But six X-ray stars in binaries are measured to be five to ten times as massive as our Sun. Such an object is called a black hole because the pull of gravity would prevent radiation such as light, or X-rays, from escaping. X-rays we see must come from gas heated to a billion degrees as it approaches the edge of the hole. There are many such black holes in our galaxy, especially near its center, where there is a large concentration of matter. The centers of some galaxies appear to have black holes a hundred million times larger than stellar black holes.
Quasars are the most powerful.
In these galaxies, millions of small black holes may have merged into one. XTE will measure X-rays from the gas as close to the centers as can be seen to study what happens at the edge of the abyss. The XTE Instruments Three instruments are present on XTE to accomplish its mission. We are interested in what you think, so please send us your comments .