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Our Galaxy - Galactic Center

The COBE (Cosmic Background Explorer) provides a portrait of what our galaxy looks like - from the side:

The galactic bulge is the bright bulge in the center. The Chandra X-Ray Observatory is able to pierce the clouds of the bulge and is able to provide for us a fantastic image of our galactic core:

The bright areas are intense energy sources believed to be driven by a black hole. This artists impression below demonstrates what a black hole might look like:

A closer look in the X-ray reveals an area in the direction of the constellation Sagittarius. This source of energy is called Sagittarius A, and the source object is called Sagittarius A* (a-star). Sagittarius A* is believed to be the Supermassive Black Hole. But why is it called a Supermassive Black Hole? A "normal" black hole is the result of a massive star's sudden exhaustion when it burns up its fuel.

Because the star is so massive, it collapses on itself creating a black hole. This will be discussed in the Star section. Because the center of a galaxy can contain thousands of stars, and because we are able to calculate the gravity effect of the black hole at the center, we learn the mass of this black hole is much much greater than a stellar black hole.

Of course, we have yet to see a black hole so we are not 100% certain that black holes exists - but we do have compelling evidence. The image below is an animated .gif that shows the region surrounding Sagittarius A*. The stars close to the center are moving rapidly compared to the background stars (you may have to reload or re-visit the page to reset the animation).

The motions of the stars are a result of the massive gravity generated by this region. This evidence, the energy generated by Sagittarius A* and the images in the X-ray are all very compelling evidence to support that a black hole is at the heart of our galaxy - as a matter of fact, many of Astronomers believe that supermassive black holes are at the heart of almost every galaxy.

Is there any reason for concern? No. The galaxy will not be swallowed whole by this black hole. But this information is valuable. We can apply our knowledge to other galaxies and perhaps unlock the door to reveal how a galaxy is formed and evolves.


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