Astrophysics (Index)About

snow line

(frost line, ice line, water line)
(distance from protostar cool enough for water to condense)

The snow line (also called the frost line, ice line, or water line) is the distance from a protostar at which ice can form and ammonia and methane can condense. The temperature is estimated at 150 K, i.e., in the 145-170 K range for a typical protoplanetary disk. The solar system's snow line is about 5 AU, nearly to Jupiter. In a general way, the snow line forms the outer bound of the habitable zone.

An analogous line further out is an ice transition radius (amorphous-to-crystalline ice transition radius or amorphous ice snow line) is the line between the ring-shaped region within the disk where water forms crystal ice versus that beyond where it forms amorphous ice. The difference can affect the tendency for the ice to clump and form planetary embryos.

Further reading:

Referenced by pages:
core accretion model
habitable zone (HZ)
planet formation