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Black holes. Exploding stars. Colliding clusters of galaxies. Our universe is home to objects that radiate so much energy that they make our Sun seem like an inconsequential ball of gas, a nonentity in the cosmic scheme of things.
Astronomers are used to dealing with large numbers, and they can accurately measure the incredible light output of these objects. But even the most brilliant minds can't truly fathom these staggering energies, since they are so far beyond the realm of human experience.
These enigmatic forces emit a large portion of their energy in X-rays rather than in visible light, so astronomers must study them in detail with X-ray telescopes to understand what’s going on. And since X-rays cannot penetrate Earth's atmosphere, this requires launching telescopes into space.
Over the past decade, X-ray observatories such as Chandra and XMM-Newton X-ray Observatory have revolutionized astronomers' understanding of the high-energy Universe. They have studied the details of how supermassive black holes shape their environments, and answered questions about how hot gas is distributed in vast clusters of galaxies. We have also learned more about how supernovae produce and distribute many of the elements necessary for life.
But some of the deepest mysteries of the high-energy cosmos remain just that—-mysteries. Does matter spiraling into a black hole behave in accordance with Einstein's General Theory of Relativity? How tightly can material be crammed into a neutron star? What is the dark energy that is causing the universe's expansion to accelerate? What are all the sources that make up a background glow of X-rays seen in every direction?
Consider a hot cloud of gas whirling around a black hole at nearly the speed of light, an environment where general relativity flexes its muscles. Things are changing incredibly fast—on a timescale of seconds to minutes. Current telescopes such as Chandra and XMM-Newton need to "stare" at this scene for hours to collect enough X-rays to make an observation. But during this long interval, they’ve missed all the action.
To obtain a freeze-frame picture of this scene, astronomers need an X-ray mission with a much larger mirror—one that can collect enough photons in just a few minutes to see the hot cloud whipping around the black hole. Scientific goals like this motivated the design for NASA's next major X-ray observatory: Constellation-X, a flagship mission in the Beyond Einstein program.
Con-X builds mostly on proven technology. It will consist of four individual X-ray telescopes housed in a single spacecraft. The total light-collecting area for taking spectra will exceed Chandra's and XMM-Newton's by about a factor of 100, a monumental improvement in sensitivity.
But this increase in size poses a technological challenge for Con-X planners. Chandra is a school-bus size observatory, one of the heaviest payloads ever launched on the Space Shuttle. Scaling Chandra's mirrors up a hundredfold would result in a spacecraft too heavy to be launched into space. In response to this challenge, scientists and engineers have developed new types of lightweight mirrors.
Astronomers also need next-generation instruments to take full advantage of Con-X's giant mirrors. So team members are developing the ultimate cold X-ray detector (called a microcalorimeter), an optical device somewhat akin to a prism for X-rays (the gratings), and a system that will image X-rays so energetic that they pierce right through the spacecraft and the other two instruments (the Hard X-ray Telescope).
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