THE BLACK HOLE AT THE CENTER OF OUR GALAXY

At the center of the Milky Way galaxy, 28,000 light-years from Earth, lies a true heart of darkness, a supermassive black hole containing the equivalent of almost three million suns in an area smaller than the orbit of Mars. Lying between the constellations Sagittarius and Scorpio, this black hole, labeled by scientists Sagittarius A*, cannot be seen with the largest visible-light telescopes because dark dust clouds hide it from our view. In recent years, however, with the advancement of radio and X-ray imaging, scientists are breathtakingly close to "seeing" a black hole. Astrophysicist Melia sys that most galaxies with a central bulge, like the Milky Way, have such a black hole at their center; he also says such black holes are scattered throughout galaxies as well, but unless we someday discover one wandering through space close to Earth—not a comforting thought—Sagittarius A* remains our best bet for exploring this mysterious phenomenon. If a star makes a wrong turn into the neighborhood of a black hole, Melia explains, it is not necessarily doomed to be captured by the latter's gravitational handcuff and dragged to oblivion. Melia uses well-chosen earthbound metaphors to explain these arcane concepts, and he lays out the theoretical underpinnings with mathematics simple enough for readers with basic college algebra or physics to follow. Astronomy buffs will find this account both engrossing and informative. 40 color, 2 b&w illus. (May)