Science Goals
Strong Gravity
Constellation-X will measure how the extreme forces of gravity operate near a black hole by mapping the distortions of space-time predicted by Einstein's Theory of General Relativity.
This artist's concept of a supermassive black hole highlights the accretion disk of gas and stars swirling around the black hole and the jets of material ejected along the poles.
Within all classes of black holes, space and time as we know them collapse. (See this article on black holes for more on the different types of black holes.) At the black hole border, called the event horizon, space is greatly distorted and time comes to a crawl. Einstein described the the three physical dimensions (length, width, height) and time as one four-dimensional concept called space-time. A black hole's gravity is so strong that it can actually bend space-time, sort of like stretching the fabric of space. A black hole (or neutron star, another dense object) is often envisioned as a heavy weight, like a bowling ball, on a mattress. The force of gravity, Einstein said, is the curvature in space-time caused by any object. When a black hole spins, it is so massive and produces a curvature so great that it can spin space-time along with it. Thus, black holes are cosmic laboratories, allowing us to explore the ultimate limits of the law of gravity and other forces.
Artist's conception of frame dragging.
Far from being science fiction, the curvature of space-time was detected by NASA's Rossi X-ray Timing Explorer. This satellite observed a phenomenon called frame dragging, where the fabric of space (not just matter) was literally shifted by a black hole. Constellation-X has the spectral resolution power to get even closer to a black hole to better observe this mechanism and confirm such an observation. The mission promises to provide an even stronger answer to that fundamental question of what goes on near a black hole, a region defined as the ultimate expression of gravity.
Constellation-X's large X-ray collecting area and superior spectral resolution, or clarity, will provide the most detailed, quantitative observations of the region surrounding a black hole. Views using current telescopes can take us near a black hole, but Constellation-X will take us within a few miles of its edge. Experiments will be able to measure the mass and spin of a black hole, two of its defining characteristics. Such measurements will enable scientists to begin to answer the many questions that remain about the formation and evolution of black holes, and about how the laws of physics – particularly those based on Einstein's equations – behave in extreme environments.
