The 12ft (4m), half-ton JET-X will be the largest X-ray telescope built. The Earth's atmosphere absorbs X-rays and so such high energy radiation can be observed only by instruments in space.
Previous observations have shown that the Sun emits X-rays, and many thousands of X-ray sources have subsequently been discovered, making the sky unexpectedly 'bright' at these wavelengths.
X-ray astronomy also picks up some of the most exotic objects in the cosmos: previous telescopes have detected candidates for Black Holes. Quasars - quasi- stellar objects which emit more energy than entire galaxies - radiate intense amounts of X-rays.
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