Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Arecibo Observatory wikipedia , lookup
Lovell Telescope wikipedia , lookup
Hubble Space Telescope wikipedia , lookup
James Webb Space Telescope wikipedia , lookup
Allen Telescope Array wikipedia , lookup
Spitzer Space Telescope wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Optical telescope wikipedia , lookup
CfA 1.2 m Millimeter-Wave Telescope wikipedia , lookup
No-Name Clickers 4D8AC7 A9EDE4A DEAEB0C E103D23 EEB8560 1E0AF2E6 23210E0C 24A429A9 24E06FAB Copyright © 2010 Pearson Education, Inc. 641AFE8 DE3856B E019A95 E1C0E1C 161E040C 2304FED9 246EB0FA 24DAC53B 25A321A7 Chapter 3 Telescopes Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Telescopes Copyright © 2010 Pearson Education, Inc. Optical Telescopes Images can be formed through reflection or refraction. Reflecting mirror Collect a large amount of light Copyright © 2010 Pearson Education, Inc. Optical Telescopes Refracting lens Copyright © 2010 Pearson Education, Inc. Optical Telescopes Reflecting and refracting telescopes Copyright © 2010 Pearson Education, Inc. Optical Telescopes Modern telescopes are all reflectors: • Light traveling through lens is refracted differently depending on wavelength. • Some light traveling through lens is absorbed. • Large lens can be very heavy, and can only be supported at edge. • Lens needs two optically acceptable surfaces, mirror only needs one. Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Chromatic aberration Question 1 Modern telescopes use mirrors rather than lenses for all of these reasons EXCEPT a) light passing through lenses can be absorbed or scattered. b) large lenses can be very heavy. c) large lenses are more difficult to make. d) mirrors can be computer controlled to improve resolution. e) reflecting telescopes aren’t affected by the atmosphere as much. Question 1 Modern telescopes use mirrors rather than lenses for all of these reasons EXCEPT a) light passing through lenses can be absorbed or scattered. b) large lenses can be very heavy. c) large lenses are more difficult to make. d) mirrors can be computer controlled to improve resolution. e) reflecting telescopes aren’t affected by the atmosphere as much. Reflecting instruments like the KECK telescopes can be made larger, and more capable, than refractors. Optical Telescopes Image acquisition: Chargecoupled devices (CCDs) are electronic devices, can be quickly read out and reset. Copyright © 2010 Pearson Education, Inc. CCD Camera Sensor Copyright © 2010 Pearson Education, Inc. Question 2 An advantage of CCDs over photographic film is a) they don’t require chemical development. b) digital data is easily stored & transmitted. c) CCDs are more light sensitive than film. d) CCD images can be developed faster. e) All of the above are true. Question 2 An advantage of CCDs over photographic film is a) they don’t require chemical development. b) digital data is easily stored & transmitted. c) CCDs are more light sensitive than film. d) CCD images can be developed faster. e) All of the above are true. Optical Telescopes Image processing by computers can sharpen images. Copyright © 2010 Pearson Education, Inc. Ground Based Telescope Copyright © 2010 Pearson Education, Inc. Early HST Copyright © 2010 Pearson Education, Inc. Computer Enhanced HST Copyright © 2010 Pearson Education, Inc. Later HST Copyright © 2010 Pearson Education, Inc. The Hubble Space Telescope The Hubble Space Telescope has several instruments. Copyright © 2010 Pearson Education, Inc. The Hubble Space Telescope Resolution achievable by the Hubble Space Telescope limited by optics and not atmosphere Ground Based – M100 Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Telescope Size Light-gathering power: Improves detail Brightness proportional to square of radius of mirror R=1 The figure, part (b) was taken with a telescope twice the size of (a) Area = p Copyright © 2010 Pearson Education, Inc. 2 R R=2 Telescope Size Multiple telescopes: Mauna Kea Copyright © 2010 Pearson Education, Inc. Telescope Size The VLT (Very Large Telescope), Atacama, Chile Copyright © 2010 Pearson Education, Inc. Question 3 Diffraction is the tendency of light to a) bend around corners and edges. b) separate into its component colors. c) bend through a lens. d) disperse within a prism. e) reflect off a mirror. Question 3 Diffraction is the tendency of light to a) bend around corners and edges. b) separate into its component colors. c) bend through a lens. d) disperse within a prism. e) reflect off a mirror. Diffraction affects all telescopes and limits the sharpness of all images. Telescope Size Resolving power: Ability to distinguish objects that are close together. Resolution is proportional to wavelength and inversely proportional to telescope size. Copyright © 2010 Pearson Education, Inc. Question 4 Resolution is improved by using a) larger telescopes & longer wavelengths. b) infrared light. c) larger telescopes & shorter wavelengths. d) lower frequency light. e) visible light. Question 4 Resolution is improved by using 10’ a) larger telescopes & longer wavelengths. b) infrared light. c) larger telescopes & shorter wavelengths. d) lower frequency light. e) visible light. 1” Diffraction limits resolution; larger telescopes and shorter-wave light produces sharper images. Telescope Size Effect of improving resolution: (a) 10′; (b) 1′; (c) 5″; (d) 1″ Copyright © 2010 Pearson Education, Inc. Question 5 Seeing in astronomy is a measurement of a) the quality of the telescope’s optics. b) the transparency of a telescope’s lens. c) the sharpness of vision of your eyes. d) the image quality due to air stability. e) the sky’s clarity & absence of clouds. Question 5 Seeing in astronomy is a measurement of a) the quality of the telescope’s optics. b) the transparency of a telescope’s lens. c) the sharpness of vision of your eyes. d) the image quality due to air stability. e) the sky’s clarity & absence of clouds. Smeared overall image of star “Good Seeing” occurs when the atmosphere is clear and the air is still. Turbulent air produces “poor seeing,” and fuzzier images. Point images of a star Question 6 Adaptive optics refers to a) making telescopes larger or smaller. b) reducing atmospheric blurring using computer control. c) collecting different kinds of light with one type of telescope. d) using multiple linked telescopes. Question 6 Adaptive optics refers to a) making telescopes larger or smaller. b) reducing atmospheric blurring using computer control. c) collecting different kinds of light with one type of telescope. d) using multiple linked telescopes. Cluster R136 Shaping a mirror in “real time” can dramatically improve resolution. High-Resolution Astronomy Atmospheric blurring due to air movements Copyright © 2010 Pearson Education, Inc. High-Resolution Astronomy Solutions: • Put telescopes on mountaintops, especially in deserts. • Put telescopes in space. • Active (adaptive) optics – control mirrors based on temperature and orientation. Copyright © 2010 Pearson Education, Inc. High-Resolution Astronomy Solutions: • Without active (adaptive) optics a 1m telescope is limited to about 2’ •With active (adaptive) optics the same 1m telescope could approach 0.1”. Copyright © 2010 Pearson Education, Inc. Radio Astronomy Radio telescopes: • Similar to optical reflecting telescopes • Prime focus • Less sensitive to imperfections (due to longer wavelength); can be made very large Copyright © 2010 Pearson Education, Inc. 105 m Green Bank, WV Question 7 Radio dishes are large because a) radio photons don’t carry much energy. b) they are painted white. c) they are cheap to make. d) they are can operate during the day. Question 7 Radio dishes are large in order to a) radio photons don’t carry much energy. b) they are painted white. c) they are cheap to make. d) they are can operate during the day. Resolution is worse with long-wave light, so radio telescopes must be large to compensate. Radio Astronomy Largest radio telescope: 300-m dish at Arecibo Copyright © 2010 Pearson Education, Inc. Question 8 Radio telescopes are useful because a) observations can be made day & night. b) we can see objects that don’t emit visible light. c) radio waves are not blocked by interstellar dust. d) they can be linked to form interferometers. e) All of the above are true. Question 8 Radio telescopes are useful because a) observations can be made day & night. b) we can see objects that don’t emit visible light. c) radio waves are not blocked by interstellar dust. d) they can be linked to form interferometers. e) All of the above are true. The Very Large Array links separate radio telescopes to create much better resolution. 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. Copyright © 2010 Pearson Education, Inc. Centaurus A Radio Astronomy Interferometry: • Combines information from several widely spread radio telescopes as if it came from a single dish. • Resolution will be that of dish whose diameter = largest separation between dishes. Copyright © 2010 Pearson Education, Inc. Radio Astronomy Interferometry requires preserving the phase relationship between waves over the distance between individual telescopes. Copyright © 2010 Pearson Education, Inc. Radio Astronomy Can get radio images whose resolution is close to optical. M51 VLA Copyright © 2010 Pearson Education, Inc. 4 m Kitt Peak Radio Astronomy Interferometry can also be done with visible light, but much harder due to shorter wavelengths. Copyright © 2010 Pearson Education, Inc. CHARA 1 m at Mount Wilson, CA Other Astronomies Infrared radiation can image where visible radiation is blocked; generally can use optical telescope mirrors and lenses. Orion Nebula Copyright © 2010 Pearson Education, Inc. Question 9 Infrared telescopes are very useful for observing a) pulsars & black holes. b) from locations on the ground. c) hot stars & intergalactic gas. d) neutron stars. e) cool stars & star-forming regions. Question 9 Infrared telescopes are very useful for observing a) pulsars & black holes. b) from locations on the ground. c) hot stars & intergalactic gas. d) neutron stars. e) cool stars & star-forming regions. Infrared images of star-forming “nurseries” can reveal objects still shrouded in cocoons of gas and dust. Other Astronomies Infrared telescopes can also be in space or flown on balloons. Copyright © 2010 Pearson Education, Inc. Other Astronomies Ultraviolet images (a)The Cygnus loop supernova remnant (b) M81 Copyright © 2010 Pearson Education, Inc. Other 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. Copyright © 2010 Pearson Education, Inc. Other Astronomies X-ray image of supernova remnant Cassiopeia A Cas A Copyright © 2010 Pearson Education, Inc. Other Astronomies Gamma rays cannot be focused at all; images are therefore coarse. Galaxy 3C279 Copyright © 2010 Pearson Education, Inc. Other Astronomies Much can be learned from observing the same astronomical object at many wavelengths. Here, the Milky Way. Copyright © 2010 Pearson Education, Inc. RADIO Copyright © 2010 Pearson Education, Inc. INFRARED Copyright © 2010 Pearson Education, Inc. VISIBLE Copyright © 2010 Pearson Education, Inc. X-RAY Copyright © 2010 Pearson Education, Inc. GAMMA-RAY Copyright © 2010 Pearson Education, Inc. Question 10 The Hubble Space Telescope (HST) offers sharper images than ground telescopes primarily because a) HST is closer to planets & stars. b) HST uses a larger primary mirror. c) it gathers X-ray light. d) HST orbits above the atmosphere. e) it stays on the nighttime side of Earth. Question 10 The Hubble Space Telescope (HST) offers sharper images than ground telescopes primarily because a) HST is closer to planets & stars. b) HST uses a larger primary mirror. c) it gathers X-ray light. d) HST orbits above the atmosphere. e) it stays on the nighttime side of Earth. HST orbits less than 400 miles above Earth – not much closer to stars & planets! But it can gather UV, visible, and IR light, unaffected by Earth’s atmosphere. Example Exam Questions One advantage of the Hubble Space telescope over ground based ones is that A. it can better focus x-ray images. B. in orbit, it can operate close to its diffraction limit at visible wavelengths. C. it is larger than any Earth-based scopes. D. its adaptive optics controls atmospheric blurring better. E. it can make better observations of the ozone layer. What problem does adaptive optics correct? A. defects in the optics of the telescope, such as the original Hubble mirror B. turbulence in the earth's atmosphere which creates twinkling C. the opacity of the earth's atmosphere to some wavelengths of light D. chromatic aberration due to use of only a single lens objective E. the light pollution of urban areas An emission line results from an electron falling from a higher to lower energy orbital around its atomic nucleus. A. True B. False The angular resolution of an 8 inch diameter telescope is _______ greater than that of a 2 inch diameter telescope. A. 2× B. 4× C. 8× D. 9× E. 16× The larger the red shift, the faster the distant galaxy is rushing toward us. A. True B. False Changing the electric field will have no effect on the magnetic fields of a body. A. True B. False Doubling the temperature of a black body will double the total energy it radiates. A. True B. False