In astronomy or planetary physics, the frost line refers to a particular distance in the solar nebula from the central protosun where it is cool enough for hydrogen compounds such as water, ammonia, and methane to condense into solid ice grains. Depending on density, that temperature is estimated to be about 150K. The term is borrowed from the notion of "frost line" in soil science. Radio telescopes are among many different tools used by astronomers Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, law of the stars) is the science of celestial objects and phenomena that originate outside the Earths atmosphere, such as stars, planets, comets, auroras, galaxies, and the cosmic background radiation. ... ã ... Protostar is a period after clouds of hydrogen, helium and dust begin to contract and before the a star reaches the main sequence. ... Water (from the Old English waeter; c. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... The frost line is the level down to which the soil will normally freeze each winter in a given area. ... Soil science deals with soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils per se; and these properties in relation to the use and management of soils. ...

The lower temperature in the nebula beyond the frost line makes many more solid grains available for accretion into planetesimals and eventually planets. The frost line therefore separates terrestrial planets from jovian planets. See also: Accretion (finance) Accretion is increase in size by gradual addition of smaller parts. ... In cosmogony, planetesimals are objects thought to exist within solar nebulae. ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ... A gas giant is a large planet that is not composed mostly of rock or other solid matter. ...

See also

• Solar Nebula Theory