Space exploration began with the launch of Sputnik and Astrophysics was born as the application of physics to the phenomena observed by Astronomy, which etymologically means laws of the stars.
There are 2759 entries in this glossary.| Term | Definition |
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| Light-Time |
The time it takes for light, or any other form of electromagnetic radiation, to travel a particular distance.
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| Ligo |
Abbreviation for Laser Interferometer Gravitational-Wave Observatory.
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| Limb |
The extreme edge of the visible disc of a body such as the Sun, Moon or a planet.
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| Limb Brightening |
An increase in the intensity of emitted radiation between the centre and the limb of the visible disc of the Sun, or other astronomical body.
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| Limb Darkening |
A decrease in the observed brightness of the disc of the Sun, or other astronomical body, between the centre and the limb.
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| Limiting Magnitude |
The magnitude of the faintest object that can be detected with a given imaging system.
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| Line Profile |
The variation in light intensity in a spectrum across a narrow wavelength range occupied by a single spectral line. When traced as a graph of intensity against wavelength, a typical stellar absorption line shows a bell-shaped profile, for example. If a line profile can be determined in some detail, information can be deduced about the physical conditions in the gas where the line originated.
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| Line Spectrum |
A spectrum that features emission lines, absorption lines, or both.
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| Linea Pl. Lineae |
An elongated surface marking on a planet.
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| Liner |
An acronym for low-ionization narrow emission line region. Such regions are found in a high proportion of spiral galaxies. Apparently they are a weak form of active galactic nucleus, which suggests that, at some level, all galaxies exhibit activity in their nuclei.
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| Linné |
A small lunar crater, 2.4 kilometres 1.5 miles in diameter, situated in the Mare Serenitatis. A mid-nineteenth-century claim that a close companion, a crater called Linné B, had disappeared seems likely to have been spurious since the observation was not confirmed. Though small, Linné is relatively conspicuous because it is surrounded by a bright area, presumably a small blanket of ejecta.
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| Lion |
English name for the constellation Leo.
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| Lion Cub |
English name for the constellation Leo Minor.
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| Lithosiderite |
Alternative name for a stony-iron meteorite.
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| Lithosphere |
The rigid outer layer of a planetary body, including the crust and part of the upper mantle, which lies above the weaker asthenosphere.
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