The comet Ikeya-Zhang exhibiting a bright, condensed coma (march 2002)
In astronomy, the nebulous envelope around the nucleus of a comet is called its coma (from the Latin word for "hair"). It is formed when the comet passes close to the sun on its highly ellipticalorbit; as the comet warms, parts of it melt and/or vaporize. The coma is generally made of ice and dust. Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure [1]. Image File history File links Comet Ikeya-Zhang (photographed on March 3, 2002). ... In ancient Greece and other early civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... Latin is the language originally spoken in the region around Rome called Latium. ... A sun is the star at the center of a planetary system. ... In mathematics, an ellipse (from the Greek for absence) is a curve where the sum of the distances from any point on the curve to two fixed points is constant. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... Icicles A natural, 4 tonne, block of ice on a beach in Iceland Ice is the solid form of water. ... Dust is a general name for minute solid particles of diameters less than 500 micrometers (otherwise see sand or granulates) and, more generally, for finely divided matter. ... Electromagnetic radiation exerts a pressure upon any surface exposed to it. ...
This gives a comet a "fuzzy" appearance when viewed in telescopes and distinguishes it from stars. 50 cm refracting telescope at Nice Observatory. ... The Pleiades star cluster A star is any massive gaseous body in outer space, just like the Sun. ...
The scientific payload was comprised of ten hardware experiments: a narrow-angle camera, three mass spectrometers for neutrals, ions and dust, various dust detectors, a photopolarimeter and a set of plasma experiments.
All experiments performed well and returned a wealth of new scientific results, of which perhaps the most important was the clear identification of the cometary nucleus.
The Johnstone Plasma Analyser detected the first presence of cometary ions 600,000 km from the nucleus at 12 hours before the closest approach.
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