The greatest extremes of gravity in the Universe are the black holes formed at the centers of galaxies and by the collapse of stars. Gravity is so overpowering here that nothing, not even light, can escape its grasp. By definition black holes are invisible. Yet these invisible bodies disturb space considerably, offering us two ways to study them: by observing matter swirling into them, and by listening to the waves of distortion they make in spacetime.
Data from X-ray satellites, such as NASA's Chandra X-ray Observatory and ESA's XMM-Newton, show signs of gas whizzing about black holes at close to the speed of light and hint that time is slowing as the gas plunges into the zone from which escape is impossible. Beyond Einstein missions will take a census of black holes in the Universe and give detailed pictures of what happens to space and time at the edges of these gravitational chasms.
One key mission will create movies from the X-ray light emitted from multimillion-degree gas as it approaches a black hole's border, called the event horizon. Another mission will listen for gravitational waves, which are ripples in spacetime predicted by Einstein. These waves are created by black hole mergers; they move undisturbed across the "sea" of space at light speed, and offer an unobstructed view of these powerful collisions.
Einstein himself never dreamed that it would be possible to detect gravitational waves, which only distort the distance between objects as far apart as the Earth and Moon by less than the width of an atom. Yet the technology now exists to do so.
 | ||||||
| ||||||
 |
| Most of the X-ray sources seen in this |
 |
+Freedom of Information Act +Privacy Policy and Important Notices. |
 |
|
