Continuing with the reading of Nature's last week (September, 4th), in a letter about candidate of our galaxy center I'm thinking about how hard can be to deduce who is the center of the galaxy.
Looking on another galaxy, with a good perspective on it, can be possible to approach to know around which structure the galaxy turns around. But when we are looking from in side this can be not so easy. As an example, the center of a galaxy is so briliant, but in a clear night from the Earth the center of the Milky way is not visible. We need to study it in the infrared spectrum, for example, because of the objects that are in the middle who block the visible light.
When we look to the center of the galaxy we are looking to the past because it's far from here, and the light expends 24k8 light years, to travel the 7k6 parsecs. Looking Andromeda we have a prespective that shows us objects from a similar time, but from inside our galaxy the light of diferent objects arribes here from different historyc moments.
By the way, our candidate as a center is Sagittarius A*, a supermassive black hole that can have 4 million solar masses, with in an space that can be 45 AU. (realize that all the planets in our solar system are closer to the sun than this distance).
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