By Garry Choy

The Milky Way: our galaxy and our home. So what is in the Milky Way? For a long time, Mars, Earth, our Sun, and some other planets rounded out our celestial neighborhood. But a few weeks ago, German astronomers announced that they had good proof of a neighbor which has been secluded for many years. This new neighbor is believed to be a massive black hole in the center of our galaxy.

A black hole is a celestial object that sucks any matter towards it. Extremely dense, its gravitational pull is very strong, such that light can't even escape - one reason why its called a "black" hole.

Although the scientists are still uncertain, this is "the best evidence that has yet existed," as said by Reinhard Genzel of the Max-Plank Institute for Extra-Terrestrial Physics. Evidence has been accumulating for the last twenty years. However, it is only in the last four years, that the scientists at the Institute started observing a subtle phenomena in the Milky Way.

The "Line-of-sight velocity" of stars orbiting a center in the galaxy indicated the possible location of a black hole. As reported in Nature magazine, they measured "proper" motions (at right angles to line-of sight velocities) of the 39 stars in the Milky Way. The results of their observations suggest that the stars move in regular circular orbits around a large mass which generates a gravitational pull. If the orbits had been less regular, the mass would have been speculated to be smaller. Genzel states "The fact that we are able to come so close to the central object and to test the velocities of the stars...that's what makes the measurements unique."

The research shows that the black hole is 2.5 million times greater in mass than the sun. Genzel hopes that by allowing the rest of the scientific community to assess the validity of the research, the theory over the findings will become more definite. Already, a publication from the University of California agreed that the German researchers "show with little ambiguity that about 2.5 million solar masses of dark matter lurks within a relatively tiny region at the center."

If no problems arise with the current theory, some time early next year, scientists, and consequently the rest of the Milky Way, will fully realize the presence this hidden but new neighbor.

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