The airglow is the very weak emission of The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. There are no exact bounds to the optical spectrum; a typical human eye will respond to wavelengths from 400 to 700 nm, although some people may be able to... visible light by the earth's atmosphere, which means that the night sky is never completely dark. It was first noticed in Years: 1865 1866 1867 - 1868 - 1869 1870 1871 Decades: 1830s 1840s 1850s - 1860s - 1870s 1880s 1890s Centuries: 18th century - 19th century - 20th century 1868 in topic: Arts Architecture - Art - Literature - Music Other topics Canada - Rail transport - Science - Sport Lists of leaders: Colonial governors - State leaders Events January 3 - Meiji Emperor... 1868 by Anders Jonas Ångström Anders Jonas Ångström ( August 13 is the 225th day of the year in the Gregorian Calendar (226th in leap years), with 140 days remaining. August Su Mo Tu We Th Fr Sa   1 2 3 4 5 6 7 8... Anders Ångström. It is caused by various processes in the upper atmosphere, such as the recombination of ions which were Photoionisation is a physical process in which a photon strikes an atom, ion or molecule, resulting in the ejection of an electron. The ejected electron is known as a photoelectron, and has a kinetic energy equal to the energy of the photon minus the electron binding energy. Photons which have... photoionised by the For other uses, see Sun (disambiguation). Sun Observation data Mean distance from Earth 149.6×106 km (92.95×106 mi) Visual brightness (V) −26.8m Absolute magnitude 4.8m Orbital characteristics Mean distance from Milky Way centre ~2.5×1017 km (26,000 light-years) Galactic period ~2... sun during the day, luminescence caused by Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. The composition includes electrons, protons, gamma rays, and atomic nuclei from a large region of the periodic table. The kinetic energies of these particles span over fourteen orders of magnitude, with the flux of cosmic rays... cosmic rays striking the upper atmosphere, and Chemoluminescence (sometimes chemiluminescence) is the emission of light (luminescence) as the result of a chemical reaction. Most simply, given reactants A and B, with an excited intermediate ◊, we have, [A] + [B] → [◊] → [Products] + light The decay of the excited state[◊] to a lower energy level is... chemiluminescence caused mainly by carbon – nitrogen – oxygen   N P       Full table General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1.2506 kg/m3 Hardness NA Appearance colorless Atomic properties Atomic weight 14.0067 amu Atomic radius (calc... oxygen and carbon – nitrogen – oxygen   N P       Full table General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1.2506 kg/m3 Hardness NA Appearance colorless Atomic properties Atomic weight 14.0067 amu Atomic radius (calc... nitrogen reacting with Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. Organic molecules containing a hydroxyl group are known as alcohols (CnH2n... hydroxyl ions at heights of a few hundred kilometres.

Even at the best ground-based observatories, airglow limits the sensitivity of telescopes at visible wavelengths. For this reason, space-based telescopes such as the Hubble Space Telescope The Hubble Space Telescope as seen from the Space Shuttle Discovery during the second servicing mission of the telescope, STS-82 Organization NASA, ESA Wavelength regime optical Orbit Height 600 km Orbit 100 min Launch date 24 April 1990 Deorbit date circa 2010 Mass 11,000 kg... Hubble Space Telescope can observe much fainter objects than current ground-based telescopes at visible wavelengths.

The airglow may be bright enough to be noticed by an observer. Although airglow emission is fairly uniform across the atmosphere, to an observer on the ground it appears brightest at about 10 degrees above the horizon, because the lower one looks the greater the depth of atmosphere one is looking through. Very low down, however, atmospheric Extinction is a term used in astronomy to describe the absorption of light from astronomical objects by matter between them and the observer. Extinction arises both from the interstellar medium and the atmosphere. In both cases, blue light is much more strongly absorbed than red light. Interstellar extinction Broadly speaking... extinction reduces the apparent brightness of the airglow.

See also

• Aurora borealis Polar aurorae are optical phenomena characterized by colorful displays of light in the night sky. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights; in the Southern Hemisphere it is called the aurora australis. Auroras are the most visible effect of... Polar aurora
• An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics Common optical phenomena are often due to the interaction of light from the sun or moon with the atmosphere, clouds, water, or dust and other particulates... Optical phenomena