compactness همپکی، همپکیدگی hampaki, hampakidegi Fr.: compacité General: The quality of being compact.
For a → compact object, a rough measure of the
importance of gravity, defined by a dimension-less quantity which is the ratio between
its gravitational radius (→ Schwarzschild radius) and its
physical radius. It is expressed as
φ = 2 GM / c2 R, where M and R are the mass
and radius of the object respectively, and
G and c are the → gravitational constant and
speed of light respectively.
For a → black hole φ is of order
unity (by definition), for a → white dwarf
it is of order 10-4, and for a → neutron star φ is around 0.5.
See also: → compact + → -ness. |
