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• Количество слайдов: 64 Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine [email protected] umass. edu Course • Course Website: – http: //blogs. umass. edu/astron 101 -tburbine/ • Textbook: – Pathways to Astronomy (2 nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator. • There is an Astronomy Help Desk that is open Monday -Thursday evenings from 7 -9 pm in Hasbrouck 205. • There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http: //www. astro. umass. edu/~orchardhill/index. html. Exam #1 • Average was 85 HW #6 • Due by Feb. 23 rd at 1 pm In the News: Meteorite • Fell in a doctor’s office in Lorton, Virginia In the News: Asteroid Collision http: //www. csmonitor. com/Science/Discoveries/2010/0202/Has-the-Hubble-Space-Telescope-spied-asteroid-on-asteroid-collision-debris Energy • Energy is the ability to generate motion Conservation of Energy • Energy is neither created or destroyed – it just changes forms • Conservation of Energy – The energy in a closed system may change form, but the total amount of energy does not change as a result of any process. Energy units • In English Units, we use calories to measure energy • In science (and in this class), we will use joules to measure energy • 1 Joule = 1 kg*m 2/s 2 Joule • One joule is defined as the amount of work done by a force of one Newton moving an object through a distance of one meter • Work is the change in enerrgy • Work = Force * distance  3 basic categories of energy • Kinetic energy – energy of motion • Potential energy – energy being stored for possible conversion into kinetic energy • Radiative energy – energy carried by light Kinetic energy • • Kinetic energy = ½ mv 2 m is mass in kg v is velocity in meters/s Remember: a joule has units of kg*m 2/s 2 • How much kinetic energy does a 2 kg rock have if it is thrown at 20 m/s? • Kinetic energy = ½ mv 2 • A) 200 J • B) 400 J • C) 40 J • D) 800 J Answer • KE = ½ * 2 * (20) *(20) = 400 joules Thermal energy (kind of kinetic energy) • Temperature is a measure of the average kinetic energy of the particles • Higher temperature – more kinetic energy, particles moving faster • For examples, air molecules around you are moving at ~600 m/s http: //eo. ucar. edu/webweather/molecules. html Temperature scales • • • In America, we use Fahrenheit Water freezes at 32 degrees F Water boils at 212 degrees F Everywhere else, they use Celsius Water freezes at 0 degrees C Water boils at 100 degrees C In Science • Temperature is measured in Kelvin • Zero Kelvin is absolute zero – nothing moves • Add 273. 15 to the Celsius temperature to get the Kelvin temperature • 273. 15 Kelvin = 0 degrees Celsius   Gravitational Potential Energy • Gravitational Potential Energy released as an object falls depends on its mass, the strength of gravity, and the distance it falls • For example, your gravitational potential energy increases as you go farther up in the air • This is because you hit the ground at a faster speed if you jump from a higher distance • KE + PE = 0 • As kinetic energy increases, potential energy decreases Converting Mass to Energy • What is the most famous formula in the world? E = mc 2 • • m is mass in kilograms c is speed of light in meters/s (3 x 108 m/s) So E is in joules very small amounts of mass may be converted into a very large amount of energy and Who came up with it?  • How much energy can be produced if you can convert 10 kg of material totally into energy? • E = mc 2 • A) 3. 0 x 108 J • B) 3. 0 x 1016 J • C) 9. 0 x 1017 J • D) 9. 0 x 1010 J Answer • • E = 10 kg * (3 x 108 m/s) E = 10* (9 x 1016) J E = 90 x 1016 J E = 9. 0 x 1017 J Mass-Energy • E=mc 2 • So Mass is a form of potential energy • Where is one place where you see mass converted into energy?  Light • Light is a form of energy Light • These are all forms of light – Gamma rays – X-rays – Ultraviolet light – Visible light – Infrared light – Radio waves Light • Can act as a particle • Can also act as a wave Particle aspect • Particles called photons stream from the Sun and can be blocked by your body Photons • Light is quantized • Comes in discrete packets called photons Wave aspect Thomas Young Experiment • http: //micro. magnet. fsu. edu/primer/java/interference/dou bleslit/ Characteristics of waves • velocity = wavelength x frequency • Wavelength = distance • Frequency = cycles per second = hertz For light • • c = wavelength x frequency In vacuum, speed of light stays the same So if wavelength goes up Frequency does down f = frequency λ = wavelength c=λxf Calculations • • • c=λxf So if the wavelength is 1 x 10 -12 m 3 x 108 m/s = 1 x 10 -12 m * f f = 3 x 108 m/s/1 x 10 -12 m f = 3 x 1020 s-1 = 3 x 1020 Hz Calculations • • • c=λxf So if the frequency is 1 x 1015 Hz 3 x 108 m/s = λ * 1 x 1015 Hz λ = 3 x 108 m/s/1 x 1015 Hz λ = 3 x 10 -7 m Energy of light • • • Energy is directly proportional to the frequency E=h*f h = Planck’s constant = 6. 626 x 10 -34 J*s since f = c/λ Energy is inversely proportional to the wavelength E = hc/λ VIBGYOR violet red Higher the frequency, Higher the energy of the photon Higher the wavelength, Lower the energy of the photon ROYGBIV • Red – long wavelength • Violet – short wavelength http: //www. arpansa. gov. au/images/basics/emr. jpg Calculations • What is the energy of a radio wave with a frequency of 1 x 107 Hz? • E=h*f • h = Planck’s constant = 6. 626 x 10 -34 J*s • E = 6. 626 x 10 -34 J*s * 1 x 107 • E = 6. 626 x 10 -27 J Calculations • What is the energy of a gamma ray photon with wavelength of 1 x 10 -15 m • E = hc/λ • h = Planck’s constant = 6. 626 x 10 -34 J*s • E = 6. 626 x 10 -34 J*s * 3 x 108 m/s / 1 x 10 -15 m • E = 1. 99 x 10 -10 J So why are some types of radiation dangerous? • Higher the energy, the farther the photons can penetrate • So gamma and X-rays can pass much more easily into your the body • These high-energy photons can ionize atoms in cells • Ionization means removes electrons from an atom More dangerous When you measure an astronomical body • You measure intensity • Intensity – amount of radiation Matter • Matter is material Atoms • • • Atoms are made up of 3 types of particles Protons – positive charge (+1) Electrons – negative charge (-1) Neutrons – neutral charge (no charge) Protons and Neutrons are found in the nucleus   Elements • http: //www. periodictable. com/ Elements • Different elements have different numbers of protons • The properties of an atom are a function of the electrical charge of its nucleus Charge • If an atom has the same number of electrons and protons, it has a neutral charge • More electrons than protons, negatively charged • More protons than electrons, positive charged • Neutrons have neutral charge so don’t affect the charge of an atom  Definitions • Atomic Number – Number of protons • Atomic Mass – Number of protons and neutrons • U 235 – atomic mass 92 - atomic number • Isotopes – Same number of protons but different numbers of neutrons Molecules • an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds • H 2 O • CO 2  • http: //www. hulu. com/watch/63320/cosmos-thelives-of-the-stars Any Questions? 