Astronomy a beginners guide to the universe 8th CHaisson mcmillan chapter 03

Astronomy A BEGINNER’S GUIDE TO THE UNIVERSE EIGHTH EDITION CHAPTER Telescopes Lecture Presentation © 2017 Pearson Education, Inc Chapter Telescopes © 2017 Pearson Education, Inc Units of Chapter • • • • • • Optical Telescopes Telescope Size High-Resolution Astronomy Radio Astronomy Space-Based Astronomy Summary of Chapter © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Images can be formed through reflection or refraction • Reflecting mirror © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Refracting lens © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Image formation © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Reflecting and refracting telescopes © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Modern telescopes are all reflectors: – – – – Light traveling through lens is refracted differently depending on wavelength Some light traveling through lens is absorbed A large lens can be very heavy and can only be supported at the edge A lens needs two optically acceptable surfaces, but a mirror needs only one © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Types of reflecting telescopes © 2017 Pearson Education, Inc 3.1 Optical Telescopes • Details of the Keck telescope © 2017 Pearson Education, Inc 3.4 Radio Astronomy • • Longer wavelength means poorer angular resolution Advantages of radio astronomy: – – – Can observe 24 hours a day Clouds, rain, and snow don’t interfere Observations at an entirely different frequency get totally different information © 2017 Pearson Education, Inc 3.4 Radio Astronomy • Interferometry: – Combines information from several widely separated radio telescopes as if it came from a single dish – Resolution will be that of a dish whose diameter = largest separation between dishes © 2017 Pearson Education, Inc 3.4 Radio Astronomy • Interferometry requires preserving the phase relationship between waves over the distance between individual telescopes © 2017 Pearson Education, Inc 3.4 Radio Astronomy • These telescopes can get radio images whose resolution is close to optical © 2017 Pearson Education, Inc 3.4 Radio Astronomy • Interferometry can also be done with visible light, but it is much harder due to shorter wavelengths © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • Infrared radiation can image where visible radiation is blocked by interstellar matter or atmospheric particles © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • Infrared telescopes can also be in space or flown on balloons © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • Ultraviolet images (a) (b) © 2017 Pearson Education, Inc The Cygnus loop supernova remnant M81 3.5 Space-Based Astronomies • X-rays and gamma rays will not reflect off mirrors as other wavelengths do; need new techniques • X-rays will reflect at a very shallow angle and can therefore be focused © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • X-ray image of supernova remnant Cassiopeia A © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • Gamma rays are the most high-energy radiation we can detect This supernova remnant would be nearly invisible without the Fermi satellite and its gamma-ray detector © 2017 Pearson Education, Inc 3.5 Space-Based Astronomies • Much can be learned from observing the same astronomical object at many wavelengths Here, the Milky Way © 2017 Pearson Education, Inc Summary of Chapter • • • • • • • Refracting telescopes make images with a lens Reflecting telescopes make images with a mirror Modern research telescopes are all reflectors CCDs are used for data collection Data can be formed into images, analyzed spectroscopically, or used to measure intensity Large telescopes gather much more light, allowing study of very faint sources Large telescopes also have better resolution © 2017 Pearson Education, Inc Summary of Chapter 3, cont • • • • • Resolution of ground-based optical telescopes is limited by atmospheric effects Resolution of radio or space-based telescopes is limited by diffraction Active and adaptive optics can minimize atmospheric effects Radio telescopes need large collection area; diffraction is limited Interferometry can greatly improve resolution © 2017 Pearson Education, Inc Summary of Chapter 3, cont • • • • Infrared and ultraviolet telescopes are similar to optical Ultraviolet telescopes must be above the atmosphere X-rays can be focused, but very differently from visible light Gamma rays can be detected This must be done from space © 2017 Pearson Education, Inc .. .Chapter Telescopes © 2017 Pearson Education, Inc Units of Chapter • • • • • • Optical Telescopes Telescope Size High-Resolution Astronomy Radio Astronomy Space-Based Astronomy Summary of Chapter. .. Education, Inc 3.4 Radio Astronomy • Largest radio telescope: 300-m dish at Arecibo © 2017 Pearson Education, Inc 3.4 Radio Astronomy • • Longer wavelength means poorer angular resolution Advantages... individual telescopes © 2017 Pearson Education, Inc 3.4 Radio Astronomy • These telescopes can get radio images whose resolution is close to optical © 2017 Pearson Education, Inc 3.4 Radio Astronomy