What types of objects in space emit x-rays? How are the x-rays detected?
Hot gases and objects having temperature above million degree K emit X rays.
Stars like Sun, galaxies, matter falling to black holes, etc. emit X rays.
Since our atmosphere is not transparent to X rays, we have to put space telescopes to find X ray sources above earth's atmosphere.
Special inclined mirror telescopes are used to detect X rays.
See attached drawing of a X ray telescope.