PHY 2049: Chapter 36 20Gemini Telescope w/ Adaptive OpticsGemini = “twins”¾ D = 8.1 m¾ Hawaii, Chile¾ Both outfitted with adaptive opticsPHY 2049: Chapter 36 21Adaptive Optics in Infrared (936 nm)9× better!PHY 2049: Chapter 36 22Pluto and Its MoonPluto and its moon Charon (0.083″ resolution)PHY 2049: Chapter 36 23Gemini North Images (7x Improvement)Resolution = 0.6” Resolution = 0.09”PHY 2049: Chapter 36 24Keck Adaptive Optics Images of UranusPHY 2049: Chapter 36 25Keck Star Image with Adaptive OpticsPHY 2049: Chapter 36 26InterferometryÎ Basic interferometer discussed in Chap. 35 (p. 978) Michaelson interferometer Change in path lengths causes interference Adjusted so that waves lined up initiallyÎ Insert material of thickness d in path 1 Before: # waves = Ninit= 2d/λ After: # waves = Nfinal= 2dn/λ # “fringes” = (2d/λ) (n − 1)Î Technique used for very precise lengthmeasurements Also used to prove that there is no “ether”carrying E&M wavesPHY 2049: Chapter 36 27Interferometry: Multiple RadiotelescopesÎCombine information from multiple radiotelescopes Atomic clocks to keep time information (time = phase) Each telescope records signals on tape with time stamp Tapes brought to “correlator” to build synthetic imageÎSingle telescope resolution Δθ = 1.22λ/D (D = diameter of dish or mirror)ÎTwo telescope resolution Δθ ~ λ/D (D = distance between telescopes)ÎSpectacular improvement in resolution Diameter of dish ~ 20 – 50m Distance between two dishes ~ 12,000 km (diameter of earth) Improvement is factor of ~ 200,000 – 500,000PHY 2049: Chapter 36 28Example of InterferometryÎTwo radiotelescopes D = 50m Separated by diameter of earth = 12,700 km 6 GHz radio waves, λ = 5 cmÎSingle telescope resolution Δθ = 1.22λ/D = 1.22 × 0.05 / 50 = 0.0012 rad = 200”ÎTwo telescope resolution Δθ ~ λ/D = 0.05 / 1.27 × 107= 4 × 10-9rad = 0.0004” Compare to 0.25” for best earthbound telescope, 0.06” for HubblePHY 2049: Chapter 36 29Radiotelescope (Mauna Kea)PHY 2049: Chapter 36 30Spaced Based Interferometry: JapanVSOP (VLBI Space Observatory Programme)http://www.vsop.isas.ac.jp/PHY 2049: Chapter 36 31VLBI Using Satellite (λ = 6cm)Quasar: VLBI ground only Quasar: VLBI ground plus spacePHY 2049: Chapter 36 32VLBI Using Satellite (λ = 17cm)Quasar: VLBI ground only Quasar: VLBI ground plus spaceSpace based ~ 30,000 km
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