Universe + Galaxy + Solar System Agha Zohaib KHan Everyday Science What is Universe? The universe is commonly defined as the totality of everything that exists or is known to exist This includes all matter and energy, planets, stars, and galaxies; and the contents of intergalactic space. The Branch of Science which deals with the study of universe is called Cosmology. 2Agha Zohaib Khan ::: www.css.theazkp.com Origin of Universe There are many theories about origin of universe, following are the major theories. 1.Big Bang Theory. According to Big Bang Universe came into existence about 15 to 20 Billion years ago, when cataclysmic explosion took place.2.The 3k Microwave Background Theory This theory supported Big Bang and states that the echo of that explosion can still be heard in the form of microwave radio single from radiation.. 3Agha Zohaib Khan ::: www.css.theazkp.com Future of Universe There are different theories presented about the future of our universe. 1.Open Universe Theory : It states that universe will keep expanding. 2.Close Universe Theory:It States that universe will shrink and collapse. 3.The Cycle Theory: It states that universe will expand and collapse. 4.Steady State Theory: It states that universe will always exist. 4Agha Zohaib Khan ::: www.css.theazkp.com Galaxy Galaxy is fundamental unit of universe. A system of millions or billions of stars, together with interstellar gas and dust, held together by gravitational attraction. There are billions of Galaxies in the Universe. Some are very small with only a few million stars. While others could have as many as 400 billion stars, or even more. There are three kinds of Galaxies, Spiral, Elliptical, and Irregular. The only difference between the three is what shape they are. 5Agha Zohaib Khan ::: www.css.theazkp.com Our Galaxy? Our Galaxy is called Milky Way. Milky Way is Spiral Galaxy. The region in space occupied by Milky Way Galaxy is called Galactic Plane. The Sun is not present at the centre of Milky Way. Arms of Spiral Galaxy are called Galactic Arms. The Sun revolves around the nucleus of galaxy once in 225 to 250 million years. This duration is called The Cosmic Year or Galactic Year. The nearest spiral galaxy to the milky way is Andromeda Galaxy. 6Agha Zohaib Khan ::: www.css.theazkp.com Solar System SolarSystemistinypartof Galaxy and consist of sun and all the objects that travel around it. Itincludestheearthand7to8 other planets, along the satellites that travel around most of them. ItfurtherincludesAsteroids, Meteoroids,Comets, Interplanetarydustand Interplanetary plasma. 7Agha Zohaib Khan ::: www.css.theazkp.com Planets of our Solar System Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto 8Agha Zohaib Khan ::: www.css.theazkp.com Mercury It is 2nd Smallest Planet Closest to the Sun, Its mean distance from sun is 0.387 (AU) Its Diameter is 4,880 km It takes 88 earth days to complete one revolution around the sun. Mercury is covered with holes called craters. Mercury has no moon. Mercury has no atmosphere. Mercury is about the same size as our Moon9Agha Zohaib Khan ::: www.css.theazkp.com Venus It is called earths twin in size and mass Venus is hotter than mercury Venus is 0.723 A.U away from the sun. Its revolution period is 225 days, its diameter is 12,104 km It has no moon, Venus is the closest planet to Earth 10Agha Zohaib Khan ::: www.css.theazkp.com Earth Earth is the third closest planet to the Sun It has atmosphere Earth is 1 A.U away from the earth Its diameter is 12756 km The Earth is the largest of terrestrial planets. It as one moon. Revolution Period 365.26 Earth days Rotation Period 23.93 hours It has one Moon called Luna, 11Agha Zohaib Khan ::: www.css.theazkp.com Mars Mars is barren desert , it is covered with red dust. It is also called Red Planet It is 1.524 A.U away from the sun. Mars orbits the sun after every 687 days. Its diameter is 6,787 km Mars has two moons called phobos and Deimos12Agha Zohaib Khan ::: www.css.theazkp.com Jupiter It has dense cloudy atmosphere of hydrogen and helium. It is the largest planet of solar system. Its diameter is 143,000 km Jupiter orbits the sun once after every11.89 years. It has 63 Knowm moons Jupiter is the planet with most moons. 13Agha Zohaib Khan ::: www.css.theazkp.com Saturn It is the second largest planet. It has special feature like rings of saturn around it. It is 9.539 A.U away from the sun It has revolution period about 29.46 years Its Diameter is 120,000 km It has 62 confirmed moons 14Agha Zohaib Khan ::: www.css.theazkp.com Uranus It has mostly hydrogen and helium atmosphere. It is 19.18 A.U away from the sun Its diameter is 51,800 km Its Revolution period is 84.01 years Uranus is big and give greenish glow It has 27 known moons 15Agha Zohaib Khan ::: www.css.theazkp.com Neptune It is somewhat similar to Uranus It is 30.06 A.U away from the sun. Its Diameter is 49,500 Km Its revolution period is 164.8 years Neptune has 13 known moons16Agha Zohaib Khan ::: www.css.theazkp.com Pluto The First Dwarf Planet Pluto is actually smaller than one of Neptune's moons, Triton. Originally classified as the ninth planet from the Sun, Pluto was re-categorized as a dwarf planet and plutoid due to the discovery that it is only one of several large bodies within the Kuiper belt. It has 4 Moons. 17Agha Zohaib Khan ::: www.css.theazkp.com IAU definition of planet The definition of planet set in 2006 by the International Astronomical Union (IAU) states that, in the Solar System, a planet is a celestial body which: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit. 18Agha Zohaib Khan ::: www.css.theazkp.com Past Papers Questions Solar System - 1999, 2002, 2003, 2008 Planets 1986, 2002 Mercury 2004 Pluto 2004, 2011 Big Bang Theory 2011 Galaxy - 2011 19Agha Zohaib Khan ::: www.css.theazkp.com