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Ch. 3 TELESCOPES.

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Presentation on theme: "Ch. 3 TELESCOPES."— Presentation transcript:

1 Ch. 3 TELESCOPES

2 INTRO observation usually precedes theory.
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

3 I. Optical Telescopes A. Telescope: A “light bucket” used to capture incoming photons & concentrate them into a focused beam for analysis.

4 B. Types of Telescopes Refractors: A glass lens bends (refracts) incoming light rays to a focus. Eyepiece magnifies.

5

6 Yerkes Observatory

7 2. Reflectors: A curved mirror (the primary mirror) reflects incoming rays to a focus.
Eyepiece magnifies.

8 D. Reflector Design 1.Newtonian: Secondary mirror reflects light to
side eyepiece. Subcategory: Dobsonian

9 2. Cassegrain: Secondary mirror reflects light back thru a hole in the primary mirror.

10 II. Telescope Size & Resolution
A. Light-gathering power: Larger collecting area - brighter image. 1. Brightness ~ Diameter2 Ex/ 10” aperture is 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)

11 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.?

12 The VLT

13

14 GranTeCan

15 Canary Islands

16 GMT: m mirrors

17

18

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20 B. Resolving Power: Ability to make sharp images of faint objects or to distinguish between 2 adjacent objects in the sky.** aka Angular Resolution

21 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

22 Pic Du Midi, French Pyrenees

23 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

24

25 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.

26 B. Large Size Necessary 1. Signals are faint 2
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)

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32 Green Bank, West Virginia - largest moveable radio dish

33 C. Value of Radio Astronomy 1. 24 / 7 2. Thru clouds, rain, snow 3
C. Value of Radio Astronomy / 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

34 1. Interferometer: Data from 2 or more scopes combined.
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

35 Allen Telescope Array (so far..)

36 Single Dish of the VLA

37 VLA in New Mexico

38 ALMA

39

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42 Largest Telescopes 2015 Refractor (lens) Yerkes Obs. 1 m Single mirror
GranTeCan Keck I & II 10.4 m 10 m Optical interferometer VLT Keck 16.4 m 14.6 m Single radio dish Arecibo 305 m Array (1 location) ATA (phase 1) VLA ALMA 42 dishes 27 dishes 66 dishes

43 A. Microwave satellites
IV. Space Telescopes A. Microwave satellites COBE (1990’s) - Measured the cosmic microwave background Proof of the Big Bang! 2. Planck (2009)

44 B. INFRARED Astronomy 1. Long wavelength IR penetrates clouds in space
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)

45 SUBARU

46 SOFIA

47 James Webb Space Telescope “Successor to the Hubble”
mirror Launch in 2018 (?) Infrared

48

49

50 C. Visible light: 1.Hubble Space Telescope 2. Spherical
aberration corrected 1993 3. Final repair mission 2009

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52 D. ULTRAVIOLET Astronomy 1. Used for hot stars
2. Done by high-altitude balloons 3. Or satellites Ex/ Galex, Hubble E. X-RAY Astronomy 1. No ground - only satellites 2. Used 4 violent events (black holes) 3. Special design (difficult to focus) Ex/ Chandra (1990’s)

53 X-ray detectors

54 F. GAMMA RAY Astronomy 1. Can’t be focused 2
F. GAMMA RAY Astronomy 1. Can’t be focused 2. Counted by special detectors 3. Scarce (~ 1 detection per day) 4. Occasional “bursts”, or GRB’s a. Hypernova – really massive star explodes / black hole formed b. Colliding binary neutron stars 5. Compton Gamma Ray Observatory (1990’s )

55 6. SWIFT (2004)

56 7. Fermi Gamma-Ray Space Telescope

57

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