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Basic Astronomy Concepts

X-Ray Astronomy

X-Ray Astronomy, astrophysicists, celestial bodies, hot gas, speed of light

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>  Detecting X-Rays

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X-Ray Astronomy, detection and study of electromagnetic energy radiating from celestial bodies in the form of X rays. X-ray astronomy provides astrophysicists with a means to study violent and energetic events in the universe. Nearly every class of astronomical object, from nearby stars to distant quasars, emits X rays at some point in its life cycle.

X rays are part of a wide spectrum of energy called electromagnetic radiation. Electromagnetic waves range from high energy, short wavelength gamma rays, to visible light, to low-energy, long wavelength radio waves. X rays have shorter wavelengths and higher energies than visible light and ultraviolet radiation, but longer wavelengths than gamma rays. They are powerful enough and have short enough wavelengths to pass through many materials that reflect or absorb visible light.

Objects and regions in space emit X rays for one of two reasons. Most X rays come from regions in which gas is heated to tens of millions of degrees Celsius or Fahrenheit. This heating may be a result of shock waves from huge stellar explosions, gas plunging into intense gravitational fields, or other energetic events, and it causes gas to emit X rays. X-ray emission caused by hot gas is called thermal emission. X rays may also be emitted when powerful magnetic fields accelerate electrons to nearly the speed of light. This kind of X-ray emission is called nonthermal emission.


Villard, Ray, B.A., M.S.

Public Information Manager, Space Telescope Science Institute. Astronomy Instructor, Howard Community College.

Article key phrases:

X-Ray Astronomy, astrophysicists, celestial bodies, hot gas, speed of light, visible light, universe, ultraviolet radiation, electrons, Fahrenheit, degrees Celsius, X rays, energies, high energy, regions, detection, space, Objects, heating, point, reasons, means, materials

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