Back when I was in grad school Andreas Ghez gave a colloquium talk about her work in my department. The basic idea behind the technique she used is that the re

Back when I was in grad school Andreas Ghez gave a colloquium talk about her work in my department. The basic idea behind the technique she used is that the resolution from images in modern telescopes is limited by atmospheric distortions. If you can get rid of the distortions, you can get much sharper images, and in her case, resolve the stars orbiting Sag A*. Adaptive optics is one way to reduce distortions from the atmopshere. With adaptive optics, you observe some star (or more commonly a spot of light created by a laser) and rapidly distort one of the mirrors in the optical path to compensate for atmospheric fluctuations. Andrea Ghez went further than this, though. Atmospheric fluctuations are fast, but they are not instantaneous. If you can take an observation faster than the atmosphere changes, you will get a much sharper image. You can sort of imagine that an any given instant, a star is a very sharp point of light (or actually several points of light due to refraction), but over time, these points of light move around randomly over an area to create a smeared out image. Of course, there a number of huge technical difficulties to taking these very rapid images. But if you can manage it, you can resolve the orbits of stars around the supermassive black hole at the center of the Galaxy. (This technique is called speckle imaging.) I also remember her joking that when most astronomers write observing proposals, they'll typically apply for a few nights of time on a telescope. But she was applying for a few seconds of observing time over the course of a decade.