Unformatted text preview: Midterm Exam 1
• This Wednesday: Feb 2 • 30-35 multiple choice questions. • About material covered in lectures. • Study:
• • • • • • Assigned seating. • Photo ID required. • No calculators! Notes. Weekly review questions on course website. Study guide – now on course website. Parts of textbook that I talked about in class. (sample questions on course web site but include much material not covered in class. • Office hours (BPS room 3270):
• Mon 12:45-2:00 • Tue 3:00-4:00 • Or by appointment Course website www.pa.msu.edu/courses/isp205/sec-1 the doppler effect measures the motion of objects out in space. t wo seperate components that are perpendicular to eachother are moving relative to eachother therefore we can figure out the distance between t he stars and the distance at which each star is moving. we are able to measure the angle b etween the two paths. Doppler effect known as the t rain whistle effect s maller wavelengths means a s maller frequency and higher p itch Measuring Radial Velocity: The Doppler effect water waves sound waves light waves. Wavelength shift is = observed - rest LIGHT: emission or absorption lines = constant “pitch”
Star moving away from us (redshift) Wavelength Star moving towards us (blueshift) v c For v = velocity of emitter, c = velocity of wave Wavelength [Fig 5.13]
Doppler Demo applet 1 Doppler Shift measures only the line-of-sight velocity component.
Doppler Shift tells full speed No Doppler Shift [Fig 5.15] Doppler Shift tells only part of speed directed away from us.
applet Galileo, 1609 Telescopes [5.3]
• Magnify images see details • Gather light over large surface area see fainter objects.
Twin Keck 26 feet dia. reflectors Mauna Kea, Hawaii, 1993 1 inch diameter lens
3 feet dia. lens 1888 Lens
No support beneath lens lens will sag upper limit on size. Reflector: Solid support under mirror can use very large mirrors 2 Radio Telescopes
Angular resolution =
smaller = sharper image Wavelength Mirror Diameter • Radio wavelengths are large need large mirror diameter to see small-angle details. Array of smaller telescopes simulates a huge aperture. • Arecibo, Puerto Rico . • 1000 ft. diameter, but same angular resolution as 0.01 ft optical telescope. Radio galaxy Cygnus A Very Large Array
Radio Telescope in New Mexico 3 Telescopes in Space
Chandra (x-rays) Hubble Space Telescope (ultraviolet/visible) Spitzer (infrared) Atmosphere smears images ht blocks lig osphere Atm
[Fig 5.25] in order to replace the HST i t will be crashed into the earth's atmosphere Hubble Space Telescope (HST) Ultraviolet/optical/infrared Above (most of) Earth s atmosphere High angular resolution Light not blocked in ultraviolet (or infrared) Low earth orbit Launched in 1990 To be replaced by James Webb Space Telescope 4 it has far sharper angular resolution - seeing the i ndividual stars a lot clearer crab nebula - expanding b lob of gas Chandra X-Ray Observatory Named after Subrahmanvan Chandrasekhar Nobel-Prize-winning astrophysicist NASA Great Observatory Far better than previous x-ray telescopes Many times higher angular resolution More collecting area
Remnant of supernova that exploded in our Galaxy in 1054 AD Optical Radio Galaxy Cluster:
Hydra A, 840 million light years away. Spitzer (Infrared) Space Telescope
Orion The Science Infra-Red (IR) radiation is not absorbed by interstellar dust. Lets us see starforming regions buried in dense, dusty gas clouds. able to see into a dense gas cloud that is not possible i n physical view. l onger wavelength is able t o come through i nterstellar gas cloud is HUGE - new stars are forming and the light wont g et out because of the dust. i t's mission is to look into t he dense gas clouds and s ee whats a goin on in there. Launched in 2003. Imaging and spectroscopy in far infrared. Earth-trailing orbit. Initially cooled by liquid nitrogen. But supply has run out. 5 ...
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- Spring '08
- Hubble Space Telescope, angular resolution, Doppler shift, Space Telescope, radio telescopes