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Ultraviolet astronomy is the observation of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma-ray astronomy. [1] Ultraviolet light is not visible to the human eye. [2]
Extremely hot stars (such as O- and B-type) emit proportionally more UV radiation than the Sun. Sunlight in space at the top of Earth's atmosphere (see solar constant) is composed of about 50% infrared light, 40% visible light, and 10% ultraviolet light, for a total intensity of about 1400 W/m 2 in vacuum. [25]
As a result, the photosphere of the Sun does not emit much X radiation (solar X-rays), although it does emit such "hard radiations" as X-rays and even gamma rays during solar flares. [14] The quiet (non-flaring) Sun, including its corona, emits a broad range of wavelengths: X-rays, ultraviolet, visible light, infrared, and radio waves. [15]
Neutral atoms or condensed matter do not have large enough energy transitions to emit EUV radiation. Ionization must take place first. EUV light can only be emitted by electrons which are bound to multicharged positive ions; for example, to remove an electron from a +3 charged carbon ion (three electrons already removed) requires about 65 eV. [1]
The deuterium then emits light as it transitions back to its initial state. This continuous cycle is the origin of the continuous UV radiation. This process is not the same as the process of decay of atomic excited states (atomic emission), where electrons are excited and then emit radiation.
Infrared light from the Sun accounts for 49% [32] of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation.
The aurora is expected to be bright and visible in multiple northern U.S. states Oct. 3 through Oct. 5 as well as from the lower Midwest to Oregon.
International Ultraviolet Explorer (IUE or Explorer 57, formerly SAS-D) [2] was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA , the United Kingdom 's Science and Engineering Research Council (SERC, formerly UKSRC) and the European Space ...