Gómez de Castro, Ana Inés Física de la Tierra, Astronomía y Astrofísica, Universidad Complutense de Madrid, Madrid, Spain.
Last reviewed:March 2019
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- Solar systems
- Interstellar medium
- Stellar astronomy
- Extreme environments
- Links to Primary Literature
- Additional Readings
The study of astronomical objects by means of information obtained from the ultraviolet wavelength range of the electromagnetic spectrum. Ultraviolet light is more energetic than the visible light our eyes see, possessing a wavelength in the approximate range between approximately 10 and 320 nm. Many of the most abundant atoms in the universe emit light in this range when their energy states are changed, up to temperatures as high as a million K (about 1 million°C or 1.8 million°F), above which x-rays and gamma rays become the main radiation emissions. Molecular gas is also very sensitive to ultraviolet radiation because the electronic transitions of the most abundant molecules, including H2, CO, OH, CS, CO2+, and C2, are in this range. Overall, ultraviolet observations are the most sensitive means of detecting and measuring the properties of diffuse matter in the universe over a very wide range of physical conditions, from the warm gas evaporating from exoplanets to the hot gas in the intergalactic medium and in supernova remnants, and the rise of energetic stars in new populations within galaxies (Fig. 1). Moreover, ultraviolet radiation from astronomical sources is a powerful ionizing agent, which helps drive astrochemistry and chemical evolution in developing planetary systems. See also: Astronomical spectroscopy; Astronomical imaging; Atom; Electromagnetic radiation; Exoplanet; Galaxy; Gamma-ray astronomy; Molecule; X-ray astronomy
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