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ความคิดเห็นที่ 21 |
http://universe-review.ca/R02-07-candle.htm#lensedq
# Gravitationally Lensed Quasars - When a galaxy is very close to the line-of-sight of a quasar, the light is deflected and many images of the quasar appear (Figure 10). As quasars are intrinsically variable objects, monitoring the luminosity variations of all images allows us to measure time delays between images, which is caused by splitting the light into slightly different paths around the lensing galaxy (see Figure 11). Computing the distance from the earth to the quasar requires the following information:
Quasar, Lensed Time Delay
1. The time delay -- which means the intensity of the background source must vary sharply, by large amounts.
2. The angular separation of the images of the background source.
3. the relative distances of lens and background source (we can use the redshift for this).
4. the mass of the lens, and its distribution (a point mass, or uniform sphere, or a sphere with varying density, or an ellipsoid).
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