Astronomical Concepts And Techniques 1-22
22 entries in the Astronomical Concepts And Techniques compendium.
Saros (astronomy)After one saros, the Sun, Earth, and Moon return to approximately the same relative geometSelenographyStudy of the Moon's surface and physical features.Sidereal timeTimekeeping system based on Earth's rotation relative to the fixed stars.Sky brightnessSky brightness describes the scattering and diffusion of light in the sky.Solar cycleAn 11-year periodic change in solar activity and sunspot numbers.SolsticeTwice-yearly event when the Sun's declination appears to stand still.Space weatherStudy of solar wind effects on the Solar System.Space physicsStudy of natural plasmas in Earth's upper atmosphere and Solar System.Spectral energy distributionA plot of energy versus frequency or wavelength used in astronomy.Spectral indexA measure of flux density's dependence on frequency.Spherical astronomyOldest branch of astronomy, locating objects on the celestial sphere.Stellar parallaxTrigonometric method for measuring distances to nearby stars.Surface brightnessSurface brightness measures extended object visibility per angular area.Time-domain astronomyStudy of how astronomical objects change with time.Tip of the red-giant branchA standard candle using the brightest red-giant-branch stars.Tropical yearTime for Sun to return to same seasonal position.TwinklingTwinkling is atmospheric scintillation affecting distant light sources.Umbra, penumbra and antumbraThree distinct parts of a shadow from an opaque object.Velocity dispersionStatistical spread of velocities in astronomical groups.UBV photometric systemFirst standardized photometric system for stellar classification.ZodiacA celestial coordinate system dividing the ecliptic into 12 signs.Zodiacal lightA faint glow of sunlight scattered by interplanetary dust.
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