time, of the order of 0.01 s. The blurring of images comes from trying to observe for longer than this. If an image were bright enough to see in this short time, we could take a picture with diffraction-limited resolution. Unfortunately, 0.01 s is not long enough to collect enough photons from a star. However, we can collect a series of 0.01 s images, observing interference between light coming through slightly different paths in the atmosphere. The final images must be reconstructed mathematically.

Even more recently, work on stellar sizes has been done on the Hubble Space Telescope, as shown in Fig. 5.14. The results of these various techniques are shown in Fig. 5.15. We can see that, on the main sequence, stars become larger with increasing surface temperature. This is why the luminosity of stars increases with increasing surface temperature at a rate greater than T4.

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