a100L12 - Astronomy 100: Descriptive Astronomy Assistant...

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Unformatted text preview: Astronomy 100: Descriptive Astronomy Assistant Professor Scott Severson Department of Physics and Astronomy Office: Darwin 300L (707) 664-2376 [email protected] Class websites: http://www.phys-astro.sonoma.edu/people/faculty/severson/a100 https://webct6.sonoma.edu/webct/logon/306004752001 A100 Fall 2009 Asst. Prof. Scott Severson 1 Astronomy 100 Course Outline Cosmic Perspective Week Tuesday Thursday Chapter Reading 1 Aug 27 2 Sep 01 Sep 03 1.1, 1.2 3 Sep 08 Sep 10 2.1-2.3 4 Sep 15 Sep 17 3.1, 3.3-3.5, 4 5 Sep 22 Furlough 5 6 Sep 29 Oct 01 6.1-6.3 7 Oct 06 Oct 08 7.1-7.2, 10.1, 11.1-11.2 8 Oct 13 Furlough 12, 13.1 9 Oct 20 Oct 22 14.1-14.2 10 Oct 27 Oct 29 15 11 Nov 03 Nov 05 16.1, 17.1-17.3 12 Nov 10 Nov 12 S3.3, 18.1-18.3 13 Nov 17 Nov 19 19.1,19.2,19.4 14 Furlough 15 Dec 01 Dec 03 20, 21.1 16 Dec 08 Dec 10 22, 23.1-23.2 17 Dec 17 HW Due (Thursday) Quizzes (Thursday) Intro 1 1 (Chapters 1-2) 2+3 4 5 6 + Review 2 (Chapters 3-6) 3 (Chapters 7-13) 4 (Chapters 14-18+S3.3) 7 Chs. 22 & 23 X-Cr. Review Due by Final 5 (Chapters 19-21) Cumulative Final Thursday, December 17 5:00 p.m. - 6:50 p.m. Quiz Today-Need NCS Scantron, #2 pencil and Student ID # 2 A100 Fall 2009 Asst. Prof. Scott Severson Public Viewing Nights at SSU Observatory A100 Fall 2009 Asst. Prof. Scott Severson 3 Public Viewing Nights Bring a flashlight and dress warmly Viewing will be cancelled for bad weather or cloud cover (707) 664-2267 A100 Fall 2009 Asst. Prof. Scott Severson 4 Reminder: Observing Assignment • 5% of grade, do not give these points away! – Submit a one-page, typed account of your experience observing with a telescope during the semester. Include the date, time, place, a description of the telescope(s) and what you observed. • Note: Please prepare to spend about 1 hour at the Observatory during the open times • A flashlight can be useful for the walk. • Viewing will be cancelled for bad weather or cloud cover • Call ahead if you are uncertain (707) 664-2267 • Dress warmly. A100 Fall 2009 Asst. Prof. Scott Severson 6 Another Extra-Credit Talk Opportunity • This Saturday, October 10th 12:00-1:00 pm • Salazar Hall 2020 • I will give a Presentation on Adaptive Optics for Parent and Family Weekend A100 Fall 2009 Asst. Prof. Scott Severson 7 How does light tell us the speed of a distant object? The Doppler Effect Asst. Prof. Scott Severson The Doppler Effect Asst. Prof. Scott Severson Explaining the Doppler Effect Asst. Prof. Scott Severson Same for Light Asst. Prof. Scott Severson Measuring Velocity Movement away from us shifts the light to longer wavelengths = redshift Movement towards us shifts the light to shorter wavelengths = blueshift Asst. Prof. Scott Severson How do we know what we know? • The answer, Light! (Electromagnetic Radiation) • What can we determine with light? – Luminosity (Brightness) – Temperature – Speed – Rotation rate – Composition – And much more, such as … – Position, distance, mass, age … Asst. Prof. Scott Severson Chapter 6 Telescopes: Portals of Discovery 10/06/2009 Asst. Prof. Scott Severson Refraction • Refraction is the bending of light when it passes from one substance into another • Your eye uses refraction to focus light 10/06/2009 Asst. Prof. Scott Severson Recording Images Digital cameras detect light with chargecoupled devices (CCDs) The inventors of the CCD won the 2009 Nobel Prize in Physics • The CCDs in digital cameras are similar to those used in modern telescopes 10/06/2009 Asst. Prof. Scott Severson What are the two most important properties of a telescope? 1. Light-collecting area: Telescopes with a larger collecting area can gather a greater amount of light in a shorter time. 2. Angular resolution: Telescopes that are larger are capable of taking images with greater detail. 10/06/2009 Asst. Prof. Scott Severson Angular Resolution • The minimum angular separation that the telescope can distinguish. 10/06/2009 Asst. Prof. Scott Severson Low High Light-collecting area Note: Astronomers want better angular resolution, magnification doesn’t matter! Low High Angular resolution What are the two basic designs of telescopes? • Refracting telescope: Focuses light with lenses • Reflecting telescope: Focuses light with mirrors 10/06/2009 Asst. Prof. Scott Severson Refracting Telescope • Refracting telescopes need to be very long, with large, heavy lenses 10/06/2009 Asst. Prof. Scott Severson Reflecting Telescope • Reflecting telescopes can have much greater diameters • Most modern telescopes are reflectors 10/06/2009 Asst. Prof. Scott Severson Mirrors in Reflecting Telescopes Twin Keck telescopes on Mauna Kea in Hawaii Segmented 10-meter mirror of a Keck telescope 10/06/2009 Asst. Prof. Scott Severson Imaging • Astronomical detectors generally record only one color of light at a time • Several images must be combined to make full-color pictures 10/06/2009 Asst. Prof. Scott Severson Imaging • Astronomical detectors can record forms of light our eyes can’t see • Color is sometimes used to represent different energies of nonvisible light 10/06/2009 Asst. Prof. Scott Severson Want to buy your own telescope? • Consider buying binoculars first (e.g. 7x35) - you get much more for the same money. • Ignore magnification (sales pitch!) • Notice: aperture size, optical quality, portability. • Consumer research: Astronomy, Sky & Telescope, Mercury magazines. Astronomy clubs. 10/06/2009 Asst. Prof. Scott Severson How does Earth’s atmosphere affect ground-based observations? • The best ground-based sites for astronomical observing are – Calm (not too windy) – High (less atmosphere to see through) – Dark (far from city lights) – Dry (few cloudy nights) 10/06/2009 Summit of Mauna Kea, Hawaii Asst. Prof. Scott Severson Twinkling and Turbulence Star viewed with groundbased telescope Same star viewed with Hubble Space Telescope Turbulent air flow in Earth’s atmosphere distorts our view, causing stars to appear to twinkle 10/06/2009 Asst. Prof. Scott Severson Adaptive Optics Without adaptive optics With adaptive optics Rapidly changing the shape of a telescope’s mirror compensates for some of the effects of turbulence in our atmosphere. 10/06/2009 Asst. Prof. Scott Severson Transmission in Atmosphere • Only radio and visible light pass easily through Earth’s atmosphere • We need telescopes in space to observe other forms 10/06/2009 Asst. Prof. Scott Severson Radio Telescopes • A radio telescope is like a giant mirror that reflects radio waves to a focus 10/06/2009 Asst. Prof. Scott Severson IR & UV Telescopes SOFIA Spitzer • Infrared and ultraviolet-light telescopes operate like visible-light telescopes but need to be above atmosphere to see all IR and UV wavelengths 10/06/2009 Asst. Prof. Scott Severson X-Ray Telescopes • X-ray telescopes also need to be above the atmosphere Chandra 10/06/2009 Asst. Prof. Scott Severson Gamma Ray Telescopes • Gamma ray telescopes also need to be in space • Focusing gamma rays is extremely difficult Compton Observatory 10/06/2009 Asst. Prof. Scott Severson Nonvisible Light • Most light is invisible to the human eye. • Special detectors/receivers can record such light. • Digital images are reconstructed using falsecolor coding so that we can see this light. Chandra X-ray image of the Center of the Milky Way Galaxy 10/06/2009 Asst. Prof. Scott Severson ...
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This note was uploaded on 11/08/2009 for the course ASTR 3048 taught by Professor Severson during the Fall '09 term at Sonoma.

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