The Universe PDF

The Universe  Cosmology The branch of astronomy that deals with the origin, large-scale properties, and the evolution of the observable universe  The Universe in astronomy, the sum total of all things which can be directly observed or whose physical effects...

The Universe  Cosmology The branch of astronomy that deals with the origin, large-scale properties, and the evolution of the observable universe  The Universe in astronomy, the sum total of all things which can be directly observed or whose physical effects on other things can be detected in simpler terms, space and all the matter and energy in it major components: – galaxies – solar systems – planets  The BIG BANG THEORY about the universe is the most widely acceptable theories with regard to the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions. All the galaxies were formed from this matter. Observations of these galaxies show that they are still moving apart from each other. The universe is expanding Some scientists have suggested another theory as "steady theory:" to explain the process of the evolution of the universe. However the general notion on which all scientists agree is the theory of Big Bang.  “Big Bang” Theory the primeval explosion of space, time, matter and energy that most astronomers think gave rise to the universe as we see it today. occurred about 13.7 billion years ago thought to have expanded within a second from something the size of a spec of dust to the size of our solar system  Edwin Hubble determined that other galaxies exist, besides the Milky Way observed that galaxies were moving away from each other – Hubble Law – the farther away a galaxy is, the faster it is moving away from us; supports the Big Image taken from: Bang Theory http://apod.nasa.gov/apod/ap960217.html  Arno Penzias & Robert Wilson accidentally detected faint radiation on a radio telescope in 1965 determined that the radiation was leftover thermal energy from the “big bang” Image taken from: http://www.einstein-online.info/en/elementary/cosmology/early_universe/index.html  Steady state theory Steady-state theory, in cosmology: a view that the universe is always expanding but maintaining a constant average density, with matter being continuously created to form new stars and galaxies at the same rate that old ones become unobservable as a consequence of their increasing distance and velocity of recession.  Steady theory is the theory about the universe and the observations by the astronomers have shown that the galaxies are moving away from each other and the universe seems to be expanding. The theory shows that the new matter is always being created to fill the space left by this expansion. The new matter moves apart and forms galaxies which continue to move apart. This means that the universe always look exactly the same. It has no beginning or end but in a steady state. However many observations have suggested that th the universe has not always looked like the same  At present the universe is expanding but the ast ronomers have questioned that whether or not this expansion will continue.Certain observations which have been made in this regard is that one possible ending of the universe will be the "big crunch” The galaxies and other matter may be moving apart but their motion is restrained by their mutual gravitational attraction. If there is a sufficient matter in the universe gravity will eventually win and begin pulling the galaxies together again causing the universe to experience a reverse of the big bang i.e., the BIG CRUNCH.  Galaxy a large assemblage of stars (and often gas and dust), typically containing millions to hundreds of billions of member stars – Star - a large hot ball of gas which generates energy in its core by nuclear reactions around 100 billion in the universe held together by the gravitational attraction of all its member stars on one another formed around 200 million years after the “Big Bang” most large ones seem to have super-massive black holes at their centers sometimes contain very bright centers called quasars 3 major types: – Spiral – Elliptical – Irregular  3 Types of Galaxies Elliptical Spiral shaped like Irregular have arms of stars, gas , spheres or eggs; faint galaxies without a and dust that curve away have almost no definite shape; smaller from the center of the galaxy dust or gas than the other types of in a spiral pattern between stars; galaxies; contain fewer Ex. – Milky Way contain old stars stars The process of galaxies colliding to create a larger galaxy is known as “galactic cannibalism.” Images taken from: http://school.discoveryeducation.com/schooladventures/universe/galaxytour/toknow.html  Types of stars The Milky Way contains both the so-called type I stars, brilliant, blue stars; and type II stars, giant red stars. Blue stars tend to be younger because they burn furiously and use up all of their fuel within a few tens of millions of years. Red stars are usually older, and use their fuel at a slower rate that they can sustain for tens of billions of years. The central Milky Way and the halo are largely composed of the type II population. Most of this region is obscured behind dust clouds, which prevent visual observation.  Main Sequence stars Red giants White dwarfs Cepheid variables Novas Super novas Neutron stars  Constellation a group of stars that form a pattern in the sky stars of a constellation are often far apart from each other, but they appear grouped together when viewed from Earth one of 88 sectors into which astronomers divide the sphere of the sky – named after a traditional constellation in that sector patterns of constellations are dynamic; therefore, the constellations of 100,000 years ago are quite different from today’s a part of a constellation that forms its own pattern in the sky is known as an asterism (ex. – The Big Dipper) Why is it not possible to see all constellations at once?  Milky way Our galaxy is a spiral galaxy about 30,000 parsecs across. There are more than 200 billion stars in the galaxy. Its disc appears as a faint white band that is responsible for dividing the white sky at the night into two. The name of our galaxy is Milky Way. The galaxy has three spiral arms called the Orion, Perseus, and Sagittarius arms and the whole system is rotating in space. The sun revolves around the nucleus of the galaxy once in 225 million years. This duration is also called the cosmic year.  Milky Way, the large, disk-shaped aggregation of stars, or galaxy, that includes the Sun and its solar system. In addition to the Sun, the Milky Way contains about 400 billion other stars. There are hundreds of billions of other galaxies in the universe, some of which are much larger and contain many more stars than the Milky Way. The Milky Way is visible at night, appearing as a faintly luminous band that stretches across the sky. The name Milky Way is derived from Greek mythology, in which the band of light was said to be milk from the breast of the goddess Hera. Its hazy appearance results from the combined light of stars too far away to be distinguished individually by the unaided eye. All of the individual stars that are distinct in the sky lie within the Milky Way Galaxy.  Solar System the sun and all things orbiting around it, including the eight major planets, their satellites, and all the smaller pieces such as asteroids and comets formed around 4.6 billion years ago Image taken from: http://asm.arc.nasa.gov/Gallery/images/generic/LG_Capableofeverything.jpg  The solar system includes nine planets and sun being at the centre. All the planets revolve around the sun.The solar system also includes the asteroids, meteors and numerous comets. All of these travel around the sun in a particular orbit.The planets which are the significant part of the solar system namely,Mercury,venus,earth,mars,Jupiter,Saturn, uranus,neptune and the Pluto. All the theories about the formation of the solar system agree on two facts. One is that the age of solar system is 4.5billion years and secondly the planets were formed from the gas and dust within the vicinity of the sun. The gas and dust condensed into tiny bodies which eventually built up the present day planetary system. MOTION OF THE PLANETS: The planets perform two types of motions. 1. rotation at their axis is 2. revolution or the orbital motion along their orbits around the sun. THE AGE OF THE SOLAR SYSTEM: Meteoric evidence suggests that the solar system is 4530+20 million years old. And that was formed in less than 25 million years. The solar system is believed to be formed from a globe of gas and dust that consisted mainly of hydrogen  Ringed planets Four the planets in the Solar System have rings. They are the four giant gas planets Jupiter, Saturn, Uranus, and Neptune. Saturn, which has by far the largest ring system, was known to have rings for a long time. It was not until the 1970s that rings were discovered around the other gas planets.  THE SUN The sun is the most significant star for the existence and life of living beings on earth. The whole life on earth depends on this brightest object in the sky. The living things get their energy from sun and the appropriate distance of earth from sun maintains an appropriate temperature which is ideal for the survival of all the life present on earth. The sun is the principle source of energy for all the planets of the solar systems.Through a constant stream of particles that flow outward from the sun, heat, radiation, light and UV rays are emitted.the UV rays that reach the earth from sun are considered to be the most harmful ones.Most of the UV and other high energy radiation are absorbed by the Ozone layer and the atmosphere of the earth.This stream of particles is called solar wind. STRUCTURE OF THE SUN: The visible surface of the sun is called photosphere which is a turbulent region and is 570 kilometer deep. The layer outside the photosphere is chromospheres which is a broad layer and is several miles thick. The outside layer of the sun is corona. Energy released by the sun passes from chromospheres to the corona and then to the outer space. EARTH The third farthest planet from the sun is earth. The earth rotates on its axis in about 24 hours. The diameter of earth is 12756 km. The earth completes its rotation along its axis in 23.9 hour and one tip along its orbit in 365 days,6 hours and 9 minutes and 9.4 seconds. The orbit of the earth is not a circle but an ellipse. STRUCTURE OF THE EARTH: The earth has four major structural components. 1. The Crust 2.The Mantle 3.The Outer core 4.The Inner Core. THE CRUST: The upper most layer of the earth is called the crust. A solid and a complex layer of the lithosphere in both physical and chemical nature. The crust is composed of wide variety of rocks which are known as sedimentary rocks. The crust is further divided into a) ocean crust and b) continental crust. THE MANTLE: According to the various kinds of scientific evidences the upper mantle of the earth is made up of silicate minerals. The temperature increases rapidly with depth in outer of the earth. Due to high temperatures the rocks start melting.These molten rocks form the basis of lava which erupt from oceanic volcanoes. THE CORE: The core starts where marked physical and chemical changes occur across the core mantle boundries. The outer core is thought to be made of mixture of melted iron and nickle. In the inner core the mixture is thought to be nickel and iron alloy. ATMOSPHERE OF THE EARTH: The chief gases in the atmosphere of the earth are, 1. Nitrogen 78.09% 2. Oxygen 20.95% 3. Argon 0.93% The remaining 0.03% is made of carbon dioxide, small quantities of neon,helium,ozone and hydrogen and minute traces ofkrypton,methane,xenon and other gases.  Planet derived from a Greek word that means “wanderer” a major object which orbits around a star in our solar system, there are eight such objects which are traditionally called “planets”  Asteroids small, solid, rocky bodies that orbit close to the Sun most found between the orbits of Mars and Jupiter in the “Asteroid Belt” thought to be leftover material from the formation of the solar system range in size from 1000 km or 621 miles (Ceres) to the size of pebbles Image taken from: http://www.windows.ucar.edu/tour/link=/our_solar_system/asteroids.html  Meteoroid, Meteor, Meteorite Meteoroid (asteroid) Meteoroid – solid debris from space (asteroids) that are moving towards Earth Meteor Meteor Meteorite – a brief streak of light produced by a small particle entering Earth’s atmosphere at high speed – often referred to as “shooting stars” or “falling stars” – travel at speeds between 11-72 kilometers per second (6.8 – 44.7 miles per second) Meteorite – a small object from outer space that passes through Earth’s atmosphere and reaches the surface  Comet a small body of ice and dust (“dirty snowball”) that orbits the Sun contain a head (coma) followed by a tail(s) of gas and dust the tail always points Image taken from: away from the sun and http://www.space.com/bestimg/index.php?guid=45b0fd31f065d&cat=bestcomet can be millions of kilometers long (but the amount of matter it contains can be very small)  Satellite an object that orbits a more massive object (i.e. – moons) probes we launch into orbit around the Earth are called “artificial satellites”  Telescope a device that gathers electromagnetic radiation Types: – Visible, infrared, ultraviolet – pick up visible, infrared, and ultraviolet waves Reflecting - use mirrors that reflect the image being viewed Refracting – using lenses, gathers light and focuses it near the opposite end of the tube; works like a magnifying glass – Radio - pick up radio waves emitted from space; not effected by variables like weather or clouds Internet Telescope  Hubble Space Telescope a reflecting telescope that was placed into orbit in 1990 sends images and measurements back Image taken from: to Earth electronically http://hubblesite.org/gallery/