- Industry: Astronomy
- Number of terms: 6727
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Planetary Science Research Discoveries (PSRD) is an educational site sharing the latest research by NASA-sponsored scientists on meteorites, asteroids, planets, moons, and other materials in our Solar System. The website is supported by the Cosmochemistry Program of NASA's Science Mission ...
Single-celled microorganisms whose cells lack a nucleus. Bacteria comprise a major domain of life called prokaryotes. In contrast, the cells in eukaryotes have a well-defined nucleus; eukarya include molds, plants, and animals. Another major domain is called archaea, microorganisms with genetic features distinct from prokarya and eukarya. Most methane-producing bacteria are actually archaea, but for simplicity many biologists informally refer to all non-eukaryotes as "bacteria.
Industry:Astronomy
Conventional unit of pressure when discussing the deep Earth: 1 GPa = 10 kilobars = 10,000 times air pressure at sea level.
Industry:Astronomy
Astronomical brightness measured on a logarithmic scale, based on the ancient practice of noting that the brightest stars in the sky were of "first importance" or "first magnitude", the next brightest being "second magnitude" etc. The human eye is a logarithmic detector, and in 1854 Pogson formalized this scale and defined a difference of 5 magnitudes to be exactly a factor of 100 in brightness. The scale is calibrated to the bright star Vega which is defined to have a magnitude of 0. For reference, the faintest naked-eye magnitude visible from a dark site is +6. Comet C/1996 B2 Hyakutake reached magnitude 0 in late March 1996.
Industry:Astronomy
The full range of frequencies, from radio waves to gamma rays, that characterizes light. The electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency (where the wavelength equals the speed of light divided by the frequency and energy equals Planck's constant times the frequency. )
Industry:Astronomy
La región del espacio entre las órbitas de Marte y Júpiter, de 2. 1 a 3. 3 AU, donde se encuentra la mayoría de los asteroides.
Industry:Astronomy
