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yksd lsod fuekZ.k GEOGRAPHY Meghwal's IAS ASTRONOMY AND SPACE SCIENCE Universe encompasses everything; every possible imagination. It is more than what we can know ever. It a possible limit of every phenomenon in the senseperception of human being. Geographically, a universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. The present overall densrty of the universe is very low, roughly 9.9 x 10-30 grams per cubic centimeter. This mass-energy appears to consist of 73 per cent dark energy, 23 per cent cold dark matter and 4 per cent ordinary matter. Thus the density of atoms is on the order of a single hydrogen atom for every four cubic meters of volume. The properties of dark energy and dark matter are largely unknown. Dark matter gravitates as ordinary matter, and thus works to slow the expansion of the universe; by contrast, dark energy accelerates its expansion. Evolution of Space: Geocentrie Theory: It was founded by Ptolemy in 140 A.D. It states that earth is at the centre of the universe. Helio-centic Theory: It was propounded by Copernicus in 1453 A.D. It states that all celestial body revolves around the sun. William Hersehel: It showed that sun is member of galaxy, Milky Way and placed at one corner of Milky Way. Edwin Hubble (1925):He proved presence of other galaxies. He also proved that galaxies are receding constant from each other. With the help of analyzing red shift (Doppler Effect), he also proved the rate at which galaxies are receding. Big Bang Theory: It was put forth by Abbe George Lemaitre. It states that receding movement of galaxies are result of implosion. Big bang occurred at least 12 billion years ago. Evidences: discovery of background radiation proved by COBE, cosmic background experiment, discovering uneven ripple of microwave radiation, which suggests sudden explosion. Wormhole theory: According to a mind-bendingnew theory, a blackhole is actually a tunnel between universes-a type of wormhole. The matter the black hole attracts doesn’t collapse in Meghwal's IAS to a single point, as has been predicted, but rather gushes out a “white hole” at the other end of the black one, the theory goes. Wormhole theory is a potential replacement for the Big Bang theory, which has explained many of the conditions of our current universe, but not all of them. Scientist Nikodem Poplawski hopes that his Wormhole theory will explain phenomena that are currently inexplicable. Wormhole theory states that our universe may not have been created from a sudden explosion of matter and energy (as the Big Bang theory posits), but that rather that our universe was created when a large planet in another universe collapsed in upon itself. Advantages over big-bang theory: It is to be noted that for some time, the Big Bang theory has been struggling to explain’ dark energy’, and has also had issues explaining how gravity interacts with electromagnetism and nuclear forces. Wormhole theory, on the other hand, might very well resolve the problems of’ dark energy’ and the elusive nature of gravity. While Wormhole theory has yet to be stringently assessed and tested, it is nevertheless an intriguing possibility. Black-holes: It is extremely concentrated matter. The pull of gravity is so powerful that nothing, not even light, can comes out from it. So, black-hole can’t be seen. Black-hole formation indicates ultimate death of a star. The collapsing star core (due to finishing up of fuel hydrogen), imparts much energy to star exterior and explosion with very high luminosity takes place. Mass less than about 1.4 times the mass of the sun become a white dwarf. Pulsating Theory: It goes beyond Big-Bang theory. It says that receding nature of galaxy will not continue forever, and gravity would ultimately stop expansion and thereafter galaxy will collapse inward and ultimately forming primordial substance once again. Event Horizon: Rim of the black-hole from which nothing could escape. Across event-horizon matter and energy pass in only one direction. Event horizon indicates beginning of black-holes. Galaxies Basically, a galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas dust, and an important but poorly understood component tentatively dubbed dark matters. The solar system is in a galaxy called the Milky Way. In 1965, American physicists Arno Penzias and Robert Wilson detected faint radio waves throughout the sky. According to the big bang theory, the waves 2 GEOGRAPHY yksd lsod fuekZ.k Office: MX-157, Near Sai Board, E-7, Arera Colony, Bhopal PH. 0755-4010498 MO. 9425416811, 9009386291 Website: loksevaknirman.com flfoy lsok o çfr;ksxh ijh{kkvkas ds fy, yksd lsod fuekZ.k GEOGRAPHY are radiation left over from the initial explosion. The strength of the radio waves appeared to be very nearly the same in every direction. But in 1992, a satellite called the Cosmic Background Explorer (COBE) detected tiny differences in the strength of radio waves coming from different directions. Scientists estimate that there are more than 100 billion galaxies scattered throughout the visible universe. Aristotle (384-322 BC) informs us in Meteorologica (DK 59 ABO), the Greek philosophers Anaxagoras (ca. 500-428 BC) and Democritus (450370 BC) proposed that the Milky Way might consist of distant stars. Giant clusters of stars; our solarsystem · is part of galaxy called ‘Milky-Way.’ The stellar disk of the Milky Way galaxy is approximately 100,000 light-years (9.5x1017 km) in diameter, and is believed to be, on average, about 1,000 ly (9.5x1015 km) thick. A light year is the distance that light travels in a vacuum in a year about 5.88 trillion miles (9 .46 trillion kilometers). Galaxies range in diameter from a few thousand to a half-million light-years. Small galaxies have fewer than a billion stars. Large galaxies have more than a trillion. It is estimated to contain at least 200 billion stars and possibly up to 400 billion stars, the exact figure depending on the number of very lowmass stars, which is highly uncertain. The Galaxy consists of a bar-shaped core region surround• ed by a disk of gas, dust and stars forming four distinct arm structures spiralling outward in a logarithmic spiral shape. It is extremely difficult to define the age at which the Milky Way formed, but the age of the oldest star in the Galaxy yet discovered, HE 1523-0901, is estimated to be about 13.2 billion years, nearly as old as the Universe itself. The most distant galaxies ever photographed are as far as 10 billion to 13 billion light-years away. Only three galaxies outside the Milky Way are visible with the unaided eye. People in the Northern Hemisphere can see the Andromeda Galaxy, which is about 2 million light-years away. People in the Southern Hemisphere can see the Large Magellanic Cloud, which is about 160,000 light years from Earth, and the Small Magellanic Cloud, which is about 180,000 light-years away. The Milky Way and the Andromeda Galaxy are a binary system of giant spiral galaxies belonging to a group of 50 closely bound galaxies known as the Local Group, itself being part of the Virgo Super cluster. Two smaller galaxies arid a number of dwarf galaxies in the Local Group orbit the Milky Way. The largest of these is the Large Magellanic Cloud Meghwal's IAS Meghwal's IAS with a diameter of 20,000 light-years. It has a close companion, the Small Magellanic Cloud. The Magellanic Stream is a peculiar streamer of neutral hydrogen gas connecting these two small galaxies. The stream is thought to have been dragged from the Magellanic Clouds in tidal interactions with the Galaxy. Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf. All galaxies emit (give off) energy as waves of visible light and other kinds of electromagnetic radiation. In order of decreasing wavelength (distance between successive wave crests), electromagnetic radiation consists of radio waves, infrared rays, visible light, ultraviolet rays, X rays, and gamma rays. All these forms of radiation together make up the electromagnetic spectrum. A small percentage of galaxies called active galaxies emit tremendous amounts of energy. This energy results from violent events occurring in objects at their center. The distribution of the wavelengths of the emissions does not resemble that of normal stars, and so the emissions are known as non-thermal radiation. The most powerful such object is a quasar, which emits a huge amount of radio, infrared, ultraviolet, X-ray, and gamma-ray energy. Some quasars emit 1,000 times as much energy as the entire Milky Way, yet look like stars in photographs. Quasar is short for quasi-stellar radio source. The name comes from the fact that the first quasars identified emit mostly radio energy and look much like stars. A radio galaxy is related to, but appears larger than, a quasar. A Seyfert galaxy is a spiral galaxy that emits large amounts of infrared rays as well as large amounts of radio waves, X rays, or both radio waves and X rays. Seyfert galaxies get their name from American astronomer Carl K. Seyfert, who in 1943 became the first person to discover one. In a major development, the scientists have discovered hundreds of galaxies just 250 million light years away from earth which had been hidden from view until now by Milky Way galaxy. Using Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) Parkes radio telescope in Australia equipped with an innovative receiver, scientists were able to see through the stars and dust of the Milky Way, into a previously unexplored region of space. The discovery could help to explain the mysterious gravitational anomaly dubbed the Great Attractor, that appears to be drawing the Milky Way and hundreds of thousands of other galaxies towards it with a gravitational force equivalent to a 3 GEOGRAPHY yksd lsod fuekZ.k Office: MX-157, Near Sai Board, E-7, Arera Colony, Bhopal PH. 0755-4010498 MO. 9425416811, 9009386291 Website: loksevaknirman.com flfoy lsok o çfr;ksxh ijh{kkvkas ds fy, yksd lsod fuekZ.k GEOGRAPHY million billion Suns. The research identified several new structures that could help to explain the movement of the Milky Way, including three galaxy concentrations (named NWl, NW2 and NW3) and two new clusters (named CWl and CW2). An average gal• axy contains 100 billion stars, so finding hundreds of new galaxies hidden behind the Milky Way points to a lot of mass we didn’t know about until now. Types of galaxies: Galaxies are of two types: (i) Regular Galaxies and (ii) Irregular Galaxies. (i) Regular Galaxies: The regular galaxies may be of either spiral or elliptical in shape. (a) Spiral Galaxies: The Milky Way and the Great Galaxy in Andromeda are illustrations of large spiral galaxies, disc-shaped with greater concentration of stats near their centers. The spiral galaxies have cured spiral arms. About 25 % of all galaxies are well supplied with the interstellar gas in which new bright, young stars form. As the rotating spiral pattern sweeps around the galaxy; it encompasses gas and dust, triggering the formation of bright young stars in its arms. (b) Elliptical Galaxies: The most abundant are probably the elliptical galaxies which are generally smaller than their spiral counterparts. They are generally symmetrical or spheroidal in shape with no obvious structure. Most of their member stars are very old and no new star forming in them. Some of them are so small that the term ‘Dwarf’ has been applied. The largest known elliptical galaxy is 200,000 light years in diameter. The biggest and the brightest galaxies in the universe are elliptical with masses of 1013 times that of our Sun. About 2/3rd of all the galaxies are elliptical. (ii) Irregular Galaxies: The irregular galaxies comprise about 1/lOth of all galaxies and come in many subclasses. The stars of the irregular galaxies are generally very old. Some of them have a mixture of the old and new stars. The Milky Way and other spiral galaxies consist of populations of old stars in the centre, and the youngest stars situated in the arms. Solar System The Solar System consists of the Sun and those celestial objects bound to it by gravity. These objects are the eight planets, and their natural satellites (such as our moon); dwarf planets; asteroids and comets. Our solar system is located in an outward spiral of the Milky Way galaxy. They called these objects planets, meaning wanderers, and named them after Roman deities - Jupiter, king of the gods; Mars, the god of war; Mercury, messenger of the gods; Venus, the goddess of love and beauty, and Saturn, father of Jupiter and god of agriculture. Meghwal's IAS Meghwal's IAS Since the invention of the telescope, two more planets have been discovered in our solar system: Uranus (1781), Neptune (1846), and a dwarf planet Pluto (1930). Pluto was reclassified as a dwarf planet in 2006. In addition, our solar system is populated by thousands of small bodies such as asteroids and comets. Most of the asteroids orbit in a region between the orbits of Mars and Jupiter, while the home of comets lies far beyond the orbit of Pluto, in the Oort Cloud. The four planets closest to the Sun - Mercury, Venus, Earth, and Mars - are called the terrestrial planets because they have solid rocky surfaces. The four large planets beyond the orbit of Mars Jupiter, Saturn, Uranus, and Neptune - are called the gas giants. The small bodies include asteroids, icy Kuiper belt objects, comets, meteoroids, and interplanetary dust. In order of their distances from the Sun, the eight planets are: Mercury; Venus; Earth; Mars; Jupiter; Saturn; Uranus; and Neptune; and Pluto (now dwarf planet). As of inid-2010, five smaller objects are classified as dwarf planets. Ceres is in the asteroid belt, and four orbit the Sun beyond Neptune: Pluto (formerly classified as the ninth planet and now regarded as dwarf planet), Haumea, Makemake, and Eris. Nearly every planet - and some moons - has an atmosphere. Earth’s atmosphere is primarily nitrogen and oxygen. Venus has a thick atmosphere of carbon dioxide, with traces of poisonous gases such as sulfur dioxide. Mars’ carbon dioxide atmosphere is extremely thin. Jupiter, Saturn, Uranus, and Neptune are primarily hydrogen and helium. When Pluto is near the Sun, it has a thin atmosphere, but when Pluto travels to the outer regions of its orbit, the atmosphere freezes and collapses to the planet’s surface. In that way, Pluto acts like a comet. There are about 170 known natural satellites (also called moons) in orbit around the planets in our solar system, ranging from bodies larger than our own Moon to small pieces of debris. Many of these were discovered by planetary spacecraft. Some of moons have atmospheres (Saturn’s Titan); some even have magnetic fields (jupiter’ s Ganymede). Jupiter’s moon Io is the most volcanically active body in the solar system. An ocean may lie beneath the frozen crust of Jupiter’s moon Europa, while images of Jupiter’s moon Ganymede show historical motion of icy crustal plates. Some moons may actually be asteroids that were captured by a planet’s gravity. The captured asteroids presently counted as moons may include Phobos and Deimos, 4 GEOGRAPHY yksd lsod fuekZ.k Office: MX-157, Near Sai Board, E-7, Arera Colony, Bhopal PH. 0755-4010498 MO. 9425416811, 9009386291 Website: loksevaknirman.com flfoy lsok o çfr;ksxh ijh{kkvkas ds fy, yksd lsod fuekZ.k GEOGRAPHY several satellites of Jupiter, Saturn’s Phoebe, many of Uranus’ new satellites, and possibly Neptune’s Nereid. I. Inner Solar System: The inner solar system contains the Sun, Mercury, Venus, Earth and Mars. The inner Solar System is the traditional name for the region comprising the terrestrial planets and asteroids. Composed mainly of silicates and metals, the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is shorter than the distance between Jupiter and Saturn. Asteroid belt composed mainly of refractory rocky and metallic minerals. The main asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the Sun. All asteroids save the largest, Ceres, are classified as small Solar System bodies, but some asteroids such as Vesta and Hygieia may be reclassed as dwarf planets if they are shown to have achieved hydrostatic equilibrium. Ceres: It is the largest body in the asteroid belt and is classified as a dwarf planet. Asteroid groups Asteroids in the main belt are divided into asteroid groups and families based on their orbital characteristics. Asteroid moons are asteroids that orbit larger asteroids. Trojanasteroids are located in either of Jupiter’s L4 or LS points (gravitationally stable regions leading and trailing a planet in its orbit); the term “Trojan” is also used for small bodies in any other planetary or satellite Lagrange point. Hilda asteroids are in a 2:3 resonances with Jupiter; that is, they go around the Sun three times for every two Jupiter orbits. The inner Solar System is also dusted with rogue asteroids, many of which cross the orbits of the inner planets. Earth is the largest of the inner planets. II. Outer Solar System: It contains a higher proportion of volatiles such as water, ammonia and methane, than the rocky denizens of the inner Solar System, as the colder temperatures allow these compounds to remain solid. The four outer planets, or gas giants (sometimes called Jovian planets), col lectively make up 99 percent of the mass known to orbit the Sun. It consists of Jupiter and Saturn are each many tens of times the mass of the Earth and consist overwhelmingly of hydrogen and helium; Uranus and Neptune are far less massive and possess more ices in their makeup. Comet Hale-Bopp: Comets are small Solar System bodies; short-period comets are believed to originate Meghwal's IAS Meghwal's IAS in the Kuiper belt, while long-period comets, such as Hale-Bopp, are believed to originate in the Oort cloud. Many comet groups, such as the Krentz Sungrazers, formed from the breakup of a single parent. Some comets with hyperbolic orbits may originate outside the Solar System, but determining their precise orbits is difficult. III. Trans-N eptunianregion: This area is still unexplored and nothing much is known. It consists of Kuiper belt which extends between 30 and 50 AU from the Sun. The largest Kuiper belt objects, such as Quaoar, Varuna, and Orcus, may be reclassified as dwarf planets. Members of the classical Kuiper belt are classified as cubewanos, after the first of their kind to be discov• ered, (15760) 1992 QBl, and are still in near primordial, low-eccentricity orbits. Pluto and Charon: Charon, Pluto’s largest moon, is sometimes described as part of a binary system with Pluto, as the two bodies orbit a barycenter of gravity above their surfaces (i.e., they appear to” orbit each other”). Beyond Charon, two much smaller moons, Nix and Hydra, orbit within the system. Haumea and Makemake: They are smaller than Pluto, are the largest known objects in the classical Kuiper belt. Haumea is an egg-shaped object with two moons. Makemake is the brightest object in the Kuiper belt after Pluto. The scattered disc, which overlaps the Kuiper belt but extends much further outwards, is thought to be the source of shortperiod comets. Scattered disc objects are believed to have been ejected into erratic orbits by the gravitational influence of Neptune’s early outward migration. and are often almost perpendicular to it. Eris is the largest known scattered disc object. It has one moon, Dysnomia. IV. Farthest regions: It is called heliopause and known as the Sun’s Rochesphere. Oort cloud: The hypothetical Oort cloud is a spherical cloud of up to a trillion icy objects that is believed to be the source for all long-period comets and to surround the Solar System. Sedna: It is a large, reddish Pluto-like object with a gigantic, highly elliptical orbit. The planets orbit the Sun in or near the same plane, called the ecliptic. Pluto is a special case in that its orbit is the most highly inclined (18 degrees) and the most highly elliptical of all the planets. The vacuum of "space" comprises the interplanetary medium. It includes various forms of energy and at least two material components: (a) interplanetary dust and (b) interplanetary gas. Interplanetary dust consists of microscopic solid 5 GEOGRAPHY yksd lsod fuekZ.k Office: MX-157, Near Sai Board, E-7, Arera Colony, Bhopal PH. 0755-4010498 MO. 9425416811, 9009386291 Website: loksevaknirman.com flfoy lsok o çfr;ksxh ijh{kkvkas ds fy,