lecture06 - Astronomy Picture of the Day An X-ray image of...

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Unformatted text preview: Astronomy Picture of the Day An X-ray image of young stars in the Orion Nebula, from the Chandra X-ray Observatory Homework For the homework assignments, please write your discussion section time at the top of the page: Isaac Newton 1:00 Section Telescopes: Historical Overview The first real astronomical telescope was built by Galileo Galilei in 1609 Discoveries included the moons of Jupiter, and the phases of Venus Newton's Reflector Newton realized that a reflecting telescope would not suffer from chromatic aberration Built the first reflector (1672) The great refractors Lick Observatory 36" Refractor 1888 (University of California) Mt. Hamilton, CA Yerkes Observatory 40" Refractor 1897 (U. of Chicago) Williams Bay, WI The first big reflectors George Ellery Hale pioneered the construction of giant reflecting telescopes in the early 1900s Mt. Wilson 60" Reflector 1908 Near Pasadena, CA The Mt. Wilson 100" Telescope Designed by Hale and completed in 1917 Later used by Hubble to discover the expansion of the Universe The Palomar 200" Telescope Hale's greatest project: the 200 inch telescope at Mt. Palomar (northern San Diego county), completed in 1948 Still a valuable and productive research telescope today Lick Observatory 3m Shane Telescope University of California 1959 Kitt Peak National Observatory 4m Mayall Telescope Arizona, 1970 Multiple Mirror Telescope 4.5 m effective aperture Smithsonian Institution & University of Arizona, 1979 The Keck Observatory Designed by Jerry Nelson (then at Berkeley, now at UCSC) Segmented mirror design to make much larger telescopes than were previously possible Two 10-meter telescopes The Keck Observatory W. M. Keck Foundation funded the construction of the Observatory with $140 million in grants Located on Mauna Kea, Hawaii Began operations in 1993 Operated by the UC System and Caltech Mauna Kea Observatories Name Keck Hobby-Eberly Subaru Very Large Telescope Gemini North Gemini South MMT Magellan Bolshoi Palomar Hale Gran Telescopio Canarias LBT Observatory Southern African Large Telescope Number of telescopes 2 1 1 4 1 1 1 2 1 1 1 1 1 Primary mirror diameter 9.8 m 9.2 m 8.3 m 8.2 m 8.1 m 8.1 m 6.5 m 6.5 m 6m 5m 10.4 m 2 8.4 m 11 m Location Hawaii Texas Hawaii Chile Hawaii Chile Arizona Chile Russia California Canary Islands Arizona South Africa The largest optical/ infrared telescopes Currently in operation Under construction The Thirty Meter Telescope (2016) being designed by the UC System, Caltech, and Canada The Thirty-Meter Mirror The LSST Observatory Large Synoptic Survey Telescope 8.4 meter telescope with a very large field of view It will be used to map the entire southern sky repeatedly with very deep images UCI is a partner in the project In space: Ideal, flat wavefronts Adaptive Optics: Correcting for Atmospheric Blurring In the earth's atmosphere: Turbulence causes the wavefronts to become "crumpled", which causes images to become blurred If we can measure the wavefront distortions, we can correct them to obtain an un-blurred image Adaptive Optics Crumpled wavefronts after transmission through the earth's atmosphere Reflected light waves now produce a much sharper image, corrected for atmospheric blurring Reflect the light off of a deformable mirror, that has the exact shape needed to "flatten" out the wavefronts Because the properties of atmospheric turbulence change rapidly, the shape of the deformable mirror must be updated more than 100 times per second to match the wavefront distortions at each instant! Secondary mirror Adaptive Optics Telescope Deformable mirror Light is collected by the telescope, then reflected off of the deformable mirror and into a camera or spectrograph Light from a very bright star must be observed to measure the wavefront distortions Primary mirror Camera Adaptive optics system Adaptive Optics Adaptive optics can correct the blurring effects of atmospheric seeing, with some limitations: Works at infrared wavelengths, not visible wavelengths (yet) Works only over a very small field of view Keck image without adaptive correction Keck image with adaptive correction Atmospheric transmission of light Ground vs. Space Observing Advantages of observing from space: Can observe Gamma rays, X-rays, ultraviolet, infrared wavelengths that can't be observed from the ground No atmosphere to get in the way- no clouds, no city lights, no atmospheric blurring Expensive to develop and launch telescopes into orbit Difficult or impossible to upgrade or repair hardware Disadvantages of space observing: The Hubble Space Telescope Idea for a large telescope in space first conceived by Lyman Spitzer in 1936 Planned and developed by NASA in the 1970s and 1980s Scheduled launch was delayed after the Challenger disaster in 1986 Finally launched in 1990, but with a defective mirror! The mirror was manufactured with the wrong shape It produced aberrated, out-of-focus images The Hubble Space Telescope A servicing mission in 1993 installed corrective optics and new cameras, and solved the mirror problem Ground-based image Hubble image before repair Hubble image after repair Before repair After repair About Hubble It is a 2.4 meter reflecting telescope It contains cameras that can observe ultraviolet, visible, and near-infrared light 4 shuttle-based servicing missions have added new cameras, solar panels, and gyroscopes since it was launched 2 of the primary instruments have failed in the past 3 years, and 2 new instruments are built and ready to be installed Hubble Images For more pictures and information see www.hubblesite.org Hubble's Future Hubble has 6 gyroscopes to control its orientation Needs at least 2 to function Currently, only 3 working gyros remain Without repair, Hubble will likely cease functioning within the next few years 2 new Hubble cameras are built and ready to fly Servicing mission is scheduled for 2008 Radio astronomy Radio telescopes use large collecting dishes to collect radio waves, and focus them on an antenna The signals are reconstructed electronically to form images The Green Bank Telescope, West Virginia (100-meter diameter) National Radio Astronomy Observatory The Very Large Array Interferometry: combining the signals from multiple, widely separated telescopes, in order to achieve higher angular resolution Image courtesy of NRAO/AUI Interferometry A single radio dish can produce images with an angular resolution (in arcseconds) of (2.5 105) / D Radio waves aren't affected by atmospheric blurring If an array of radio telescopes are used together as an interferometer, we can create images where the resolution is given by (2.5 105) / L, where L is the largest baseline in the array ...
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lecture06 - Astronomy Picture of the Day An X-ray image of...

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