X-rays are a type of electromagnetic radiation with wavelengths between 0.01 and 10 nanometers, shorter than ultraviolet light and longer than gamma rays.

Stars typically emit X-rays only during certain stages of their life cycle, such as when they are young or when they are undergoing a supernova explosion. Supernova remnants, black holes, and neutron stars are all known to emit X-rays more consistently.

In celestial objects, X-rays are primarily produced through a process called synchrotron radiation, which occurs when high-energy electrons spiral in a magnetic field.

X-ray telescopes are specialized instruments designed to detect and study X-rays from celestial objects. They typically use mirrors or other optical elements to focus X-rays onto a detector.

ROSAT (Röntgensatellit), launched in 1990, was the first X-ray telescope to be placed in orbit around Earth.

While X-ray telescopes have been used to study the solar corona and the composition of neutron stars, they are not typically used to detect water on planetary surfaces.

X-ray telescopes are typically designed to detect X-rays in the energy range of 1 keV to 10 keV, which corresponds to wavelengths between 0.1 and 1 nanometer.

White dwarfs, which are the remnants of low-mass stars, typically do not emit significant amounts of X-rays.

The Earth's atmosphere absorbs most X-rays, making it challenging to detect and study X-ray sources from space. X-ray telescopes must therefore be placed above the atmosphere, either on high-altitude balloons or in Earth orbit.

Reflecting telescopes are not commonly used in X-ray astronomy because X-rays are not easily reflected by materials. Instead, X-ray telescopes typically use grazing-incidence mirrors or other specialized optical elements to focus X-rays.

The Chandra X-ray Observatory, launched in 1999, is a powerful X-ray telescope that continues to provide valuable insights into the high-energy universe.

While X-ray astronomy is used to study a wide range of astrophysical phenomena, searching for exoplanets is not a major scientific goal of this field.

Modern X-ray telescopes, such as the Chandra X-ray Observatory, have an angular resolution of approximately 1 arcsecond, which allows them to resolve fine details in X-ray images.

White dwarfs, which are the remnants of low-mass stars, typically do not emit significant amounts of X-rays and are therefore not commonly detected by X-ray telescopes.

XMM-Newton, launched in 2000, is a powerful X-ray telescope operated by the European Space Agency.