Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Astro midterm part 2
| Question | Answer |
|---|---|
| When is the separation of stars considered barely resolved according to the Rayleigh Criterion? | When the separation of stars equals the Rayleigh limit. |
| The width of the slit/aperture is | the diameter of the telescope |
| Telescope beam | the resulting diffraction pattern is sometimes called this |
| Resolution | the FWHM of the diffraction pattern is called the telescope______ |
| higher resolution | the bigger the scope or smaller the wavelength. It means sharper images, finer the detain can be seen. It means that the smallest angular scale that can be clearly seen is small. |
| Low resolution | means that the smallest angular scale that can be clearly seen is large. theta is a large number |
| Rayleigh criterion/telescope resolution defines | the minimum angular separation of two point sources that can still be seen as two sources and also define the smallest detail that can be clearly seen. AKA diffraction limit |
| seeing | the atmosphere can distort images. Can be different at the same location on different days. Atmosphere can completely block light at different wavelengths |
| Active optics | keep the telescopes shape a perfect paraboloid even under gravity loading. Actuators adjust shape of mirror. takes care of deformation of primary mirror, not seeing |
| Adaptive optics | uses active optics to keep a reference star image as concentrated as possible, also removes atmospheric seeing effects, maintains clear images |
| Adaptive optics uses | a deformable 3rd (tertiary) mirror to keep a reference star as compact as possible |
| Keplers law | We orbit the sun in 1 year, 1 AU away, 1 solar mass |
| Black Body spectrum | objects emit light at wavelengths that depend on their temperature. (black body or Planck curve) |
| UV sees | the VERY hot universe |
| Optical/Near IR sees | the hot universe (mostly stars and emission nebulae) |
| Far IR/millimeter/radio sees | the cool universe (cool gas and dust aways from stars) |
| opacity | amount of material light has to pass through, and depends on wavelength |
| Radio telescopes | are big because signals are weak, wavelengths are large. Because wavelength is long, we need a large aperture (diameter of reflecting mirror) |
| Limits to telescope aperture size | For a given wavelength resolution gets better as D increases. Telescope needs to get bigger, to get same resolution as a good optical telescope |
| Interferometeres | 2 telescopes separated by a distance B can simulate the resolution of a single, monolithic telescope with a mirror diameter of B. Sensitivity is proportional to 2((D^2)/4) |
| B | Baseline. Largest distance between telescopes in the array |
| Optical Interferometers | Not limited to radio telescopes, have to take in different coefficients of expansion and contraction into account |
| Equatorial Plane | the reference plane. latitude of 0 degrees and perpendicular to rotation axis (is the only line of latitude that is a great circle) |
| Parallels of latitude | small circles parallel to equator |
| Meridians | are semi circles (great circles): run pole to pole (AKA lines of longitude) |
| Longitude | the angle between the meridian and the meridian of 0 degrees. The 0 degree meridian is the Greenwich meridian or the prime meridian |
| The pole | is the intersection between rotation axis and all the meridians of longitude |
| The horizontal system | is tangent to earth's surface at location of observer. |
| Horizon | Intersection between the horizontal plane and the celestial sphere |
Created by:
user-1996284