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Universe in Geography


The word universe is derived from Old French 4univers \ which again is derived from Latin universum, 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’. The universe is everything that we can perceive and more. It is all the mass that exists, from the largest galaxies to the tiny subatomic particles, and since mass is exchangeable with energy, it is also all the forces and energies that exist.

Geography Origin of Universe

  • There are only two legitimate options for the origin of the universe : ( 1 ) Someone made the universe ( Intelligent Design ) or ( 2 ) The universe made itself ( Random Chance ).
  • In general, theists attribute the origin of the universe, to some sort of transcendent, intelligent Designer. Atheists envision a natural, undirected process by which Universes spring into existence spontaneously.
  • Einstein’s theory of gravity and Hubble’s astronomical observations preclude an eternal universe. We now know beyond a reasonable doubt that the universe began at some point in the finite past.

Geography Big Bang Theory

  • The Big Bang Theory has been the dominant scientific theory about the origin of the universe for long. According to the big ban & the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter in all directions,
  • In 1927, the Belgian priest Georges Lemaitre was the first to propose that the universe began with the explosion of a primeval atom.
  • His proposal came after observing the red shift in distant nebulas or nebulae by astronomers In a model of the universe based on relativity.
  • Years later, Edwin Hubble found experimental evidence to help justify Lemaitre’s theory. He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.
  • The big bang was initially suggested because it ex-plains why distant galaxies are traveling away from us at great speeds.
  • The theory also predicts the existence of cosmic back-ground radiation the glow left over from the explosion itself.
  • The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964 by Amo Penzias and Robert Wilson, who later won the Nobel Prize for this discovery.

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Geography Inflation Universe Theories

  • The original big bang theory is no longer the dominant scientific explanation for the atheistic origin of the universe.
  • Starting with Alan Guth in the late 1990’s ( The Infla – tionary Universe : The Quest for a New Theory of Cosmic Origins ), the scientific community has now proposed roughly 50 different IUT variants.
  • The Inflation Theory, developed by Alan Guth, Andrei Linde, Paul Steinhardt, and Andy Albrecht, proposes a period of extremely rapid ( exponential ) expansion of the universe leading to the Big Bang expansion, during which time the energy density of the universe was dominated by a cosmological constant term that later decayed to produce the matter and radiation that fill the universe today.
  • The Inflation Theory links important ideas in modern physics, such as symmetry breaking and phase transitions, to cosmology.

Geography String Theory

  • In the last few decades, string theory has emerged as the most promising candidate for a microscopic theory of gravity. It attempts to provide a complete, unified, and consistent description of the fundamental structure of our universe.
  • String theory suggests that the big bang was not the origin of the universe but simply the outcome of a pre – existing state.
  • Our current knowledge about the subatomic composition of the universe is summarized in what is known as the Standard Model of particle physics.
  • It describes both the fundamental building blocks out of which the world is made, and the forces through which these blocks interact.
  • There are twelve basic building blocks. Six of these are quarks – having the interesting names of up, down, charm, strange, bottom and top. ( A proton, for instance, is made of two up quarks and one down quark. ) The other six are leptons – these include the electron and its two heavier siblings, the muon and the tauon, as well as three neutrinos.
  • The essential idea behind string theory is this all of the different fundamental’ particles of the Standard Model are really just different manifestations of one basic object – a string. Ordinarily, an electron is picturised as a point with no internal structure.
  • A point cannot do anything but move. But, if string theory is correct, then under an extremely powerful ‘microscope’ we would realize that the electron is not really a point, but a tiny loop of string.
  • A string can do something extra than moving – it can oscillate in different ways ( like a guitar string ). If it oscillates in a certain way, then from a distance; unable to tell that it is really a string, we see an electron. But if it oscillates in some other way, we call it a photon, or a quark, or something else. So if string theory is correct, the entire world is made of strings.

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Geography of Universe New Theory

  • A New Zealand theorist, Peter Lynds, presented his second paper on the theory of origin of universe on 1 November 2007, and has suggested that time is ‘cyclic’.
  • Thus, the universe’s clock has neither a start nor finish, yet time is finite. The cyclic view of time was also held by ancient thinkers such as Plato, Aristotle and Leonardo da Vinci.
  • However, the Christianity and the Church established the view of time being linear and going in a straight line.
  • Lynds’ theory involves the second law of thermo-dynamics. All of the laws of physics – with the exception of the second law of thermodynamics – are time reversible and work equally well in opposing directions.
  • This is in contrast to previous theories involving thermodynamic time reversed, including those by Thomas Gold in the 1960s and Stephen Hawking in the 1980s, which all involve the second law of thermodynamics being breached.
  • Such theories have generally been dismissed by physicists because of contradictions directly resulting from such a second law violation.
  • Lynds asserts that if many billions of years from now the universe stops expanding and contracts to a big crunch, such a revised conception of thermodynamic time reversal leads to a coherent picture of the cosmos in which there is no differentiation between past and future, and the so called beginning of the universe, the big bang, can equally be said to be in the past or future of the big crunch.
  • This means that the big bang’ and the big crunch can also equally be said to cause one another, therefore providing an answer to that most intractable of questions : what caused the big bang?’ His theory asserts that the universe is finite, but yet also has no beginning or first cause ( because the big bang is caused by the big crunch, and the big crunch is caused by the big bang, in a cyclical occurence ).
  • Cosmogony, or cosmogeny, is any theory concerning the coming into existence or origin of the universe. Cosmogony can be distinguished from cosmology, which studies the universe at large and throughout its existence, and which technically does not inquire directly into the source of its origins.
  • The difference between space and outer space is that space means the whole universe including the earth while outer space means all space other than earth. In fact, outer space begins where the earth’s atmosphere ends and extends on and on in all directions.


Geography of Galaxies

  • A – galaxy is a huge collection of gas, dust and billions of stars held together by their mutual gravity. Almost all the galaxies display red shift in their spectra indicating they are moving from us.
  • There are an estimated 50 thousand million galaxies in the universe, and a typical galaxy contains 50 thousand million to 100 thousand million stars.
  • Our sun and the surrounding planets orbit around the center of the Milky Way galaxy once every 250 million years.
  • The Local Group of Galaxies : This is our group of galaxies. It was first recognized by Hubble, at the time of the first distance determinations and red – shift measurements.

The Milky Way Geography

  • The Milky Way is our galaxy, Le., it is the home of our Solar System together with at least 200 billion other stars ( more recent estimates have given numbers around 400 billion ) and their planets, and thousands of clusters and nebulae, including at least almost all objects of Messier’s catalog which are not galaxies on their own.
  • Light year : The Light year is a measure of distance not time. It is the distance that light travels in a vaccuum in one year at the speed of 300,000 km / s or 186,000 miles per second. In one year, at that speed, light travels approximately 6 million miles or around 9.5 trillion kilometres. Light travels one Astronomical Unit ( AU ) in only 8 minutes.
  • Astronomical unit : We classify distances in space according to the mean distance between the sun and the earth, which is one AU. One AU is equal to 93 million miles or 150 million kilometers. So that means the sun is 93 million miles away from Earth. Light travels this distance in 8.3 min approx. 9.
  • Messier’s catalog : During the years from 1758 to 1782 Charles Messier, a French astronomer ( 1730 -1817 ), compiled a list of approximately 100 diffuse objects that were difficult to distinguish from comet through the telescopes of the day. Discovering comets was the way to make a name in astronomy in the 18th century. Messier’s first aim was to catalog the objects that were often mistaken for comets.

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Geography of Universe Andromeda Galaxy

  • Andromeda is the nearest major galaxy to our own Milky Way Galaxy. It j is a large spiral galaxy, very similar in appearance to, and slightly larger than, our own Galaxy, and our closest normal galaxy companion ( the very dose Magellanic clouds are classified as irregular galaxies ).
  • The farthest one can see with the naked eye is 2.4 million light years away or ( 140,000,000, 000,000,000, 000 miles. ) That’s the distance to the giant Androm – edii Galaxy.
  • The light arriving at earth from the Andromeda Galaxy is shifted toward the blue end of the spectrum, whereas the light from all other cosmic sources exhibits red shift.
  • Magellanic Clouds : The two Magellanic Clouds ( Large Magellanic Cloud and Small Magellenic Cloud ) are irregular dwarf galaxies, which are members of our Local Group of galaxies.

Geography Types of Galaxies

  • Three main classes of galaxy were originally described by Edwin Hubble in his 1936 work, The Realm of the Nebulae – ellipticals, lenticulars and spirals – based on their visual appearance ( originally on photographic plates ). A fourth class contains galaxies with an irregular appearance.
  • Spiral Galaxy : Spiral galaxies consist of a flat, rotating disk of stars, gas and dust, and a central concentration of stars known as the nuclear bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular dusters.
  • Elliptical Galaxy : Elliptical galaxies have smooth, featureless and light profiles and range in shape from nearly spherical to highly flattened, and in size from hundreds of millions to over one trillion stars.
  • Lenticular galaxy : It is a type of galaxy which is intermediate between an elliptical galaxy and a spiral galaxy in galaxy morphological classification schemes. Lenticular galaxies are disc galaxies ( like spiral galaxies ) which have used up or lost their interstellar matter ( like elliptical galaxies ). Because of their ill – defined spiral arms, if they are inclined face – on, it is often difficult to distinguish between them and elliptical galaxies.
  • Irregular galaxy : A galaxy that does not fall into any of the regular classes of the Hubble sequence. These are galaxies that feature neither spiral nor elliptical morphology. They are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.
  • The Hubble sequence : It is a morphological classification scheme for galaxies invented by Edwin Hubble in 1936. To this day, the Hubble sequence is the most commonly used system for classifying galaxies, both in professional astronomical research and in amateur astronomy.

{tab= Stars}

Geography of Universe Stars

  • Stars account for 98% of the matter in a galaxy. The rest of 2% consists of interstellar or galactic gas and dust in a very attenuated form.
  • Stars come in different colors. Hot stars give off blue light, and the cooler stars give off red light.
  • The nearest star to us is the Sun. The nearest star to our Sun is Alpha Centauri, which is over 4 light years or 25 trillion miles away..
  • Betelgeuse ( pronounced “beetle jooze”, is a red giant star located at the left shoulder of the constellation Orion and is the largest known star in our galaxy ).
  • A star is a celestial body of hot gases or a massive, luminous ball of plasma that radiates energy derived from thermonuclear reactions in the interior. They group together to form a galaxy.

Birth of a Star Geography

  • Nebulae : It is the plural of nebula, which means an interstellar cloud of dust, hydrogen gas and plasma. It is the first stage of a star’s cycle. These young stars undergo further collapse, forming main se – Ili quence stars.
  • Orion Nebula : The Orion Nebula ( also known as Messier 42, M42, or NGC 1976 ) is a diffuse nebula situated south of Orion’s Belt. It is one of the brightest nebulae, and is visible to the naked eye in the night sky.
  • Protostar : Stars are born in nebulae. Later, huge clouds of dust and gas collapse under gravitational forces, forming protostars. For a solar – mass star, the protostar stage lasts about 100,000 years. It starts with a core of increased density in a molecular cloud and ends with the formation of a Tauri star, which then develops into a main sequence star. This is her aided by the T Tauri wind, a type of ‘Super solar wind that marks the change from the star accreting mass into radiating energy.
  • Red giant : Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. This is a red giant or a red super giant ( depending on the initial mass of the star ). It will eventually collapse and explode. Its fate is determined by the original mass of the star.
  • It will become either a black dwarf, a neutron star, or a black hole. A red giant is a luminous giant star of low or intermediate mass that is in a later phase of its evolution, with nuclear fusion going on in a shell outside the core but not in the core itself.

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Lifecycle of a Star Geography

  • There are three possibilities, based on the initialass of the star.
  • 1. Stellar nursery ( stars form in a nebula, from collapsing clouds of interstellar gas and dust ). 2. Sunlike stars ( up to 1.5 times the mass of the Sun ). 3. Red giant. 4. Planetary nebula: 5. White dwarf. 6. Black dwarf.
  • 1. Stellar nursery ( stars form in a nebula, from collapsing clouds of interstellar gas and dust ). 2. Huge stars ( from 1.5 to 3 times the mass of the Sun ). 3. Red supergiant. 4. Supernova. 5. Neutron star.
  • 1. Stellar nursery ( stars form in a nebula, from collapsing clouds of interstellar gas and dust ). 2. Giant stars ( over 3 times the mass of the Sun ). 3. Red supergiant. 4. Supernova. 5. Black hole.

Death of a Star Geography

  • Planetary Nebula : A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. The name originates from a similarity in appearance to giant planets when viewed through a small optical telescope, and is unrelated to planets of the solar system.
  • Supernova : It is a stellar explosion. After the core of an aging massive star ceases to generate energy frol} 1 nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star’s outer layers.
  • Alternatively, a white dwarf star may accumulate sufficient material from a stellar companion to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it.
  • Stellar cores whose furnaces have permanently gone out, collapse when their masses exceed the Chandrasekhar limit ( roughly 1.38 times the mass of the Sun ). The material that is exploded away from the star is now known as a supernova remnant.
  • White Dwarf : It is a tiny, dense, hot star, representing, a late stage in the life of a star like the sun. The core of a very hot young white dwarf cools down over the course of the next billion years or so. Many nearby, young white dwarfs have been detected as sources of soft ( Le. lower – energy ) X – rays.
  • Black Dwarf : It is a tiny blackened corpse of a star like the sun. Ultimately it disappears into the blackness of space.
  • Neutron star : A neutron star is formed from the collapsed remnant of a massive star after supernova. Models predict that it consists mostly of neutrons. A neutron star is one of the few possible conclusions of stellar evolution.
  • Chandrasekhar limit : The Chandrasekhar limit named after Subrahmanyan Chandrasekhar  is the maximum non – rotating mass which can be supported against gravitational collapse, by electron, degeneracy pressure.

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Geography of Pulsars

  • Pulsars are highly magnetized rotating neutron stars which emit a beam of detectable electromagnetic radiation in the form of radio waves. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the light – house effect and gives rise to the pulsed nature that gives pulsars their name.
  • Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. For some pulsars, the regularity of pulsation is as accurate as an atomic clock. Pulsars are known to have planets orbiting them.
  • Variable star: are stars that show varing degree of luminosity. Delta cephei was the first of this type of stars noticed in 1784 by the deaf and dumb English astronomer John Goodriche.

Geography of Quasar

  • A Quasar is an enormously bright object at the edge of our universe with the appearance of a star when viewed through a telescope. It emits massive amounts of energy, more energy than 100 normal galaxies combined.
  • The name comes from a shortening of quasi stellar sources of radio radiations. Current theories hold that quasars are one type of active galactic nuclei ( AGN ).
  • Many astronomers believe supermassive black holes may lie at the center of these galaxies and power their explosive energy output. In one second, a typical quasar releases enough energy to satisfy the electrical energy needs of Earth for the next billion years.

Geography of Constellation

  • A constellation is anyone of the 88 areas into which the sky – or the celestial sphere is divided. The term is also traditionally and less formally used to denote a group of stars visibly related to each other in a particular configuration or pattern.
  • Some well – known – constellations contain striking and familiar patterns of bright stars. Examples are Orion ( containing a figure of a hunter ), Leo ( containing bright stars outlining the form of a lion ), Scorpius ( a scorpion ), and Crux ( a cross ).

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Geography of Black Hole

  • John Wheeler, a US Physicist, first used the term ‘black hole’ for a completely collapsed star at a meeting at the Institute for Space, New York, in 1967.
  • The nearest known black hole is 1,600 light years ( 10 quadrillion miles / 16 quadrillion kilometers ) away.
  • Black holes may not be totally black. Infalling material can get hot enough to glow.
  • Sometimes black holes are so bright they can out-shine an entire galaxy.
  • A black hole is a region of space in which the gravitational field is so powerful that nothing can escape after having fallen past the event horizon.
  • The name comes from the fact that even electro – magnetic radiation ( e.g. light ) is unable to escape, rendering the interior invisible.
  • However, black holes can be detected if they interact with matter outside the event horizon, for example by drawing in gas from an orbiting star.
  • While the idea of an object with gravity strong enough to prevent light from escaping was proposed in the 18th century, black holes, as presently understood, are described by Einstein’s theory of general relativity, developed in 1916.
  • This theory predicts that when a large enough amount of mass is present within a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, forcing all matter and radiation to fall inward.
  • Event horizon : In general relativity, event horizon is a general term for a boundary in spacetime, an area surrounding the black hole, beyond which events cannot affect an outside observer. Light emitted from inside the horizon can never reach the observer and anything that passes through the horizon from the observer’s side is never seen again.
  • Escape velocity is the velocity needed for an object to become essentially free of the gravitational effect of another object. Thus, event horizon can also be defined as the distance from the center of a black hole where the escape velocity is equal to the speed of light.

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Geography of Wormhole

  • A theoretical shortcut through space caused when a black hole punches through the fabric of spacetime. While possible mathematically, in reality they probably do not exist.

Geography of Sun

  • The sun is 92% hydrogen, 7.8% helium.
  • Our sun is only 4.5 billion years old and is only half way through its life cycle of 10 billion years. That means, in. about 5 billion years, the sun would grow to such an enormous extent that it would even en – gulf Earth.
  • The sun’s core temperature is over 15 million degrees Celsius.
  • The sun has a diameter of 863,700 miles ( 1,390,000km ). Also, it is over 2.5 million miles around at its equator.
  • The sun also rotates, but different parts of the sun rotate at different rates. The equator of the sun completes one rotation in 25 days while the poles take 36 days for a full rotation.
  • The Sun does not explode or collapse in on itself, because the gravitational pressure form its mass is proportional to the outward pressure of the expanding gases.
  • Every eleven years the magnetic poles of the sun switch. This cycle is called Solarmax.
  • The sun is so large it takes several thousand years for the energy released from the fusion process in the core, to teach the surface as light or radiation. It takes only 8 minutes for sunlight to travel from the sun to the earth, which also means that, when the sun sets, it actually set 8 minutes ago. In Spit Bergen, Norway at one time of the year the sun shines continuously for three and a half months. More than 1 million earths would fit inside the sun. The sun is 330,330 times larger than the earth.
  • The force of Gravity is so much greater on the sun that a man Weighing 150 pounds on earth would weight 2 tons on the sun. The Sun is also the source of energy ( as in light and heat ) for Earth. The Sun provides our planet with 126,000,000,000,000 horsepower of energy every day.
  • The sun generates energy through fusion of its hydrogen atoms. We know that the sun is made of hydrogen because every element has a distinct spectrum and on earth we know the spectrum of Hydrogen. Through observations of the sun with a spectrograph, we could conclude that the sun is made of Hydrogen.
  • No solar eclipse can last longer than 7 minutes 58 seconds because of the speed at which the sun moves.
  • The Sun is the closest star to Earth and is the center of our solar system. A giant, spinning ball of very hot gas, the Sun is fueled by nuclear fusion reactions. The light from the Sun heats our world and makes life possible. The Sun is also an active star that displays sunspots, solar flares, erupting prominences, and coronal mass ejections. These phenomena impact our near – Earth space environment and determine our space weather.
  • Solar atmosphere : The visible solar atmosphere consists of three regions : the photosphere, the chromosphere, and the solar corona. Most of the visible ( white ) light comes from the photosphere. This is the part of the Sun we actually see. The chromosphere and corona also emit white light, and can be seen when the light from the photosphere is blocked out, as occurs in a solar eclipse.
  • The sun emits electromagnetic radiation at many other wavelengths as well. Different types of radiation ( such as radio, ultraviolet, X – rays, and gamma rays ) originate from different parts of the sun. Scientists use special instruments to detect this radiation and study different parts of the solar atmosphere.
  • The solar atmosphere is so hot that the gas is primarily in a plasma state, i.e., electrons are no longer bound to atomic nuclei, and the gas is made up of charged particles ( mostly protons and electrons ).
  • In this charged state, the solar atmosphere is greatly influenced by the strong solar magnetic fields that thread through it. These magnetic fields, and the outer solar atmosphere ( the corona ) extend out into interplanetary space as part of the solar wind.
  • Rising above the Sun’s chromosphere, the temperature jumps sharply from a few tens of thousands degrees Kelvin to as much as a few million degrees in the Sun’s outer atmosphere, the solar corona.
  • Understanding the reason, why the Sun’s corona is so hot, is one of the many challenges facing solar physicists today. Because of the very high temperatures, the corona emits high energy radiation land can be observed in the form of X – rays. The Earth’s atmosphere absorbs X – rays,
  • Solar Activity: The Sun is not a quiet place, but one that exhibits sudden releases of energy. One of the most frequently observed events are solar flares, i.e., sudden, localized, transient increases in brightness that occur in active regions near sunspots.
  • The number of sunspots and the levels of solar activity vary with an 11 year period known as the solar cycle.


Geography of Planets

  • Planets, meaning wanderers, are named after Roman deities : Mercury, messenger of the gods; Venus, the god of love and beauty; Mars, the god of war; Jupiter, king of the gods; Saturn, father of Jupiter and god of agriculture; Uranus, god of sky; Neptune, god of the sea.
  • The three most recently discovered planets were Uranus in 1781, Neptune in 1846, and Pluto in 1930. Venus and Uranus are the only planets that rotate opposite to the direction of their orbit.
  • All the planets in the solar system rotate anticlockwise, except Venus. It is the only planet that rotates clockwise,
  • International Astronomical Union ( IAU ) members, gathered at the 2006 General Assembly, agreed that a ‘planet’ is defined as a celestial body that ( a ) is in orbit around the Sun, ( b ) has sufficient mass for its self – gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium ( nearly round ) shape, and ( c ) has cleared the neighborhood around its orbit. .
  • This means that the Solar System consists of eight planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
  • Dwarf planets : A new distinct class of objects called ‘dwarf planets’ was also decided. It was agreed that planets and dwarf planets are two distinct classes of objects. The first members of the dwarf planet category are Ceres, Pluto and 2003 UB313, given the name Eris.
  • More dwarf planets are expected to be announced by the IAU in the coming months and years. Currently a dozen candidate dwarf planets are listed on IAU’ s dwarf planet watchlist, which keeps changing as new objects are found and the physics of the existing candidates becomes better known.
  • Inner planets : Mercury, Venus, Earth, and Mars are called inner planets.
  • Gas giants : These are large planets of our solar system which are not primarily composed of rock or other solid matter. There are four Gas giants in our Solar System : Jupiter, Saturn, Uranus, and Neptune. Gas giants are sometimes called Jovian planets after the planet Jupiter.
  • Terrestrial planet : A terrestrial planet, telluric planet or rocky planet is a planet that is primarily composed pf silicate rocks. The term is derived from the tin word for Earth, Telara’ so an alternative definition would be that these are planets which are, in some notable fashion, ‘Earth – like’.
  • Terrestrial planets are substantially different from Gas giants, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium and water existing in various physical states.
  • Earth’s solar system has four terrestrial planets : Mercury, Venus, Earth and Mars, and one terrestrial dwarf planet, Ceres.

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1. Geography of Planet Mercury

  • It is the closest planet to the sun.
  • Mercury is also one the brightest planets visible to us on earth. However, since it is so close to the sun it is only visible just before sunrise and sunset.
  • At its closest point to the sun ( perihelion ) it is 29 million miles or 47 million kilometers away. The aphelion, the farthest position of orbit, is 44 million miles ( 71 million km ).
  • Mercury does not have an atmosphere but does contain a thin atmospheric layer of sodium and helium.
  • An asteroid approximately 62 miles wide struck mercury and created an impact basin about 810 miles wide. The basin is called the Caloris Basin and was once covered with molten lava.
  • The surface temperature on Mercury varies more than 630 degrees Celsius ( 1,130°F ). Before sunrise, Mercury is at – 300°F ( – 184°C ) and at noon, it is almost 800°F ( 427°C ).
  • Since Mercury has a highly elliptical orbit, the view of the sun would be strange. The sun would seem to stop moving east to west and reverse directions, then reverse again.
  • Mercury is the innermost and smallest planet in the solar system ( before Pluto was renamed as a dwarf planet, it was the second smallest planet of our solar system ), orbiting the Sun once every 88 days. The Romans named the planet after the Roman god Mercurius, equated to the Greek Hermes.
  • Natural satellites : Mercury has no moon. Exploration : Mercury was visited by the Mariner 10 space – craft that returned images on March 29, 1974.

2. Geography of Planet Venus

  • Venus is the brightest planet of our solar system. Venus is the closest planet to earth and is also similar in size.
  • It is one of the most hostile planets in the solar system. The surface temperature can reach over 900 degrees F ( 480 C ).
  • Venus is the hottest planet in the solar system because the atmosphere in Venus consists of dense gases and mostly Carbon dioxide ( 96% ) which traps the heat inside.
  • Venus is covered by an atmosphere of sulphur dioxide, which is why it has yellow color. It even rains sulphuric acid.
  • Venus takes more time in rotation than in revolution.
  • There is a very low probability of life existing on Venus because of the extreme heat. Not only would the heat prevent life from developing, the atmospheric pressure on Venus is so strong, it would easily crush any living organism found on earth. Also water is only found as vapor on Venus.
  • Venus is the second – closest planet to the Sun. It is the brightest natural object in the night sky, except for the Moon. It is sometimes called Earth’s ‘sister planet’, for the two are similar in size, gravity, and bulk composition. It’s named after the Greek goddess of love, Venus.
  • Natural satellites : Venus has no moon. Exploration : The Soviet Union managed to send several satellites called the Venera series into Venus. Some were destroyed easily and the Venera 4 was the first to send back data before succumbing to Venus’s hostile environment.
  • The Venera 7 actually landed on the surface and sent the first spectacular images of Venus’ surface. The United States sent the Mariner series of satellites to explore Venus and also managed to send back data of its atmospheric contents.
  • The Magellan spacecraft, launched in August 1990 was of America’s most successful ventures to Venus. It revealed many features of Venus with high – resolution radar images and orbited Venus over 15,000 times and mapped over 98% of the surface. The Magellan on October 12, 1994 finally succumbed to its death as it burned up in Venus’ atmosphere.

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3. Geography of Planet Earth

  • The only planet in the solar system to support life.
  • On its trip around the sun, the earth travels over a million and a half miles per day.
  • Earth moves along its orbit at 30 km per second, covering its own diameter in 7 minutes.
  • A speed of 6.95 miles per second is required to escape the Earth’s gravitational pull.
  • Earth is the densest planet in the solar system and the only one not named after a god.
  • One year on earth is 365.26 days long. One day is 23 hours, 56 minutes, and 4 seconds long. The extra day in a leap year was introduced to compensate for the discrepancy in the Gregorian calendar.
  • Earth is slowing down – in a few million years there won’t be a leap year.
  • There is zero gravity at the centre of earth.
  • Almost two – thirds of the earth’s surface is covered by water. If the earth were flat, water would cover everything in a layer two miles deep.
  • Earth is the third planet from the Sun and is the largest of the terrestrial planets in the Solar System in both diameter and mass. Earth, as seen from satellite images is a beautiful, bright blue planet filled with patches of white water vapor ( clouds ) that cover about 40% of the earth.
  • Scientists theorize that earth was formed 4.5 billion years ago when many other planets formed. Earth takes about 365 days to orbit the sun and completes one rotation in approximately 24 hours.
  • Earth’s orbit is somewhat elliptical with only a 3% difference from a circular orbit. The tilt of the earth’s axis is 23.5 degrees, which accounts for the seasons on earth. The tilt causes certain parts of the planet to be heated differently thus causing seasonal changes.

4. Geography of Planet Mars

  • Many scientists believe there could be a possibility of life on Mars, but not complex, just microorganisms.
  • Beneath its thin atmosphere, Mars is barren, covered with pink soil and boulders.
  • It is the most similar planet to earth. Mars completes one rotation in 24.6 hours. Its axis is tilted 25.2°, while earth’s is 23.5°.
  • Mars is also very different from earth. Mars’ orbit is much more elliptical than earth’s. As a matter of fact, Mars’ orbit is the third most elliptical.
  • Unlike Earth’s atmosphere, Mars’ atmosphere is made up of 95.3% carbon dioxide and only 0.2% oxygen.
  • Mars is the fourth planet from the Sun in the Solar System. It is named after Mars, the Roman god of war it is also referred to as the ‘Red Planet’ because of its reddish appearance as seen from Earth.
  • Natural satellites : Mars has two moons, Phobos and Deimos.
  • Exploration : Three probes which landed on Mars are : the Viking 1, which landed on Mars on July 20, 1976. The Viking 2 also landed successfully in September 1976.
  • Mars Pathfinder landed in 1977. Mars is currently host to three functional orbiting spacecraft – Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. This is more than any planet except Earth. The surface is also home to the two Mars Exploration Rovers – Spirit and Opportunity.

5. Geography of Planet Jupiter

  • An unusual phenomenon of Jupiter is the speed of its rotation. It completes one rotation in only 9 hours and 55 minutes.
  • A distinctive feature of Jupiter is the Great Red Spot found on the Southern Hemisphere of the planet. It has been found that this great red, spot is in fact a giant hurricane that rotates counterclockwise.
  • Jupiter’s moon Ganymede is the largest moon in the Solar System, and is larger than the planets Mercury and Pluto.
  • Jupiter is the fifth planet from the Sun and the largest planet within the solar system. Over 1000 earths could fit inside Jupiter. It is two and a half times as massive as all of the other planets in our solar system combined. It is named after the Roman god, Jupiter, the god of light and sky.
  • Natural satellites : Jupiter has 17 known satellites ( moons ) : 10, Europa, Ganymede, Callisto, Metis, Adrastea, Amalthea, Thebe, Leda, Himalia, Lysithea, Elara, Ananke, Carme, Pasiphae, Callirrhoe, Sinope. The four largest moons are called Galilean Satellites: Ganymede, Callisto, 10 and Europa, in the order. Some scientists claim that Jupiter has 63 satellites, including the recent findings.
  • Exploration : The Pioneer 10 sent back images in December, 1972. Pioneer 11 also flew by Jupiter and sent back data on its atmospheric composition and information about Jupiter’s moons. The Voyager missions also sent back data from Jupiter. The Galileo spacecraft reached Jupiter in December 1995 and was the first to orbit Jupiter.

6. Geography of Planet Saturn

  • Titan is the largest of Saturn’s moons. It is the second largest moon in the solar system. In fact, it is larger than both Mercury and Pluto.
  • Of all the satellites, Titan has an atmosphere and is believed to contain organic molecules. The atmosphere is 80% nitrogen and contains common galsses found on earth such as methane, ethane, argon, and hydrogen.
  • Saturn is the sixth planet from the Sun and the second largest planet in the Solar System after Jupiter. It is named after the Roman god Saturn us, equated to the Greek Kronos ( the Titan father of Zeus ). Even though Saturn is so large, it has the lowest density in the solar system. The most prominent feature of Saturn is its rings. Saturn also rotates extremely, fast which causes the bulges at its equator. Saturn rotates once in 10 hours and 40 minutes.
  • Natural satellites : Saturn has about 30 discovered moons, though some scientists put the figure at 60. Some of them are : Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, lapetus, Pan, Atlas, Prometheus, Pandora, Epimetheus, Janus, Calypso, Telesto, Helene, Phoebe, Daphnis, Methone, Pallene, Poly deuces, Paaliaq and Ymir.
  • Exploration : The Pioneer 11 was the first spacecraft to reach Saturn and it sent back some images of Saturn on September 1, 1979. Both Voyagers photographed Saturn. The next spacecraft, to study Saturn and its moons was Cassini.

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7. Geography of Planet Uranus

  • Not unlike Jupiter and Saturn, Uranus also has rings.
  • Uranus is covered in a light blue color because of the methane clouds on Uranus atmosphere.
  • Uranus axis is at 97 degrees. It means that it orbits on its side. ( Most of the planets spin on an axis nearly perpendicular to the plane of the ecliptic but Uranus axis is almost ( parallel to the ecliptic. ) )
  • Uranus, the seventh planet from the Sun, is the third largest and fourth most massive planet in the solar system. It is named after the ancient Greek deity of the sky Uranus. Uranus was discovered by William Herschel, a British astronomer in 1781. He also discovered the largest moons of Uranus, Oberon, and Titania.
  • Natural satellites : Uranus has seventeen discovered satellites, however, once again, some claim the number to be 27. 17 moons are: Miranda, Ariel, Umbriel, Titania, Oberon, Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Caliban, Sycorax.
  • Many of the names are borrowed from names of the characters in William Shakespeare’s, A Midsummer Nights Dream.
  • Exploration : Uranus was visited only by the voyager 2 in 1986.

8. Geography of Planet Neptune

  • A Great dark spot has been found on Neptune, a gaint storm where wind blows at 2000 km / h.
  • It has a counter clockwise rotation.
  • Neptune emits about 2.3 times more energy than it receives from the sun.
  • Triton is its largest moon.
  • Neptune is the eighth planet from the Sun in the Solar System. It is named after the Roman god of the sea. It is also the fourth largest planet by diameter, and the third largest by mass.
  • Neptune was officially discovered by Johann Gottfried in 1846 after the planet’s mass and location were already calculated by John Couch Adams and Urbain Leverrier. They had managed to calculate the mass and location of Neptune because of the gravitational effect Neptune has on Uranus.
  • Natural satellites : It has 9 satellites ( some claim 13 ) : Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, Nereid and Rsamathe. Of these, Triton is the largest. Another oddity of Triton is the fact that it orbits Neptune clockwise while all the other moons around Neptune orbit counterclockwise.
  • Neptune completed its first orbit around the sun in 165 years after its discovery on 13 July 2011.

9. Geography of Planet Pluto

  • Pluto was discovered by Clyde Tombough. NASAs spacecraft, New Horizon, started its journey towards Pluto on 19 January, 2006, carrying the bones of Clyde Tombough to Pluto, and is to study Charon, the moon of Pluto.
  • From the time of its discovery in 1930 until 2006, Pluto was counted as the Solar System’s ninth planet. In the late 20th and early 21st centuries, however, many objects similar to Pluto, were discovered in the outer solar system, notably the scattered disc object Eris which is 27% more massive than Pluto.
  • On August 24, 2006 the IAU ( International Astronomical Union ) defined the term ‘planet’ for the first time.
  • This definition excluded Pluto, and reclassified it as a member of the new category of dwarf planets along with Eris and Ceres. After the reclassification, Pluto was added to the list of minor planets and given the number 134340.
  • Pluto is the second – largest known dwarf planet in the Solar System ( after Eris ) and the tenth – largest body observed directly orbiting the Sun. Pluto is now recognised as the largest member of a distinct region called the Kuiper belt.
  • Like other members of the belt, it is composed primarily of rock and ice – and is relatively small – approximately a fifth the mass, of the Earth’s Moon and a third of its volume.
  • It has an eccentric orbit that takes it from 30 to 49 AU ( Astronomical Unit ), i.e., 4.4 to 7.4 billion km from the Sun, and is highly inclined with respect to the planets. As a result, Pluto occasionally comes closer to the Sun than the planet Neptune does.
  • Pluto and its largest moon, Charon, are often treated together as a binary system. The IAU ( with headquarters at Prague ) has yet to formalise a definition for binary dwarf planets, and until it passes such a ruling, Charon is classified as a moon of Pluto. Pluto has two more known smaller moons, Nix and Hydra, discovered in 2005;

Moon Geography

  • The moon is the only satellite of the earth.
  • The Moon keeps one side permanently turned towards Earth.
  • The moon orbits the Earth at an average speed of 2,300 miles an hour ( 3,700 kilometers an hour ).
  • The Moon is the only surface in the Solar System ( other than Earth ) to have been stepped on by human beings.
  • Footprints on the Moon will remain there for millions of years.
  • The Moon is the fourth biggest moon in the Solar System ( after Ganymede and Callisto of Jupiter, and Titan of Saturn ).
  • It takes about 1.25 seconds for moonlight to reach the Earth.
  • The Moon is also larger than the dwarf planets Pluto and Eris. It is the 14th largest known object in the Solar System.
  • Selenophobia is the name given for the persistant and irrational fear of the Moon.
  • The Moon is Earth’s natural satellite. The Moon, unlike the Earth, has no atmosphere and has a weaker gravitational force because its mass is only about 1% of Earth’s mass.
  • The surface of the Moon is covered with craters, basins, and cratered highlands, called terrae. The soil that covers the Moon is called regolith, and is composed of rock fragments and fine dust grains.
  • The maria ( Latin for seas ) are lowland plains that were once craters that were later flooded by lava. From Earth the terrae appear bright and the maria are dark.
  • Exploration : The Moon has been visited by several spacecrafts since 1959. The first Moon landing was made by Apollo 11, on July 20,1969 ( Apollo 11 was launched on 16th July 1969 ). Neil Armstrong and Buzz Aldrin were the first human beings to walk on an extraterrestrial body.
  • The last manned moon landing was three years later on 11th December 1972 ( Apollo 17 was launched on 7th December 1972 ). A series of 12 Americans have so far landed on the moon.
  • Our Moon is bigger than Ruto. And at roughly one-fourth the diameter of Earth, some scientists think the Moon is more like a planet. They refer to the Earth – Moon system as a “double planet.” Pluto and its moon Charon are also called a double – planet system by some.
  • Same face : Moon takes the same amount of time for its rotation and revolution, about 27.3 days. This means that the moon always shows, the same face to the Earth.
  • The surface gravity of the moon is only one – sixth that of the Earth. The force gravity exerts, on a person determines the person’s weight. Even though your mass would be the same on Earth and the moon, if you weigh 132 pounds ( 60 kilograms ) on Earth, you would weight about 22 pounds ( 10 kilograms ) on the moon.
  • The Moon has no atmosphere. It is through atmosphere that light is dispersed ( spread ) and sound waves travel. This means that no sound can be heard on the Moon. The sky is always black because light cannot be spread, unlike on Earth where light spreads to give the sky a blue colour and on Mars where it spreads through its thin atmosphere to give the sky a pinkish / reddish colour.

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Geography of Asteroid Belt

  • The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter.
  • It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt region is also termed the main belt to distinguish it from other concentrations of minor planets within the Solar System, such as the Kuiper belt and scattered disk.
  • Asteroids: Asteroids are small bodies that are believed to be left over from the beginning of the solar system 4.6 billion years ago. They are rocky objects with round or irregular shapes up to several hundred km across, but most are much smaller.
  • Meteors : Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky.
  • They are sometimes called ‘shooting stars or ‘falling stars’, though they are not stars at all. Meteors are caused by the entry of small pieces of rock, dust, or metal from space into the atmosphere at extremely high speeds.
  • These particles are called ‘meteoroids’ when they are floating around in space. The incredible pressure meteoroids experience when they collide with Earth’s atmosphere shatters them, transferring energy to atoms and molecules in the atmosphere, which then release the energy by glowing. This glow produces the bright trails of light in the sky we see as meteors. Very rarefy, a larger meteoroid actually survives to strike the ground. These chunks of rock or metal are called “meteorites’.

Geography of Comets

  • Not all comets have tails.
  • The tails takes shape only when the comet gets close to the sun.
  • Comet tails always point away from the sun because of the force exerted by solar wind and radiation on the cometary material.
  • The period of Encke’s comet is only 3.3 years, Halley’s comet – 76 years, Hale -Bopp is about 4000 years, and Kohoutek’s comet is about 75,000 years.
  • Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth.
  • The comets that pass close to the Sun originally came from one of two places : either the Oort Cloud or the Kuiper Belt.
  • The Kuiper Belt : The Kuiper belt is the most recently observed section of the Solar System. The Kuiper belt extends from Neptune’s orbit to three billion kilometers beyond it. It contains lumps of icy material with organic compounds. That makes them like comets. These lumps are called Kuiper belt objects or minor planets.
  • The Oort Cloud : A vast cloud exists at the outer reaches of the solar system. This has come known as the Oort Cloud.

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