- 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 ...
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 central region of a planet or moon frequently made of denser materials than the surrounding regions (mantle and crust). Earth and the Moon are thought to have cores of iron and nickel.
Industry:Astronomy
These minerals have layered structures that contain silicon and oxygen in some multiple of Si<sup>2</sup>O<sup>5</sup>.
Industry:Astronomy
The scientific study of meteorites to better understand the origin, geologic history and evolution of our Solar System.
Industry:Astronomy
Groups of thousands to millions of old stars held together in orbits about their own center of mass and arranged in almost symmetrical (spherical) clusters.
Industry:Astronomy
Cool, luminous, and pulsating red giant stars. Most stars in the Universe that have left the main sequence will reach their final evolutionary stage as stars on the asymptotic giant branch.
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
Oldest exposed areas on the surface of the Moon; extensively cratered, and chemically distinct from the maria.
Industry:Astronomy
