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Astronomical Observations What Wavelengths To Use?

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Presentation on theme: "Astronomical Observations What Wavelengths To Use?"— Presentation transcript:

1 Astronomical Observations What Wavelengths To Use?
Type Atmosphere Radio Waves No effect Microwaves Mostly blocked Infrared Blocked Visible Light Slight blurring Ultraviolet Blocked X-rays Blocked Gamma Rays Blocked

2 Lenses and Light Lens Image Incoming Rays Outgoing Rays Focal Plane
Light waves going through a lens are bent They converge on the focal plane of the lens An image forms on the focal plane The greater the distance to the focal plane, the bigger the image

3 Lenses and Light Focal Plane Lens Object Eye
Working in reverse, a lens can magnify a small object making it look big and far away The closer the focal plane is, the bigger the image You can also magnify an image

4 A Basic Refracting Telescope
Focal Plane Image of Point 2 From Point Source 1 Eye Image of Point 1 From Point Source 2 Eyepiece Objective Lens Two lenses together make a telescope Changing the eyepiece changes the magnification The amount of light gathered depends on the size of the objective

5 What To Do With The Light
Prism View directly CCD camera Spectrometer From the Telescope The Spectrometer Uses prism or (more likely) diffraction grating Breaks light into different colors/wavelengths/frequencies

6 CCD Detector

7 Mirrors and Light Mirror Incoming Rays Focal Plane Reflected Rays
Mirrors can also create images - in some ways, better than lenses Large telescopes are always reflectors

8 The Largest Optical Telescopes in the World
Gran Telescopio Canarias 10.6 m diameter Keck 1 and Keck 2 10 m diameter each

9 What Makes a Good Telescope
The bigger the diameter, the better Bigger diameter = more light gathering power Bigger diameter = less diffraction (blurring) Avoid atmospheric distortion and light pollution Space Mountains Away from light pollution Magnification is not the main issue Eyepiece changes magnification Outside the solar system, you can never decrease the distance Too far away Q. 21: Why is the Hubble Telescope in Space?

10 Space Based Visible Light Telescopes
Gaia Several advantages of going to space No atmospheric distortion No light pollution Can see infrared/ultraviolet Hubble Telescope Brite Constellation NEOSSat

11 Active Optics Incoming Rays Focal Plane Reflected Rays Mirror
It is hard to make large mirrors It is easier to make several small mirrors You can use motors & computer to line them up

12 Adaptive Optics Focal Plane Mirror
Light gets distorted by the atmosphere It ends up imperfect at the telescope This ruins the focus, blurring the image

13 Adaptive Optics Focal Plane Mirror
Computers can respond to imperfections Motors can adjust the mirrors This fixes the blurred image

14 What Wavelengths to Use?
Type Atmosphere Radio Waves No effect Microwaves Mostly blocked Infrared Blocked Visible Light Slight blurring Ultraviolet Blocked X-rays Blocked Gamma Rays Blocked Q. 22: The Other Earth-based Observations

15 Radio Telescopes Antenna Incoming Radio Waves Reflected Radio Waves
Reflector Always use a radio reflector (like a mirror) High precision reflector is not necessary because radio waves are very long Most radio sources are quite weak

16 Robert C. Byrd Green Bank Telescope, about 100 m
Radio Telescopes Robert C. Byrd Green Bank Telescope, about 100 m FAST Telescope, 500 m

17 Radio Interferometry No atmospheric blurring Background Problem
Huge diffraction limit problem (about 1o) Signal can be combined from multiple radio telescopes Effective size is distance between telescopes Effective resolution better than optical

18 Radio Interferometry Very Large Array

19 Very Long Baseline Array
Radio Interferometry Very Long Baseline Array

20 What Wavelengths to Use?
Type Atmosphere Radio Waves No effect Microwaves Mostly blocked Infrared Blocked Visible Light Slight blurring Ultraviolet Blocked X-rays Blocked Gamma Rays Blocked Mostly restricted to space Limited microwave and IR from Earth

21 Infrared and Ultraviolet Space Telescopes
Spitzer Space Telescope Hisaki Space Telescope

22 X-Ray Space Telescopes
Chandra X-Ray Observatory NuSTAR HXMT Astrosat HETE XMM Newton Swift

23 Gamma-Ray Space Telescopes
AGILE INTEGRAL Fermi Gamma-Ray Space Telescope

24 End of Material for Test 1
P2 = a3 c = 3  108 m/s c = lf (M + m)P2 = a3 E = h f F = ma Questions? P = knT lmax T = 2900 Km

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