1	Astro 1050 Fri. Sep. 20, 2002 Today: Tools of Astronomy Astronomy Articles?
2	The Electromagnetic Spectrum Radio waves Microwaves Infrared Visible Ultra-violet X-Rays Gamma rays
3	Numerical Relationship between wavelength and photon energy Inverse relationship: Smaller l means more energetic c = speed of light = 3.00 ´ 10⁸ m/s h = Planck’s constant = 6.63 ´ 10^-34 joule s Note: Joule is a unit of energy 1 Joule/second = 1 Watt Energy of a single photon of 0.5 mm visible light? Seems very small, but this is roughly the energy it takes to chemically modify a single molecule. Photons from a 100 W lightbulb (assuming all 100W goes into light?)
4	Optical Telescopes and Cameras Properly curved lenses and mirrors can form “Images” The light leaving one point on object gets “reassembled” at one point on the image.
5	Why do astronomers need large telescopes? Large telescopes can collect more light Can detect fainter objects Have more light for specialized analysis. Large telescopes can form more detailed images Waves spread out as they go through an opening. The larger the opening, the less they spreads out. The longer the wavelength the more they spread out Angle of spread q µ l/D where D is Diameter of telescope Radio telescopes have to be much bigger than visible ones
6	Kinds of measurements made with telescopes Measure brightness of objects (photometry) Record images using electronic “CCD” detectors Split it into different wavelengths with “spectrometers”
7	Dark Side of the Moon What is wrong with this picture? Front: Not all primary colors (eg, pink, magenta), also refraction angles inconsistent Back: Spectrum is Convergent – I think done for art’s sake
8	Observing over the entire electromagnetic spectrum Different phenomena produce different wavelength waves Ordinary stars: Visible light Cool planets or dust clouds: Infrared light Moving charged particles, cool molecules: Radio waves Very hot objects: X-Rays and Gamma Rays Quasars: ALL wavelengths Only visible, some IR, and radio make it through atmosphere Need to observe from space for other wavelengths Going into space also lets you obtain more detailed images On Earth telescope size isn’t only limit on image resolution Temperature fluctuations in atmosphere cause “seeing” (blurring)
9	Bad “seeing”/Good “seeing”
10	Active/Adaptive Optics
11	Hubble Space Telescope (HST)
12	Chandra X-ray Observatory
13	Radio Telescopes
14	Infrared Telescopes
15	Infrared Telescopes
16	The Electromagnetic Spectrum Radio waves Microwaves Infrared Visible Ultra-violet X-Rays Gamma rays
17	For Next Time: