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Astronomy 1020 Stellar Astronomy Spring_2016 Day-13
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Course Announcements 1 st “Hot Topics in Science”: Tues. 2/23 6-8pm E106B Topics this semester are: Human Cloning, Environmental Toxicology, & Fracking … includes pizza. Dark Night Observing: Mon. 2/29 & Wed. 3/2 – 7:30pm at the APSU Observatory Exam-2 – Fri. 3/4 Chapters 5 & 6 Smartworks Chapters 5 & 6: Due Fri. 3/4 Spring Break Mar. 5-13 (Sat.-Sun.) APSU Research and Creativity Forum April 15, 2016 Abstracts are due: 4:00pm Fri., March 18 Feb. 29 – Last day to drop with an automatic “W” Apr. 1 – Last day to drop a class with W, F, FA
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Course Announcements Colloquium on Friday, Feb. 19. @3:00pm B310 Dr. David James, Cerro-Tololo InterAmerican Obs. Open Clusters, Stellar Evolution and Calibrating the Ages of Stars: Blanco 1 Galactic open clusters are laboratories, provided by nature, for us to study stellar evolution. Using 1m-, 4m- and 8m-class telescopes, I will show how spectroscopic and photometric observations of solar-type stars in open clusters allow us to establish a stellar chronometer, and create an age-ranking system for an ensemble of nearby, well-studied clusters. With the aid of new observations of Blanco 1, an high-Galactic latitude, Pleiades-age cluster, I will show how deriving stellar age must be based upon very high quality observational data and a diverse range of stellar models.
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Accelerating charges (think electrons and protons) produce light – electromagnetic radiation! But, where does light actually come from?
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Photons Light also behaves as a particle. Photon: particle of light. Photons carry energy and can have different amounts of energy. Photons with high energy = light with high frequency. Photons with low energy = light with low frequency. Atoms can absorb or emit photons.
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Einstein (Nobel Prize) In 1905 Einstein calculated the energy of a particle of light (photon) and proposed the photoelectric effect. E photon = hc/ = h e- photon
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Light moves at 300,000 km/s in a vacuum. First measured by Rømer when observing Jupiter’s moons. Speed is slower in other materials, e.g., glass.
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Wavelength ( ): length between crests. Amplitude: height. Frequency (f): number of waves that pass by each second. Period (P): time to complete one cycle.
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A long wavelength means low frequency. A short wavelength means high frequency. The speed of light, c, is constant.
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Light is a wave of combined electricity and magnetism, called an electromagnetic wave. Changing electric and magnetic fields create a self-sustaining electromagnetic wave.
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Maxwell – EM Field Theory Scottish physicist James Clerk Maxwell showed mathematically in the 1860s that light must be a combination of electric and magnetic fields.
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Knowing the speed of light and one other variable, either the wavelength or frequency of the light in question, you can find the remaining quantity. Example: Find the wavelength of the light wave coming from a radio station broadcasting on 770 AM: MATH TOOLS 5.1
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Like the flavors of Ice cream – they each provide us with different information. EM Spectrum But what do you get when you put all the flavors (light) together?
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Lecture Tutorial EM Spectrum: (pg. 47) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.
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