An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Covered or marked with an unclean substance. → dirty ice, → dirty iceball model.

→ dirt + suffix -y.

Interstellar ice grains with graphite, silicates, or other chemical compounds adsorbed on their surfaces.

→ dirty; → ice.

A model for a → cometary nucleus proposed by Fred Whipple (1950-51), according to which the nucleus is a solid body (a few kilometers across) made up of various → ices (→ frozen water, → methane, → ammonia, → carbon dioxide, and → hydrogen cyanide) in which → dust is embedded. Dust particles are liberated when the ices vaporize as the → comet approaches the → Sun, and they get blown away by → solar radiation pressure, often forming impressive, gently curved → dust tails.

→ dirty; → ice; → ball; → model.