Editing X-ray astronomy (section)

==X-ray telescopes and mirrors==
{{main|X-ray telescope}}
[[File:XRISM s X-ray mirror assembly.jpg|thumb|One of the mirrors of [[XRISM]] made of 203 foils]]

Satellites are needed because X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. X-ray telescopes (XRTs) have varying directionality or imaging ability based on glancing angle reflection rather than refraction or large deviation reflection.<ref name=swift>{{cite web |title=SWIFT X-ray mirrors |url=http://swift.sonoma.edu/about_swift/instruments/xrt.html }}</ref><ref name=chandra>{{cite web |url=http://chandra.harvard.edu/about/telescope_system.html |title=Chandra X-ray focusing mirrors}}</ref>
This limits them to much narrower fields of view than visible or UV telescopes. The mirrors can be made of ceramic or metal foil.<ref name=xrayoptics>{{cite web |url=http://astrophysics.gsfc.nasa.gov/xrays/MirrorLab/xoptics.html |title=X-ray optics }}</ref>

The first X-ray telescope in astronomy was used to observe the Sun. The first X-ray picture (taken with a grazing incidence telescope) of the Sun was taken in 1963, by a rocket-borne telescope. On April 19, 1960, the very first X-ray image of the sun was taken using a pinhole camera on an Aerobee-Hi rocket.<ref name=Blake>{{cite journal|last=Blake|first=R. L.|author2=Chubb, T. A. |author3=Friedman, H. |author4=Unzicker, A. E. |title=Interpretation of X-Ray Photograph of the Sun|journal=Astrophysical Journal|date=January 1963|volume=137|page=3|doi=10.1086/147479|bibcode = 1963ApJ...137....3B |doi-access=free}}</ref>

The utilization of X-ray mirrors for extrasolar X-ray astronomy simultaneously requires:
* the ability to determine the location at the arrival of an X-ray photon in two dimensions and
* a reasonable detection efficiency.