Introduction to Small Bodies Node
Glossary
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Introduction to Small Bodies NodeGlossary |
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albedo:
- a measure of how efficiently a surface or dust particle reflects light; sometimes defined as the ratio of the amount of light reflected by an object and the amount of incident light; a body with the albedo of 0 reflects no light, with the albedo of 1 reflects 100% of the incident light.
astronomical unit (AU):- a unit of length in astronomy; it is equal to the average distance from the Earth to the Sun; 1 AU = 149,597,870 kilometers (92,955,806 miles).
color:- a measure of the asteroid/comet brightness variations with the wavelength; often color is determined as the difference of brightness in two wavelengths or two filters; if an object is equally bright as seen through different filters, it is referred to as gray; if the body is brighter at longer wavelength or red filters, it is referred to as being red.
eccentricity:- a measure of how far from a circular shape an ellipse is; numerically, the eccentricity e = 1 - ( perihelion / semi-major axis). The eccentricity e = 0 for a circle and e = nearly 1 for very long, skinny ellipses.
ellipse:- a close curve resembling a flattened circle; the sum of the distances from a point on the ellipse to two fixed points (foci) is always constant.
ion:- an atom or group of atoms (molecule) that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.
ionized:- to be converted into ions by gaining or losing electrons.
major axis:- the axis passing through the foci of an ellipse; the largest diameter distance between opposite points of an ellipse.
perihelion (perihelia, pl):- the point in the orbit of a planet, comet, asteroid, etc. that is closest to the Sun.
semi-major axis:- half the length of the major axis of an ellipse; the semi-major axis of an orbiting body is equal to the average distance from the body to the Sun.
silicate:- a chemical compound that contains silicon, oxygen, and usually one or more other common elements (often metals); silicates are the main rock and mineral forming compounds.
solar wind:- a tenuous flow of gas and energetically charged particles, mostly protons and electrons -- plasma -- which stream from the Sun.
spectrum (spectra, pl):- electromagnetic radiation arranged in order of wavelength; a rainbow is a natural spectrum of visible light from the Sun; spectra are often punctuated with emission or absorption lines, which can be examined to reveal the composition and motion of the radiating source.
sublime (or sublimate):- the turning of a solid directly into a gas without going through the intermediate liquid phase, e.g., the vapor of "dry ice" (the sublimation of frozen carbon dioxide).
Other Glossaries
Terms and Definitions from Solar Views
Definitions provided by: Dr. Ludmilla Kolokolova
Last Update: Puneet Khetarpal (January 06, 2005)
Contact: puneetk at astro.umd.edu