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Delve into the advancements in telescope technology, from optical instruments to space telescopes, covering radio astronomy and interferometry. Discover how these tools revolutionize our understanding of the cosmos.
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INTRO In astronomy, observation usually precedes theory. Ex/ New solar syst.; acc. univ. Telescopes have grown in size and complexity and now cover the entire EM spectrum
I. Optical Telescopes A. Telescope: A “light bucket” used to capture incoming photons & concentrate them into a focused beam for analysis.
B. Types of Telescopes • Refractors: A glass lens bends (refracts) incoming light rays to a focus. Eyepiecemagnifies.
2. Reflectors: A curved mirror (the primary mirror) reflects incoming rays to a focus. Eyepiece magnifies.
D. Reflector Design 1.Newtonian: Secondary mirror reflects light to side eyepiece. Subcategory: Dobsonian
2. Cassegrain: Secondary mirror reflects light back thru a hole in the primary mirror.
II. Telescope Size & Resolution A. Light-gathering power: Larger collecting area - brighter image. 1. Brightness ~ Diameter2 Ex/ 10”apertureis 25 x brighter than 2”aperture (or 25 x faster exposure) 2. Largest: VLT in Chile (16 m) Keck I & II in Hawaii (14 m) TMT (2018); Giant Magellan Telescope (2016)
Ch. 5 Example Problem How long would it take a telescope with a 9” aperture to produce the same image that a 3” scope can make in 45 min.?
B. Resolving Power: Ability to make sharp images of faint objects or to distinguish between 2 adjacent objects in the sky.** aka Angular Resolution
C. Atmospheric Blurring 1. Hinders ground-based scopes Ex/ “twinkling” stars 2. Best locations- high, dry, & dark Ex/ Arizona; Chile; Hawaii 3. Another solution - space. Ex/Hubble (1993) - 20 x better than previous best
D. Adaptive Optics: Mirror changes shape to compensate for atmosphere. a. Lasers pierce atmosphere, create “artificial star” b. Some now sharper than Hubble! Ex/ Subaru (IR), Keck, VLT
III. Radio Astronomy & Interferometry A. Radio telescopes 1. Only since the‘50’s Grote 2. Pioneers- Karl Jansky, Reber 3. Curved metal dish focuses radio waves to a focal point. 4. Instruments located at the prime focus.
B. Large Size Necessary 1. Signals are faint 2. Long wavelength radio diffracts greatly - poor resolution a. Surface doesn’t have to be smooth like optical scopes b. It’s easy to make them large Ex/ Largest: Arecibo– 1000 ft. wide!(305 m)
C. Value of Radio Astronomy 1. 24 / 7 2. Thru clouds, rain, snow 3. Objects visibly dim may be strong radio sources. Ex/ *4. Radio penetrates dust in space. Ex/ Center of our galaxy
D. INTERFEROMETRY 1. Interferometer: Data from 2 or more scopes combined. Ex/ VLA in N. Mex (27 dishes) ATA (2007)- 42 dishes ALMA (2012) - 66 Square Kilometer Array (2020) - 150 dishes 2. Behaves like a single dish whose diameter is the distance between dishes. Ex/ Compound eye
A. Microwave satellites IV. Space Telescopes • COBE (1990’s) - Measured the cosmic microwave background Proof of the Big Bang! 2. Planck (2009)
B. INFRARED Astronomy 1. Long wavelength IR penetrates clouds in space. 2. Good for star or planet-forming clouds of warm dust & gas. 3. Mountaintops Ex/ Subaru 4. Airplanes Ex/ SOFIA 5. Or Space Ex/ Spitzer James Webb Space Tel. (2018)
James Webb Space Telescope“Successor to the Hubble” ~ 6.5 m mirror Launch in 2018 (?) Infrared
C. Visible light: 1.Hubble Space Telescope 2. Spherical aberration corrected 1993 3. Final repair mission 2009