed by mountain ranges that form the creator walls and can be thousands of meters high. ASTEROIDS , COMETS , AND METEOROIDS ASTEROIDS,COMETS AND METEROIDS are all debris remaining from the nebula from which the solar system formed 4.6billion years ago .Asteroids are rocky bodies up to about 1,000kilometers in diameter, although must are much smaller .most of them orbit the sun in the asteroid belt, which lies between the orbits of Mars and Jupiter. cometary nuclei exist in a huge cloud(called the oort cloud)that surrounds the planetary part of the solar system . As the comet approaches the sun ,the cometary nucleus starts to vapourize in the heat ,producing both a brightly shining coma (a huge sphere of gas and dust around the nucleus ),and a gas tail, and a dust tail. Most meteoroids burn up in the atmosphere. The remnants of the few that are large enough to reach the earth's surface are termed meteorites. If a meteoroids enters the earth's atmosphere, it is heated by friction and appears as a glowing streak of light called a meteor (also known as a shooting star).